Biofuel from wine waste

Global wine production leaves an estimated 13 million tonnes of grape marc waste each year. It is estimated that Australia generates several hundred thousand tonnes annually, which is generally disposed of at a cost to the winery.

Researchers from the University of Adelaide have discovered a new use for the waste — creating a competitive biofuel from the skins, stalks and seeds that are left over from winemaking.

Published in the journal Bioresource Technology, the researchers showed that up to 400 L of bioethanol could be produced by fermentation of a tonne of grape marc.

“This is a potentially economic use for what is largely a waste product,” said Associate Professor Rachel Burton, Program Leader with the Australian Research Council (ARC) Centre of Excellence in Plant Cell Walls in the School of Agriculture, Food and Wine.

PhD candidate Kendall Corbin analysed the composition of grape marc from two grape varieties — cabernet sauvignon and sauvignon blanc — and found that the majority of the carbohydrates found in the waste could be converted directly to ethanol through fermentation with a yield of up to 270 L per tonne of grape marc. The leftover product was suitable for use as an animal feed or fertiliser.

Ethanol yields could be increased up to 400 L a tonne by pretreatment with acid and enzymes.

“Using plant biomass for the production of liquid biofuels can be difficult because of its structurally complex nature that is not always easily broken down,” said Corbin.

“Grape marc is readily available, can be sourced cheaply and is rich in the type of carbohydrates that are easily fermented.”

Associate Professor Burton said: “We’ve shown that there is a potential new industry with the evolution of local biofuel processing plants to add value to the grape for an environmentally friendly biofuel.”