EVALUATING THE QUALITY OF COFFEE HUSK AND BREWERS’ SPENT GRAIN COMPOSTS BY ENZYME ACTIVITY, PHYSICAL PARAMETERS AND YIELD OF WHEAT

Every year huge amounts of coffee and beer industries byproducts are produced. Fates of these byproducts are several, including landfill or accumulation in natural areas where they may give environmental side effects such as leaching of phenolic compounds and contaminants. . Composting of coffee husk and brewers’ spent grain with addition of organic amendments or alone is one of the best ways for their management. Composting is a virtuous oxygen-driven biological process able to detoxify byproducts and produce valuable amendments to be used in agriculture. Composting experiments were done in the greenhouse of the Università Politecnica delle Marche (Ancona, Italy) during the 2018/2019 winter season. Raw materials were coffee husk (CH), brewer’s spent grain (BSG), and cow manure (CM), which were mixed in three piles with the ratio of 2:1 (CH+BSG), 4:1 (CH+CM), and 5:3:2 (CH+BSG+CM). Composting lasted for 90 days. Compost was made by aerated static pile method by stacking piles inside plastic boxes of about 1 m3 volume that were installed with pipes in the bottom for aeration. After mixing 300 kilograms of materials in every pile, they were covered with plastic cloth to maintain humidity and temperature. To favour air movement, the piles were built including layers of wood chips between raw materials so as to increase porosity. Aeration was ensure by compressor every ten days for 15 minutes, and excess water was allow to drained out of the boxes by holes . The coffee husk was rather moist that was spread on plastic cloth for one month to allow it loosing water before to be stacked into the boxes. The dynamics of enzyme activity, microbial diversity and physical parameters of compost were monitored over all the composting period.