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The solid waste left over from winemaking could make a competitive biofuel, University of Adelaide researchers have found.
Published in the journal Bioresource Technology, the research showed that up to 400 litres of bioethanol could be produced by fermentation of a tonne of grape marc (the leftover skins, stalks and seeds from winemaking).
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Global wine production leaves an estimated 13 million tonnes of grape marc waste each year, and it’s generally disposed of at a cost to the winery.
‘Using plant biomass for the production of liquid biofuels can be difficult because of the structurally complex nature, which 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.’
Kendall Corbin, PhD candidate
PhD candidate Kendall Corbin analysed the composition of grape marc from two grape varieties, cabernet sauvignon and sauvignon blanc. She also investigated pre-treatment of the grape marc with acid and enzymes.
Ms Corbin 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 litres per tonne of grape marc. The leftover product was suitable for use as an animal feed or fertiliser.
Ethanol yields could be increased by up to 400 litres a tonne through pre-treatment with acid and enzymes.
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