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Fossil fuels offer a lower energy return than previously believed

A new study from the University of Leeds has carefully analyzed how much energy is produced by fossil fuels compared to the amount of energy that is used to acquire them. Although the estimated ratios for energy return on investment (EROI) have historically favored fossil fuels over renewable energy sources, the researchers found that these estimates are not accurate. 

Oil, coal, and gas are calculated to have an EROI of at least 25:1, which means that the energy return on one barrel of oil is about 25 barrels. Renewable energy sources often have much lower estimated ratios that are below 10:1.

The fossil fuel estimates, however, do not take into account the energy that is needed beyond the extraction process to transform oil, coal, or gas into the finished product. 

“Measuring energy return on investment of fossil fuels at the extraction stage gives the misleading impression that we have plenty of time for a renewable energy transition before energy constraints are a concern,” said study co-author Dr. Paul Brockway.

“Those measurements are essentially predicating the potential energy output of newly-extracted sources like crude oil. But crude oil isn’t used to heat our homes or power our cars. It makes more sense for calculations to consider where energy enters the economy, and that puts us much closer to the precipice.”

“The ratios will only continue to decline because we are swiftly reaching the point where all the easily-accessible fossil fuel sources are becoming exhausted. By stepping up investment in renewable energy sources we can help ensure that we don’t tip over the edge.”

For the current investigation, the research team calculated the EROI for fossil fuels over a 16-year period. The results showed that, after the finished fuel stage, the ratios for fossil fuels are much closer to those of renewable energy sources at roughly 6:1. In the case of electricity, the EROI for fossil fuels was as low as 3:1.

The experts warn that the increasing energy costs of extracting fossil fuels will cause the ratios to continue dropping, pushing energy resources toward a “net energy cliff” where the net energy available to society experiences a sharp decline. The researchers emphasise that these findings make a strong case for rapidly stepping up investment in renewable energy sources.

“There is too much focus on the initial economic costs of transitioning to renewable energy ” said study co-author Dr. Lina Brand-Correa. “Renewable infrastructure, such as wind farms and solar panels, do require a large initial investment, which is one of the reasons why their energy return on investment ratios have been so low until now.”

“But the average energy return on investment for all fossil fuels at the finished fuel stage declined by roughly 23 per cent in the 16 year period we considered. This decline will lead to constraints on the energy available to society in the not-so-distant future, and these constraints might unfold in rapid and unexpected ways.”

“Once the renewable infrastructure is built and dependency on fossil fuel decreases, the energy-return-on-investment for renewable sources should go up. This must be considered for future policy and energy infrastructure investments decisions, not only to meet climate change mitigation commitments but to ensure society continues to have access to the energy it needs.”

The study is published in the journal Nature Energy.

By Chrissy Sexton, Staff Writer

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Image Credit: Shutterstock/Kodda

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