Meet Jay Keasling, a synthetic biologist experimenting with ways to produce a cleaner-burning fuel from biological matter. Keasling's approach involves genetically engineering microbes to eat simple sugars found in plant matter and then excrete fuel. 

The video from KQED's QUEST explains two techniques that may enable Keasling to accomplish this: metabolic engineering and directed evolution. It also suggests that creating biofuels from plants may actually contribute to global warming rather than help combat it.