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.