As well as being the early morning fuel for billions of office workers, researchers have discovered that coffee, in the form of spent grounds, makes a pretty decent biofuel.

The Nevada-based team recently pointed out that one barrier to greater eco-friendly biofuel use is a missing source of high-quality, low-cost fuel-producing material, which is where coffee enters the frame. By weight, spent coffee grounds have around 11% to 20% of oil remaining inside. That figure compares well with more usual biofuels like palm, rapeseed and soybean.

The team estimates that of the 16 billion pounds of coffee bean grown annually--which when spent ends in the trash or on compost heaps--up to 340 million gallons of biodiesel could be made. To demonstrate this, they collected used grounds from one multinational coffee house, extracted the oil and used a cheap-to-run process to turn it into biodiesel with 100% conversion efficiency. Because it's packed with antioxidants, the resulting coffee-fuel is actually more stable than some other biodiesels.

It sounds like a complete win-win: a trashed product makes a biofuel cheaply, the environment benefits, and the spare products from biofuel-making can be used to make ethanol or compost. Best of all--the fuel actually smells like coffee.

[American Chemical Society via Dvice]