In my last post, I referred to the work of Charles Hall on Energy Return on Investment (EROI) and biophysical economics. Following an exchange of e-mails with Professor Hall, he directed me to some of his more recent work, including a January 2014 paper titled “EROI of Different Fuels and the Implications for Society” published in Energy Policy (free access). The paper looks at the critical EROI question: “How many units of energy do you extract for each unit of energy you invest?”.
The paper is a veritable chartfest of all things EROI, but I will wet your appetitive with just three. First up, is an EROI comparison between different fossil fuel and biomass energy sources (click for larger image).
The bad news here is that coal remains the king of EROI since you get around 40 times as much energy out for each unit of energy you put in. Hardly good for CO2 emissions trajectories and climate change.
Next up is the decline in global oil and gas EROIs (click for larger image):
The decline is unsurprising since we are trying to exploit ever more geologically marginal sources of oil and gas in ever more unconventional forms.
Finally, a chart showing fossil fuels up against renewables (click for larger image):
I was genuinely surprised at this one because both wind and photovoltaic (PV) came in higher than I expected. Hall flags all the major problems with wind and PV (need for base load and so on) and also points to disputes over PV EROI methodology. Nonetheless, I have heard arguments in the past that PV is almost break-even in EROI terms; this does not appear to be the case.
There is a lot more in the paper, including numerous interesting references. When I get time, I will come back to the EROI of renewables as it seems such an important topic.