Previous comments have raised an important issue: land can only be used for one purpose at the same time. If you grow biofuel crops, you are not growing food. So, is the concept of biofuels doomed by the need for food? I do not think so, and I hope to convince some of you, although I must emphasize, biofuels could only ever provide some of our current transport requirements; it is most unlikely that we can get away without changing some of our habits. I am convinced there is no single answer to the transport problem, and we shall need multiple contributions.
One promising source, in my opinion, is wastes. One simple calculation I did was that municipal solid waste (MSW) could be converted to hydrocarbon fuel at a rate of about 2 litres per person per week, based on 1980s MSW production. That may not seem a lot, but it includes all those who do not use vehicles. That is gross production, but it is effectively net because fuel is needed to collect the waste. You cannot simply leave the refuse on the streets. Forestry wastes are another source. Currently these are usually left lying, or buried, but they could produce very large amounts of fuel if properly used. Agricultural wastes are slightly more difficult to assess, because many of them, while they could produce large amounts of fuel, are also valuable for returning nutrients to the soil and conditioning it. However, food processing wastes are highly suitable, because there is no other use for them. Think of the huge volumes of waste after pressing olive oil. Sewage sludge is unlikely to have serious conflicting uses. The advantages of using wastes is that in most cases, using them solves another problem, namely what to do with them.
Objecting to growing crops seems wrong to me unless those crops have better uses. While there are food shortages, these are in specific localities, and elsewhere, farmers have been paid to grow nothing. They might as well grow something useful. Think of sugarcane in Brazil. If you did not use it for fuel, what would you do with it? And why not use the mountains of bagasse that are created? I have driven through selected parts of Brazil, and there are vast tracts of land that are essentially doing nothing, and have little environmental benefit either. Maybe they are not much use for growing food, but if so, is it wrong to grow fuel-crops? Then there is marginal land. Members of the Euphorbiaceae frequently have relatively high lipid or hydrocarbon contents and are alleged to grow on marginal land; the problem with this is that marginal land may support special plants, but the yields are usually marginal, and whether it is worth the effort is another matter.
The aqueous environment also offers scope. One project I have been involved in is to use microalgae grown in sewage ponds. This option has two advantages: besides producing fuels, and some interesting chemical options, microalgae also scrub excess nutrients from the water, thus reducing pollution. Similarly, the marine environment offers further opportunities. Macrocystis is one of the fastest growing plants on the planet, and it is really fascinating to have a small plant growing under a microscope: you can watch the cells divide right before your eyes. More to the point, the US Navy once demonstrated that you could grow this on rafts in deep water. Whatever else we are short of, ocean area is not one of them.
What is interesting is that most of these opportunities are currently being ignored. All require serious technical work, but is that not what scientists should be advocating? For example, the US Navy project had no problem growing the plants, but because the rafts were anchored to the seafloor, the project was destroyed in a storm. Such a failure, though, is no reason to give up. There are other ways of going about such a problem. (The project also probably wound up then because the price of crude began falling rapidly.) All of which raises the question, how does society recognize its options and organize itself to carry out the necessary actions in a timely fashion. Current evidence is that society is half asleep at the wheel. Yes, in principle it sees a problem, but that will be in the distant future, or so it believes. What it does not realize that developing technology to deal with such problems, and implementing them on the necessary scale, cannot be done in a few years. We need to be doing more now.
