Composting and co‑composting of coffee husk and pulp with source‑separated municipal solid waste: a breakthrough in valorization of coffee waste

Purpose In this study, the composting and co-composting potential of coffee husk and pulp with source-separated municipal solid waste (SSMSW) was investigated. Methods Coffee husk and pulp were mixed independently with SSMSW in different proportions (0, 33, 50 and 100%), and composted in triplicates with a total of 24 composting piles for 3 months. From each compost type, different physicochemical parameters were analyzed. In addition, the seed germination, growth and fresh head weight yield of each compost type were investigated on each matured compost type using cabbage seed (Brassica oleracea). Results The results indicate that the two coffee by-products can be composted alone or co-composted with SSMSW yielding very mature and stable compost. The results indicated that the addition of 1/4th of local soil (wt/wt) on C8 compost type yields the optimum fresh head weight of the cabbage among all field experiments. In addition, when C8 compost type is mixed with local soil in 3:1 ratio, it could yield an optimum fresh head weight of the cabbage (572 ± 10 g/kg of compost). This could be due to the relatively higher concentration of total nitrogen in the C8 compost sample. Conclusions Generally, the final compost can be served for unrestricted type of agricultural purposes. Thus, co-composing of coffee husk and pulp with SSMSW can alleviate the multidimensional problems of rural and urban dwellers.