Ars Technica has a very interesting article this morning on biofuels vis a vis global warming.
My problem with it is that they are looking at the wrong fuel.
Ethanol has poor energy density, takes a lot of energy to produce, can only be (efficiently) produced from a limited subset of feedstocks, and requires extensive modification of the entire fuel infrastructure and the vehicles intended for its use.
Biodiesel on the other hand has comparable energy density to petrodiesel, requires very little energy input to produce, can be made from a huge range of feedstocks*, and requires almost no modification of the fuel infrastructure or the vehicles** intended for its use.
So why are we still talking about ethanol? Why has "biofuel" come to only refer to ethanol?
Now. If you will allow me, I will devote a good chunk of this post to expounding on the set of asterisks above. Don't like it? Fire me.
*This is actually a slight problem. I am aware of at least one biodiesel production facility that was killed in the proposal stage because someone had convinced the land use board that biodiesel created from each feedstock would have to be approved separately. Furthermore, each blend of biodiesel created from any feedstock would have to be approved separately. And so on. This despite the fact that the properties of biodiesel are already controlled under ASTM D6751.
**I am still pissed at VW (and others) for taking the lazy way out with the catalyst regeneration procedure for their bluemotion system. The catalyst they use needs to be occasionally heated to burn off the accumulated particulate deposits. Caterpillar achieves this putting an extra injector in the exhaust stream. VW achieves this by having the in-cylinder injectors occasionally shoot an extra shot into the cylinder during the exhaust stroke. What is the big deal about that? Biodiesel has a lower evaporation point than petrodiesel. The bio will preferentially condense on the cylinder wall and eventually make it past the piston rings and into the crankcase. While biodiesel has better lubrication properties than petrodiesel, it is nothing compared to the lubrication properties of engine oil. Too much bio in the crankcase can cause premature engine failure. But that's not all! Biodiesel burns at a lower temperature on the catalytic converter, so it takes more regeneration cycles before the temperature has reached a point where the engine computer decides that it is "clean". Even worse, the particulates associated with burning biodiesel are more reactive than those for petrodiesel. Less regeneration is required, but the computer has no way of knowing how "dirty" the converter is directly. It has to infer the catalyst condition indirectly through measuring temperature. So most of the regeneration the engine is desperately trying to get is entirely unnecessary. All because VW wanted to save $20 on an extra injector.