Methane: Risk and Opportunity
The risk side of this question is pretty clear. Simply put, while there is much less methane in the atmosphere than carbon dioxide, it carries quite a global warming punch–roughly 28x that of CO2 over a 100-year timescale and 86x more over a 20 year one.
The opportunity comes from its shorter lifespan in our skies, approximately 12 years, vs carbon dioxide which can stay there for many hundreds of years. That means if we curtail the amount of methane going into the atmosphere now, it will have a significant impact in terms of reducing global warming in a relatively short time period. Before going into more detail on this, however, let’s get some of the basics established about methane.
What is methane?
It is a colorless, odorless, flammable gas - the simplest hydrocarbon, consisting of one carbon atom and four hydrogen ones: CH4.
Where does it come from?
Courtsey of CCA Coalition
Answer: from both natural and man-made sources.
Natural sources include decaying biological materials in swamps, forests and oceans.
Sources related to human activities include the production, transport and burning of fossil fuels (coal, natural gas, oil), the decay of organic material in municipal landfills, as well as emissions from livestock (particularly cattle) and other agricultural practices such as rice farming.
That human action is the main source of the problem can be seen in the fact that since the Industrial Revolution, methane concentrations in the atmosphere have risen by c.150%, accounting for an estimated 20% of the warming our planet has experienced since then.
Methane is flammable and is used as fuel worldwide. It is a principal component of natural gas. Burning methane in the presence of oxygen releases carbon dioxide and water. This in itself is obviously a contributor to global warming. But the greater damage comes from the direct release of methane via flaring of natural gas in the production process and leaks from pipelines. It is also released in large amounts along coal mining seams.
Global warming, a human-induced acceleration, could cause a major tipping point in terms of methane release if it leads to further melting of permafrost in the Arctic. Permafrost holds vast amounts of frozen biological material, literally billions of tons of carbon, which could be released as CO2 or methane as the region warms and soil thaws. The latest update to the Global Methane Budget, an international collaboration that estimates sources and sinks of methane around the world, suggests that, thankfully, this has not yet happened to any noticeable extent. Were it to do so, it could cause a “positive feedback loop” where more greenhouse gases are released as global temperatures rise, thus reinforcing the warming and so on. For more details, see this article.
Why is methane so harmful?
All greenhouse gases (GHGs) warm the Earth by absorbing energy and slowing the rate at which energy reflected from the planet’s surface escapes to space. In effect, they act like a blanket insulating the Earth. The more these gases build up in the atmosphere, the more they keep heat in, thus causing global warming.
Different GHGs have different effects on the Earth's warming primarily due to their varying ability to absorb energy (their "radiative efficiency"), and their lifetime - how long they stay in the atmosphere.
The Environmental Protection Agency (EPA) uses a measure called Global Warming Potential (GWP) to measure how much energy the emission of 1 ton of a gas will absorb over a given period of time relative to the emission of 1 ton of CO2. The larger the GWP, the more a given gas warms the Earth compared to CO2 over that time period. The time period usually used for GWPs is 100 years.
CO2, by definition, has a Global Warming Potential of 1. Methane is estimated to have a GWP of 28, ie its impact on climate change is 28x that of CO2 over 100 years. Over a 20 year period, it is 86x greater than CO2. Worse still, it also has indirect effects as it is a precursor to ozone, which is itself a greenhouse gas. Thus, despite its shorter atmospheric lifespan of only 12 years, methane packs a big punch due to its higher absorption of energy.
Note that the other main greenhouse gases have a much higher Global Warming Potential but occur in much smaller amounts. (See pie chart below.) Nitrous Oxide (N2O) has a GWP 265–298 times that of CO2 for a 100-year timescale and it tends to remain in the atmosphere for more than 100 years on average. Fluoridated gases like chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) are sometimes called high-GWP gases because, for a given amount of mass, they trap substantially more heat than CO2. The GWPs for these gases can be in the thousands or tens of thousands.
For a full discussion on the science, read this article.
What can we do to reduce methane pollution in the atmosphere?
Nothing can be done about natural sources of methane production. But we can cut methane emissions substantially in both the fossil fuel and agriculture industries. This is not rocket science and it is definitely within our grasp.
The fossil fuel industry: Of carrots and sticks
Legislate limits for methane leaks from pipelines and flaring by gas and oil producers. Follow this up with high-tech tracking via satellites and institute strict fines for exceeding allowed limits. That is the stick.
The carrot can come from tax incentives for good behavior and for innovative methods of reducing emissions. But it also should come from pure corporate self-interest: leaks and flaring are nothing but waste, literally burning money.
A lot of methane also leaks from poorly capped wells that have finished their useful life. Yet no fines are imposed on the companies responsible.
The Trump administration, true to form, withdrew nearly all curbs on methane emissions by the oil and gas industry and related infrastructure.
Thankfully, President Biden has pledged not only to restore those rules but to strengthen them. A bill has already made its way through the Senate to this end. And whereas the Obama legislation only put limits on new production facilities, the Biden administration plans to apply them to all oil and gas facilities and infrastructure. He has also proposed a major effort with federal funding to employ currently unemployed oil workers to properly cap leaking wells. In my view, that job should be forced onto and paid for by the offending companies. The same applies to stopping methane leaks from coal mines. But any progress on this issue is to be cheered.
It is worth noting too that the oil and gas industry itself is has seen the writing on the wall, with several companies being openly supportive of the Biden initiatives. Indeed, the oil industry group, the American Petroleum Institute, which lobbied aggressively to try to stop the Obama government’s policies, earlier this year said that it supports regulation of methane leaks.
The agricultural industry: Changing feed and farming techniques
Livestock produces significant amounts of methane as part of their normal digestion. Ruminants–cattle, buffalo, sheep, goats and camels–have a fore-stomach or rumen containing microbes called methanogens, which are capable of digesting coarse plant material but produce methane as a by-product. This methane is then released into the atmosphere by the animal belching.
Some fats and oils added to cattle feed have shown the ability to reduce methane emissions by 15-20% while also increasing food absorption.
Even better is the potential of seaweed as a feed additive. The Asparagopsis species of seaweed produces a bioactive compound called bromine which prevents the formation of methane by inhibiting a specific enzyme in the gut during the digestion of feed. Studies have suggested that using this seaweed in low volume (less than 1% in a feedlot trial) could reduce the production of enteric methane by more than 80% with positive benefits for feed conversion and overall meat productivity as well.
As for methane release caused by rice farming, studies have shown that full implementation of intermittent aeration of continually flooded paddies (known as alternate wetting and drying cultivation) could reduce emission by over 30%.
The good news: Methane is a problem we can deal with now!
All of the above are reasons for optimism. Some changes in law and technology are needed, but none are particularly difficult or beyond our reach.
Reducing CO2 emissions and increasing natural sinks to absorb it (planting forests both on land and at sea kelp, etc) must be a priority as well. But it is a very long-term process.
Tackling the methane challenge can be done now, and given its short life in the atmosphere, it can have a substantial impact on global warming in a relatively rapid timeframe.
The Global Methane Assessment, a scholarly work authored by the Climate and Clean Air Coalition of the UN Environmental Program in 2021 concludes that human-caused methane emissions can be reduced by up to 45% this decade. Such reductions would avoid nearly 0.3°C of global warming by 2045 and would be consistent with the Paris Climate Agreement’s goal to limit global temperature rise to 1.5 degrees Celsius (1.5˚C).
Specifically, the study estimates that emissions from coal mining and the oil and gas sector could be reduced by over 65% by preventing gas leakage during transmission and distribution, recovering and using gas at the production stage, and by pre-mine degasification and recovery of methane during coal mining.
In agriculture, their models agree with the studies mentioned above and conservatively suggest that rapid and large-scale implementation of improved livestock feeding strategies and increasing aeration of rice paddies could reduce their global methane emissions by 20-30% by 2030.
What can you do?
The key thing we as individuals can do is to put pressure on our political representatives to support and expand the methane legislation that the Biden administration and other governments are preparing at this very moment. If the USA acts (the world’s largest producer of oil and gas and one of the largest livestock producers), it could galvanize similar action from other countries, including China, the leading emitter of methane from coal mines.
Look online at planning for the UN Climate Conference in Glasgow in November and you will see that it has as its banner “Uniting the World to Combat Climate Change”. Let us hope it achieves this objective across a wide range of environmental areas. But the easiest to tackle is methane.
Sources:
https://www.britannica.com/science/methane
https://www.ccacoalition.org/en/slcps/methane
https://www.ccacoalition.org/en/activity/global-methane-assessment-benefits-and-costs-mitigating-methane-emissions
https://www.future-feed.com/
https://www.epa.gov/ghgemissions/overview-greenhouse-gases
https://www.epa.gov/ghgemissions/understanding-global-warming-potentials
https://www.carbonbrief.org/scientists-concerned-by-record-high-global-methane-emissions