Fossil fuels have long been regarded as a robust energy source because producers spend much less energy to extract the fuels than to produce them.
But a study published in July 2019 in Nature Energy follows a new method for calculating energy cost and argues that fossil fuels are more energy expensive than previous estimates indicated. The results place fossil fuels in line with the energy costs from renewables and emphasize that fossil fuels will be even more costly in the future.
“The general energetic cost of production of finished fuels of electricity, gasoline, diesel, and gas is much lower than people think,” first author Paul Brockway, a university academic fellow at the University of Leeds, told Eos. “This study really gives the green light for even faster decarbonization by moving to renewables.”
Apples and Pears
In the 1980s, researchers began calculating the energy cost of the fossil fuel industry, defining the term “energy return on investment.” Researchers focused on a simple ratio to determine how efficient fossil fuels were: They compared the energy required to extract the fuel with the amount of energy the raw product would produce. For oil, for example, they’d divide the number of barrels of oil piped up at an oil rig by the amount of energy used to extract it. Their calculation takes into account only the energy used to get oil to the wellhead.
Yet when renewable energy gained ground, researchers looked at the energy cost a different way: They compared the electricity created at the end of renewable production with the energy spent on installing and creating the materials used in generation.
Using each method, fossil fuels appear more favorable and cost-efficient, even though the numbers were “like comparing apples and pears,” said Brockway.
Fossil fuels had energy return on investment numbers of 30:1 and higher, whereas renewable energy, calculated a different way, had values of 5:1 or 10:1, ranging widely depending on the technology. But Brockway said that many people are not aware that the numbers come from disparate methods, and the comparison was “one kind of stick that was beaten over a renewable energy’s head,” he said.
As researchers and policy makers predict the future of energy use around the world, the mismatched numbers spelled a kind of “economic shock” when the world switches to renewables, said Brockway.
“Our paper demonstrates that actually that probably isn’t the case,” he said.
An Equal Playing Field
To compare renewables and fossil fuels on an equal playing field, the latest paper analyzes the energy required to take fossil fuel from a raw product to a source of electricity or fuel using a global data set from 1995 to 2011.
Using a method often employed in carbon emissions accounting, the researchers sussed out the indirect energy related to the infrastructure used in fossil fuel production, including metals and raw materials. In the example of oil, they took into account not only the wellhead but also the pipelines, tankers, trains or other transportation methods, and processing in oil refineries.
All told, the latest paper gave fossil fuels an energy return on investment of 6:1, much lower than previous estimates of 30:1, placing fossil fuel energy costs on par with renewables.
Moreover, energy return on investment for fossil fuels fell throughout the study period, a trend projected to continue. As fossil fuel reserves dwindle and the energy required to access them spikes, fossil fuels are returning a lower net energy payout year after year.
Professor emeritus Charles Hall of the State University of New York told Eos that the latest research “emphasizes the painful lack of good science” in this area as well as the “precariousness of our situation.”
Senior research fellow Marco Raugei from Oxford Brookes University voiced concerns as well.
“These are sobering results with significant policy implications, especially now that the world is on the brink of a major energy transition,” Raugei told Eos. “The concept of energy return on investment is deceptively simple at face value, but in truth the devil is in the details.”
Michael Carbajales-Dale, an assistant professor at Clemson University, said the latest paper gives a “much better comparison” than measures used in the past, though he voices that more transparency is still needed when comparing renewables and fossil fuels.
For Brockway, the results quell fears about the future of renewables. As technologies advance, renewables could actually be a “lifeboat” for future energy needs, he said, and the results couldn’t come soon enough.
“We can’t wait, because those numbers for fossil fuels are declining year on year,” noted Brockway. “We don’t have that kind of luxury of time.”
—Jenessa Duncombe (@jrdscience), News Writing and Production Fellow