Among the greenhouse gases contributing to global warming, methane (CH4) has the potential to be transformative in efforts to curb emission levels. Though it has greater warming potential than carbon dioxide (CO2), it is, in comparison, short-lived in the atmosphere so can be part of the solution. Combating the methane question – that is, how to make the most of this potential solution – will play a vital role in efforts to prevent climate change escalating further.
The United Nations Environment Programme (UNEP) Emissions Gap Report 2021 states that methane has a warming potential over 80 times that of CO2 in the short term. Annual global emissions of methane are currently estimated at 365 megatonnes (Mt), according to the report. Considering the potential for warming is much greater than that of carbon dioxide in the near term, the concern over unrestricted emissions is clear. Concentrating too heavily on CO2, rather than looking at greenhouse gases as a whole, will not go far enough to keep warming below the agreed 1.5°C limit.
Around the world, there are three primary sources of methane emissions: fossil fuels, waste and agriculture, which contribute the greatest share of anthropological emissions of methane. In the short term, cutting emissions from these areas could prove to be the “most effective means available” in reducing warming, as a report from the International Energy Agency (IEA) describes. The potential for quick results from emissions reductions is down to the properties of the gas itself. Unlike CO2, CH4 is not long-lived in the atmosphere – it breaks down after around 15 years, whereas carbon dioxide remains present for anywhere between 300 and 1000 years, thus a rapid reduction in warming is possible due to this short atmospheric lifespan.
Agriculture contributes the greatest share of methane at 40%. The rearing of cattle for meat and dairy products is a well-known contributor, but paddy rice cultivation at scale is also having a big impact. Work is already under way in the livestock sector to develop feed additives to reduce methane emissions from cattle, with considerable potential reductions identified in early testing. However, just reducing the emissions per animal may not be enough; potential reductions in herd size and improved efficiency of production are also needed. In paddy rice production, different approaches to flooding and management of the systems to control anaerobic bacteria growth are being developed to support lower methane production. As consumers, we need to consider how frequently and how much of these products we consume to support the lowering of methane emissions as a whole.
Fossil fuel processing accounts for 35% of anthropogenic methane and there are a number of low-cost solutions available that would support reductions in these emissions, for example, improvements to the efficiency of these processes would prevent leakages in the system. A significant volume of methane is emitted due to leaks in the production and supply of fossil fuel products. The extraction, processing and distribution for oil and gas result in emissions, 70% of which the IEA estimates are “technically feasible to prevent”. Ahead of cutting our fossil fuel use altogether, reducing the potential for losses and reusing resources that are leaked could result in a 40–50% emissions reduction, by UNEP estimates.
The last of the big three methane emitters is landfill waste at 20% of total anthropogenic emissions. Waste material that sits in landfill sites, particularly organic waste, breaks down over time, releasing methane in the process. The practice of burning waste that otherwise would have been disposed of in landfill is also a notable source, the better management of which would limit emission levels. When considered as a fuel source, the emissions captured from burning waste for use as power could present a potential solution. Utilising this potential energy source will also offer the opportunity to displace the current use of natural gas in some contexts. Simple changes to practices, such as ensuring food waste is separately processed and is redirected to compost or biofuel, will contribute directly to reducing the emissions from global landfill sites.
The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report, published earlier this year, observes that “strong rapid and sustained” reductions in methane levels would have considerable limiting potential on warming effects. With a concerted effort, and at a low cost, it is possible to significantly reduce methane emissions across these three sectors. The UNEP report estimates that taking rapid action now could result in a reduction in global warming by around 0.3°C by 2050, and if sustained, up to 0.8°C in the longer term.
The potential environmental benefit of action is clear; the methane question, and how to maximise the opportunity presented by it, will play a determining role in our efforts to limit the extent of future warming. Will the Global Methane Pledge, signed by 103 nations at COP26 representing 70% of the global economy, be enough? Only action will tell.