A new analysis published on 11 July in Nature Energy reveals increasing ‘energy cost’ associated with fossil fuels, which means renewables may be quickly catching up (1). The authors suggest a faster transition to renewables could prevent a further decline in the global return on energy investment (EROI).
One of the main arguments for the continued use of fossil fuels is the high energy return on energy investment making fossils fuels the most lucrative and economically viable source of energy. But while the EROI does tend to be much higher for fossil fuels compared to renewable energy, this new study suggests EROI estimates for these “dirty” sources of energy may, in fact, be too high.
The current approach for estimating EROIs — the ratio of energy produced to how much energy is required to extract it — only considers oil, coal, or gas at the extraction stage and does not account for the energy required to transform these raw materials into the final product, such as petrol. This paints fossil fuels in a more favourable light in terms of energy returns the authors suggest.
Measurements are typically based on crude oil, which is not the final product that is used, for instance, to heat and cool our homes. And the authors warn that the growing costs of extracting these finite resources may be pushing us towards a “net energy cliff”. In other words, a so-called parasital process in which all the available energy is used up to create new energy.
The recent study was performed as part of the UK Energy Research Centre programme. The researchers from the Sustainability Research Institute at the University of Leeds calculated the energy return on investment (EROI) for fossil fuels over a 16 year period and found the EROIs for all fossil fuels at the finished fuel stage declined by around 23 per cent over this period. And this will eventually place constraints on the energy available.
So, it appears these ratios may be much closer to those of renewables than previously thought — around 6:1 and for electricity production, possibly as low as 3:1. Moreover, once the infrastructure for renewable energy is established and fossil fuels are gradually phased out, the EROI for renewable sources will likely go up.
“We are swiftly reaching the point where all the easily-accessible fossil fuel sources are becoming exhausted”, says Dr Paul Brockway of the Sustainability Research Institute and a co-author of the study. But he suggests that by “stepping up investment in renewable energy sources we can help ensure that we don’t tip over the edge”.
Brockway explains that “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.”
(1) Brockway, P. et al. Estimation of global final stage energy-return-on-investment for fossil fuels with comparison to renewable energy sources. Nature Energy (2019). DOI: 10.1038/s41560-019-0425-z