biofuel

Fuel made directly from biological sources. Primary examples include methane, biodiesel, ethanol, methanol, and vegetable oil. Oil is not considered a biological source due to the time frame involved. Aside from energy put into production, biofuels are generally considered to be "carbon neutral" because some or all of the carbon in the fuel comes from the atmosphere, and is released back when burned.

We have the technology to replace 100% of our transportation fuels with biofuels from algae. You use solar thermal heat pipes to move seawater into the desert, and then grow algae on thermal raceways with solar paddlewheels. The lipids become green diesel and the remainder is processed for Butanol.