A new article in Financial Times discusses a controversial academic paper by Cornell University professor Robert Howarth that has reignited the debate over liquefied natural gas (LNG) and its environmental impact.
Howarth’s peer-reviewed paper, published in Energy Science and Engineering, claims that LNG has a 33% larger emissions footprint than coal over a 20-year period, challenging the oil and gas industry’s assertion that LNG is a cleaner alternative.
Let’s take a closer look at Howarth’s assumptions and conclusions, but first a quick review of the science behind carbon emissions.
Understanding Carbon Emissions
Oil, coal, and natural gas are hydrocarbons. That means they are comprised of hydrogen and carbon. When they are burned, these elements respectively form water and carbon dioxide. Fossil fuels with a higher percentage of hydrogen, like natural gas, produce less carbon dioxide per unit of energy produced. That is why natural gas is cleaner burning than coal with respect to carbon emissions.
Over the past 15 years, the U.S. has seen a major shift from coal to natural gas for electric utilities. This is why the U.S. has seen the largest decline in carbon emissions of any country over that period.
Professor Howarth acknowledges that methane is a cleaner burning fuel. So, how does he reach the conclusion that methane is dirtier than coal?
It is important here to compare methane and carbon dioxide as greenhouse gases. Carbon dioxide (CO2) is more abundant in the atmosphere (~420 parts per million) and has a long atmospheric lifetime. It can persist in the atmosphere for centuries, making its cumulative effect substantial.
Methane (CH4), on the other hand, is a much more potent greenhouse gas in the short term. As mentioned in the article, methane is more than 80 times more powerful than carbon dioxide at trapping heat when considered over a 20-year period.
However, methane is present in the atmosphere at much lower concentrations (~2 PPM). It is also more reactive and therefore has a shorter atmospheric lifetime, typically around 12 years, after which it breaks down into CO2 and water vapor.
Howarth’s Assumptions
Howarth’s paper, which influenced the Biden administration’s decision to pause approvals for new LNG export terminals, argues that methane emissions from LNG production, liquefaction, and transport offset any benefits from lower carbon dioxide emissions compared to coal. His assumptions are not without controversy, because they presume:
- A significantly higher leak rate than U.S. Environmental Protection Agency Estimates.
- The leakage rate would not decline as leaks are identified and fixed.
- A time frame limited to 20 years, exaggerating methane’s impact which trails off over longer periods.
In other words, Howarth makes a number of worst-case assumptions to arrive at his conclusions.
Opposition to Howarth’s Conclusions
Howarth’s paper has sparked opposition, with Republicans criticizing the research as flawed and the oil and gas industry disputing its methodology.
Industry representatives, such as the American Petroleum Institute, argue that Howarth’s study uses worst-case scenario assumptions and contradicts previous government-commissioned research, in particular a 2019 U.S. government-commissioned study. That earlier research concluded that using American LNG for electricity generation in Europe and Asia would not lead to higher greenhouse gas emissions when considering the entire life cycle of the fuel.
It is also worth noting that Howarth has a long history of opposition to hydraulic fracturing (fracking), and his research is funded by the Park Foundation, an environmental group with a history of funding anti-fracking research and activism. This suggests a potential reason for using worst-case assumptions in his study.
Conclusions
So, is LNG dirtier than coal? Probably not. Professor Howarth’s paper has reignited that debate, but his findings contrast sharply with previous studies. While his research has influenced policy discussions, it is important to consider the assumptions and funding behind his findings.
The controversy surrounding this issue highlights the complexities of evaluating energy sources and their true environmental impact, emphasizing the need for objective research to guide responsible energy policy decisions.
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