Researchers from the University of Adelaide in South Australia claim that as many as 400 litres of bioethanol could be produced through the fermentation of a tonne of grape marc.
Wine makers globally generate every year about 13 million tonnes of grape marc -- the leftover skins, stalks and seeds. This waste product has carbohydrates that can be converted directly to ethanol through fermentation, the university said in August.
A study by PhD candidate Kendall Corbin has concluded that grape marc from cabernet sauvignon and sauvignon blanc can yield of up to 270 litres of the biofuel per tonne. The leftovers from that process can then be used as animal feed or fertiliser. The output per tonne could reach 400 litres via pre-treatment with acid and enzymes. 
“Grape marc is readily available, can be sourced cheaply and is rich in the type of carbohydrates that are easily fermented,” Corbin commented. The results of the study have been published in the journal Bioresource Technology.

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