Starbucks' Food Waste Fuels Experimental Biorefinery

An experimental biorefinery turns spent coffee grounds and old pastries from Starbucks into a building block for plastic. Using food waste as fuel might improve the sustainability of biobased chemical production, the researchers say.

Oil refineries clean up crude oil to produce fuel for cars, trucks and planes. Side products from that process include building blocks for plastics, fabrics and detergents, like lactic acid, succinic acid and glycerol.

Biorefineries could reduce our dependence on fossil fuels by creating fuel from renewable sources of energy like plant biomass. Right now, many biorefineries consume sugars and starches from corn – a plant we eat as food. Should food supplies become scarce, humans and biorefineries would compete for fuel. Energy from food waste, instead of food plants, could make biobased chemical production more sustainable.

Carol Lin, at the City University of Hong Kong, and her coworkers developed a tabletop biorefinery to run on food waste from Starbucks. Fungi first break down the food into sugars. Then bacteria transform those sugars into succinic acid, a chemical building block for plastics, spandex, detergents and deicing solution.

Starbucks Hong Kong donated money to help fund Lin’s research, which she presented at a meeting of the American Chemical Society last week. The company produces nearly 5000 tons of food waste yearly in Hong Kong alone, which would normally be burned or buried in landfills.

Lin says she is adapting the biorefinery to make other chemicals from the pastry waste. And there is funding to test the technology on a pilot scale in Germany, she said in a statement.

Some companies already produce succinic acid using sugars in wheat and corn. BioAmber, based in Minneapolis, Minnesota, is running a pilot plant in France and plans to open a larger plant in Ontario in 2013. The new plant will produce 18 thousand tons of succinic acid at first, scaling up to more than 38 thousand tons at peak production. Reverdia will soon open a plant in Italy that can produce about 10 thousand tons of succinic acid yearly.

The “food versus fuel” debate over the sugar source for biorefineries often involves biofuel production more than chemical production. About 33 to 40% of corn in the U.S. goes towards making ethanol. And in a year where drought affects corn supplies, some groups are pushing government agencies to reduce their biofuel mandates.
Meanwhile, biobased chemical production remains under their radar.

One way to sidestep this debate – for both fuels and chemicals – involves using cellulose in wood pulp and dried corn stalks as a sugar source. But this approach can't produce cost-competitive biofuels right now. It takes too much energy to disassemble rigid cellulose fibers into edible sugars for biorefinery microbes. Nevertheless, some companies hope to find ways to use cellulose for biobased chemical production.

One day our favorite fuels, plastics and detergents may come from plant and food waste instead of fossil fuels.