Grape seeds, skins and stems are the marc (the solid that
remains after pressing the grapes during wine production), which
can be separated from the must through mechanical methods (cold
pressing). Approximately 100 kg of grapes get 80–85 kg of must,
9–10 kg of husks, 3–4 kg of stalks and 3–4 kg of seeds. In Italy,
the production of wine waste is 2.3 million tons per year