Biofuels ”“ made from algae and non-food plants ”“ are emerging as a potentially viable alternative to conventional jet fuels. Although big challenges remain, the reductions in greenhouse gas emissions could be major.

Two decades after the Exxon Valdez spilled 11 million gallons of crude oil into Alaska’s waters, the Prince William Sound, its fishermen, and its wildlife have still not fully recovered.

A number of companies, including one headed by biologist and entrepreneur Craig Venter, are developing genetically engineered biofuels that they say will provide a greener alternative to oil. But some environmentalists are far from convinced.