Co-composting winery waste and zeolite: a sustainable valorisation example

he paper aims to valorise winery waste into a co-composting process with natural clinoptilolite zeolite to improve the agronomic value of compost and simultaneously achieve sustainable recycling of organic wastes. The innovation of this study lies in the role of natural zeolite in winery waste valorisation and recycling.The winery waste materials after the harvest were composted in the presence of natural clinoptilolite zeolite at the following rates: (1) zeolite 0% wastes 100% (0Z, control); (2) zeolite 10%: waste 90% (10Z); (3) zeolite 30%:waste 70% (30Z). The experimentation was set up in Tuscany-Italy, characterised by a typically Mediterranean semiarid climate. We evaluated the response of chemical and biochemical properties to different rates of zeolite in the winery waste composting process.The presence of zeolite at the two rates (10Z and 30Z) during the composting of winery wastes enabled higher retention of nutrients (N, P and K), enzymatic activity and humification of the organic matter concerning control compost (0Z). In addition, in zeolite based-composts, a decrease in electrical conductivity and an increase in germination index were observed, thus indicating the improvement of the agronomic quality of the compost.Moreover, the winery waste-based compost with zeolite mainly responds to the threshold level of the current EU Fertiliser Regulation (1009/2019), which promotes the EU Market production and using fertilisers from recycled biowaste.