For those people who do not accept the environmental reasons to significantly reduce/eliminate our dependence on fossil fuels, there is another compelling reason to eliminate our dependence on them, the falling ratio of energy return on investment, or net energy.
Energy return on investment (EROI) or energy returned on energy invested (EROEI) is a way of measuring the quality of different fuels and fuel sources by calculating the useful energy left after the energy investment to capture and deliver the fuel is subtracted. The table below shows some of our main non-renewable and renewable fuel sources and their respective EROI.
|Oil and Gas (US), 1930||Greater than 100|
|Oil and Gas (Global), 1999||35|
|Oil and Gas (Global), 2006||18|
|Tar Sands (Mineable)||3|
|Tar Sands (In Situ)||5|
|Coal (at mine mouth) US, 2007||60|
|Coal (at mine mouth) China, 2010||27|
|Renewables (renewable EROIs are location dependent)|
|Hydropower||Greater than 100|
|Solar Photovoltaic||6 to 12|
|Sugar-cane based ethanol||0.8-10|
|Nuclear||5 to 15|
Data adapted from .A.S. Hall et al. (2014) and Murphy et al. (2011).
We can see from the table that the EROI of oil and gas is declining. The non-conventional sources of oil such as the Canadian tar sands and US shale oil have low EROIs compared to conventional sources meaning that the newer sources of oil are harder to get to and/or more expensive to extract.
Why should we care? Today’s economy has been built on the steady, consistent and cheap flow of energy. So when energy costs more, less of our money is available for discretionary spending unless we go into more debt. If that is the cast then why is the current price of a barrel of oil so cheap? The market pricing of oil only looks at the availability now and in the immediate future, it does not reflect the long term outlook.
What about renewable energy source? Looking at the above table we can see that renewable energy sources have generally lower EROIs than conventional fossil fuels. Also, fossil fuels, particularly oil are very energy dense, are easily transported and stored for use at any time.
Many renewables tend to be used to produce electricity which cannot be as easily stored. Also renewable energy sources have the challenges of being: not as energy dense; a tendency to be intermittent; poor transportability and they need new infrastructure. The sector that would be particularly affected would be transportation; batteries tend to be large and heavy and made from materials that are relatively scarce.
So what can we do now? Only use fossil fuels where they are absolutely necessary; use our remaining cheaper resources to build an infrastructure and an economy fuelled by renewable energy; cut our energy use in general. This does not need to be terrifying, it will just be different and there will be some challenges in adjusting.
We do not need to rely on some magic new technology, yet to be invented. Using food as an example, traditional farms using the sun, people and animals, in general produces 10 kilocalories of food energy for every one kilocalorie expended on cultivation. Modern industrial farming typically produces 1 kilocalorie of food for every 10 kilocalories of energy expended on cultivation (fertilizers, tractors, pesticides etc). We are essentially eating oil! Yuk!
The most exciting part of this change is that we have a great opportunity to re-imagine our lives and potentially create something new and better. There will be huge challenges ahead and many governments, corporations and some individuals will want to keep the status quo until we encounter a significant crisis. In terms of this blog, that is enough of the scary reasons of why we need to wean ourselves quickly from fossil fuels, now we focus on the solutions.
Source Materials and More information
Hall, Charles AS, Jessica G. Lambert, and Stephen B. Balogh. “EROI of different fuels and the implications for society.” Energy policy 64 (2014): 141-152.
Murphy, David J., and Charles AS Hall. “Year in review—EROI or energy return on (energy) invested.” Annals of the New York Academy of Sciences 1185.1 (2010): 102-118.