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by Luke McGrath (Bloomberg)  Fossil fuels, long regarded for their high-energy return on investment, are not as efficient as once thought. In fact, their final yields are not much better than those of renewable options, according to a new study.

Oil, coal and natural gas have generally returned energy at a ratio of 25:1, meaning that for every barrel of oil used in production, 25 barrels have been made. But that measurement, called energy return on investment (EROI), has traditionally been taken when fossil fuels are removed from the ground, and fails to account for energy used during the refining process.  READ MORE

Fossil fuels increasingly offer a poor return on energy investment (Science Daily/University of Leeds)

Estimation of global final-stage energy-return-on-investment for fossil fuels with comparison to renewable energy sources (Nature Energy)

Excerpt from Science Daily:  Researchers have calculated the EROI for fossil fuels over a 16 year period and found that at the finished fuel stage, the ratios are much closer to those of renewable energy sources — roughly 6:1, and potentially as low as 3:1 in the case of electricity.

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The study, undertaken as part of the UK Energy Research Centre programme and published today in Nature Energy, warns that the increasing energy costs of extracting fossil fuels will cause the ratios to continue to decline, pushing energy resources towards a “net energy cliff.” This is when net energy available to society declines rapidly due to the increasing amounts of “parasitical” energy required in the energy production.

The researchers emphasise that these findings make a strong case for rapidly stepping up investment in renewable energy sources and that the renewables transition may actually halt — or reverse — the decline in global EROI at the finished fuel stage.

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“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.

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“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.” READ MORE