Henry Ford (above, at the wheel of a Model T)
designed his "Tin Lizzie" to run on either gasoline or a hemp-based
fuel. But with the discovery of large crude-oil deposits in the early 20th
century, oil prices dropped and gasoline derived from the oil became
Ford's and other carmakers' fuel of choice. Unlike fossil fuels,
biofuels come from renewable resources, typically plants. Although biofuels
have many advocates, skeptics point out that they currently require too many
resources to be used on a widespread commercial basis.