It doesn’t take a lot of energy to dig up coal or pump oil from the ground. In contrast, most renewable sources of energy involve obtaining and refining resources, sophisticated manufacturing, and installation. So, at first glance, when it comes to the energy used to get more energy—the energy return on investment—fossil fuels seem like a clear winner. That has led some to argue that transitioning to renewables will create an overall drop in net energy production, which nobody is interested in seeing.
A new study by researchers at the UK’s University of Leeds, however, suggests that this isn’t a concern at all—in most countries, renewables already produce more net energy than the fossil fuels they’re displacing. The key to understanding why is that it’s much easier to do useful things with electricity than it is with a hunk of coal or a glob of crude oil.
Energy efficiency and utility
The basic idea behind the new work is that while it’s energetically cheap to extract fossil fuels, the stuff that comes out of the ground isn’t ready to be put to use. There are energetic costs to making it into a useful form and transporting it to where it’s needed, and then there is lost energy when it’s being put to use. That’s especially notable for uses like internal combustion engines, where significantly less than half of the energy available in gasoline actually gets converted into motion.
So, the researchers propose an alternate form of the energy return on investment (EROI)—something they call useful-stage EROI. This measures how much energy is needed to put a unit of energy to work in a way that society values—heating a home, moving a car, lighting a room, and so on. This is also a more complicated measure because it depends on how the energy is put to use, which will vary from country to country. So, even though natural gas has the same EROI at extraction, it’ll have different useful-stage EROIs in a country that primarily uses gas for heating versus one that’s using it for electricity generation since those two activities have different efficiencies.
