Used coffee grounds have been turned into a cheap, renewable fuel that can be used in wood-burning stoves, according to a young entrepreneur who claims his invention will cost half the price of coal, wood or charcoal.

Bio-bean, which was founded three years ago by architecture student Arthur Kay, collects coffee slops from a network of coffee shops, retailers, airports and coffee factories, and turns them into biofuel.

The grounds are stripped of oil and packed together to form small bricks, which do not release an aroma when burnt, despite being made from used coffee.