Fugitive Emissions from Energy Production

Source: World Resources Institute, via Our World in Data

When we burn fossil methane, it produces only half as much CO2 as coal does, and fewer harmful pollutants like SOx and NOx. This is why the oil and gas industry, whose PR execs branded fossil methane the friendly-sounding name “natural gas,” has been able to tout it as a “bridge fuel” between the coal-burning past and a future powered entirely by zero-carbon energy sources. However, this story leaves an important feature of methane out of the picture: at every step of its journey from gas wells to homes, businesses, powerplants and factories, it leaks.

This “fugitive,” uncombusted methane escaping into the atmosphere is a powerful greenhouse gas. When we count upstream emissions of fugitive methane together with the CO2 emitted when methane is burned, methane can be just as bad for the planet as coal, or worse.

How big a problem is fugitive methane? If we look at the emissions pie chart above, which we have been taking as our guide throughout this site, we get what looks like a clear answer: according to this chart, fugitive emissions from energy production constituted 5.8% of global GHG emissions in 2016. However, there are two reasons to think fugitive methane emissions from the energy system might pose a much larger climate danger than this figure indicates:

  1. Unmeasured fugitive emissions
  2. Methane’s effect on near-term warming

Unmeasured fugitive emissions

Methane leaks when it is extracted from wells (and also when oil or coal is taken out of the earth); it leaks when it is compressed, when it travels through bulk-transmission pipelines, and when it travels through the complicated network of smaller pipes under our roads that distribute it to homes and businesses in cities and suburbs; and it leaks inside our homes, businesses and factories. And when wells are abandoned at the end of their life, many are never properly sealed, and so continue to leak indefinitely.

Credit: Global Energy Monitor

How much methane leaks from all of these sources? Until very recently, we had very little idea. Methane is odorless and invisible to the human eye. (When you smell gas in your home, that’s because local gas distribution utilities have added a chemical so that you can detect it.) The US EPA and other regulators rely almost entirely on engineering estimates of leakage rates from gas companies.

However, in the last few years, technologies like infrared cameras on drones and satellites have made it much easier to see leaks in real time, and scientists have begun to use these tools for empirical studies.

Source: PBS

Source: MethaneSat

Over and over, each time scientists have looked at a new part of the energy system, they have found leakage rates that are much higher – often multiple times higher – than had been estimated. Even inside homes, scientists have found that stoves leak gas when they are turned off, and that in addition to methane, the leaked gas contains a cocktail of more than 20 known toxins including benzene, a powerful carcinogen. Because leaks are distributed at every point of a huge system (including underground distribution networks), we still do not have a full picture. But each new study has ratcheted our estimates of overall leakage up further.

The trend of these studies helps to make sense of something we can measure: the rapidly increasing concentration of methane in the atmosphere. This methane comes from many sources. (Cattle and rice-farming are also large and increasing human-caused sources of methane, which we discuss separately on our page on Agriculture, Forestry and Other Land Use; so are liquid and solid waste, including in landfills, which we discuss in our page Waste; and there are natural sources, too, such as decaying organic matter in wetlands, which climate change may be exacerbating.) But given the rapid growth in total atmospheric methane, there is reason to suspect that the energy system may be playing a larger role than estimates had allowed.

Credit: Bloomberg

Methane’s effect on near-term warming

The pie chart at the top of the page converts methane emissions and other GHG emissions into CO2-equivalents (CO2-eq). It does this by comparing the total global warming potential (GWP) of a ton of methane (or other GHG) over a 100-year period (that is, how much energy from the sun that ton of methane or other GHG will trap over 100 years) with the total GWP of a ton of CO2 over the same, 100-year period. This basis for comparison is called GWP-100. It is the measure that is used by most governments, as well as by the pie chart above, to establish the CO2-equivalent of a ton of other GHGs. In the most recent (AR6) report of the International Panel on Climate Change (IPCC), the GWP-100 of methane was calculated as 27.9. That is to say, measured over a 100-year period, one ton of methane is equivalent to 27.9 tons of CO2. This is a useful comparison; however the choice of any single measure, reflecting any single time horizon, obscures important differences between CO2 and methane (and other GHGs).

CO2 is very stable. It does not break down chemically in the atmosphere, and it remains there until it is eventually absorbed into a carbon sink. Most of a ton of CO2 will remain in the atmosphere for hundreds of years, and a fraction of it will remain for thousands of years. As long as those CO2 molecules are in the atmosphere, they will continue trapping energy from the sun.

By contrast, methane is a very short-lived GHG. Most of a ton will break down chemically (into CO2 and water) within about twelve years of being emitted. Once it has broken down, it will no longer contribute to warming (except as CO2).

Credit:  EDF, from IPCC data

This difference cuts two ways. If we want to think about the very long-term effect of our emissions, then we will want to compare methane and CO2 on long time scales. In fact, the 6th IPCC report calculates the GWP-500 of methane (the warming potential of a ton of methane over 500 years) as only 7.95. If we used this number to calculate the CO2-eq of the world’s (estimated) fugitive emissions, we would see them making a pretty small contribution to 500-year warming, and so occupying a much smaller sliver of the emissions pie chart at the top of this page. From this 500-year perspective, fugitive methane looks less bad.

On the other hand, if we think that warming in the near-term is important, we would want to compare warming from methane and CO2 over a much shorter time horizon. The IPCC calculates the GWP-20 of methane as 81.2. If we used this figure to calculate CO-eq, we would see fugitive methane as a much greater contributor to (near-term) warming, occupying a much bigger chunk of the pie chart – even with the likely underestimate of the amount of fugitive methane. Looking at GWP on a short time scale helps us see that a ton of methane hits the climate hard and fast.

There’s no single right time frame to use, and so there’s no single, right measure of CO2-equivalance for different GHGs. But we do have some very good reasons to care a lot about near-term warming, and so to pay attention to measures with a short time horizon, like GWP-20. (New York’s Climate Law, the CLCPA, uses GWP-20, instead of the more common GWP-100, because it recognizes the importance of near-term warming.)

Look at these two “conceptual pathways” from the IPCC’s 2018 special report, Global Warming of 1.5°.

Credit: IPCC

On both of these pathways, the world will limit warming to 1.5° by the end of the century; but on the second, “overshoot” pathway, the world exceeds 1.5° in the near term, before returning to 1.5° later on. The second pathway will see more disasters of all kinds for human beings in the near term: deadly heat waves and other extreme weather events; droughts and famines; millions of people forced to migrate as their homes become uninhabitable, and the social and political backlashes, instability, and wars that large-scale migration often gives rise to. More species will be driven to extinction on this pathway. And more natural systems will be pushed past tipping points, generating dangerous feedbacks. For instance, this pathways would see more forest fires, which would themselves release more CO2 into the atmosphere and so further accelerate climate change; it might see the Amazon rainforest turn into a savannah, and in so doing turn from a large carbon sink into a massive, additional source of CO2. These changes will make it harder to return to 1.5° at the end of the century, and they will mean that if we do manage to follow the second pathway back to 1.5°, much irreversible damage will have been done when we get there.

These reasons to care about near-term warming are reasons to view fugitive methane emissions as worse than their small place on the GWP-100-based pie-chart indicates: they make a larger contribution than the chart indicates to warming we should care about. This thought has a flip side. Because methane is short-lived in the atmosphere, rapidly cutting methane emissions now can have an immediate, powerful effect in the near term. In fact, cutting methane emissions in half, over the next decade, could cut global temperatures in 2040 by 0.3°C.

There is a further reason we need to cut near-term warming from methane, and so secure the rapid temperature cut that we can get by addressing it. Right now, we are polluting the atmosphere with large quantities of sulfur dioxide (SO2). This pollution counteracts the effects of GHGs, because SO2 molecules in the atmosphere reflect some of the sun’s energy back into space, keeping the earth cooler than it would otherwise be. If sulfur and other aerosol pollution were not in the atmosphere, the CO2, methane, and other GHGs already in the atmosphere would be enough to warm the earth well above 1.5°C. As it is, aerosol pollution masks about 0.4°C of that warming, so that we currently only experience around 1.3°C of warming.

Almost all SO2 comes from burning fossil fuels – especially coal and the dirtiest grades of oil. We need to stop burning these dirty fuels quickly, both because they contribute to climate change and because their pollution, including SO2, is responsible for an estimated eight million human deaths annually. SO2 has an atmospheric life of less than ten days, so SO2 pollution will disappear almost as soon as we stop burning these fuels. This means, however, that we will see a jump in temperatures to above 1.5°C as the warming from existing GHGs is unmasked – unless we can rapidly cut methane pollution (along with other short-lived GHGs) at the same time that we are cutting SO2. If we manage things well (and are lucky) these two effects might about cancel each other out, so that we can avoid a rapid spike in temperatures as we cut dangerous SO2 pollution. If we are to do this, we cannot use fossil methane as a “bridge fuel” between coal and renewables: we need to wind down our use of coal, oil, and methane at the same time.

⇒Listen to this super-illuminating interview with Erika Reinhardt, co-founder of Spark Climate.

What can we do?

So far, we’ve tried to show that there’s almost certainly more fugitive methane than we know, that it’s very bad because of its contribution to near-term warming, and that we need to get rid of it fast.

There are some reasons for optimism. At the COP26 Climate Conference in Glasgow in 2021, more than 90 countries signed on to a “Global Methane Pledge,” saying they would slash their methane emissions by 30% by 2030. The US Inflation Reduction Act, passed in 2022, charges polluters $900 per ton of methane released in 2024, rising to $1200 per ton in 2025; and in 2023, the US EPA enacted new regulations designed to slash fugitive emissions from oil and gas infrastructure by 80% over fifteen years. These pledges and regulations have real teeth, because a new generation of satellites launched by the Environmental Defense Fund, other non-profits, and governments are coming online with the capacity to detect methane leaks in real-time. And most leaks are, in fact, easy to fix – sometimes no more is required than a wrench.

⇒Listen to this interview with EDF’s Mark Brownstein about their new MethaneSat.

All of these tools are powerful; but it would be a mistake to think that they mean that we can fully clean up fossil methane – or, for that matter, biogenic methane (“Renewable Natural Gas,” or RNG) that is produced by bacteria breaking down organic material in anaerobic digesters. Satellites can detect large gas leaks, and drones and hand-held devices can detect some smaller ones. But it is unlikely that they will be able to catch the millions of smaller leaks (many of them in underground pipes) throughout the vast gas network; and millions of small leaks can still add up to large amounts.

Our takeaway: Methane is worse than it looks, and worse than the most commonly-used calculations show. The reasons rapidly to electrify everything, and to kick methane out of electricity generation, are stronger than many people appreciate.

⇒For more of the story, watch this amazing episode of Climate Town.