Fossil fuels increasingly offer a poor return on energy investment

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An evaluation of the global energy return on investment for fossil fuels and renewable sources reveals a much more level playing field than previously believed.

An enduring argument for the ongoing use of is their high on . This refers to the ratio of how much a source such as coal or oil will produce compared to how much energy it takes to extract.

Previously, the estimated ratios for energy return on investment (EROI) have favoured fossil fuels over . Oil, coal and gas are typically calculated to have ratios above 25:1, this means roughly one barrel of oil used yields 25 barrels to put back into the energy economy. Renewable energy sources often have much lower estimated ratios, below 10:1.

However, these fossil fuel ratios are measured at the extraction stage, when oil, coal or gas is removed from the ground. These ratios do not take into account the energy required to transform oil, coal and gas into finished fuels such as petrol used in cars, or electricity used by households.

A new study, co-authored by scientists from the Sustainability Research Institute at the University of Leeds, has 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.

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 .

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.

Study co-author Dr. Paul Brockway, an expert in energy-economy modelling at the School of Earth and Environment at Leeds, said: "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.

"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."

Study co-author Dr. Lina Brand-Correa, an expert in the social aspects of energy use on the Living Well within Limits (LiLi) project at Leeds said: "There is too much focus on the initial economic costs of transitioning to renewable energy.

"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 decreases, the energy-return-on- for 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."


Explore further

Low-carbon energy transition requires more renewables than previously thought

More information: 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 , https://www.nature.com/articles/s41560-019-0425-z
Journal information: Nature Energy

Citation: Fossil fuels increasingly offer a poor return on energy investment (2019, July 11) retrieved 16 July 2019 from https://techxplore.com/news/2019-07-fossil-fuels-increasingly-poor-energy.html
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Jul 11, 2019
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.


Except they didn't count in the massive energy loss of storing and stockpiling renewable energy.


Jul 11, 2019
Not to mention the enormous energy cost of transporting fossil fuels like coal to the point they will be consumed.

This article is confusing. It's not clear whether costs like infrastructure to mine and transport fossil fuels or build renewable infrastructure are taken into account. I though most of this had already been worked out with end to end EROI calculations. The 'advance' this article cites still seems like it doesn't take in the whole picture.

Jul 12, 2019
Not to mention the enormous energy cost of transporting fossil fuels like coal to the point they will be consumed.


That's actually quite small, because the gravimetric energy density of chemical fuels is very high.

For example, a tank truck loaded up with fuel consumes about 60 liters of diesel fuel per 100 km. It can carry up to 43,900 liters of fuel, so it consumes about 1.4% of the energy of the fuel for every 1000 km transported.

Translated to efficiency, that's 98.6% which isn't all that shabby. The average transmission loss on the electric grid on the other hand is about 6-7% or as an efficiency: 94%. The tanker truck clearly wins.

This is the same sort of non-intuitive question as, "Which has the greater data rate: a DSL or a donkey loaded up with DVDs". It also shows the power of propaganda: people assume the fuel is worse because it's the socially correct answer.


Jul 12, 2019
Railroads use exceptionally little energy. It's not uncommon to move a ton of freight nearly 500 miles on a gallon of diesel fuel.

Coal is 24 GJ/ton which is about 6700 kWh, which compares to diesel fuel at about 38 kWh per gallon, so the comparable efficiency over 1000 km is over 99%

Also, the average transmission distance on the electric grid is just over 200 miles (320 km). It's actually very wasteful to transmit energy as electricity.

Jul 12, 2019
And as for the EROEI:

https://www.scien...16301379

The article in the link discusses an estimation of solar energy return of energy. The main point is that the energy returns in areas of moderate insolation, such as central Europe, the inclusion of battery storage or other can push the energy return to negative figures, making solar power an energy sink rather than a source.

They're also counting the capital cost of the system, which measures the amount of money (economic activity) you have to pay for the panels, which translates to energy used elsewhere in the ecosystem that is normally not counted in the energy budget, which only takes into account the manufacture etc. This is an important point, because you can't assume that the person who installs the solar panels doesn't eat food, drive a car, live in a house... and yet all that's necessary for you to have the solar panels on your roof.

Jul 12, 2019
Have you hugged a fracker today? You should.

Jul 12, 2019
We are running out of petroleum.
Time to invest in deep geothermal.

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