Corn-based ethanol is neither cheap nor green. It requires almost as much energy to produce (more, say some studies) as it releases when it is burned. And the subsidies on it cost taxpayers, according to the International Institute for Sustainable Development, somewhere between $5.5 billion and $7.3 billion a year.
Ethanol made from sugar cane, by contrast, is good. It produces far more energy than is needed to grow it, and Brazil, the main producer, has plenty of land available on which to grow sugar without necessarily reducing food production or encroaching on rain forests. Other developing countries with tropical climates could prosper by producing sugar ethanol and selling it to rich Americans to fuel their cars.
There is a brighter prospect still out there: cellulosic ethanol. It is made from feedstocks rich in cellulose, such as wood, various grasses and shrubs, and agricultural wastes. Turning it into ethanol requires expensive enzymes, but much research is under way to make the process cheaper.
That is still some way off. In the meantime, the U.S. should trash its silly policy. If it stopped taxing good ethanol and subsidizing bad ethanol, the former would flourish, the latter would wither, the world would be greener and the U.S. taxpayer would be richer.
Ethanol is not going to solve the world's energy problems on its own. But its proponents do not claim that it would. Ethanol is just one of a portfolio of new energy technologies that will be needed over the coming years. Good ethanol, that is - not the bad stuff the U.S. is so keen on.
If you stop and think about it for a minute, it should be reasonably obvious that growing this huge 7 or 8' tall plant, and then throwing away almost all of it except for some tiny little seed kernels, is a huge waste of energy. By contrast, cellulosic ethanol can be made from (among many other things) the otherwise thrown away corn stalks, which comprise a huge percentage of total corn plant mass. And we still get to eat the corn, too.
It's also worth noting that algae based oils appear to have a lot of potential.