Original URL: https://www.theregister.com/2009/05/08/bioelectric_cars_will_save_us_all/
US prof says 'bioelectric' cars much better than biofuel
Still trying to run modern society by burning crops
Posted in Science, 8th May 2009 14:38 GMT
Analysis A prof in California has made the unsurprising observation that you can produce more transport miles from an acre of cropland by growing biomass for generators and using electric vehicles than by burning crop biofuels in ordinary engines.
Assistant professor Elliott Campbell and his colleagues compared two different ways of using plants to power vehicles. The first method, already an option today, was to grow feedstocks such as corn or switchgrass and convert them into ethanol fuel.
Ethanol can be burned in ordinary cars with only minor modifications, which is one reason it has already gained some traction. Another is that powerful American and European farming lobbies hope that it could mean big money for them.
The second method considered by Campbell and his collaborators was to grow biomass and use this in generators to produce electricity - so-called "bioelectricity" - to charge the batteries of electric cars.
According to the researchers:
Bioelectricity outperforms ethanol across a range of feedstocks, conversion technologies, and vehicle classes. Bioelectricity produces an average 81% more transportation kilometers and 108% more emissions offsets per unit area cropland than cellulosic ethanol. These results suggest that alternative bioenergy pathways have large differences in how efficiently they use the available land to achieve transportation and climate goals.
This is hardly a surprise, though it has seemed startling enough to the media that it's gone mainstream. After all, conventional car engines of the sort used to burn ethanol put out barely 20 per cent of their fuel's energy at the drive shaft. By contrast, an electric motor can beat 80 per cent without trouble.
Of course there are other losses in the bioelectricity method - at the generator, in charging up batteries - but this is also true for making ethanol fuel out of crops, a process which requires a lot of heat energy to accomplish. It's not exactly startling that "bioelectricity" comes out somewhat ahead.
"We found that converting biomass to electricity rather than ethanol makes the most sense for two policy-relevant issues, transportation and climate," said Campbell. "We also need to compare these options for other issues such as water consumption, air pollution and economic costs."
Are you sure there's enough land, Professor?
Let's hope that Campbell never bumps into Dr Richard Pike, head of the Royal Society of Chemistry here in the UK. Pike is deeply scathing about the idea of using plants to power transportation by any means - electric or ethanol. He notes that you get 2,000 per cent more energy per acre by covering land with solar cells, making Campbell's measly 80 per cent improvement look pretty rubbish.
Solar cells would seem to be conclusively ahead on water use and air pollution, too, as well as transportation and climate. They can also make use of empty land unsuitable for crops, rather than leading to high food prices, starvation and/or deforestation as cropland biofuel - and bioelectricity - inevitably would if they became big factors.
Solar cells by the acre would cost an awful lot, of course; but so would electricity if you had to make it by burning corn or switchgrass. You would normally use up the whole of a country's arable land trying to satisfy even a minor portion of its energy needs using either biofuel or bioelectricity.
This is why proper heavyweight boffins, in trying to construct plans for a reasonably comfortable and wealthy society without fossil fuels, generally assume that the only real purpose for having bio-energy plantations is to allow some aviation to continue. (Aircraft can't convert to electricity the way road transport can: and switching to electrically-made hydrogen may or may not be feasible.) The aviation industry themselves, well aware that they can't remain anything like their present size on cropland fuel, pin their hopes for the future on "second generation" biofuels - ones using algae grown on water, or jatropha nuts grown in deserts.
All these things are well known, so the idea of using decent or decent-ish land to grow energy remains at best marginal, at worst bonkers. You have to wonder why Campbell is still going on about it - he was already famous for claiming that the US could generate six per cent of its energy needs from surplus marginal farmland - and why people are still writing him up. ®