Published in the journal Bioresource Technology, the Australian researchers showed that up to 400 liters of bioethanol could be produced by fermentation of one metric ton of grape marc (the leftover skins, stalks and seeds from wine-making).
Global wine production leaves an estimated 13 million metric tons of grape marc waste each year. In Australia alone it is estimated that several hundred thousand metric tons are generated annually and it is generally disposed of at a cost to the winery, the researchers say.
The study found that the majority of the carbohydrates found in grape marc could be converted directly to ethanol through fermentation with a yield of up to 270 liters per metric tons of grape marc. The leftover product was suitable for use as an animal feed or fertilizer.
Ethanol yields could be increased by pre-treatment with acid and enzymes up to 400 liters per metric ton.
In July, United Airlines announced a $30 million investment in biofuel developer Fulcrum BioEnergy. United says this is the single largest investment by a US airline in alternative fuels.