This article explains the drivers and impacts of methane (CH4) emissions in En-ROADS. Watch the video below for a summary.
En-ROADS includes options to reduce methane emissions in energy, agriculture, and waste through both decreased production and adoption of emissions best practices.Overview and Messages
En-ROADS users have the ability to simulate various scenarios for methane emissions and explore their impact. This can be achieved by adjusting policies and practices in three key sectors: energy, agriculture, and waste. In En-ROADS, emissions from these sectors can be specifically targeted by adjusting the main sliders or advanced settings for Agricultural Emissions, and Waste and Leakage. Other sliders across the En-ROADS interface can also address methane emissions, as explained below.
In each sector, policies and practices can influence emissions in two ways: by altering the overall production scale (e.g. fossil fuel, agricultural, or waste production) and/or the methane intensity of that production (i.e., the emissions generated per unit of production).
There are two ways to reduce methane emissions: decreasing the scale of methane-producing activities and/or reducing the intensity (i.e., methane emissions per unit of production).
When changing policies with the sliders, users can simulate the actions that can help us meet goals such as the Paris Agreement or the Global Methane Pledge (e.g., En-ROADS Scenario), which seeks to reduce global methane emissions at least 30 percent below 2020 levels by 2030.
Delays play a key role in shaping methane dynamics. The adoption of best practices takes time to spread globally, and outdated and inefficient infrastructure must either be retired or retrofitted.
Main Graphs
En-ROADS has a graph of overall global anthropogenic Methane Emissions (on the above left), and the more detailed, stacked version of the graph, Methane Emissions by Source (on the above right), (both under Graphs > Greenhouse Gas Emissions > Methane).
Anthropogenic methane emissions come from three major sectors: Energy, Agriculture, and Waste.Context on methane emissions
Methane emissions come from human activities and also occur naturally. According to the IEA’s Global Methane Tracker report, 67% of global methane emissions are anthropogenic, primarily produced from the energy, agricultural, and waste sectors.
Biogenic emissions account for the other 33% and arise from biological processes in living organisms. However, human activities can amplify biogenic emissions, as seen with permafrost release, which would not occur in the absence of temperature increases driven by human activities.
Methane is a potent greenhouse gas that contributes to around 20% of global anthropogenic greenhouse emissions in 2024. It is a short-lived greenhouse gas with a global warming potential 27.9 times higher than CO2. Additionally, methane contributes to the formation of ground-level ozone, which affects human health and crop yields.
Methane from Energy
The energy sector is a significant source of methane emissions through the use of coal, oil, natural gas, and biomass sources. Methane leaks along the entire fossil fuel supply chain, from extraction to processing and distribution, as well as during combustion. Incomplete combustion of bioenergy also generates methane, as shown in the “Methane emissions from energy by source” graph below (under Graphs > Greenhouse Gas Emissions > Methane).
There are two ways to reduce methane emissions from energy: 1) decreasing fossil fuel and bioenergy consumption, and 2) implementing improved practices to reduce methane leakage across the fossil fuel supply chain.
To calculate methane emissions from energy, En-ROADS distinguishes between the scale of total production of Primary Energy from Fossil Fuels (graph above on the left) and the Methane Intensity of Primary Energy (graph above on the right). En-ROADS calculates the emissions rate due to leakage and off-gassing from fossil fuel infrastructure, which can change as infrastructure is replaced or retrofitted. En-ROADS also calculates the methane produced by incomplete combustion, which occurs in bioenergy and certain fossil fuel applications. The methane intensity of primary energy is calculated from the ratio of these emissions to primary energy demand.
Users can simulate a reduction in coal, oil, natural gas, and bioenergy production through policies such as taxes, carbon pricing, electrification, energy efficiency, and renewables subsidies, distributed across the simulator interface. Any action that reduces these energy sources, helps to reduce methane emissions.
Even when production of coal, oil, natural gas, and bioenergy production is unchanged, methane emissions can be reduced through the production process from extraction to combustion through implementing emissions best practices. The result is a lower methane intensity for energy. Users can adjust either the Waste and Leakage slider, which will change intensity for both energy and the waste sector, or the "Methane leakage from energy systems” slider in the advanced view to just focus on energy infrastructure. The adoption of best practices, such as leak detection and repair, improved flaring practices, and capture technologies at coal mines, affects the methane intensity of primary energy. More details are available in the User Guide.
Methane from Agriculture
Methane emissions from the agricultural sector come from crops (e.g., rice) and livestock (e.g., enteric fermentation in cows, and manure).
There are two ways to reduce agricultural methane emissions: 1) reducing total agricultural production by shifting to plant-based diets and reducing food waste, and 2) implementing improved practices that minimize the amount of methane released per ton of agricultural production.
To calculate anthropogenic methane emissions from agriculture, En-ROADS distinguishes between the scale of Total Agricultural Production (graph above on the left) and the Methane Intensity of Agriculture (graph above on the right). The amount of crop and livestock production times their respective emissions factors, results in the methane emissions from each which are added together to get total methane from agriculture, shown as the yellow wedge in the Methane Emissions by Source graph below.
Users can affect the scale of Total Agricultural Production, by modifying the percentage of food waste and food from animals, in the advanced view of the Agricultural Emissions slider. Economic growth and population also influence the total agricultural production, since increased food demand and higher meat consumption typically accompany rising wealth levels and a growing population. It is important to note that while methane emissions from agriculture can be reduced, they cannot be fully eliminated because it is intrinsic to any kind of food production.
Users can also simulate the adoption of emissions best management practices and technological improvements in the agricultural sector, by using the Agricultural Emissions slider on the main screen, or the detailed settings in the advanced view. These actions reduce methane—as well as nitrous oxide—emissions from livestock and crop production.
For livestock, the solutions with highest mitigation potential are manure management and reducing enteric fermentation in livestock through methods like enhanced livestock health, diet optimization, genetic selection, and feed additives.
For crops, best practices include improved rice cultivation techniques to manage water, and sustainable agricultural practices such as rotational grazing, crop rotation, and soil health management.
Methane from Waste
Waste production is the third contributor of anthropogenic methane emissions, originating from landfills and wastewater.
To reduce methane emissions from waste, users can simulate the adoption of emissions best practices and technologies that tackle both waste generation and greenhouse gas emissions from the waste.Users can affect emissions from waste by using the Waste and Leakage slider on the main screen and the "Methane and nitrous oxide from waste" slider in the advanced view. En-ROADS shows the effects of these policies in the brown wedge of the Methane Emissions by Source graph (graph below on the left), and the Methane Intensity of Waste (graph below on the right).
When one of the En-ROADS sliders for waste is moved it simulates policies and practices that reduce waste generation at the source. This includes practices and technological improvements like reduced consumption, recycling, and diverting organic waste from landfills by composting. Additionally, practices in landfills and wastewater treatments can reduce the methane intensity of the waste produced, and includes various methods like aeration systems, sludge management, advanced bioreactors, landfill gas capture, and waste-to-energy.
Key Dynamics for Methane Emissions
- Diffusion dynamics. Best practices require time for development, improvement, and implementation, along with the necessary policy support for adoption. By default, achieving most of the target reductions for methane, nitrous oxide, and F-gases through the adoption of best practices takes 30 years to complete. For certain practices, such as the adoption of subsidized farm practices, the timeframe can range from 10 to 60 years. Users have the option to adjust the default adoption time using the "Years to achieve…" sliders in the advanced views of Agricultural Emissions and Waste and Leakage.
- Capital stock turnover delays. The retirement and replacement of higher-emitting infrastructure (e.g., power plants, fuel processing facilities, and industrial plants) with new, lower-emitting capital or retrofitting them to reduce emissions also takes time.
- Scale and intensity. There are two ways to change emissions: decrease the overall scale of production, and decrease the emissions intensity of that production through adoption of best management practices.
Advanced Features
In addition to the graphs and sliders featured above, here are a few others that are helpful for testing the policies to reduce methane emissions.
“Methane Intensity of GDP” graph
The "Methane Intensity of GDP" graph (below) displays the amount of methane emitted for every million dollars of global GDP, reflecting how much economic growth is tied to methane emissions. When we switch away from methane-emitting sources (e.g. using renewables instead of natural gas) and/or decrease methane emitted per unit of production, the economy can maintain the same level of products and services while generating fewer methane emissions.
“Methane Emissions per Capita” graph
The "Methane Emissions per Capita" graph (below) shows the amount of methane emitted per person, per year. This measure can be reduced with all actions that tackle methane emissions from energy, agriculture, and waste.
“Max potential abatement of new capacity” slider
The "Max potential abatement of new capacity" slider (under Simulation > Assumptions > Energy > Methane Leakage) controls the maximum abatement potential of new fossil fuel infrastructure, by default set at 60%, to change within a range of 40-80%, set to be consistent with IEA's Methane Tracker (2023).
Tipping points related to biogenic methane emissions
Feedback and tipping points related to biogenic methane emissions are integrated into the simulator.
- The "Effect of temperature on CH4 respiration rates" (under Simulation > Assumptions > Land carbon and methane cycles) represents a feedback mechanism whereby temperature increases resulting from human activities influence the rates of methane release from biomass and soil anaerobic respiration.
- "Temperature threshold for permafrost and clathrates" (under Simulation > Assumptions > Land carbon and methane cycles) represents a tipping point. When the temperature surpasses the threshold specified, emissions from permafrost and clathrates begin to increase linearly with temperature, triggering a reinforcing feedback loop that results in additional temperature rise and increased thawing. For more details on how to simulate this and other tipping points, read here.
