We need some quick wins to limit the impacts of climate change. Targeting methane, the second most potent greenhouse gas, could buy us time while we get our act together to cut CO2
We need some quick wins to limit the impacts of climate change. Targeting methane, the second most potent greenhouse gas, could buy us time while we get our act together to cut CO2
By Mark Rowe
What do we do with a problem like methane? On the back of nine successive record-warming months, attention is turning to meaningful ways to address climate change’s second most important gas. While CO2 accounts for 66 per cent of the increase in heat to the world’s surface, methane emissions contribute 16 per cent. Despite its smaller market share of climate change emissions, methane has accounted for roughly 30 per cent of global warming since pre-industrial times, according to the US National Oceanic and Atmospheric Administration, and is proliferating faster than at any other time since record-keeping began in the 1980s. Even as CO2 emissions decelerated during the pandemic-related lockdowns of 2020, atmospheric methane shot up and now stands at its highest level for 800,000 years. Methane was present at 800 parts per billion (ppb) in the pre-industrial atmosphere; today, the figure is 1,800 ppb.
### POTENT BUT SHORTER-LIVED
Methane (CH4) odourless, colourless and flammable, is the main component of fossil gas. It’s far more potent than CO2, even though it lingers for less time in the atmosphere. Methane absorbs heat in a narrow stretch of the infrared spectrum known as the ‘atmospheric window region’, an area avoided by CO2 and where heat can usually escape to space most easily. ‘On a per molecule basis, methane is much more efficient at absorbing radiation that would otherwise escape to space than CO2,’ says Fiona O’Connor, science fellow at the Met Office. The CO2 we emit today will continue warming our planet for up to 100,000 years, but methane only lasts for around 12 years. Over a timescale of one century, methane is 28 times worse than CO2; over 20 years, however, it’s 80 times worse. ‘Emissions of CO2 may have been larger in the historical record [when expressed in terms of mass of carbon, methane’s emissions are the equivalent of about three per cent of CO2 emissions], but methane’s change in abundance and radiative efficiency make it a problem,’ adds O’Connor.
### THE BIG THAW
Our warming planet is driving the thawing of permafrost at high latitudes. Vast swathes of the tundra in Siberia and Canada are starting to thaw. ‘When permafrost thaws, you are seeing a lot of carbon and methane released, and we know the Arctic is warming to a larger extent than the mean,’ says Fiona O’Connor of the Met Office. Recent data indicate that the isotopic signatures of anthropogenic-driven methane – markers that identify the provenance of the gas – may be changing, suggesting that a combination of livestock and wetlands, rather than fossil fuels, is becoming the greater driver. ‘It’s possible the projections of permafrost methane release are vastly underestimated,’ says O’Connor. In such a context, the race to develop means to capture methane, rather than turn it off at source, may become vital.
### SLOWING THE WARMING
Methane’s relatively short lifespan gives it potential as a quick, easy win for the climate. Cutting methane emissions won’t halt climate change but will slow down the rate at which the Earth heats up. This is particularly so in the short to medium term, according to the Intergovernmental Panel on Climate Change, the United Nations Environment Programme (UNEP) and the Climate and Clean Air Coalition.
‘Methane has warming super-powers,’ says Rob Jackson, professor of energy and environment at Stanford’s School of Earth, Energy & Environmental Sciences. ‘But among greenhouse gases, methane is short-lived. Because of this shorter lifetime, methane is the only greenhouse gas that gives us the chance to slow warming in a timely fashion.’
In its 2021 Global Methane Assessment, UNEP found that human-caused methane emissions could be reduced by as much as 45 per cent within a decade. This would avert nearly 0.3°C of global warming by 2045, helping to limit global temperature rise to 1.5˚C and giving humanity a chance of meeting the Paris Agreement targets.
In March this year, the UK’s House of Lords Environment and Climate Change Committee launched a parliamentary inquiry into methane, seeking to explore the UK’s progress on its existing commitments to reduce domestic methane emissions, and what further progress can be made in relation to UK methane emissions in agriculture, waste and waste management, and fossil fuels.
All this represents something of a volte-face among international decision makers. Natural gas emits half as much carbon per kilowatt as coal, so methane has been seen as ‘cleaner’, or less polluting and therefore preferable to coal and oil. The EU even endorsed labelling some natural gas projects as ‘green’. Now, a UNEP spokesperson points out: ‘Without relying on future massive-scale deployment of unproven carbon-removal technologies, expansion of natural gas infrastructure and usage is incompatible with keeping warming to 1.5°C.’
Jackson’s new model – developed by the UK Met Office – examines methane removal’s potential impacts while accounting for its shorter lifetime compared to CO2. Under a high-emissions scenario, analysis showed that a 40 per cent reduction in global methane emissions by 2050 would lead to a temperature reduction of about 0.4°C. Under a low-emissions scenario, methane removal of the same magnitude could reduce the peak temperature by up to 1°C.
A reduction in atmospheric methane brings other benefits. Methane is shorter-lived because it’s much more reactive, so is converted to CO2, water vapour and ozone. All three of these are greenhouse gases, but ground-level ozone is also a hazardous air pollutant and greenhouse gas. Reducing anthropogenic methane would reduce ozone levels enough to prevent roughly 260,000 premature deaths a year and 775,000 asthma-related hospital visits. Its impact on global warming could save 73 billion hours of lost labour from extreme heat and 25 million tonnes of crop losses. ‘Methane mitigation is a win–win for the climate and for air quality,’ says O’Connor.
### KEY HUMAN-DRIVEN RESOURCES
Cutting methane is a feasible option because 60 per cent of atmospheric methane is human-driven. Primary culprits include agricultural sources such as livestock, which emit methane in their breath and manure, and rice fields, which produce methane when flooded. Food waste, landfills and fossil fuel extraction also contribute substantial emissions. The remaining 40 per cent of methane arises from natural sources such as soil microbes in wetlands.
The focus on tackling methane is on stopping emissions at source in the human-driven sectors, and less on capturing it. As with carbon capture and storage, the technology for extracting methane from the air is unproven and even more nascent. Methane is challenging to capture from air partly because its concentration is so low, and its physical characteristics make it all the more difficult to capture. ‘Methane is a stubborn molecule,’ says Jackson. ‘It’s symmetrical, so there’s nothing that sticks out to latch onto. It’s non-polar, so you can’t use a charge to attract it. It’s about the same size as the common nitrogen molecule, so you can’t filter it from the air easily based on its size. Chemically, it’s a beast.’
### IN NUMBERS
– Atmospheric methane concentrations have more than doubled in the past 200 years (Nasa Earth Observatory)
– Methane is around 30 times more potent than CO2 (over the span of a century) (Nasa Giss Science Brief)
– The oil and gas industry burned just under 140 billion cubic metres of gas in 2022 – enough to power the whole of Africa (World Bank)
A class of crystalline materials called zeolites, capable of soaking up the gas, hold the promise of a solution, says Jackson, but this requires funding to see how technology could scale up and evaluate the costs and negative byproducts. ‘Carbon dioxide removal has received billions of dollars of investments, with dozens of companies formed. We need similar commitments for methane removal,’ says Jackson. ‘Literally, we can extract methane from the atmosphere. Cost-effectively, the answer is no.’
The emphasis needs to be on those quick wins, he adds. ‘Keeping methane out of the air will always be cheaper than removing it later,’ he reasons. ‘Think of a drop of food colouring. If you need clear water, blotting a drop of food colouring before it hits the water will always be cheaper than filtering it from a swimming pool.’
### PLUG THE LEAKS
Unsurprisingly, the oil and gas sector is in the crosshairs. In 2022, thousands of gas flares at oil-production sites worldwide burned about 139 billion cubic metres of gas in 2022 – 350 million tons of CO2 equivalent, more than enough to power all of Africa. Flared gases – resulting from the inefficiency of the flare combustion process – emit a potent mix of CO2, methane and black soot, which pollute the air and accelerate global warming.
‘Flaring methane is a market failure,’ says Jackson. ‘No-one likes it – not oil companies, regulators, nor the public. Companies do it because they’re allowed to and because it’s better than doing nothing. But it’s a colossal waste of energy. It should be banned.’
Tackling methane flaring would go some way to underpinning the overhaul of the global energy system by 2030 set out by Paris and reinforced by Dubai. The practice was the focus of an agreement at COP28 in the UAE, where 29 national oil companies, representing 40 per cent of global oil production, signed the Oil and Gas Decarbonization Charter for near-zero methane emissions. This agreement was given a cautious, wry welcome by Inger Andersen, executive director of UNEP. ‘Transparency is going to be critical because trust is low,’ she said. ‘Sure, companies are saying the right things. Yet the coal, oil and gas production planned for 2030 is more than double the levels consistent with 1.5°C. It would require serious mental gymnastics for oil and gas companies to convince themselves they are doing all they can for the climate.’ The World Bank has established a US$250 million trust fund to provide a financial incentive for oil and gas companies to avoid flaring. A number of companies, including Chevron and Exxon Mobil, have so far declined to cough up for the fund.
### LACK OF TRUST
Not all leaks are down to error, points out Drew Shindell, chair of the Science Advisory Panel Climate and Clean Air Coalition. ‘We need to change practices that lead to deliberate releases, which are required for maintenance, due to lack of infrastructure to handle gas at oil operations. These companies are making so much money on extraction that many of them don’t care about anything else, and they’ll even ignore methane controls that pay for themselves in a short time. We need regulations to force them to use the best available technologies, which takes political will to regulate.’
UNEP is clear about how the industry needs to clean up its act, reduce methane at the point of emission and along production/transmission lines: upstream and downstream leak detection and repair; recovery and utilisation of vented gas; capture of associated gas from oil wells; regular inspections; recovery and utilisation of vented gas with vapour recovery units and well plungers; and flooding abandoned coal mines. Targeted technology for these steps is readily available, says UNEP.
More widely, 155 countries have signed up to the 2021 Glasgow climate summit’s Global Methane Pledge, committing to a 30 per cent cut from 2020 methane emissions levels by 2030. Few have detailed how they will achieve this. Ahead of COP28, the world’s biggest emitters – the EU, USA and China – aligned on commitments around methane-emission reductions. The USA announced standards that are expected to cut its methane emissions by nearly 80 per cent by 2030. China is by far the biggest methane emitter, producing more than 14 per cent of global methane emissions, and has said it will include methane and non-carbon-dioxide greenhouse gases in its 2035 national climate plan – but it hasn’t issued any firm targets for reducing those emissions, only goals for re-using them as fuel. ‘We really need strong action from major emitters around the world,’ says Shindell, pointing to China, India, Brazil and Russia. ‘The signs there aren’t yet very clear. Only Brazil has joined the Global Methane Pledge.’
### RE-USE, RECYCLE, REDIRECT
Re-using or re-directing methane from flaring could save more than 700 million tonnes of CO2 every year, according to UNEP. ‘As a mitigation measure, it makes sense to capture the methane and use it as a fuel,’ says O’Connor. One option being explored by companies such as Siemens is for methane captured from flaring to be utilised to power energy-hungry data centres. By 2025, the amount of data produced by the world is projected to reach 181 zettabytes (one zettabyte is equivalent to one trillion gigabytes).
Methane produced by food decomposing in landfills – where nourishing elements and the lack of oxygen encourage methane-producing bacteria to thrive – makes up 1.6 per cent of all human-made greenhouse gas emissions. ‘There are challenges of financing for some sectors, such as waste, for which some places don’t really have functioning municipal waste collection systems or well-managed landfills,’ says Shindell.
But this natural process of fermentation of biodegradable materials in the absence of oxygen, driven by micro-organisms called archaea, could be turned to the planet’s advantage, she suggests. The poor practice of dumping food waste in landfills could be replaced with collection and placing waste in a digester, enabling the methane to be used as a source of energy.
### THE PROBLEM WITH BURPING
Livestock production accounts for 31 per cent of global methane emissions. According to the European Environment Agency, within the EU, anthropogenic methane emissions comprise 27 per cent waste, 17 per cent fossil fuels, 55 per cent agriculture, of which 54 per cent is livestock. The need to address this is urgent, says UNEP, because population growth, economic development and urban migration have stimulated unprecedented demand for animal protein. Ruminants are the most methane-intense livestock because their digestive system (the rumen) allows them to digest cellulose-rich plants, such as grass and fodder through enteric fermentation. According to a 2023 Greenpeace report, Global Heating at Full Throttle, the burping of cows contributes to methane emissions in Europe to the tune of 5.7 million tonnes per year – as much as the total greenhouse gas emissions of 24 million Europeans.
The world needs to ‘rethink our approaches to agricultural cultivation and livestock production’, says a UNEP spokesperson, shift towards plant-rich diets and embrace alternative sources of protein. Scientists are also experimenting with alternative types of feed to reduce the methane produced by cows and looking at ways to manage manure more efficiently by covering it, composting it, or using it to produce biogas.
### GREEN GOLD
Innovative feeds are being explored in the quest to cut ruminant burping at scale. In Australia and New Zealand, an aquaculture innovation by the company CH4 Global, has developed formulated animal feed products based on asparagopsis, a red seaweed that has potent anti-methanogenic properties. Products such as ‘Methane Tamer’, which includes a natural supplement of asparagopsis, reduce methane emissions by up to 90 per cent if given in small daily amounts,’ according to CH4 Global. The organisation says it’s rapidly building capacity and has a goal of reaching 150 million beef and dairy cattle – ten per cent of the world total – on all continents by 2030. This would prevent the emission of one gigaton of CO2 equivalent, or more climate benefit than decommissioning 50–100 million fossil-fuelled cars. Other companies are also studying asparagopsis, which can be grown in seawater tubes, in tanks or on land in ponds.
The same principle of methane-producing fermentation unfolds in paddy fields, which are traditionally continuously flooded. UNEP is encouraging alternate wetting and drying approaches that could halve emissions. Paddies could be irrigated and drained two to three times throughout the growing season, limiting methane production without affecting the yield. Such a process would also require one-third less water.
### ONE COW AT A TIME
In practice, some mitigations will be easier to implement than others, acknowledges Jackson. ‘Most methane emissions come from producing food and the sources individually are small,’ he says. ‘We don’t have a technology yet that eliminates methane from cow burps. We will soon, but even when we do, we’ll have to treat 1.5 billion cows, one at a time, daily, maybe weekly. That’s much harder than turning a wrench on a giant gas leak in an oil field.’ Shindell recognises that this practical roadblock means that ‘ruminants are not a low-hanging fruit. The obvious solution, fewer cows, is the most effective but it’s a slow process to change an embedded behaviour like raising beef and dairy cows.’
O’Connor expresses optimism that tools and knowledge are falling into place to inform decision-makers who choose to act in a meaningful way. ‘Satellites are providing fantastic information for targeting sources of methane leaks,’ she says. International regulations increasingly categorise methane as a regulated gas, although arguably not quickly enough. ‘The Global Methane Pledge is a positive initiative. I think we are building sufficient information to guide the mitigation process. In many cases, the costs are not high, they may even be negative.’
Jackson has more sympathy for governments when it comes to food and the quandaries they face. ‘Cutting emissions from fossil fuel use is a matter of political appetite, which descends into arguments about, “Our operations are already cleaner than their operations”,’ he suggests. ‘Climate solutions are more complicated when they’re tied to food security, to beef and rice production. Suggesting an American eat less beef is different than telling an Eritrean, where protein deficiency often still harms children.’
Methane reduction can happen quickly, says O’Connor, but should not be an excuse for inaction on CO2. ‘If we don’t act on CO2, then these actions buy us two or three decades. Methane mitigation will temporarily slow the rate of warming and delay peak temperatures. But the long-term rate of warming will still be determined by the cumulative emissions of CO2. The gains will be relatively short-lived.’
Shindell agrees that the spotlight must be on both gases. ‘We have done such a poor job of addressing greenhouse gas emissions that we’re now seeing damage around the world in heatwave, fires, severe storms. So, we are now unable to solve our problem by dealing with either gas alone and we have to dramatically reduce emissions of both CO2 and methane.’
### EYES IN THE SKY
In a step intended to make the oil and gas sector more accountable, an observation satellite, appropriately called MethaneSAT, was launched in March this year by the New Zealand Space Agency and the Environmental Defense Fund, a US organisation. Carrying a high-performance spectrometer