Biofuels probably are going to be a necessary transition. However, because they are carbon-based, these fuels do not overcome problems with our existing energy cycle that contribute to global warming.

True, biofuels are made of plants that capture atmospheric carbon dioxide, which is later released when the biofuel is burned, so they are regarded as carbon-neutral. But that doesn't account for the CO2 we've already released and which is already a factor in the global warming cycle.

In the long run we need to reduce such emissions, not prolong them through prolonged use of carbon-based fuel sources. Indeed, biofuels certainly will have environmental impacts of some kind. If it were to turn out that biofuels are relatively economical, they could nevertheless still contribute to environmental problems that will obviate their benefits. What good will biofuels be in Third World countries -- or even the United States -- where increasing mean temperatures make it harder if not impossible to grow the plants that are their raw material?

Carbon sequestration is one possible solution, but of course that will require additional energy consumption, more money, and a sizable, long-lasting social commitment.

Secondly, biofuels represent a zero-sum game. Huge tracts of farmland would be needed to produce enough biofuel to supplant petroleum. But the world is already short of food. As James Jordan and James Powell of the Polytechnic Institute of New York wrote in a July article in the Washington Post, "Considering projected population growth in the United States and the world, the humanitarian policy would be to maintain cropland for growing food -- not fuel. Every day more than 16,000 children die from hunger-related causes -- one child every five seconds."

Biofuel development might benefit developed nations and a subset of Third World citizens and businesses, but not the great masses who are already struggling to get enough to eat. Could waste byproducts from food farms suffice to produce enough biofuel? It doesn't seem likely.

Of course, another possibility is that we could encourage population controls, but in Third World countries, large families are almost a necessity for survival, and the transition to a mechanized, energy-intensive economy won't come before such controls can be realized, assuming everyone even agrees they should be a goal.

For environmental and cost reasons, over many areas of the planet and Third World countries especially, photovoltaics and solar heating arguably remain better options as the oil era winds down.