I have written on the subject of various kinds of biofuels, and broadly concluded that even if we were to stop growing food in the U.K. we could at best match only somewhere between 16% and 50% of our current transportation fuel based on petroleum, depending on whether biodiesel or bioethanol is the substituting fuel. My figures are based the requirements for the U.K., but they broadly scale-up to similar conclusions for the U.S., in terms of the greater area of arable land available but the greater overall "national" fuel consumption. It amounts to the same for European countries in addition to the U.K., nonetheless, everybody seems to be going hell-for-leather for biofuels.
George Bush wants to free his country from the need for fuel imports from the Middle East especially, and probably from a less friendly South America too (notably Venezuela), although its supplies from Canada are likely to be fairly secure for the foreseeable future. The U.S. imports almost three quarters of its fuel from abroad, and consumes one quarter of the world's production. However, other nations are in a flux of rapid and massive development (China and India) and so the tug-of-war over the world's oil reserves is becoming a fraught and complex game with many more than a simple two sides pulling at them. In short every nation wants to be set free from demand on oil, for the simple reason it is running out, but how much time can biofuels really buy us? If the amount of them we can produce without starving, is a fraction of the energy equivalent currently supplied from petroleum, at best we have a shallow safety-net, that "might", and I use that word advisedly, make the bumpy ride down the oil-poor edge of Hubbert's Peak a little smoother. But there is no doubt we will end-up in a world with much less transportation fuel, even if wholesale coal liquefaction is done to make it, and on environmental grounds, e.g. climate change, this would seem unacceptable.
I have no doubt that many environmental concerns will take a back seat to attempts to maintain economic growth, and so I expect the U.S. will begin to produce synthetic hydrocarbons from coal, given their enormous reserves of it, some 30% of those known in the world; however, since much of this will be scraped from the Earth in open-cast pits, it is going to create quite a mess, and I'm sure too that Europe will not be too far behind in implementing the technology, and China and India are already considering large scale coal liquefaction projects. Now coal is an obviously dirty material, but what about biofuels - even if the amount we can feasibly make of them is limited, the technology is at least clean...or is it?
I am skeptical how much environmental good will be done by blending biofuels with petrol, in relatively low proportions (5 - 10% say), partly in terms of emissions and probably more impact will be made there as petrol begins to run out and we have less fuel to burn and pump CO2 into the atmosphere. However, America wants to double its biofuel production to 7% of the total within 18 months, while Europe aims more modestly for just under 6% by the end of the decade (slightly under 3 years). It is intended that the share of the market from biofuels will grow to 15% in the U.S. and around 10% in the EU. To encourage its own market the U.S. has imposed tough import tariffs on Brazilian-made ethanol but subsidises its own corn-ethanol. However the Brazilian product can be produced at a yield of around 6,000 liters per hectare and is the world's most efficient, whereas its corn-based equivalent is the least so.
There are fears that forested land will be cleared to grow fuel crops, as is happening in Asia, mainly in Indonesia and Malaysia, to produce palm-oil, diesel from which overall is ten times as polluting in terms of CO2 emissions than petroleum-based diesel. According to Friends of the Earth, 87% of deforestation that occurred in Malaysia between 1985 and 2000, was carried out to provide palm oil plantations. The U.K. government has said that a "significant proportion" of this country's biofuels will be imported, from places where they grow best, like Brazil and Indonesia, leaving both direct and indirect consequences of deforestation to follow. Economically, it is a difficult transitional period too, because the "second generation biofuels" made from cellulose are expected to come on stream perhaps in five years and so why would companies want to invest in massive biofuel production now, when these "first generation" plants would then have to be decommissioned? The second-generation approach sounds good, because it is intended to use household waste, sewage, chaff from food crops and so on, but the technology remains to be proven on the grand scale as is true of producing biodeisel from algae, which looks particularly promising.
In my opinion the jury is still out on how much biofuel can be produced altogether, and although I am optimistic about some of the putative technologies for doing so, I don't believe we can ever match the amount of petroleum-based fuel we now get through, and bearing in mind that the world supplies of oil are running out. In less than 20 years there will be practically no conventional oil left, and it is against this backdrop that all other considerations must be contrasted.
(1) "Biofuels: The great green con", by Tim Webb. http://news.independent.co.uk/business/analysis_and_features/article2516619.ece
(2) "A Lethal Solution," by George Monbiot. http://www.monbiot.com.archives/2007/03/27/a-lethal-solution/