Cutting human-caused methane emissions is one of the most cost-effective ways to rapidly reduce the rate of global warming, a new report from the United Nations (UN) has said.
Fossil fuels, waste and agriculture are the three main human-related sectors that contribute to global methane emissions.
Targeted methane reduction measures can help reduce human-caused methane emissions by as much as 45%, or 180 million tonnes a year (Mt/yr) by 2030.
This will avoid almost 0.3°C of global warming by the 2040s and complement all long-term climate change mitigation efforts, according to the UN’s Environment Programme report Global Methane Assessment: Benefits and Costs of Mitigating Methane Emissions.
Such action would also prevent 255,000 premature deaths, 775,000 asthma-related hospital visits, 73bn hours of lost labour from extreme heat and 26m tonnes of crop losses globally, according to the report.
More than half of global methane emissions come from human activities in three sectors: fossil fuels (35% of human-caused emissions), waste (20%) and agriculture (40%).
In the fossil fuel sector, oil and gas extraction, processing and distribution account for 23%, and coal mining accounts for 12% of emissions.
In the waste sector, landfills and wastewater make up about 20% of global anthropogenic (human-caused) emissions.
In the agricultural sector, livestock emissions from manure and enteric fermentation represent roughly 32%, and rice cultivation 8% of global anthropogenic emissions.
In the agriculture sector, continued growth in the number of ruminant animals, due to rising demand for meat from an increasing and increasingly affluent global population, will drive increases in emissions from enteric fermentation and manure management of around 6 Mt/yr.
The UN report says that existing targeted measures could reduce methane emissions from the agricultural sector by around 30Mt/yr by 2030.
Methane emissions from rice cultivation could be reduced by 6 to 9Mt/yr.
However, the mitigation potentials from livestock are less consistent, ranging from 4 to 42Mt/yr.
It said that behavioural change measures and innovative policies are particularly important to prevent emissions from agriculture, given the limited potential to address the sector’s methane emissions through technological measures.
Three behavioural changes - reducing food waste and loss; improving livestock management; and the adoption of healthy diets (vegetarian or with a lower meat and dairy content, where their intake is above the recommended guidelines) - could reduce methane emissions by 65 to 80Mt/yr over the next few decades.
The UN report outlines a number of ways to reduce enteric fermentation in cattle, sheep and other ruminants, such as:
Livestock manure management measures it recommends include:
For rice paddies, the measures to be tackle include:
Methane (CH4 ) is a powerful greenhouse gas.
It is a short-lived climate pollutant with an atmospheric lifetime of roughly a decade.
It contributes to the formation of tropospheric ozone, which, like methane, is a short-lived but powerful greenhouse gas, and surface ozone is also an air pollutant with detrimental effects on people, ecosystems and crops.
The amount of atmospheric methane has more than doubled since pre-industrial times.
It has been second only to carbon dioxide in driving climate change during the industrial era.