From Ecoworld:

Will Biofuel Replace Crude Oil? There is a lot of discussion these days about biofuel, and there should be. Biofuel is an excellent fuel – it burns cleaner than petroleum-based fuels and is easier on the internal combustion engine. Moreover, we can grow biofuel, which means it is totally renewable. But can biofuel completely replace crude oil?

The answer, at least for now, is absolutely not. As the table below shows, even if a fairly high-yielding biofuel crop were planted all over the world, yielding 1,000 barrels of oil per year per square mile, and even if this biofuel were grown on every available scrap of farmland on earth, we would only replace 20% of the energy we’re currently getting from crude oil. The algebra is immutable – about 10% of the world’s land area consists of arable farmland, about 5.7 million square miles. If 100% of that land was planted with biofuel crops yielding 1,000 barrels of oil per square mile, each year that would produce 5.7 billion barrels of biofuel. But world consumption of crude oil currently stands at 85 million barrels per day, which equates to 31 billion barrels per year. Biofuel will greatly supplement crude oil supplies, and is an important part of future energy solutions, but that’s as far as it goes.