Saturday, February 9, 2008

The Latest on Biofuels

This week's Science Magazine (or Science Lite as it's sometimes called) includes a story that's got a lot of press coverage (way to go, guys!) but really just fills out the picture slightly.

The authors make the point that if you increase plant cultivation for biofuels, you either have to displace existing crops or clear additional land. But if you displace existing crops then the demand for food leads to the clearing of additional land, anyway. And it's the clearing of additional land that causes the problem. This seems obvious if the clearing is done in forests, as it usually is. A mature forest contains decades' worth of accumulated carbon so if the forest is burned then most of that carbon goes into the atmosphere as CO2. It's not as obvious but, according to the authors, plowing up grassland to grow biomass also releases more CO2 than it saves.[LA Times]

It's been known for a long time that ethanol is a loser.[source] It takes as much fuel to produce it as the process yields. So, in the US at least, it's always been a boondoggle aimed at making farmers rich. Still, some researcher think switchgrass can offer a better payoff ratio.

There's been some hope that oil-bearing crops could produce biodiesel, but so far the results aren't much more promising.[source]

So that seems like a daunting challenge by itself. But then we look at the land requirements and the prospects are even more dismaying. As we showed in another article, there isn't enough arable land available to grow the amount of biomass that would be required.

Maybe all this attention will do some good. Most people whose knowledge of enviromental subjects comes mainly from popular media have the idea that biofuels are a practical solution. A closer look shows that, by themselves, biofuels can at best be only an expensive non-solution, an illusory exercise that benefits a few people financially but only aggravates the problem.

As we face this bleak outlook, there's only one thing going for us. Hydrogen can increase biofuel yields by a factor of three. Then, biofuels can function mostly as a medium for hydrogen. They provide an imperfect means for onboard storage of hydrogen fuel for motor vehicles.

The most efficient way to convert water to hydrogen is with high-temperature processes, at temperatures nuclear reactors can provide. The nominal efficiency is over 45%.[source] But the heat left over from the conversion can be used to generate electricity, so the hydrogen production is effectively 100% efficient.

If we're lucky, a better way of storing hydrogen will be invented so biofuels won't be required. Either way, hydrogen is going to be the fuel of the future. The best way to produce hydrogen is with nuclear energy.[source]

1 comment:


Bio fuels, really important for the future.