Researchers at the University of Nevada-Reno claim that waste coffee grounds can provide a cheap, abundant, and environmentally-friendly source of biodiesel fuel for cars and trucks.
The major barrier to wider use of biodiesel fuel is lack of a low-cost, high-quality source, or feedstock.
Spent coffee grounds contain between 11 and 20 per cent oil by weight - about as much as traditional biodiesel feedstocks such as rapeseed, palm, and soya bean oil.
The used or 'spent' grounds remaining from coffee production often end up in the rubbish or find use as soil conditioner.
The Nevada scientists estimate, however, that spent coffee grounds can potentially add 340 million gallons of biodiesel to the world’s fuel supply.
To verify it, the scientists - Mano Misra, Susanta Mohapatra, and Narasimharao Kondamudi - collected spent coffee grounds from a multinational coffeehouse chain and separated the oil.
They then used an inexpensive process to convert 100 per cent of the oil into biodiesel.
The resulting coffee-based fuel had a major advantage in being more stable than traditional biodiesel, due to coffee's high antioxidant content, the researchers said.
Solids left over from the conversion can be converted to ethanol or used as compost.
The scientists now plan to develop a small pilot plant to produce and test the experimental fuel within the next six to eight months.
The researchers published their work online in the American Chemical Society’s (ACS) Journal of Agricultural and Food Chemistry, a bi-weekly publication.