I filled up my car for just under $3 a US gallon yesterday and got a short-lived sugar high, followed by the predictable crash. Gasoline in the US retails for about half what it should counting its climate effects and the taxes it should carry for road use, so this is overall, and importantly, a Bad Thing, as is anything that makes fossil fuels cheaper rather than more expensive.

Of course $55 oil is a very big deal in an world addicted to petroleum in other ways, like selling it, as the Russians and Venezuelans will tell you. Oil companies, of course, are scrambling. BP, trying to stop the bleeding across its operations, is also pulling the plug on its cellulosic biofuels projects. I am quite ambivalent about this last development. On the one hand, the BP-funded Energy Biosciences Institute here at Cal has done a lot of good science and people I like and respect have worked there for several years, mostly trying to make liquid fuels out of whole plants. They are going to be seriously dinged by BP’s pullback.

On the other hand, I am broadly skeptical of liquid biofuels generally, and especially of trying to make them out of whole plants, and I think BPs retreat signals twilight for the latter enterprise.  Getting the lignin off the cellulose, and then breaking the cellulose down into something a yeast will eat, has been very refractory. If you have a big pile of biomass in one place to use for energy, why take a bunch of thermodynamic hits doing chemistry on it to make liquid fuel?  Just throw it in a boiler in place of any fossil fuel (especially coal), burn it directly, and make electricity.

A cautionary example, and a special case, is ethanol from sugarcane, especially in Brazil, where they have spent many years getting really good at it.  This is a C4 grass, the most efficient solar collecting kind of plant, grown where there’s lots of sun and (except this year) water, that only has to be planted every six years or so, and makes sugar that can be fermented directly, so no enzymes to dismantle starch.  Because the whole plant stem has to be hauled to the refinery to be squeezed, the fibrous residue is burned as fuel to run the plant and make electricity to put back in the grid. (If the Brazilian grid were less green-they have a lot of hydro-it would be better.)  Like any crop-based biofuel, it displaces food production and winds up pushing agriculture into forest land, with a big carbon discharge from land clearing.  This is about as good as whole-plant liquid fuel can get, and it’s still only about a third less carbon-intensive than gasoline; it will be very hard for cellulosic liquid fuels to come close, especially at tolerable cost.