Why measuring methane matters

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Key points:

  • Oil & gas companies typically rely on component-based inventory methods to estimate methane emissions over time which do not account for large-scale leaks.
  • The methodology used for estimating methane emissions was developed by the oil and gas industry and has been found to under-estimate methane emissions at a global level.
  • Methane emission rates reported by major oil and gas companies are 94% lower than indicated by independent estimates of the sector’s emissions.
  • The potential significant discrepancies between companies’ reported emissions and independently assessed emissions at a global level raises questions for investors and regulators regarding the reliability of oil and gas companies’ claimed emissions reductions.
  • Emissions accounting methods should be updated to include site-based measurements to understand the true magnitude of methane emissions.

Oil & gas industry is a major methane emitter 

Methane is a potent greenhouse gas, with a warming impact nearly 30 times greater than carbon dioxide over a 100 year period. Methane emissions are responsible for around 30% of the rise in global temperatures, according to the International Energy Agency (IEA). The oil and gas industry accounts for around a quarter of global methane emissions, second only to agriculture. Methane leaks or is released throughout the oil and gas supply chain – from extraction, processing and transport to use. 

Reducing methane emissions from the hydrocarbons sector is crucial to meeting climate goals. The IEA estimates that achieving a 75% reduction in emissions from fossil fuel operations would satisfy most of the 30% reduction in global methane emissions by 2030 targeted by the Global Methane Pledge.

The first step to effective mitigation is to accurately measure the size of the problem. In recent years, advances in satellite imagery and remote sensors have enabled the identification and quantification of large methane-emitting sources globally. The use of these advanced methods has revealed that methane emissions are significantly higher than what has been historically reported based on estimation techniques.

The problem with current methane estimates

Methane emissions can be measured using new technologies to gather emissions data in real time. These can be classified as bottom-up (e.g., emissions measured at a facility) or top-down (e.g., facility emissions observed using satellite imagery).

By contrast, methane emissions can be estimated by using a set of assumptions about the equipment used – known as a ‘component by component’ approach. This methodology uses a bottom-up analysis to generate the rate at which an individual activity or component leaks methane into the atmosphere, known as the ‘emission factor’.

Once an emission factor has been established for each component within a project or piece of infrastructure, it is multiplied based on the level of activity at that project (e.g. the amount of oil and gas being extracted) to estimate the emissions produced in a given time period. These are then combined for all activities and components in a project to produce an estimate of its total methane emissions.

Research studies have identified that emissions measured using bottom-up and top-down approaches are consistently higher than those obtained through national reporting frameworks that rely on component-by-component estimations:1See Alvarez et al 2018, Riddick & Mauzerall 2022, Zavala-Araiza et al. 2015, Riddick et al. 2019, Chen et al. 2023, MacKay et al. 2021

The significant discrepancy between reported emissions and those produced by independent estimates calls into question the accuracy of the emission factors used.

A notable constraint of estimating emissions through component-based emission factors is that they neglect to consider the distinctive characteristics of individual assets and their actual operations over time. Sampling measurements used to establish emission factors typically fail to capture abnormal high-emitting events.

These rare events, commonly known as super-emitters, have been estimated to contribute as much as half of total emissions from natural gas production sites. Although the exact source of emission discrepancy may vary from one asset to another, super-emitter events serve as a prime example of why real-time measurements are indispensable for understanding the performance of an asset.

How big is the difference?

The Global Carbon Project, a non-governmental global research project working to quantify greenhouse gas emissions, and the IEA estimate oil and gas methane emissions at 80  and 77 million tonnes per year, respectively, using a mix of ground-based measurements and satellite data.

These figures are more than double the United Nations Framework Convention on Climate Change’s (UNFCCC) estimate of 38 million tonnes, which relied on country-level self-reported data. This discrepancy highlights a gap between the reporting frameworks used by national governments to estimate their emissions from the oil and gas sector and their real world emissions.

Fig. 1: Estimated methane emissions from the oil and gas industry

Oil and gas companies also frequently rely on methodologies consistent with those used by governments to submit estimates to the UNFCCC.2For example, the US EPA GHG Reporting methodologies are used to develop the GHG emissions national inventory https://www.epa.gov/ghgreporting/ghgrp-and-us-inventory-greenhouse-gas-emissions-and-sinks. For details of the EPA GHG use of emissions factors see https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-98/subpart-W However, recent analysis by the IEA has shown that companies’ reported emissions may be dramatically under-estimating total emissions. More than 80 companies reported 1.3 million tonnes of methane emissions to the Oil and Gas Methane Partnership 2.0 (OGMP 2.0), the United Nations Environment Programme’s oil and gas reporting and mitigation programme. If this rate of leakage was scaled to all oil and gas production, the IEA calculated that this would equate to just 5 million tonnes, 94% less than the Global Carbon Project and IEA estimates. 

The IEA suggests that the companies reporting to OGMP 2.0 may be the best-performing companies on methane emissions, and therefore might not be representative of the whole industry. However, it also highlights that as these company figures rely on emission factors they may be missing super-emitter events, which account for a large proportion of the industry’s emissions.

Identifying the source of emissions estimates 

While not all major oil and gas companies disclose their emission-estimation methodology, national reporting frameworks such as the US EPA, EU Emissions Trading System Monitoring and Reporting Regulation, or the American Petroleum Institute Compendium of Greenhouse Gas Emissions Estimation Methodologies (referred to as the API Compendium) are frequently cited as a basis of estimations by sector players.

The API Compendium describes itself as a “foundational document to estimating GHG emissions from the oil and natural gas industry”. The most recent edition of the API’s guidance, released in 2021, was developed by a working group consisting solely of representatives of 19 oil and gas companies, including Exxon, Chevron, Shell and BP. 

The API Compendium employs component-by-component estimates to calculate emissions, and is used by governments and state bodies, including by the US EPA, Australia and Canada, to produce national guidance on emissions estimates. These, in turn, are used by oil and gas companies to produce their reported emissions. A reliance on emission factors produced by the API may be resulting in a significant underestimation of the scale of the industry’s methane emissions.

Fig. 2: Current methane emissions monitoring structures and players
Source: Zero Carbon Analytics

Why it matters

Accurately measuring emissions is crucial to ensure that ambitions to reduce methane in the atmosphere are aligned with actual levels.

The industry has promoted its own success through initiatives such as the Oil and Gas Climate Initiative (OGCI) whose 12 member companies claim to have reduced methane emissions by 50% since 2017 as of mid 2024. 

While the OGCI is expanding its use of satellites to gather emissions data, the organisation’s guidance to members for estimating GHG emissions allows for three methodologies: those based on measurements, calculations using emissions factors (including from API) and estimates. The body advises that, “Whenever economically and technically possible, the most accurate available category of quantification should be preferred”. 

While the OGCI members may continue to rely on calculations and estimates, it is not possible to confirm whether those companies have achieved the methane emission reductions they have claimed.

Industry’s early steps

With companies still in the early stages of deploying technologies like site-based measurements, satellites and aerial surveys to detect methane emissions, it is critical that the real-time measurements obtained from these technologies be incorporated into emission estimates.

The industry is moving in this direction with initiatives like the OGMP 2.0, which requires companies to transition towards site-based measurements for both operated and non-operated assets. This will be a slow process, with companies given between three and five years to move to site-based measurements for operated and non-operated assets, respectively, after signing up to the initiative.

What’s needed next

As technology advances and climate change worsens, regulators and the scientific community will need better estimates of methane emissions to verify company and country reported emissions.

In light of the discrepancies between estimated and measured emissions, governmental regulators should re-examine the methodologies used by oil and gas companies to report their emissions. Where these rely on the API or other industry-led models and emissions factors, results should be reviewed by independent third parties to ensure their accuracy.

There are significant risks in public regulators relying on the industry to set the standards for measuring its impact on the climate. Ultimately regulators will need to shift to requiring oil and gas companies to report measured, rather than estimated emissions, to ensure they have accurate data to assess climate action within the sector.

Legislators and regulators in the US have already begun to identify and address the gaps in the current emission factor based framework, with the Inflation Reduction Act giving the EPA authority to fine oil and gas producers for methane emissions above a certain threshold. To do this, the EPA has adjusted its rules to calculate methane emissions within its reporting framework. While this represents a step forward, regulators will ultimately need companies to provide solely measured emissions data to ensure accuracy.

For companies, improving knowledge of methane emissions from their assets is necessary to deliver emission reduction targets and effective management of their infrastructure. This requires a concerted effort to obtain quality data for non-operated assets and accelerate the transition to measurement-based initiatives.

The use of real-time measurements is critical in bridging the reporting gap and providing a better understanding of methane emissions from oil and gas infrastructure. Investors and regulators will need to treat industry-reported data on methane emissions and emissions reductions with caution when considering risk to climate targets.

COP28: Assessment of the Oil and Gas Decarbonization Charter

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Key Points:

  • 50 oil and gas companies signed up to the Oil and Gas Decarbonization Charter at COP28 in Dubai, including 29 nationally owned companies.
  • Under the initiative, the oil and gas companies pledged to reduce their greenhouse gas emissions. The deal is voluntary and broadly repeats previous pledges made in 2021.
  • The agreement sets targets for reducing carbon dioxide and methane emissions, but does not affect oil and gas production or emissions from consumption.
  • Notable new net zero operational emissions targets include: Bapco, KazMunaiGas, Pertamina, National Oil Company of Libya, Socar, Sonangol & YPF.
  • Major investor-owned oil companies notably absent from the Charter include Chevron, ConocoPhillips and Suncor.
  • Major nationally owned oil companies notably absent from the Charter include Kuwait Petroleum Corporation, QatarEnergy, Iraq’s State Oil Marketing Company, China’s Sinopec, CNOOC and PetroChina and the National Iranian Oil Company.

Voluntary pledges repeated

At COP28, the United Arab Emirates government and company executives launched the Oil and Gas Decarbonization Charter (OGDC), which aims to reduce the greenhouse gas pollution of 50 major oil and gas companies. Twelve of these companies are also members of the Oil and Gas Climate Initiative (OGCI) launched nearly a decade ago. The new alliance is similar in approach to the OGCI (see Table 1). Companies set their own emissions reductions plans and meeting targets is voluntary. There is no penalty for not meeting self-imposed goals, for example on the continuation of gas flaring.1Gas flaring is the process of burning the natural gas which comes out of the ground during oil drilling.

Production and Scope 3 emissions

The Decarbonization Charter, as well as previous voluntary initiatives, are not aligned with the Paris Agreement goal of limiting warming to 1.5°C. Under the agreements, companies have not set targets to reduce Scope 3 emissions, which make up 80-95% of emissions from the oil and gas industry.2Scope 1 emissions are direct emissions from sources owned or controlled by a company, Scope 2 are indirect emissions from the energy it uses, and Scope 3 includes emissions the company is indirectly responsible for in its value chain, including from the use of the products it sells. Pledges on reducing carbon intensity and methane flaring could be achieved while these firms continue levels of oil and gas production that are incompatible with climate goals. In its updated net zero scenario released in September 2023, the International Energy Agency (IEA) said “no new long-lead time upstream oil and gas fields are needed” to achieve net zero by 2050.

Table. 1: Comparison of old and new voluntary commitments to decarbonise
Source: OGDC press release, OGCI strategy, 2021.

How the charter falls short

The OGDC made several pledges related to reducing emissions and investing in energy systems. However, these fall short of what is needed to reach the Paris Agreement goals of limiting global warming to well below 2°C and pursuing efforts to limit global temperature increase to 1.5°C.

Pledge 1: Reducing emissions

Charter signatories claim to support the Paris Agreement goals and the goal of reaching net zero by 2050.

  • These goals set no short term targets, despite the IEA showing that Scope 1 and 2 emissions from oil and gas need to be reduced by 60% by 2030 to remain on track for global net zero emissions by 2050.
  • The companies do not commit to cutting back oil and gas activities under the agreement. A report from United Nations experts recommends that oil and gas companies end production, expansion of reserves and exploration for new fields in order to reach net zero emissions. It concluded that “non-state actors cannot claim to be net-zero while continuing to build or invest in new fossil fuel supply”.
  • For their goals to be meaningful, and not just pay lip service to the Paris Agreement, charter signatories must also align their lobbying efforts and leave associations that are opposed to Paris-aligned climate policies.
Pledge 2: Investment in energy systems

OGDC members pledged to invest in the energy system of the future.

  • Without any quantifiable targets, this promise is too vague to be meaningful and needs to be accompanied by a phase-out date for oil and gas production.
  • A new IEA report finds that the industry allocated just 2.5% of its capital expenditure to clean energy 2022 and that this will need to rise to 50% by 2030 in order to align with the Paris Agreement.
Pledge 3: Methane and flaring

Members pledged to achieve near zero methane emissions by 2030.

  • Intensity targets do not guarantee overall reductions in emissions if production volumes are increasing. Instead, targets should be set for absolute methane emissions reductions, in line with the 75% reduction by 2030 called for in the IEA Net Zero scenario.3The IEA’s net zero scenario provides a pathway for the global energy sector to achieve net zero carbon dioxide emissions by 2050.
  • Previous initiatives, such as the Zero Routine Flaring Initiative launched by the World Bank in 2015, failed to reduce flaring. While flaring intensity has improved as a result of decoupling from oil production, total volumes of gas flaring have not materially declined since 2010. The industry’s own efforts have also not led to sufficient reduction in flaring.

Agency of oil and gas industry

Ahead of COP28, several governments called for a phase out of fossil fuels, and this is a crucial issue at the summit taking place in Dubai. Companies often seek to get ahead of the regulatory curve. By proactively announcing the speed at which it will decarbonise, the oil and gas industry seeks to reinforce its own agency to tackle climate change. For an industry with billions in sunk investments in oil and gas wells, pipelines and refineries, this is preferable to rules imposed by governments, which it will have less control over.

  • The High Ambition Coalition – including ministers from the Marshall Islands, Tuvalu, Austria, Kenya, Spain, the Netherlands and Ethiopia – recently called for a plan, to be reflected in a negotiated decision at COP28, to accelerate renewable energy and “phase-out fossil fuel production and use”.
  • A number of countries, including Denmark and France, have made commitments to end oil and gas production as members of the Beyond Oil and Gas Initiative.
Table. 2: OGDC goals compared to signatory company pledges
Company commitments listed for the most significant OGDC signatory companies.
Source: GDCA press release, company websites: BP, Shell, Eni, ExxonMobil, Aramco, ADNOC, Bahrain Petroleum Company (Bapco), Petrobras, Petronas, Pertamina, Occidental, Ecopetrol, Equinor, Repsol, SOCAR, TotalEnergies, NNPC, PTTEP, Woodside. Accessed December 2023.
Table. 3: Selected companies with significant new net zero operational emissions targets
Full list of signatories to the Oil and Gas Decarbonization Charter from COP28 press release

Nationally-owned oil companies: ADNOC, Bapco Energies, Ecopetrol, EGAS, Equinor, GOGC, INPEX Corporation, KazMunaiGas, Mari Petroleum, Namcor, National Oil Company of Libya, Nilepet, NNPC, OGDC, OMV, ONGC, Pakistan Petroleum Limited (PPL), Pertamina, Petoro, Petrobras, Petroleum Development Oman, Petronas, PTTEP, Saudi Aramco, SNOC, SOCAR, Sonangol, Uzbekneftegaz, ZhenHua Oil, YPF.

International (privately-owned) oil companies: Azule Energy, BP, Cepsa, COSMO Energy, Crescent Petroleum, Dolphin Energy Limited, Energean Oil & Gas, Eni, EQT Corporation, Exxonmobil, ITOCHU, LUKOIL, Mitsui & Co, Oando, Occidental Petroleum, Puma Energy (Trafigura), Repsol, Shell, TotalEnergies, Woodside Energy Group.
  • 1
    Gas flaring is the process of burning the natural gas which comes out of the ground during oil drilling.
  • 2
    Scope 1 emissions are direct emissions from sources owned or controlled by a company, Scope 2 are indirect emissions from the energy it uses, and Scope 3 includes emissions the company is indirectly responsible for in its value chain, including from the use of the products it sells.
  • 3
    The IEA’s net zero scenario provides a pathway for the global energy sector to achieve net zero carbon dioxide emissions by 2050.

Analysis of US methane & fossil fuel announcements at COP27

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Key points:

  • The proposed 87% reduction in methane emissions from oil and gas by 2030 in the US Methane Reduction Action Plan is more ambitious than the IEA and the average of IPCC scenarios to limit warming to 1.5oC
  • However, US methane emissions from the oil and gas sector are more than double those in the US government’s own official figures, and are still rising, according to Climate TRACE.
  • The Joint Declaration from Energy Importers and Exporters on Reducing Greenhouse Gas Emissions from Fossil Fuels aims “to minimise flaring, methane, and CO2 emissions across the fossil energy value chain to the fullest extent practicable.”
  • Limiting warming to 1.5oC requires a rapid reduction in fossil fuel use as well as in methane and supply chain emissions. 
  • However, the US accounts for 41% of the world’s LNG capacity that is currently under development (either proposed or in construction). US gas production is forecast to increase by 9% between 2021-2030, but to align with the IEA Net Zero Emissions scenario, gas production would need to reduce by 25% over this period.

Importance of methane reduction

Ambitious domestic oil and gas methane reduction

US oil and gas methane emissions more than double official figures

  • Officially-reported methane emissions in the US are significantly underestimated
  • According to the latest official US data, total reported methane emissions from the oil and gas sector in 2020 were 212 million tonnes of CO2 equivalent. 11https://cfpub.epa.gov/ghgdata/inventoryexplorer/#energy/naturalgasandpetroleumsystems/allgas/gas/all
  • Our analysis of data released this week from Climate TRACE – which is sourced independently and primarily based on direct observations of activity – suggests oil and gas production actually emitted 17.4 million tonnes of methane, or 519 million tonnes of CO2 equivalent, more than double the official figure. 12https://climatetrace.org/downloads conversion from CH4 to CO2e using GWP100 of 29.8, from IPCC AR6 WG1 Table 7.15
  • Similarly, US EPA data show US methane emissions from oil and gas fell by 2% between 2015-2020, whereas Climate TRACE data suggest they actually rose by 34% over the same period. 13https://cfpub.epa.gov/ghgdata/inventoryexplorer/#energy/naturalgasandpetroleumsystems/allgas/gas/all
  • If the 87% reduction is achieved on actual emissions, as measured by Climate TRACE, this would have a significant impact. However, if measurement and reporting remain weak and inaccurate, claimed reductions may have little relationship with real-world methane emissions.

US expansion of gas production and LNG exports threatens global climate targets

Biogas and its role in the energy transition

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Key points

  • Reliance on biogas and biomethane as a decarbonisation solution should be limited to hard-to-abate sectors where there are currently no feasible, economic alternatives for emissions reduction (such as petrochemical production or industrial heating)
  • Use of biogas in electricity generation, heating and transportation should be limited given there are already cost effective options for electrification of end-use using renewable energy
  • Biogas’ potential to reduce agricultural emissions is limited to sources of emissions arising from manure and crop residuals, which contribute to a minority of agricultural emissions overall. The source and sustainability of feedstock is critical to the overall lifecycle emissions and costs
  • Biogas deployment should be carefully weighed against known limitations and risks, which include the impact of fugitive emissions, potentially limited availability of sustainable feedstock, high cost and reliance on public investment, and safety concerns.

What are biogas and biomethane?

Biogas is produced from the controlled decomposition of organic matter (through processes like anaerobic decomposition), where the gases that form as a result are captured. These gases are usually a mixture of methane (waste and agriculture account for roughly 60% of global methane emissions) and CO2, which are both potent greenhouse gases. Additional processes can be applied to remove the CO2 from biogas, leaving only methane, which is known as biomethane. For the purpose of this briefing, the term biogas is used to encompass both biogas and biomethane. 

Biogas can be a substitute for current uses of fossil fuel-based natural gas, ranging from electricity generation to heating – the IEA estimates that biogas has the potential to replace 20% of current demand for natural gas. Some argue that by capturing methane from waste and agricultural products and using it as a substitute for natural gas, biogas is a necessary renewable solution for limiting global warming to 1.5oC. This briefing examines the potential and limitations of using biogas for reducing global emissions.

Mitigation potential of biogas

Agricultural byproducts are the main source of biogas feedstock today. However, biogas feedstock is not the only valuable use of agricultural byproducts. For example, animal waste can be used as fertiliser.

Biogas can reduce emissions in two ways:

  • Mitigate methane and other greenhouse gas emissions in the agriculture sector, where livestock emissions represent roughly 32% of global methane emissions
  • Substitute the use of natural gas by producing methane from waste materials.

Using biogas for electricity generation and heating still requires methane to be combusted, which produces CO2, the greenhouse gas driving climate change more than any other. 

Therefore, the emissions benefit of biogas depend on:

  • The sustainability of its production method as a feedstock
  • The emission reduction potential compared to other low or zero-emission alternatives 
  • Feasibility and potential for uptake given the cost and availability of feedstock 
  • The net lifecycle emissions from the production of feedstock, including any potential leakages
  • Whether a high rate of carbon capture and storage is deployed if the biogas is combusted.

It is also worth noting that common technologies for producing biogas from manure management (such as anaerobic digestion) tend to be inefficient and often produce large amounts of CO2, which require processing to upgrade into biogas.

Biogas’ potential to mitigate agricultural emissions

Biogas’ potential to reduce agricultural emissions is limited to sources of emissions arising from manure and crop residuals, which contribute to a minority of agricultural emissions out of the five main sources: 

  • Enteric fermentation: 44.3% of agricultural emissions
  • Manure left on pasture and management: 23% of agricultural emissions
  • Crop residuals: 5.9% of agricultural emissions
  • Feed: 13.5% of agricultural emissions
  • Other emissions (land use change, energy use): 13.3% of agricultural emissions.

Therefore, capturing emissions from manure and crop residuals to produce biogas will, at best, address 28.9% of global agricultural emissions, leaving the majority of emissions unabated. And this is likely to be an overestimate given that more than 80% of the world’s farms are held by smallholders in developing countries with less than two hectares of land that meet the technical and financial requirements needed to install an anaerobic digester. Comparatively, US livestock farms need to meet the following criteria to be potential candidates for anaerobic digestion:

  • Minimum of 500 head of cattle, 2,000 hogs with anaerobic lagoons or liquid slurry manure management systems, or 5,000 hogs with deep-pit manure management systems
  • Minimum of 90% of manure is regularly collected.

Beyond using manure and crop residuals as sources of feedstock, biogas production requires farming energy crops, and this has been criticised by the IPCC for causing biodiversity loss, undermining food security and excessive water use, as well as creating the potential for temperature overshoot.

The REPower EU plan

In the RePower EU plan, the European Commission announced a target of 35 billion cubic metres (bcm) of production volume in Europe by 2030. This is a twelvefold increase of the current 3 bcm biogas (specifically biomethane) produced in the EU each year. 

An assessment by the Institute for Energy and Environmental Research (IFEU) for the European Climate Foundation of how much sustainable biogas could be produced in Europe found only 17 bcm could be produced by 2030. 

It found that, in order to achieve the 35 bcm biomethane target, the residues available for biogas production would not be sufficient and a considerable amount of crop-based biomass would have to be used. This would have considerable disadvantages. In a realistic scenario, around five to six million hectares of arable land would be required. This equals 5% of the arable land and 20% of the land used for wheat cultivation in the EU27. It would be more than the area that is used in the Ukraine for rapeseed production. Occupying land for biomethane production would thus lower the land availability for food production significantly.

Biogas as a substitute for fossil fuel-based natural gas

Most biogas produced today (64%) is used for electricity generation, predominantly in Europe and North America. Around 27% is used for heating in buildings. Acting as a substitute for fossil fuel natural gas can help avoid the current emissions impact of natural gas extraction, and its associated environmental impact. However, this substitution effect assumes that natural gas will continue to be used in electricity generation and heating. But viable alternatives such as renewable energy and widespread electrification already exist today. A study that evaluated the lifecycle environmental impacts of biogas electricity in comparison to other renewable alternatives looked at 11 environmental indicators (including emissions, human toxicity and ozone layer depletion) found that “biogas electricity can help reduce greenhouse gas (GHG) emissions relative to a fossil-intensive electricity mix; however, some other impacts increase. If mitigation of climate change is the main aim, other renewables have a greater potential to reduce GHG emissions.” 

In fact renewable energy is now the cheapest source of energy in most countries. Given the continued cost reductions in wind and solar and high implementation cost of biogas production, it is unlikely that biogas electricity generation will be competitive against renewable energy on a levelised cost of electricity (LCOE) basis.

There may be a limited role for biogas as a substitute for fossil fuel-based natural gas for hard-to-abate sectors such as petrochemical production and industrial heat, where there are fewer options for electrification using renewable energy. However, achieving the volume and cost reductions needed to supply biogas for these purposes is by no means a given.

Risks and limitations for deployment of biogas

Fugitive emissions reduce the benefits of biogas

The IPCC has found that fugitive emissions generated by biogas plants can reduce the potential benefit of biogas production from an emissions perspective. A 2022 study found that supply chains for biomethane and biogas release more than twice the amount of methane previously estimated by the International Energy Agency, with 62% of leaks originating from a small number of facilities. 

Another study examined 10 biogas plants in the UK and found that the rate of fugitive emissions reached a maximum of 9%, suggesting biogas plant methane emissions may account for up to 3.8% of total UK methane emissions. The research reached the conclusion that “the sustainability of biogas plants and the UK Net Zero Commitment may be jeopardised unless robust, consistent emission measurements and legal requirements are put into practice in the near future.”

High cost and reliance on subsidies

Biogas production and consumption require significant investment for:

  • the construction of biodigestion facility 
  • feedstock collection
  • processing
  • transport and conversion
  • application of carbon capture and storage.

The cost of each component is highly dependent on the location of feedstock and its ultimate end use. This means biogas production tends to be more economically feasible in countries where the location of the feedstock is close to the source of final conversion and use, and where there is already transportation infrastructure in place. As a result, biogas production barely exists in countries like Australia, and remains challenging to implement in other regions (such as Latin America, Africa or Southeast Asia). 

In Europe and the US, the high capital cost of installing biodigesters (around 70%-95% of total biogas costs) means significant subsidies are required to make projects financially feasible. A detailed geospatial analysis recently revealed that 40% of the amount that is technically available would still be uneconomic by 2050 without subsidies. In Germany, small plants have been found uneconomic, needing combinations of 50% of investment subsidised and EUR 11.50/MWh (USD 11.30/MWh) feed-in tariffs to make the projects economic. 

The application of carbon capture and storage to limit the emissions of carbon dioxide when biogas is burnt at its end use would also increase costs significantly. Given alternatives that exist to reduce waste and agricultural emissions, and limited situations where biogas can be a credible substitute for hard-to-abate sectors, the public investment in biogas should be balanced against other investment opportunities in decarbonisation.

Safety concerns

Many biogas facilities operate at small and medium scales, and they are not subject to the same safety standards as large-scale operations. Major hazards from biogas facilities include:

  • Explosions and fires
    • When inappropriately mixed, air and methane is explosive
    • Ammonia has explosive and flammable properties
    • Hydrogen sulfide is extremely flammable
  • Toxicity
    • Hydrogen sulfide is highly toxic. 

A study suggests that between 1994-2015, 169 accidents occurred in the biogas sector, 12% of which could be classified as serious. One hundred and sixty-three of these occurred in Europe, mostly in Germany, which has the highest number of biogas plants. Of these, 53% resulted in fire, 40% resulted in explosion and 7% were related to toxic release.

Alternatives for reducing agricultural emissions

There are cost-effective alternatives for reducing emissions in agriculture and waste management that are ready for deployment. For example, transitioning to sustainable agriculture methods as well as a shift to a more sustainable food system are cost effective ways to reduce existing emissions in the agriculture industry. The IPCC found that economic mitigation options (less than USD 100 per tonne of CO2 reduced) such as improving soil management, agroforestry and livestock management have the mitigation potential of 4.1 GtCO2e each year. Shifting to sustainable healthy diets, reducing food waste and other demand side measures have the mitigation potential of 2.2 GtCO2e each year.

The effectiveness of animal feed supplements in cutting methane emissions

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Key points:

  • Various natural and synthetic supplements for reducing methane emissions from cattle, sheep and goats are being developed, each with its own set of positive and negative characteristics    
  • Most supplements have only been tested in feedlots. Effectively administering them to animals on pasture, where cattle, sheep and goats spend most of their time and where most methane is produced, could prove challenging
  • The methane offset potential varies considerably among studies of the same supplement, highlighting the fact that impacts are difficult to predict     
  • The lifecycle emissions of many supplements are poorly understood, and so a full understanding of their mitigation potential is lacking
  • Scaling-up the production of some of these supplements in the near-term comes with its own set of challenges.

Methane from ruminant (animals with four-chambered stomachs, including cows, sheep and goats) burps is the  single largest human-caused methane source across all sectors, contributing 25%–30% of global methane emissions. Due to urbanisation, a growing human population and an expanding middle class, global demand for milk and meat is expected to increase by 58% and 74% respectively by 2050 compared to 2010. To combat this rise, several measures for curbing methane from burps are being developed.

One of these measures involves feeding ruminants supplements that inhibit methane production in the stomach. Cows eat carbon contained in plants, and this carbon is converted into methane in the stomach by microbes before being burped out. These supplements work either by physically disrupting methane production, or by shifting the composition of the microbial community away from methane-producing microbes.

Though some supplements have shown promise for reducing methane emissions and are already being sold as voluntary carbon credits, questions remain about the scientific credibility, practicality, scalability, safety and efficacy of these products.

Natural supplements

Red seaweed (Asparagopsis) has received a lot of media focus in recent years on the back of trials reporting methane emission reductions of up to 98% (when as little as 0.2% of the diet is supplemented with dried seaweed powder). It is estimated that if just 20% of the beef and dairy market in developed countries incorporated the supplement into feed, up to 15% of global methane emissions from burps could be avoided.

The main active ingredient in the seaweed is a compound called bromoform, which is a methane-production inhibitor and probable human carcinogen – although concerning levels of bromoform have not been detected in the tissue or milk of cows fed red seaweed. These seaweeds are also rich in iodine, excessive amounts of which can cause thyroid dysfunction in humans. Concerns have also been raised about the ozone-depleting properties of bromoform. Levels of the inhibitor vary naturally due to the environment and genetics, which could translate into variation in the efficacy of the product.

Probably the biggest barrier to rolling-out this seaweed supplement in the near term is producing enough of it. Harvesting wild populations alone would be unsustainable, so aquaculture techniques would need to be developed, along with land for growing and drying facilities. Ideally, these facilities would be located near farms to avoid transport and other processing emissions, although growing seaweed does have potential environmental benefits, such as CO2 sequestration, water quality improvement and ocean acidification reduction. The development of these aquaculture facilities could support regional economies by using local labour for seaweed growing and processing. 

More modest methane reductions of up to 30% have been achieved using garlic and citrus extract supplements, marketed under the name Mootral. However, this is only based on a few animal trials. In one trial, statistically significant results were only seen after 12 weeks, although the authors attribute this to the refusal of the animals to eat the feed at the start of the experiment. However, no safety concerns have been raised with the use of this product.  

The methane offsets from Mootral are being sold as voluntary carbon credits, called CowCredits, which are issued by Verra. With no lifecycle assessment available, and only a small handful of animal trials published in peer-reviewed scientific journals, it is difficult to properly evaluate the offset potential or efficacy of this product.

Methane reductions of up to 30% have also been found when adding nitrate-rich foods into the feed, as this modifies the microbial community. Nitrate has obtained better results in dairy cows than in beef cows, with a lifecycle assessment of the potential net greenhouse gas reductions in the US dairy industry estimating a 5% reduction in CO2 equivalents. However, a major barrier to nitrate supplements is toxicity from nitrite – a by-product of nitrate metabolism in the stomach.

Synthetic supplements

One supplement that has received regulatory approval in Brazil, Chile and, soon, the EU, and for which there is substantial scientific evidence from animal trials, is 3-nitrooxypropanol, or 3-NOP. It is marketed under Bovaer (a combination of ‘bovine’ and ‘air’). The methane reduction potential averages 30% and lifecycle assessments report 11.7%–14% decreases in whole-farm dairy net greenhouse gas emission intensity when 3-NOP is used. 3-NOP also shows more promising results in dairy cattle than in beef cattle, with the same dose reducing methane emissions more in dairy cows than in beef cows. 

The safety risks of 3-NOP to animals and humans are low. However, the compound degrades rapidly in the animal stomach so it needs to be supplied constantly, for example by incorporating it into feed, in order to work. This may be impractical for animals raised outside the feedlot (a yard or building where animals are fed in intensive production systems).

Typical lifecycle of beef cows in pastures and feedlots in the US

To understand how applicable these supplements may be in highly-developed, intensive beef-production systems, we can use the US as an example. The US is the largest beef-producing nation in the world (12.3 million tonnes in 2019), and the production system has a high proportion of cattle finished in feedlots – though Australia and South America are catching up. 
In the beef production system in the US, a permanent herd of cattle is kept in order to produce calves (called the calf-cow operation). These cattle typically graze on inexpensive pastures such as grass. Of the calves born to this herd, about 60% will be raised on pasture for anywhere between 10 and 23 months (called the stocker operation) after which they will be finished in the feedlot (called the feedlot operation) for a further 100 to 300 days. The other 40% of calves go directly into feedlots for 240 to 280 days before going to slaughter. It is estimated that the permanent herd is responsible for up to 82% of the methane produced in the beef production system.

Methane production across the different operations of the beef production system

The feedlot issue

One obstacle shared by all the above supplements is that they have only been tested in feedlots. While they could, in theory, be given to cows raised on pasture, the practicality of doing so is likely to prove challenging, as feed is not as carefully controlled in pasture systems as it is in feedlots. Moreover, although some may consider cows raised on pasture to be more sustainable because they are eating fibrous plants that humans and other livestock otherwise cannot eat, pasture-raised cows actually burp more methane than cows that are fattened on more easily-digestible and nutrient-dense grains in feedlots. As most of the world’s cows spend the majority of their life on pasture and generally burp more methane than feedlot cows, an effective feed supplement must be effectively applicable to pasture-raised cattle. 

Reducing emissions in pasture-raised animals

For pasture-raised animals, switching to more easily digestible legume forages could help reduce methane emissions. Tannin-rich forages or additives are another natural supplement option that can also be readily used in pasture systems. However, they have more modest reduction potential compared with some of the supplements mentioned above, with results varying greatly depending on the type of tannin. Tannins may negatively impact nutrient and protein digestibility and stomach health, affecting the animal’s ability to convert feed into milk and meat. It has been suggested that 3-NOP (Bovaer) could be supplied in lick-blocks or slow-release stomach devices for cattle on pasture, but the practicality of this has not been assessed. The effectiveness of 3-NOP was also found to decrease when higher amounts of fibre are eaten, implying that even if it were made available to cows on pasture, it may not be effective when low-quality forage is being eaten.     

Environmental considerations 

Though grain-fed feedlot cows produce less methane than grass-fed pasture cows, supplying these grains also comes with its own environmental impact. Feedlots are also significant sources of hydrogen sulphide (a toxic air pollutant) and major polluters of waterways with ammonia, pathogens and antibiotics. Concerns around increased antibiotic resistance are also growing. However, pasture systems come with their own set of concerns. For instance, if cattle production in the US were to shift from feedlot-based to pasture-based, herd size would need to increase by 30% to maintain present-day numbers because cows would take longer to fatten up and there would be less meat per cow. This shift would also result in greater methane emissions and other environmental costs, such as soil erosion, loss of native vegetation and water eutrophication (when water becomes overly enriched with nutrients, depleting oxygen levels). 

Below is a table summarising the attributes of the supplements discussed, including the science (the number of studies and quality of the studies), scalability (how easily could this technology be scaled up for use in the near future), deployability (how readily could the technology be deployed), safety (potential safety concerns to humans, livestock and the environment), reduction potential (the extent to which methane could be reduced) and pasture use (the potential for the supplement to be used in pasture-based systems).    

Summary of the supplements

In summary, many of these supplements are only in pilot phases or need more rigorous scientific research, especially animal trials, to fully understand their potential. There are major discrepancies in the methane reduction potentials reported among studies testing the same supplement, suggesting complex interactions of multiple variables, with impacts that are difficult to predict. Perhaps the biggest limitation of most of these supplements is that they have only been tested in feedlots. Controlling and monitoring the consumption of these supplements by cows in pasture systems, which produce the majority of global methane emissions from cattle, could prove particularly challenging, especially considering the palatability of many of them is low.

IPCC Sixth Assessment Report: Mitigation of climate change

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The Intergovernmental Panel on Climate Change (IPCC) has released the third of its four-part, Sixth Assessment Report (AR6) in April 2022. The Working Group III (AR6 WGIII) report is the most comprehensive review of how we can mitigate climate change since the 5th assessment (AR5) in 2014, and the IPCC’s three recent special reports (SR1.5 in 2018 and the 2019 SRCCL and SROCC). 1WGIII will be third of  four separate reports published in the AR6 cycle. ‘The Physical Science Basis’ which detailed the current state of the climate was published on 9 August 2021 and the second report ‘impacts, adaptation and vulnerability’ was released in March 2022.

The report has been ratified after a plenary negotiation in which governments formally approved the summary for policymakers, ensuring high credibility in both science and policy communities. The report covers a broad spectrum of topics, from mitigation pathways and in-depth sectoral analysis to finance, international cooperation, net-zero and carbon dioxide removal. For the first time in IPCC history, chapters dedicated to technology, innovation and demand-side measures are included.

This briefing covers some of the major developments in our knowledge of mitigation since the IPCC’s AR5 was published in 2014. Today, mitigation literature largely reflects the 2015 Paris Agreement, increasing net-zero commitments and the growing need for action from non-governmental stakeholders including businesses, industry and financial institutions.

1. Since AR5 greenhouse gas emissions have continued to climb

We are nowhere near on track to achieve the Paris targets of keeping warming below 2°C, and ideally 1.5°C. Current national climate plans (NDCs) will see us warm by about 2.7°C this century, or possibly even higher 2These numbers are based on pre-Glasgow estimates. If you add all pre-Glasgow net-zero pledges to the NDCs this brings the world on track for 2.2°C, according to UNEP (or about 2.1°C in IEA assessments), page 12, section 7 of the 2021 Emissions Gap Executive Summary..  If CO2 emissions continue at current rates, we will exhaust the remaining 1.5°C carbon budget in the early 2030s 3Most recent estimates show that only 440 Gt CO2 is left from 2020 to stand even a 50% chance of 1.5°C. Global emissions were over 40 Gt CO2 in 2019, and if annual emissions are similar in the next decade it will be used up in the 2030s.. The energy infrastructure from planned and current fossil fuels alone commits us to about 846 GtCO2 (more than double what’s left in our 1.5°C carbon budget) and every year we add more carbon-intensive infrastructure than we decommission. 

Of the greenhouse gases (GHGs), CO2 causes most warming due to its high concentration and long lifetime in the atmosphere. Despite efforts to reduce emissions, our burning of fossil fuels adds more CO2 to the atmosphere, pushing the cumulative atmospheric concentration to unsustainable highs. Between 1850-2019, coal, oil and gas accounted for ~66% of cumulative CO2 emissions, with land-use change responsible for about 32%. 

But since AR5, there has been greater recognition of increasing emissions of methane (CH4) and nitrous oxide (N2O). Both are potent GHGs that trap about 34 and 300 times more heat than CO2 respectively (over a 100 year period). Methane is responsible for almost a quarter of human-caused warming to date, and concentrations are increasing faster now than at any time since the 1980s. Today, methane emissions are two-and-a-half times above pre-industrial levels. The AR6 WGI SPM authors emphasised that “strong, rapid and sustained reductions” in methane emissions would have the dual impact of limiting “the warming effect resulting from declining aerosol pollution” and improving air quality.

Between 2008-2017, agriculture and waste contributed most to the rise, followed by the fossil fuel industry. However, estimating by exactly how much, and from where, methane emissions are increasing is a topic of continued research and debate. For example, some researchers have found that the role of North American shale gas (so called “fracking”) has been significantly underestimated in calculating the global methane emissions. 

Emissions of N2O have risen 20% from pre-industrial levels, with the fastest growth observed in the last 50 years, mainly due to nitrogen additions to croplands through fertilisers. 

In 2018, global GHG emissions were about 57% higher than in 1990 and about 43% higher than in 2000. Emissions continued to rise in 2019, when they reached about 59 GtCO2e. But in 2020, the COVID-19 pandemic led to a historical large drop in CO2 emissions from fossil fuels and industry. During the height of global lockdowns, daily emissions dropped by 17% compared to 2019, levels not seen since 2006, and people around the world were allowed a short respite from deadly air pollution. Since then, emissions have rebounded, and were the highest yet last year. However, research has shown that rebuilding the economy in a more green, sustainable, just and climate-centred way represents a far greater opportunity than the short, lockdown-triggered emissions break, which will have little impact in the long run.

2. Without a drastic boost in climate ambition, our hopes of  achieving the Paris Goals of 1.5°C and 2°C without “overshoot” are out of reach

We are increasingly likely to “overshoot” average global temperatures of 1.5°C and 2°C (meaning that global average temperature temporarily (on order of decades) exceeds the temperature target before reducing again. This can only occur if atmospheric GHG concentrations are lowered – and this is through carbon dioxide removal (CDR), which is by no means a given (see below)). Growing research shows that, for the same end of century temperature increase, overshooting is likely to lead to more climate damages (some of which are irreversible) – like biodiversity loss and extreme weather – than if we get there with no overshoot 4Zickfeld, K. and Herrington, T., 2015. and; Ricke, Katharine L., and Caldeira, K., 2014 and; Tachiiri, K., Hajima, T. and Kawamiya, M., 2019.. 

Delaying mitigation means we will have to cut more emissions each year to stay Paris-aligned by 2030. We already knew the dangers of delayed mitigation in 2014, when the IPCC stated that scenarios with high emissions through to 2030 would have higher long-term economic costs, and would “substantially increase the difficulty of the transition” and “narrow the range of options consistent with… 2°C”. Today, average annual emissions cuts needed to stay below 1.5°C are four times higher than they would have been if collective mitigation and ambition started in 2010, according to UNEP. This highlights the need to act fast.

Investment levels are also nowhere near to what we need to stay Paris aligned. The 2015 Paris Agreement recognised the key role finance plays in both mitigation and adaptation – it placed investors and financial commitments centre stage for climate policy and action. However, climate finance has only increased slightly since AR5, reaching about USD 579 billion in 2018/2017. This is about ten times less than the estimated USD 6.3 trillion needed every year by 2030 to stay Paris aligned. 

Since AR5, the split between public and private climate finance has remained relatively stable (about 44% public and 56% private in 2018). Private finance has, however, outpaced public finance in the energy sector, and increasingly so in transport, reflecting a more mature renewable energy market and the fact that projects are now perceived to be less risky. The private sector is expressing increasing concern over the risks of climate impacts, but climate-related financial risks remain underestimated by financial institutions and decision makers 5Some disclosure measures, like the Task Force on Climate-Related Financial Disclosure (TCFD) may also be largely ineffective, as the assumption that transparency will automatically lead investors to ‘rationally’ respond by moving climate finance from high- to low-carbon assets could be oversimplified..

3. The richest 1% emit more than twice the poorest 50%

Since AR5, there has been increased interest in the ‘national responsibility’ for climate change, as well as the links to other sustainability, development and social issues. The US is responsible for about 20% of cumulative historical emissions, followed by China, Russia, Brazil and Indonesia. Just looking at national emissions does not, however, complete the picture, as the unequal size, wealth and carbon intensity of populations need to be factored in. Looking at emissions relative to population size, developing countries tend to have lower per-capita emissions and, if emissions are normalised to population, China, Brazil and Indonesia do not even make the top 20. 

The richest 1% worldwide emit more than twice the combined share of the poorest 50%, according to UNEP. Activities that emit a lot, but only benefit a few, include flying and driving SUVs. For example, if emissions from SUVs were counted as a nation, it would rank 7th in the world. As COVID-19 caused carbon emissions to fall last year, the SUV sector continued to see emissions rise. In 2018, only 2% to 4% of people got on an international flight, and 1% of the global population are responsible for about half of CO2 emitted from all commercial flights. The aviation industry is responsible for 2.4% of global emission, as such these 1% users could be contributing about 450 million tonnes of CO2 each year – about the same as South Africa’s annual emissions. 

Research, including last month’s landmark AR6 WGII report, shows that climate change affects people differently by gender, race and ethnicity, and these all link to economic vulnerability. Marginalised groups have less access to energy, and use less. For example, women’s carbon footprints are generally lower than men’s, mostly due to reduced meat consumption and driving, though this varies across nations 6See reference 1, 2 and 3. But, even though women generally emit less, their inclusion in policy making can lead to better climate policy. Climate groups are now recognising that disadvantage is the result of many interacting systems of oppression.

4. But there is hope: since AR5 national and corporate net-zero commitments have exploded and renewable energy has continued to outperform forecasts

Since AR5, there has been a substantial growth in climate policy, legislation and treaties at both international, national and sub-national levels. Most importantly, in 2015, the Paris Agreement was signed. The Paris Agreement Article 4 seeks to achieve a “balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases”, which can be interpreted as net zero greenhouse gas emissions (not just CO2). Renewable energy has also continued to massively outperform forecasts, making it a post-AR5 success story. Just in 2020, the amount of new renewable electricity capacity added rose by 45% to 280 gigawatts, the largest year-on-year increase since 1999 (more in box below), while costs have fallen sharply in that time. And, more recently, the concept of ‘net-zero’ entered the policy arena in full force. 

In 2014, the IPCC was not directly using net-zero language, but concluded that limiting the cumulative emissions of GHGs to zero was key to stopping climate change. In 2018, the IPCC outlined that to limit warming to 1.5°C, CO2 emissions would need to fall by about 45% in 2030 (relative to 2010 levels), and global net-zero had to be reached around 2050. WG1 of AR6 (released in August 2021) outlined the need not only for a cut in CO2 emissions, but also strong reductions in other GHGs 7IPCC AR6 WGI D.1. In 2019, the UK became the first G7 economy to legislate for net-zero. Today, 136 countries with 85% of the world’s population, covering 88% of global emissions have set net zero targets, although the targets and timing of how they are delivered remain under criticism for being too vague. This 2021 paper sets out ways that governments could begin to add clarity and accountability; issues considered key to delivering net zero GHG emissions, in pursuit of the Paris targets.

What does achieving net-zero actually look like?

There are many scenarios assessing how we can get to net-zero, and we await the IPCC’s assessment to get an up-to-date, global view. However, some of the key points likely to appear are summarised here. 

Achieving the Paris goals requires rapid mitigation across the full range of GHGs. Scientists have shown that, even if CO2 emissions are Paris-aligned, ignoring methane emissions will lead to overshooting the Paris agreed temperature goals, while abating N2O emissions would help achieve the temperature targets as well as a suite of Sustainable Development Goals (SDGs). 

Renewable electrification is key. A consistent success story since AR5 is the rapid deployment and falling costs of Renewable Energy (RE), such as solar, wind and batteries, which have massively outpaced and exceeded the expert expectations outlined in AR5. But we still need to ramp up. The amount of solar PV and wind deployment has to be twice what has already been announced globally to stay on a 1.5°C trajectory, according to the IEA. We also need to boost funding to clean energy solutions, as many of the technologies needed for hard-to-abate sectors are still in development and annual investment into clean energy needs to triple to USD 3.6 trillion through 2030. 

Fossil fuel use needs to decline dramatically. Global coal emissions needed to have peaked in 2020, and all coal-fired power plants need to be shut by 2040 at the latest, a Climate Analytics analysis based on the IPCC’s 2018 report shows. For OECD nations, all coal use should be phased out by 2031. This was echoed by the IEA in 2021 – it concluded that for net-zero, all unabated coal and oil power plants need to be phased out by 2040. Increasing energy efficiency is also key. In the IEA’s net-zero compliant scenario, the energy intensity of the global economy decreases by 4% a year between 2020 and 2030 – more than double the average rate of the last decade.  

Some degree of carbon removal is needed. Net-zero is achieved when the emissions going into the atmosphere are balanced by those removed. It is possible to achieve global net-zero while still allowing for emissions in some sectors – as long as these ‘hard to abate’ emissions are also being removed and permanently stored. Methods of removal range from enhancing natural carbon drawdown through reforestation, restoration and the protection of nature, to ‘negative emissions technology’ like direct air capture (DAC) and bioenergy with carbon capture and storage (BECCS). In the last few years, more attention has been paid to the ‘net’ part of net-zero, as pretty much all published scenarios that bring us within 1.5°C or 2.0°C rely on some form of CDR. 

Transforming the Agriculture, Forestry and Other Land Use (AFOLU) sector is crucial. Today, it accounts for nearly a quarter of global GHG emissions and sectoral emissions have been climbing in recent years. Livestock production and rice cultivation are the main culprits. The sector is also a carbon sink, as plants and biomass draw CO2 from the atmosphere when they grow. Transforming the sector can both reduce emissions – for example, by changing farming and livestock methods – as well as remove emissions from the atmosphere, including measures like planting more (and protecting existing) forests. However, reforestation and better land management alone will not be enough. Some estimates suggest that transforming the AFOLU sector could at most account for 30% of the mitigation needed to stay below 1.5°C. However, the recent hype that planting trees and investing in land can solve the climate crisis is risking delayed mitigation and greenwashing.

Urban planning needs to consider carbon emissions from the get go. The current scale and speed of urbanisation is unprecedented in human history, and since AR5 it has become even more clear that urban areas contribute the majority (about 70%) of the global footprint, posing an enormous challenge for climate mitigation. New urban planning presents a unique opportunity to reduce carbon lock-in. 

Many more aspects of mitigation and gaps in our knowledge will be explored by the IPCC in this report. For example, the IPCC will dedicate a chapter to demand-side mitigation for the first time, which will explore how behaviour and lifestyle changes can reduce emissions, like shifts in diets, transport, buildings and the efficient use of materials and energy. In general, scientists agree that systemic infrastructural and behavioral change will be part of the transition to a low-carbon society, but the feasibility and mitigation potential of demand-side measures remain a knowledge gap.

5. Looking ahead, transparency is key

Net-zero targets should not be seen as end-points, but rather as milestones on the path to negative emissions, milestones that require detailed roadmaps as well as short-term goals. NGOs, scientists and the public continue to demand mitigation plans and net-zero targets that are clear and transparent, asking policymakers, businesses and financiers to clarify the scope, fairness and approach to decarbonisation. 

Over the past years, integrated assessment models (IAMs) have been a critical tool for climate policymakers, but they have also come under intense scrutiny due to issues like the huge reliance on CDR, especially BECCS, in many scenarios. However, over reliance on IAMs have been criticised given its opaque design and economic assumptions which can result in modelling outcomes that overemphasise CDR. 

In a 2020 paper, the co-chairs of the upcoming WGIII report outlined how the IPCC has taken steps to increase transparency this time around. They said the new report will contain some notable criticisms of IAMs, including the uncertainties, CDR and limits to land. It is, however, important to note that the IPCC itself is not advocating for any scenarios, including those with large amounts of CDR. Instead, the IPCC findings are a reflection of the state of climate modelling, as well as previous emissions pathways and scenario research.

Is it possible to stay Paris aligned without carbon removal?

Many of the scenarios used in earlier IPCC reports (including the special report on 1.5C) relied heavily on negative emissions in the second half of the century. Modelled negative emissions were primarily achieved by inputting a large amount of BECCS and/or forest protection/planting in the future scenarios. 

The numbers for future CDR are often huge, though they vary across models and scenarios. For example, in the IPCC’s special report on 1.5°C, the cumulative carbon removal needed by the end of the century was estimated to be somewhere between 100 and 1000 billion tonnes of CO2. For perspective, we emit more than 40 billion tonnes a year now, so even in the very lowest scenario we would have to remove more than two years’ worth of global CO2 emissions. 

Academics and NGOs have also pointed to the fact that all methods of carbon removal come with side effects and trade-offs that are context and method dependent – such as the huge land areas needed for BECCS, or energy requirements for Direct Air Capture with Carbon Storage (DACCS) (a technology  which some scientist predict could remove tens of GtCO2 by the end of century). Land-based carbon removals also come with other trade-offs, such as increased competition for agricultural land and disruption of biodiversity. There has also recently been an increased recognition that unrealistically high carbon removal projections could be encouraging delayed action and greenwashing. 

In this report, the IPCC intends to explain the limitations and trade-offs of carbon removal carefully, while assessing the amount of CDR in many of the scenarios. There has also been a new wave of scientific literature looking at how to achieve the Paris goals with no carbon removal whatsoever. These pathways show us that net-zero without the ‘net’ (let’s call it ‘true zero’) requires much more rapid transformations of the energy system and larger near-term emissions cuts. These scenarios also lead to multiple other benefits (so-called ‘co-benefits’) like avoiding drastic land-use change, as well as benefiting food systems, biodiversity and the environment in the long-term.

6. Further reading and academic papers

1. Since AR5 greenhouse gas emissions have continued to climb

Explainers and reports 

Selected academic research studies and reviews  

2. A lack of ambitious mitigation has made us increasingly likely to ‘overshoot’ the Paris Goals of 1.5°C and 2°C.

Explainers and reports 

Selected academic research studies and reviews  

3. The richest 1% emit more than twice the poorest 50% 

Explainers and reports 

Selected academic research studies and reviews  

4. But there is hope: since AR5 national and corporate net-zero commitments have exploded and renewable energy has continued to outperform forecasts

Explainers and reports 

Selected academic research studies and reviews  

5. Looking ahead, transparency is key  

Explainers and reports 

Selected academic research studies and reviews  

  • 1
    WGIII will be third of  four separate reports published in the AR6 cycle. ‘The Physical Science Basis’ which detailed the current state of the climate was published on 9 August 2021 and the second report ‘impacts, adaptation and vulnerability’ was released in March 2022.
  • 2
    These numbers are based on pre-Glasgow estimates. If you add all pre-Glasgow net-zero pledges to the NDCs this brings the world on track for 2.2°C, according to UNEP (or about 2.1°C in IEA assessments), page 12, section 7 of the 2021 Emissions Gap Executive Summary.
  • 3
    Most recent estimates show that only 440 Gt CO2 is left from 2020 to stand even a 50% chance of 1.5°C. Global emissions were over 40 Gt CO2 in 2019, and if annual emissions are similar in the next decade it will be used up in the 2030s.
  • 4
    Zickfeld, K. and Herrington, T., 2015. and; Ricke, Katharine L., and Caldeira, K., 2014 and; Tachiiri, K., Hajima, T. and Kawamiya, M., 2019.
  • 5
    Some disclosure measures, like the Task Force on Climate-Related Financial Disclosure (TCFD) may also be largely ineffective, as the assumption that transparency will automatically lead investors to ‘rationally’ respond by moving climate finance from high- to low-carbon assets could be oversimplified.
  • 6
    See reference 1, 2 and 3
  • 7
    IPCC AR6 WGI D.1

IPCC WGIII report: The land sector and climate mitigation

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This briefing summarises the Working Group III (WG3) of the IPCC’s main insights about the mitigation options with the Agriculture, Forestry and Other Land Uses (AFOLU) sector. The term “land sector” will be used throughout this briefing for clarity. The briefing also summarises the findings on the needs and limitations of land-based carbon dioxide removal (CDR).

Key points

  • Rapid deployment of mitigation in the land sector is essential in all 1.5°C pathways. It can provide up to 30% of the global mitigation needed for 1.5°C and 2°C pathways.
  • The sector offers significant near-term mitigation potential at relatively low cost. The global land-based mitigation potential is ~8–14 billion tonnes of CO2 equivalent (GtCO2-eq) each year between 2020-2050. About 30-50% of this potential could be achieved under USD20 per tCO2-eq. Options costing USD100 per tCO2-eq or less could reduce global GHG emissions by at least half the 2019 level by 2030 (SPM C.12). But land-based mitigation cannot compensate for delayed emissions reductions in other sectors.
  • The IPCC recognises that carbon dioxide removal (CDR) is necessary to achieve net-zero GHG globally. Modelled scenarios rely heavily on forest planting and BECCs as main options to remove emissions from the atmosphere to achieve it. 
  • But, the IPCC is not advocating for large-scale CDR. There are many uncertainties, risks and a lack of social licence for these options. It is still uncertain whether CDR through some land-based measures can be maintained in the very long term because sinks can saturate, for example. CDR cannot be deployed arbitrarily and given the time needed to ramp-up CDR, it can only make a limited contribution to reaching net zero in the timeframe required.
  • There is a substantial investment gap in the sector. The IPCC estimates that, to date, only USD 0.7 billion a year has been invested in land-based mitigation, well short of the more than USD 400 billion per year needed to deliver the up to 30% of global mitigation effort in deep mitigation scenarios.

The land sector is key to climate mitigation, but only within limits

The land sector is both a carbon source and a carbon sink. It accounted for ~13%-21% of global greenhouse gas (GHG) emissions between 2010-2019. 1Chapter 7, p.4. This is different from emissions of the entire food system, which are estimated to account for  23-42% of global GHG emissions in 2018 – Ch.12, p.4. For sinks there is also a error of aprox +/- 5.2 But the land sector is also a carbon sink, as it draws CO2 from the atmosphere when plants grow (through the process of photosynthesis). When the sector’s sources and sinks are added up, the land sector is considered a net sink of emissions – removing about 6.6 GtCO2 a year for the period of 2010-2019. 2Chapter 7, p.4. This is different from emissions of the entire food system, which are estimated to account for  23-42% of global GHG emissions in 2018 – Ch.12, p.4. For sinks there is also a error of aprox +/- 5.2. Chapter 3, p.42 : But there are still large uncertainties on net CO2 human emissions and its long-term trends. Currently, national GHG inventories (NGHGI) tend to overestimate the amount of CO2 absorbed by sinks when compared to other global models. There is a gap of ~5.5 GtCO2 a year between NGHGI and Bookkeeping models and dynamic global vegetation models. The difference largely results from different definitions of what “anthropogenic” means, which leads NGHGIs to estimate that more CO2 is taken up by sinks.

The IPCC clearly states that the land sector has huge potential for mitigation. It can both reduce emissions – for example by changing farming and livestock practices – as well as remove them from the atmosphere, via measures like planting more forests and protecting existing ones. But the sector “cannot fully compensate for delayed action in other sectors”. (SPM C.9)

Overall, the IPCC estimates that the global land-based mitigation potential is ~8–14 billion tonnes of CO2 equivalent (GtCO2-eq) each year between 2020-2050, at costs below USD 100/tCO2. 3Chapter 7, p.41. The bottom end represents the mean from IAMs and the upper end the mean estimate from global sectoral studies. The economic potential is about half of the technical potential from AFOLU, and about 30-50% could be achieved under USD20 tCO2-eq-1. Note that the IPCC uses a different methodology for individual AFOLU options than for the total sector potential. These estimates are slightly higher than those in AR5. Considering both integrated assessment models (IAMs) and sectoral economic potential estimates, WG3 states that “land-based mitigation could have the capacity to make the sector net-negative GHG emissions from 2036 although there are highly variable mitigation strategies for how [its] potential can be deployed for achieving climate targets”. 4Chapter 7, p.42. “Economic mitigation potential is the mitigation estimated to be possible at an annual cost of up to USD100 tCO2 -1 mitigated. This cost is the price at which society is willing to pay for mitigation and is used as a proxy to estimate the proportion of technical mitigation potential that could realistically be implemented.” There are many options that can help reduce and remove emissions (Box 1). Most of the options to reduce emissions are available and ready to deploy, whereas CDR needs more investment. 5Chapter 7. 42

The IPCC does not use the term ‘nature-based solutions’ (NbS), but ‘land-based mitigation measures’. When evaluating the mitigation potential within the sector, it discusses 20 measures, both supply and demand-side (Box 1). However, when it analyses mitigation pathways, it only includes a few options because of how climate models are currently built (see the role of CDR in mitigation pathways section for more detail).

Box 1. What are the main ways the land sector reduces and removes emissions between 2020-2050? 

Forests and other ecosystems have the highest potential for carbon mitigation, according to global sectoral models. Protecting, managing and restoring these ecosystems is likely to reduce and/or sequester up to 7.4 billion tonnes of CO2 equivalent each year between 2020 and 2050. 6SPM, p.43 Crucially, the IPCC finds that protecting ecosystems has the highest potential. The report also stresses that halting deforestation and restoring peatlands is vital to keeping temperature rises below 2C. 

Agriculture and demand-side measures provide the second and third highest potential for mitigation, potentially reducing and/or sequestering up to 4.1 and 3.6 billion tonnes of CO2 equivalent a year respectively between 2020 and 2050. 7SPM, p.43 For agriculture, the measures that have the greatest potential are soil carbon management in croplands and grasslands, agroforestry, biochar and rice cultivation, as well as livestock and nutrient management. On the demand-side, it’s shifting to healthy diets and reducing food waste and loss.

Land sector mitigation measures can have important co-benefits, but only if done properly. For example, “reforestation and forest conservation, avoided deforestation and restoration and conservation of natural ecosystems and biodiversity, improved sustainable forest management, agroforestry, soil carbon management and options that reduce CH4 and N2O emissions in agriculture from livestock and soil, can have multiple synergies with the sustainable development goals.” 8SPM, p. 53

But there are many risks and trade-offs. Large-scale or poorly planned deployment of bioenergy, biochar, and afforestation of naturally unforested land. (high confidence) for instance, can compete with scarce resources, such as agricultural land. 9SPM, p. 55 This can threaten food production and security and reduce adaptive capacity. The use of non-native species and monocultures (e.g. planting one type of tree) in forest projects can also lead to biodiversity loss, and negatively impact ecosystems. 10Chapter 7 of WGIII provides an overview of 20 mitigation measures, evaluating the co-benefits and risks from land-based mitigation measures, estimated global and regional mitigation potential and associated costs according to literature published over the last decade. There are also risks in relation to land’s ability to continue to act as a carbon sink in the future, which can reduce land sector measures’ capacity to mitigate emissions. 11Chapter 7.4

Joint and rapid effort is key to achieving high levels of mitigation in the sector, the IPCC says. But there has been a lack of funds to support these efforts. The IPCC estimates that, to date, only USD 0.7 billion a year has been invested in the sector, well short of the more than USD 400 billion per year needed to deliver the up to 30% of global mitigation effort envisaged in deep mitigation scenarios.12Chapter 7, p.6. This is based on land-based carbon offsets (i.e. money from the Clean Development Mechanism, voluntary carbon standards, compliance markets and reduced deforestation).

What does the IPCC say about the scale of land-based CDR?

Mitigation potential of different CDR options

CDR is defined by the IPCC as “human activities that remove emissions from the atmosphere and durably store it”. Thus, CDR excludes uptake of emissions not directly caused by humans. CDR can help in several phases of mitigation: 

  1. Reducing net CO2 or GHG emission levels in the near-term 
  2. Counterbalancing residual emissions from hard-to-transition sectors like industry and agriculture to help reach net-zero CO2 or GHG emissions targets in the mid-term 
  3. Achieving and sustaining net-negative CO2 or GHG emissions in the long-term if deployed at levels exceeding annual residual emissions. 13SPM, p. 48 Therefore, offsets are discussed in the report as a way to counterbalance residual emissions, highlighting that hard-to-abate sectors could have more social licence to rely on CDR. 14The IPCC evaluates previous offsets measures, such as REDD+, offsets within emissions trading systems, among others in chapter 7;Chapter 3, p. 14-15

Currently, the only widely practised CDR methods include afforestation, reforestation, improved forest management, agroforestry and soil carbon sequestration. 15SPM, p. 47 Figure 1 presents the options that can be deployed on land as well as in the oceans. The IPCC discusses these options, presenting a summary of their mitigation potential, risks, co-benefits and costs. (Table 1 in the appendix)  However, the IPCC does not go into detail on all options. For example, it mentions that the choice of feedstock for BECCS could lead to positive or negative impacts, but does not explore all feedstock options and their related consequences.

Figure 1. CDR methods across Land sector and Oceans (​​IPCC- WG3 Chapter 12, p.37)
The role of CDR in mitigation pathways

The WG3 report looks at what the science says about mitigating the climate crisis. As established in most scientific literature, achieving net zero by mid-century is the safest way to stay Paris aligned. There are, however, many different routes to net zero. Thus, the scope of this report is to chart the options, limits, benefits and trade-offs of pursuing a net-zero emissions society. To do this, the IPCC reviewed more than 3000 pathways, including over 1200 scenarios, to develop five “Illustrative Mitigation Pathways” (IMPs) and two high-emissions pathways for reference.

The report finds that “CDR is a necessary element to achieve net-zero CO2 and GHG emissions, and counterbalance residual emissions from hard-to abate sectors”. 16Chapter 12, p. 35 It is also a key element in scenarios that are likely to limit warming to 2°C or lower by 2100”. 17Chapter 12, p. 35 All of its IMPs use land-based CDR, which is dominated by BECCS, afforestation and reforestation. 18Chapter 12, p.4 and p. 55

In most scenarios that limit temperatures to 2°C or lower, the IPCC predicts cumulative volumes of CO2 removed between 2020-2100 could reach (all median values): 19Chapter 12, p. 5

  • BECCS – 328 GtCO2 
  • Net CO2 removal on managed land (including afforestation and reforestation) – 252 GtCO2
  • Direct Air Capture Capture and Storage (DACCS) – 29 GtCO2

To put this into perspective, the remaining carbon budget assessed by WG1 from the beginning of 2020 onwards is 500 GtCO2 for limiting warming to 1.5°C with a 50% chance of success. 20Summary for policymakers, p. 6 The IPCC also predicts that mitigation measures in 2°C or below pathways can significantly transform land all around the world. These pathways are “projected to reach net-zero CO2 emissions in the land sector between the 2020s and 2070, with an increase in forest cover of about 322 million hectares (-67 to 890 million ha) [an area almost as big as the US and India combined] in 2050 in pathways limiting warming to 1.5°C with no or limited overshoot”. 21Chapter 3, p. 6

Delaying action will result in larger and more rapid deployment of CDR later, especially if there is a temperature overshoot. Then, large-scale deployment of CDR will be needed to bring temperatures back. 22Smith et al. 2019; Hasegawa et al. 2021 Since IAM pathways rely on afforestation, reforestation and BECCS, delayed mitigation can lead to a lot of changes in land use, with negative impacts for sustainable development. 23IPCC 2019, Hasegawa et al. 2021  The IPCC points out that “strong near-term mitigation to limit overshoot, and deployment of other CDR methods than afforestation / reforestation and BECCS may significantly reduce the contribution of these CDR methods in scenarios limiting warming to 1.5 or 2C”. 24Chapter 12, p. 56 “Stronger focus on demand-side mitigation implies less dependence on CDR and, consequently reduces pressure on land and biodiversity”. 25Chapter 3, p. 7  It adds that: “Within ambitious mitigation strategies…, CDR cannot serve as a substitute for deep emissions reductions”. 26Chapter 12, p. 38 To put this into perspective, the market for carbon offsets today, which include these CDR measures, reduce global emissions by about 0.1%, according to the Energy Transitions Commission.

But while most scenarios in WG3 still rely on CDR to achieve net-zero, the IPCC is not advocating for large amounts of it. Instead, the reliance on CDR reflects the state of climate modelling and research (see box 2 in appendix). The IPCC discusses the uncertainty, risks and lack of social licence for CDR, such as concerns that large-scale CDR could obstruct near-term emission reduction efforts or lead to an over-reliance on technologies that are still in their infancy. 27Chapter 12, p. 39 It stresses that there is uncertainty about how much CDR will be deployed in the future and the amount of CO2 it can remove permanently from the atmosphere. 28Chapter 12, p. 39 This is because some measures in the land sector cannot be maintained indefinitely as these sinks will ultimately saturate, while trees can also be cut down, burnt or die prematurely. 29Chapter 3, p.7

Box 2. A word about climate models and the potential and limitations of land sector mitigation 

Since the last IPCC reports, there have been more assessments of the total mitigation potential of the land sector. 30Chapter 7, p.40 These can be split into:

  • Sectoral models: These estimate the potential of the sectors and/or individual measures. But they rarely capture cross-sector interactions, making it difficult for them to account for land competition and trade-offs. This could lead to double counting when aggregating sectoral estimates across different studies and methods. 31Chapter 7, p.40-42 They usually show higher mitigation potential as they include more land-based mitigation options than IAMs. 32Chapter 3, p. 64
  • IAMs and integrative land-use models (ILMs): IAMs assess multiple and interlinked practices across sectors, and thus account for interactions and trade-offs (i.e. land competition). IMLs combine different land-based mitigation options, which are only partially included in IAMs. Both have extended their coverage, but the modelling and analysis of land-based mitigation options is new compared to sectoral models. Consequently, “[Land sector] options are only partially included in these models, which mostly rely on afforestation, reforestation and BECCS”. 33Annex III- p.29; Chapter 7, p.86
  • Currently, most models do not consider, or have limited consideration of, the impact of future climate change on land. 34Chapter 7. 42.And there is still uncertainty about land’s ability to act as a sink in the future and how this will impact mitigation efforts. 35Chapter 7. 116  Bottom-up and non-IAM studies show significant potential for demand-side mitigation. 36Chapter 3, p. 7 (see Table 2 in the Appendix)

When evaluating the potential of different land-based mitigation measures, AR6 uses mainly sectoral models and compares to IAM’s, when available. But, AR6 still relies on IAMs/ILMs to devise mitigation pathways. This can be problematic in two main ways:

  • Climate change impacts on land and future mitigation potential: Given the IPCC WG1 finding that land sink efficiency is decreasing with climate change, relying too much on land to remove CO2 from the atmosphere could be problematic. This could create a false sense of security and allow for land mitigation to be used as an excuse for not making deep emissions cuts. This is key as many corporations are relying on offsetting emissions in the land sector instead of reducing them. 

Unrealistic CDR projections (over-reliance on BECCS and afforestation and reforestation): The volumes of future global CDR deployment assumed in IAM scenarios are large compared to current volumes of deployment. This is a challenge for scaling up. Similarly, the lack of representation of other options makes it difficult to compare different measures and envisage a different future that alters the contribution of land in terms of timing, potential and sustainability.

Appendix – Mitigation potential of different CDR measures

  • 1
    Chapter 7, p.4. This is different from emissions of the entire food system, which are estimated to account for  23-42% of global GHG emissions in 2018 – Ch.12, p.4. For sinks there is also a error of aprox +/- 5.2
  • 2
    Chapter 7, p.4. This is different from emissions of the entire food system, which are estimated to account for  23-42% of global GHG emissions in 2018 – Ch.12, p.4. For sinks there is also a error of aprox +/- 5.2. Chapter 3, p.42 : But there are still large uncertainties on net CO2 human emissions and its long-term trends. Currently, national GHG inventories (NGHGI) tend to overestimate the amount of CO2 absorbed by sinks when compared to other global models. There is a gap of ~5.5 GtCO2 a year between NGHGI and Bookkeeping models and dynamic global vegetation models. The difference largely results from different definitions of what “anthropogenic” means, which leads NGHGIs to estimate that more CO2 is taken up by sinks.
  • 3
    Chapter 7, p.41. The bottom end represents the mean from IAMs and the upper end the mean estimate from global sectoral studies. The economic potential is about half of the technical potential from AFOLU, and about 30-50% could be achieved under USD20 tCO2-eq-1. Note that the IPCC uses a different methodology for individual AFOLU options than for the total sector potential.
  • 4
    Chapter 7, p.42. “Economic mitigation potential is the mitigation estimated to be possible at an annual cost of up to USD100 tCO2 -1 mitigated. This cost is the price at which society is willing to pay for mitigation and is used as a proxy to estimate the proportion of technical mitigation potential that could realistically be implemented.”
  • 5
    Chapter 7. 42
  • 6
    SPM, p.43
  • 7
    SPM, p.43
  • 8
    SPM, p. 53
  • 9
    SPM, p. 55
  • 10
    Chapter 7 of WGIII provides an overview of 20 mitigation measures, evaluating the co-benefits and risks from land-based mitigation measures, estimated global and regional mitigation potential and associated costs according to literature published over the last decade.
  • 11
    Chapter 7.4
  • 12
    Chapter 7, p.6. This is based on land-based carbon offsets (i.e. money from the Clean Development Mechanism, voluntary carbon standards, compliance markets and reduced deforestation).
  • 13
    SPM, p. 48
  • 14
    The IPCC evaluates previous offsets measures, such as REDD+, offsets within emissions trading systems, among others in chapter 7;Chapter 3, p. 14-15
  • 15
    SPM, p. 47
  • 16
    Chapter 12, p. 35
  • 17
    Chapter 12, p. 35
  • 18
    Chapter 12, p.4 and p. 55
  • 19
    Chapter 12, p. 5
  • 20
    Summary for policymakers, p. 6
  • 21
    Chapter 3, p. 6
  • 22
  • 23
  • 24
    Chapter 12, p. 56
  • 25
    Chapter 3, p. 7
  • 26
    Chapter 12, p. 38
  • 27
    Chapter 12, p. 39
  • 28
    Chapter 12, p. 3
  • 29
    Chapter 3, p.7
  • 30
    Chapter 7, p.40
  • 31
    Chapter 7, p.40-42
  • 32
    Chapter 3, p. 64
  • 33
    Annex III- p.29; Chapter 7, p.86
  • 34
    Chapter 7. 42
  • 35
    Chapter 7. 116
  • 36
    Chapter 3, p. 7

Reducing methane emissions is key to the climate fight

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With the upcoming IPCC WGI report set to include a chapter on short-lived climate forcers for the first time, this briefing asks why are methane emissions so important to climate change?

Human greenhouse gas (GHG) emissions are driving climate change. Since the pre-industrial period, these emissions have caused all of the earth’s observed warming, with carbon dioxide (CO2) responsible for the majority of it. After CO2, methane (CH4) is the biggest contributor to climate change. The new IPCC report (working group 1 of AR6) is likely to focus on the role of methane in driving climate change. 

Methane emissions are a huge problem because while the gas only stays in the atmosphere for about nine years, it has 28 times more warming power than carbon dioxide over 100 years. Methane concentrations are increasing faster now than at any time since the 1980s, reaching more than two-and-a-half times pre-industrial levels. This is well above the safe limits outlined by the IPCC in AR5. Methane is now responsible for almost a quarter of warming, bringing us closer to breaching the 1.5°C temperature target. Cutting human-caused methane emissions is one of the most cost-effective ways to rapidly reduce the rate of warming and limit temperature rise to 1.5°C.

What are the key emitting sectors and mitigation opportunities?

Methane emissions come from natural sources, such as wetlands, but more than half of total global methane emissions come from human activities. Three sectors – agriculture (40% of human-caused emissions), fossil fuels (35%) and waste (20%) account for the majority of human methane emissions. Almost a third (32%) of agricultural methane emissions come from livestock production 1 Estimating methane emissions is an ongoing topic of research, particular in the livestock sector as the amount of methane emitted depends on many factors, such as the number of animals or the type of feed consumed.. Oil and gas extraction, processing and distribution account for 23% of methane emissions in the fossil fuel sector and coal mining accounts for 12% of emissions. Landfills and wastewater comprise 20% of methane emissions in the waste sector. 

Many cost-effective mitigation measures are readily available, such as reducing emissions that escape  along the natural gas supply-chain, better treatment of solid waste, and improving livestock and crop management (see table below for some examples). Mitigation options across the three sectors represent some of the best levers to reduce warming and its climate impacts over the next 30 years. In particular, the fossil fuel industry has the greatest potential for methane cuts by 2030, according to the UN – up to 80% of oil and gas measures and up to 98% of coal measures could be implemented at negative or low cost. But action across all three sectors is needed to ensure emissions are in line with 1.5ºC. All together, cutting methane  in those three sectors could reduce human methane emissions by 45% by 2030. This would avoid nearly 0.3°C of global warming by the 2040s, helping to keep temperatures below 1.5ºC while preventing 255,000 premature deaths and 26 million tonnes of crop losses globally.

Policy measures to reduce methane emissions in top three emitting sectors
Source: Global Methane Assessment, 2021; IPCC SRCCL report 2019 – chapter 6.

Methane and Agriculture: An overlooked problem

Most methane emissions (32%) from agriculture come from raising livestock via enteric fermentation – a ruminant animal’s natural digestive process – and manure. Other key agricultural sources are landfills, waste and rice cultivation. The upcoming IPCC AR6 report is expected to confirm the link between livestock production and increased methane emissions. 

While countries recognise agriculture as a source of methane emissions, most do not take concrete action to cut them. In fact, methane emissions from agriculture are expected to continue to grow as demand for meat increases, particularly in low and middle-income countries. 
Given agriculture’s huge footprint, actions to reduce methane emissions in the sector are key for reaching climate targets. A robust evidence base indicates that reduced food waste and loss, improved livestock management, and eating fewer animal products could reduce emissions by 65–80 million tonnes a year over the next few decades 2In the livestock sector, options differ between production systems. For example, improving management via feed additives, vaccines can reduce enteric fermentation in more intensive systems, such as dairy in the US. Manure management is more applicable in farms where manure can be easily collected, such as in smallholder, mixed crop-livestock systems.. Widespread adoption of such measures could bring anthropogenic methane emissions in line with those in 1.5ºC scenarios. But, governments should carefully choose policies because some models show that achieving very low emissions per kilogram of protein involves large-scale industrialised agriculture. This is problematic as adopting industrial agriculture methods come with many social and environmental impacts that are not captured in models and can increase GHG emissions. If these were accounted for, industrial agriculture would put the 1.5ºC target out of reach. Farming systems that shift away from industrial agriculture, such as agroforestry and organic farming, not only help to reduce emissions of all GHG, but also improve farmers’ livelihoods, food security and biodiversity.

What have governments done to reduce methane emissions?

Now more than ever, global action on methane emissions is needed. But governments have often failed to cut emissions, partly due to a lack of reliable emissions data and reporting from the industries themselves. Meanwhile, countries’ climate targets – known as nationally determined contributions (NDCs) – only address methane in general terms, without a clear target or strategies to reduce emissions. Only nine of the 174 countries that have submitted NDCs set a separate target for methane emissions. Lack of measurable targets to abate methane emissions is apparent especially in the agricultural sector. Close to 80% of countries (148 out of 189) that have submitted NDCs include agriculture, but NDC targets are vague. Most (128 out of 148 countries or 86%) include the sector in overall economic or broader targets and do not elaborate on concrete actions to reduce emissions from farming. Very few also set targets in relation to other parts of the food system that emit methane, such as adopting sustainable diets. As a result, the potential to reduce global emissions of methane remains largely untapped.

Decarbonisation strategies without methane-specific policies are insufficient to keep warming below 1.5ºC . These strategies – which target carbon dioxide –  only achieve about 30% of the methane reductions needed over the next 30 years in a 2ºC scenario, for example. Moreover, cutting methane emissions now is more cost effective as mitigation costs increase with delayed action. If countries abate methane emissions by 2030, costs could be less than USD 600 per tonne of methane, especially in the waste and coal sectors in most regions. In 2050, costs could be roughly 50% higher than 2030. At the same time, without relying on future, massive-scale deployment of unproven carbon removal technologies, expansion of natural gas infrastructure and current levels of livestock farming is incompatible with keeping warming to 1.5°C.

Resources

  • 1
     Estimating methane emissions is an ongoing topic of research, particular in the livestock sector as the amount of methane emitted depends on many factors, such as the number of animals or the type of feed consumed.
  • 2
    In the livestock sector, options differ between production systems. For example, improving management via feed additives, vaccines can reduce enteric fermentation in more intensive systems, such as dairy in the US. Manure management is more applicable in farms where manure can be easily collected, such as in smallholder, mixed crop-livestock systems.

IPCC’s upcoming 6th Assessment Report: Physical Science

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The Intergovernmental Panel on Climate Change (IPCC) – the UN body responsible for climate science – is releasing the first of its three-part 6th Assessment Report (AR6) on 9 August, after a virtual plenary held between 26 July and 6 August. This will be an important media moment. The Working Group I (AR6 WGI) report will be the biggest update of the state of knowledge on climate science since the release of AR5 in 2014, and its three recent special reports (SR1.5, SRCCL, SROCC). The reports are ratified after a plenary negotiation in which governments formally approve the summary for policymakers, ensuring high credibility in both science and policy communities. 

The AR6 assessment will consist of three separate reports. ‘The Physical Science Basis’ is the first AR6 report and will detail how the greenhouse gases (GHG) we emit are causing unprecedented damage. The outline for the first report is approved. It will cover topics like extreme weather, human attribution, the carbon budget and feedback cycles, and will chart the current and future state of the climate. 

In preparation for the release of the first AR6 report, this briefing covers some of the major climate science developments since AR5 that are relevant to the current science discourse.

1. Human influence on the climate is an established and indisputable fact

Extreme event attribution studies can also tell us if, and how, climate change made a particular extreme weather event more likely or more intense. The expanded attribution literature shows that heatwaves, droughts, tropical cyclones and compound events are directly linked to human activities. In fact, new research has shown that some extreme events would have been impossible without climate change, like the Siberian heat wave in 2020 and the extreme heat across Asia in 2016. Today, scientists can also conduct attribution studies within a few days of an event occurring. One group of scientists published a study showing climate change made the 2018 European heatwave more likely while it was still going on. Another group was able to make an event attribution forecast prior to 2018’s Hurricane Florence.

The COVID-19 pandemic reminded us how much our actions matter: during the peak of global lockdowns daily emissions dropped by 17% compared to 2019, levels not seen since 2006, and people around the world were allowed a short respite from deadly air pollution. Since then, however, emissions have been rapidly ticking up again. Research has shown that the biggest opportunity from the pandemic is not the short lockdown-triggered emissions break, which will be negligible in the long run, but the potential to now tilt the economy towards a green, sustainable, just and climate centered recovery. 

2. We are closer to important temperature targets

Since AR5, we have emitted nearly 300 billion additional tonnes of CO2, bringing us closer to crucial temperature targets. In its 2018 special report, the IPCC predicted that the 1.5°C target would be breached between 2030 and 2052 in the event that we didn’t change our trajectory. Refined methods and research has since suggested that our carbon budget, a simplified (albeit imperfect) way of assessing how much more CO2 can be released, is slightly smaller than estimated in the IPCC report – leaving only 440 Gt CO2

left from 2020 to stand even a 50% chance of 1.5°C. Global emissions were over 40 Gt CO2 in 2019, and if annual emissions are similar in the next decade, the budget will be used up in the 2030s. 

The way in which scientists measure global temperature change is also more sophisticated: AR5 based its assessment of historical warming on the UK Met Office’s global temperature dataset, HadCRUT4, now an updated version (HadCRUT5) is available for AR6. The new dataset draws on an improved record of global sea surface temperatures, benefitting from more reliable methods of measuring ocean temperatures, and the record also fills in some of the gaps in Arctic data. The Arctic is the fastest warming region on the planet, so the inclusion of this data increases historic global temperature estimates by about 0.1°C. 

Adjustments to the historic warming record may, however, not directly relate to meeting the forward-looking temperature targets of the Paris Agreement. In all previous IPCC assessments there are some scenarios that see us achieve 1.5°C, but the ability to meet this target is driven by the political will and choices of decision-makers, rather than the science itself. It is also difficult to determine at what exact point we exceed a target like 1.5°C. Research from the World Meteorological Organization states there’s a 20% chance that global temperatures could average 1.5°C or above in one of the next five years. But importantly, this should not be confused with exceeding 1.5°C as a long-term average, or breaching the Paris target. 

There has also been an increased recognition that abrupt (and sometimes irreversible) changes to the climate, often called ‘tipping-points’, are more likely to occur in a world where we overshoot 1.5°C. Risks include a destabilisation of the polar ice sheets: future sea level rise is very dependent on what happens to the Antarctic and Arctic ice sheets with destabilisation potentially causing tens of centimetres of sea level rise by the end of the century. In addition, deforestation and global warming could increase the risk of the Amazon crossing into a dry state (so-called forest dieback). Researchers have also shown that passing one tipping point could increase the likelihood of others occurring, compounding risks. 

3. New and updated models have added to our understanding of the climate 

Preliminary results from AR6’s new climate models (CMIP6) have already been picked up by the media, due to suggestions that rising CO2 levels will cause more warming than previously thought. Or, in climate science speak, that the Earth has a higher “climate sensitivity”. The Equilibrium Climate Sensitivity (ECS), defined as the warming that occurs when there is double the amount of CO2 in the atmosphere relative to preindustrial times, is a crucial number for understanding climate change. 

The ECS describes the final warming after the climate fully adjusts over hundreds of years, and was first estimated at 1.5-4.5°C over 40 years ago. In comparison, the new CMIP6 models produce ECS values between 1.8-5.6°C, but almost all scientists working on the CMIP6 project have now ruled out the highest estimates. Recent research narrowed down the range further and excluded the most extreme values, arguing that the best estimate sits somewhere between 2.6-4.5°C. 

Another metric, the Transient Climate Response to cumulative Emissions of CO2 (TCRE), which describes the initial amount of warming we can expect in the coming decades, is more directly relevant to the remaining global carbon budget agreed in Paris. Since AR5, our understanding of the TCRE has expanded, with some model results indicating that it is similar or slightly higher than previous estimates, and new research has narrowed the range by about 30%. Intense debate is ongoing about the exact sensitivity numbers (ECS & TCRE), as well as the uncertainties and how the values influence carbon budgets. 

AR6 also draws on new future scenarios, built by teams of economists, climate scientists and modellers. These ‘Shared Socioeconomic Pathways’ (SSPs) explore how global economy and society may change over the next century, allowing a wider range of possible futures and offering a broader view of “business-as-usual” than the ‘Representative Concentration Pathways’ (RCPs) in AR5. 

4. Scientists are concerned about non-CO2 greenhouse gases, especially rising levels of methane

Achieving the Paris Agreement’s goals requires rapid mitigation across the full range of greenhouse gases. Methane and nitrous oxide concentrations are now higher than at any point in the last 800,000 years.

Since the pre-industrial period, CO2 has caused most warming, followed by methane – a particular focus of research in recent years. The concentration of methane is already running well above the safe limits outlined in AR5, increasing steeply since about a decade, and some scientists have suggested that methane’s warming effect is higher than estimated in AR5 (over a 100 year period). Even though there is over 230 times more CO2 in the atmosphere, methane is responsible for almost a quarter of warming. Methane only stays in the atmosphere for about 12 years, but it has a warming potential approximately 30 times that of CO2 over a century, and almost 90 times in a 20-year period.

Human activities were responsible for 50-65% of total methane emissions between 2008-2017, with agriculture and waste contributing most to the rise (56-60%), followed by the fossil fuel industry. But estimating by exactly how much, and from where, methane emissions are increasing is a topic of continued research and debate. Both coal mining and oil and gas production have grown along with methane emissions. By looking at the “atmospheric fingerprints” (isotopes) of methane some researchers have found that the role of North American shale gas – or fracking – has been significantly underestimated. Scientists have also investigated potential natural leaks of methane, and the risk of sudden methane releases from thawing Arctic permafrost.

AR6 will also be the first IPCC assessment to dedicate a whole chapter to so-called “short-lived climate forcers”, like aerosols, particulate matter and other reactive gases (such as ozone) that exist in the atmosphere for a few hours to a few months. In contrast to CO2, mitigating these gases can have an immediate impact on temperature due to their shorter lifetime. Since in most cases their reduction could also improve air quality and save lives, this is seen as a ‘win-win’ policy option. 

5. We know more about net-zero and the potential plus pitfalls of carbon removal 

Half of global GDP is generated in regions that have set (or are debating) net-zero targets, representing over 2.6 billion people. Net-zero is a target guided by science. Studies show that the climate system will continue to warm unless we reach net-zero greenhouse gases globally. Scientists continue to demand net-zero targets that are transparent: asking for them to clarify the scope, fairness and approach. Net-zero targets are in themselves not end-points, but better understood as a milestone on the path to negative emissions and therefore require long-term roadmaps as well as short-term goals.

The refined estimates of Earth’s climate sensitivity has led to some debate about the implications for our timeline to both achieve net-zero and stay below the 1.5 or 2°C temperature targets. But the relationship between these two factors is complicated and indirect. Regardless, scientists continue to stress that the best way to mitigate and avoid the most devastating impacts of climate change is to cut emissions early on and deeply in this decade with the aim of reaching net-zero as early as possible.

So what happens after net-zero is achieved globally? Scientists generally agree that net-zero will lead to a stop in temperature rise. Though models still vary on exactly how long this will take after zero. A cessation in temperature rise, however, must not be confused with a temperature reduction. As CO2 is cumulative, the amount that is in the atmosphere when we hit net-zero will determine peak temperature, unless that CO2 is removed. And even if all emissions stop, ice sheet melting and resulting sea level rise will continue, albeit slower than if we continue warming the planet. As such, the need for adaptation policies and finance, as well as provision for Loss and Damage for poor and affected communities, will remain. 
But new research finds that rapid emissions cuts reduce our risks of ‘unprecedented rates’ of warming, which would make it harder for ecosystems and societies to adapt. As such, near term emissions cuts will bring significant benefits within our lifetimes, not just in the long run. To achieve this, however, governments and businesses need to follow ambitious near-term Paris-aligned climate plans. 

Pretty much all scenarios that bring us within 1.5°C or 2.0°C rely on some form of carbon dioxide removal (CDR). Methods of removal range from enhancing natural carbon drawdown through reforestation, restoration and the protection of nature, to “negative emissions technology” like direct air capture (DAC) and bio-energy with carbon capture and storage (BECCS). 

Our reliance on CDR is however somewhat naive, as all methods of carbon removal come with side effects and tradeoffs that are context and method dependent – such as the huge land areas needed for BECCS, or energy requirements for DAC. Delayed mitigation has increased our dependence on CDR and the simple truth is that the more carbon we emit now, the more we will rely on negative emissions to stay within our target temperatures. It is fundamentally necessary, however, to immediately protect biodiversity, ecosystems and restore nature. Not just for the climate, but also to warden the rich diversity of life on our planet and to maintain people’s livelihoods.  

Scientists have studied the so-called “overshoot scenarios”, that see emissions in the near-term compensated by carbon removal that reaches “net-negative” in the latter half of the century. They found that delayed reaction time of several climate processes means even a temporary overshoot of temperature goals will result in more climate change in comparison to no overshoot (i.e. more sea level rise, acidification of the ocean, permafrost loss or perturbation of the carbon cycle). 

In the IPCC’s most recent special report (SR1.5), only 9 out of the 222 assessed temperature pathways have no overshoot, and only 44 go over 1.5°C by less than 0.1°C (low overshoot). However, there are no IPCC scenarios that completely guarantee 1.5°C. Even the most ambitious pathways see a 66% chance of keeping global temperature rise to under 1.5°C, meaning that the chances of overshooting is a subject of continued scientific uncertainty.  

Finally, there have been several more studies looking at more invasive geoengineering approaches, like solar radiation management. Though these interventions might help to reduce temperatures immediately and regionally, some of them are seen as high risk endeavours with undesired side effects, especially on the water systems and hence food security. Solar geoengineering also brings novel, and unprecedented, social justice and political challenges. It remains to be seen how the IPCC deals with assessing these technologies. The special report on 1.5°C was the first IPCC report to separate solar geoengineering from more “mainstream” carbon removal. We suspect AR6 will continue this split. 

6. Further reading: Explainers and scientific papers 

The list below summarises some of the important commentaries and scientific papers, focusing on those published in the last two years. It is not a comprehensive review of the scientific literature; think of it as a start. To explore the specific topics further, please refer to the reference lists within these publications.

1. Human influence on the climate is an established and indisputable fact 

Explainers and reports 

Selected academic research studies and reviews  

2. We are closer to overshooting important temperature targets

Explainers and reports

Selected academic research studies and reviews  

3. New and updated models have added to our understanding of the climate 

Explainers and reports

Selected academic research studies and reviews  

4. Scientists are taking account of non-CO2 greenhouse gases

Explainers and reports

Selected academic research studies and reviews  

5. We know more about net-zero and the potential plus pitfalls of carbon removal 

Explainers and reports 

Selected academic research studies and reviews   

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