Grape pomace and other grape processing residues, when released in the environment, can lead to serious pollution, ranging from surface and groundwater pollution to foul odours. They also attract flies and pests. The use of these products for fertilizers or composts on soils can cause an increase in nitrogen leaching and oxygen depletion due to the presence of tannins and other compounds (Bekhit et al., 2016). Disposing of pomace as fertilizer back into the vineyards may cause phytopathological issues (Baumgärtel et al., 2007). These products also contain heavy metals. Better environmental management of these wastes and their utilization for other purposes, including livestock feeding, is increasingly necessary, and there is strong legislative pressure in that direction (Bekhit et al., 2016). It is possible that grape pomace is still underused in animal feeding: in the late 1980s, it was estimated that only 3% of grape pomace produced in the Mediterranean area was fed to livestock (Magnier, 1991).
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