Global wine production leaves an estimated 13 million tons of grape marc (the leftover skins, stalks and seeds from wine-making) waste every year. This is generally disposed of at a cost to the winery. Researchers from the University of Adelaide have now revealed that this solid grape waste left over from wine-making could be used to prepare bio-fuel. The researchers suggested that up to 400 liters of bio-ethanol could be produced by fermentation of a ton of grape marc.
Rachel Burton said, "This is a potentially economic use for what is largely a waste product." The researchers analyzed the composition of grape marc from two grape varieties - cabernet sauvignon and sauvignon blanc. Burton also investigated pre-treatment of the grape marc with acid and enzymes.
The researchers 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 ton of grape marc. The leftover product was suitable for use as an animal feed or fertilizer. Ethanol yields could also be increased by pre-treatment with acid and enzymes up to 400 liters a ton.
Co-researcher Kendall Corbin said, "Using plant biomass for the production of liquid bio-fuels can be difficult because of it structurally complex nature that is not always easily broken down. Grape marc is readily available, can be sourced cheaply and is rich in the type of carbohydrates that are easily fermented."
The findings were published in Bioresource Technology.