Greenbang has been covering a bunch of different biofuel sources lately, everything from confiscated booze to poo to milk. In fact, it makes us wonder what can’t be turned into a biofuel.

To answer the question, Earth2Tech has helpfully put together a guide to the biofuel economy, giving an A to Z of alternative fuels, from apples and beer (why, we ask) to Xylose and Zeolite. Read on…

Coffee: Starbucks brand biofuels? Well, maybe. Apparently, coffee grains have enough sugar content to be turned into ethanol. Research paid for by Columbia’s Federación Nacional de Cafeteros (National Coffee producers Federation, Federcafé) found that coffee has an even higher sugar content per bushel than corn. If accurate, coffee prices could soar, and Starbucks might be in trouble.