"...grape skins, like all plant matter, contain carbohydrates that can be broken down into sugar and fermented. And enough ethyl alcohol can be distilled from the skins to make a decent source of biofuel or gas additive. After the annual pressing, Caviro alone procures 100,000 tons of marc from vineyards and farms across Italy."
News and information about Biodiesel & alternative fuels.
This month's Wired has an interesting article about how they're starting to make wine-based ethanol in Italy: