Biofuels are a complex matter and Giampietro and Mayumi use almost 300 pages to eviscerate it in all its aspects. The main point of their analysis is based on fundamental physics: the efficiency of photosynthesis is low and the result is that the areas needed for cultivation are large. If we are thinking of amounts of biofuels comparable to the present needs for transportation, the task is simply unthinkable: there would be no space left for food production. As the authors flatly state at page 128 of the book, “Full substitution of fossil energy with agro-biofuels is impossible.”
The large area needed is only one of the problems with biofuels. More in general, agriculture is a good technology for producing food, but it is terribly expensive in terms of the resources it requires. It needs land, water, fertilizers, pesticides, mechanical work; all supplies that normally come from fossil fuels. Taking all that into account, the EROEI (energy return for energy invested) of biofuels is generally low; unless the invested energy is supplied by low cost human labor, as it is the case for Brazilian sugar cane. Apart from Brazil, the need of an energy subsidy in the form of fossil fuels makes biofuels unable to deliver their promise of being a “sustainable” technology. They can’t help us in reducing our dependency on fossil fuels nor in reducing the emission of greenhouse gases in the atmosphere.
Of course, the biofuel story is more complex than that and Giampietro and Mayumi examine the whole spectrum of possibilities in their book. Are there better biofuels? Or, perhaps, ways of using the present form of biofuels in a more effective way? Yes, of course; there is the promise of “second generation” fuels (cellulosic ethanol) and the possibility of cultivating marginal areas, unsuitable for food production. But the physical factors of the problem don’t change much and, right now, biofuels and conventional agriculture are already competing for land and resources. One of consequences may be the increase increase in food prices that we have been seen during the past few years.In the end, what do we want to do, exactly, with biofuels? Do we really think that the way to solve our energy problems is to use an inefficient technology to support an already inefficient transportation system? The only explanation I can think of for so much emphasis on biofuels is that, once a bad idea is implemented, it starts to gain momentum and then it becomes nearly impossible to stop.
Read the whole post at Peak Oil: Exploring Hydrocarbon Depletion