Coal vs Natural Gas: Are They Equally Responsible For Global Warming?
While carbon dioxide emissions from natural gas combustion are only half as much as coal, methane leaks during processing and transportation of natural gas might offset that advantage
R.K. Singh, the Union Minister for Power, New and Renewable Energy, said on December 5, 2022 that natural gas is just as responsible as coal for global warming, if not more.
"In COP26 they added a line, they wanted to add… phase-out of coal. But thereafter India objected so they added phase-down of coal. …Now that was totally hypocritical and inequitable because coal is not the only fossil fuel which causes global warming. In fact, natural gas is responsible for as much global warming if not more, because of the methane factor," Singh said at Idea Exchange, an event organised by the Indian Express.
"We use one fossil fuel which we have, we have coal so we use it. [If] somebody has gas, that country uses gas… Now if you want transition you have to phase down all these fossil fuels, so why single out coal?," the minister added.
Singh's comments came after the 27th Conference of the Parties (COP27) – the largest international climate conference – held in Sharm el-Sheikh, Egypt from November 6-20, 2022. India had pushed for a phase-down of all fossil fuels, and not just coal, IndiaSpend reported in November 2022. But all countries did not agree to adding a phase down of all fossil fuels [such as oil and natural gas], and the final plan from COP27 reiterated the agreement at the 26th COP in 2021 on a coal phase-down and a phase-out of inefficient fossil fuel subsidies.
Coal is India's main source for electric power, accounting for nearly 50% of its installed power generation capacity. On the other hand, natural gas is the United States' top power source, with nearly 39% of the US's total energy generated through gas. Gas is also used extensively for heating by European countries and others that have extreme winters, IndiaSpend reported in November 2022.
So, does Singh's statement, that natural gas is as polluting as coal, check out? FactChecker looked at existing bodies of research and spoke to experts to delve into the various angles of the coal versus natural gas debate. Here's what we found.
In theory, natural gas is 'cleaner' than coal
When fuels such as coal, natural gas, or oil are burnt, they produce carbon dioxide (CO2), a heat-trapping greenhouse gas (GHG). Human-caused emissions of CO2 are among the primary causes of global warming. CO2 alone was responsible for about two-thirds of the total heating influence of all human-produced GHGs in 2021, according to the United States' National Oceanic and Atmospheric Administration.
In this respect, natural gas is less emission-intensive than coal – it releases almost half the amount of CO2 during combustion as compared to coal, showed an analysis comparing coal-fired and natural gas power plants in the US.
For India specifically, the 'lifecycle' GHG emissions from burning imported liquified natural gas (LNG) were lower than GHG emissions associated with coal-based power by 54%, a 2018 study by Delhi-based policy think-tank Council for Energy Environment and Water estimated.
Lifecycle analysis is used to assess the overall GHG impacts of a fuel – including each stage of its production, distribution, and use.
But, there is a challenge – methane emissions during natural gas production
During extraction, processing, storage and transmission, some portion of natural gas, which is primarily composed of methane, leaks into the atmosphere. This is the "methane factor" in natural gas that Singh was referring to.
But how much methane has to be lost for natural gas to lose its advantage over coal? There are different estimates, within the range of 3%-5%. A research paper published in 2012 in the Proceedings of the National Academy of Sciences estimated that leakage of more than 3.2% of the gas from a natural gas well through delivery at a power plant, would make natural gas lose its leading edge over coal. A more recent study in 2021, published in the journal Nature, pegs this threshold value at 4.9% in the natural gas supply chain.
Methane is the second largest contributor to global warming after CO2. It has far greater heat trapping capacity than CO2 – in 20 years, methane can trap 80 times as much heat in the earth's atmosphere as CO2 does, IndiaSpend reported in July 2022.
Therefore if natural gas' theoretical advantages over coal are to be maintained, it is crucial to accurately identify the quantity and scale of these methane 'leaks' and prevent them from happening.
Estimates on how much methane is lost through leakage, however, differ substantially, and there is little public data from India on these leaks.
The United States' Environment Protection Agency (EPA) in 1996 had estimated that leaks are 1.4% of production on a national basis. More recently, in 2018, researchers from United States-based non-profit Environmental Defense Fund (EDF), estimated that methane emissions were as much as 2.3% of US' gross gas production, 60% higher than what the US government's Environmental Protection Agency estimated. Another Stanford-led study conducted in New Mexico's oil and gas rich Permian Basin found that the leaks might be even higher than that – to the tune of 9% of all methane produced in the area.
In July 2022 as part of the Chasing Methane project, IndiaSpend's methane tracker, based on satellite data, had reported methane leaks in India in various concentrations (ranging from 10 to 4,400 metric tonnes per month), from pipelines passing from western part of the country to the northern and eastern part of India.
Some studies on methane emissions are based on satellite imaging, Parth Kumar, Programme Manager at the Industrial Pollution Unit at the Centre for Science and Environment (CSE), told FactChecker. But this particular technology has its limitations, as only major leakages of natural gas can be captured through satellite imaging, and small leakages are often missed. So, nobody knows exactly the number of methane leaks happening, he added. IndiaSpend has previously reported on why it is important to fill this data gap on methane leaks.
So, can natural gas be used as a transition fuel between coal and renewable sources?
"The countries with the first right to use gas as a transition fuel are developing economies that are still working to remove energy poverty, and not developed nations that have been historical polluters," Kumar told FactChecker.
Moreover, technologies such as leak detection, installing emissions control devices, and replacing components and devices that emit methane in their normal operations are essential if LNG has to be used as a bridge-fuel between coal and renewable sources of energy.
In its move towards using renewable energy as its main power source, India is already promoting natural gas as a 'transition fuel', planning to increase the share of gas in its energy mix from nearly 6% to 15% by 2030. The length of this transition phase depends on how quickly green power storage options become economical, IndiaSpend reported in October 2021.
We reached out to R K Singh's office via call, and via email with our findings, seeking clarity on his statement. By the time of publishing this article, we had not received a response, and will update the story when we receive a response.
We have also reached out to the power ministry, the petroleum and natural gas ministry and the environment ministry for any data they might have on methane leaks from India's natural gas infrastructure, and for their comments on the relative emissions from these two sources. We will update the story when we receive a response.