Synthetic liquid fuels program is about finding ways to make fuels, like gasoline for cars and jet fuel for airplanes, out of something other than oil. Scientists are trying to use materials like plant waste, water, and air to make fuels so that we don't have to use so much oil. Oil is a fuel that comes from the ground, and it's a limited resource — so when it runs out, we need to have something else to run our cars and planes. The synthetic liquid fuels program is trying to figure out how to do this.