One fuel is a lump of carbon. Another is a gas combining four atoms of hydrogen with just one of carbon. It should be obvious which is worse for the climate. However, some dubious studies, and environmentalists’ enthusiasm to believe them, threaten to unleash bad policy.
Fortunately, a paper from my colleague Robert Kleinberg, at Columbia University’s Centre on Global Energy Policy, illuminates the issue. About two-thirds of global warming is currently driven by emissions of carbon dioxide from burning coal, oil, gas, forests and heating limestone to make cement.
But 20 per cent to 30 per cent of human-caused heating so far comes from methane, the main constituent of natural gas. The atmospheric concentration of carbon dioxide has now reached 421 parts per million (up from 280 ppm before the Industrial Revolution). Methane, meanwhile, is just 1.9 ppm, up from 0.7 ppm. But, molecule-for-molecule, it is a much more potent greenhouse gas.
Methane breaks down quickly to carbon dioxide – its average lifetime in the atmosphere is about 8-12 years. By contrast, once in the air, carbon dioxide sticks around from 300 to 1,000 years, according to Nasa. This leads to the use of a common benchmark, global warming potential, under which methane, tonne-for-tonne, creates about 85 times as much warming as carbon dioxide over twenty years, and about 33 times as much over 100 years.
When natural gas is produced, transported and used, some of it leaks. Flaring of unwanted gas, a by-product of oil extraction, is particularly bad, since not all of it combusts – part of the methane escapes. Some major oil producers, including Iraq, Iran, Russia – and areas of the US – have particularly bad records on flaring. Elsewhere, such as in Turkmenistan, outdated valves, wells and other parts of the system apparently leak seriously. Incidentally, coal mining also releases some methane, which escapes from the coal as it is brought to the surface.
This leads to the argument, most vocally propounded by Robert Howarth, a professor at the US’s Cornell University, that the climate impact of natural gas is worse than that of coal. His research reportedly influenced the decision of President Joe Biden’s administration in January to put a moratorium on approvals of new projects to export liquefied natural gas from the US.
Because of the energy-intensive liquefaction process and the lengthy supply chain via ships in which leakage may occur, liquefied natural gas production might indeed contribute more to the greenhouse effect than local use of gas transported by pipeline. But worse than coal?
The question has wider implications than just US LNG exports. How tightly will Europe regulate LNG, and might it end up restricting imports that do not meet its standards? Will Asia turn from its predominant coal to gas in partnership with renewables such as wind, solar and hydroelectricity as its transition mix? Could LNG from the Middle East gain an advantage?
Those betting on LNG’s success think it will help fuel Asia’s growth, clean up its skies, and reduce greenhouse gases in the medium term. Proponents include major companies with growth plans – Adnoc Gas, QatarEnergy, Oman LNG, Shell and others. In an alternative scenario, though, these methane leak concerns continue the current contradictory coal and clean energy combo.
Enter, Professor Howarth. His latest paper, published in October in Energy Science and Engineering, concludes that US LNG delivered to China has about twice the greenhouse gas footprint of consuming local Chinese coal. This contrasts with, for example, previous US government analysis finding that the footprint of LNG was more than 30 per cent lower. He concludes that “ending the use of LNG should be a global priority”.
A long-awaited US Department of Energy study is due to be released this week. Its conclusions could be important for US LNG in the long term, even if the incoming Trump administration ignores it.
There is indeed major uncertainty around these estimates, particularly the amount of methane that escapes at different points in the supply chain. Better measurement, including by drones and satellites, is beginning to resolve this.
However, crucial methodological choices tilt the conclusions one way or another. These crucial issues have been overlooked by most environmentalists and media reporting of the controversy. The Guardian newspaper, for example, ran a headline saying, “Exported gas produces far worse emissions than coal”.
A more balanced appraisal needs to consider three crucial factors. First, what is the fuel used for? For modern power plants, running on coal produces 2.4 times more carbon dioxide. For thermal uses such as industry and heating, coal yields 1.8 times the carbon dioxide as gas.
Second, the GWP is a crude and misleading metric. If we stop leaks, the methane problem will largely resolve itself within a couple of decades. But emitted carbon dioxide has loomed overhead for centuries. While cutting methane today is a vital route to easing short-term warming, the worst problems from climate change are going to manifest in the second half of this century.
Removing carbon dioxide from the atmosphere will be far more expensive than not putting it there in the first place. As Dr Kleinberg explains, a proper assessment of gas versus coal needs to use detailed climate models.
Third, much of the assessment of methane and LNG’s carbon footprint in general assumes that nothing better can be done. But modern practices can stop many methane leaks, use ship engines that don’t allow gas to slip through, and improve energy efficiency in liquefaction plants. In contrast, capturing emissions from end-use of coal or gas requires carbon capture and storage – costlier and more difficult for coal because of its higher carbon content and other contaminants.
The greenhouse gas intensity of export projects can be dramatically reduced by employing carbon capture and storage, as QatarEnergy’s new facilities will do, or powering them on nuclear and renewable electricity, as with Adnoc’s Ruwais plant. As Dr Kleinberg helpfully pointed out to me, the lower carbon footprint of such Middle Eastern LNG plants should be favourable for them, and weighted more heavily than methane.
Climate-conscious countries should set strict standards on the greenhouse gas footprint of their imported gas, and penalise or outright ban supplies that cannot comply. These standards should be applied not on a country basis but per-project or company, so that measurement improves, producers clean up their act, and good performers are rewarded.
Decisions on gas and LNG are too crucial for energy policy and climate futures to rely on broad-brush analyses, assumptions and misleading metrics.
Robin M. Mills is chief executive of Qamar Energy, and author of The Myth of the Oil Crisis
