Windrow composting: a viable option for the management and conversion of various agro- industrial organic wastes in Ethiopia

Windrow composting is a biotechnological process where microorganisms decompose and stabilize solid organic wastes under aerobic conditions, creating stable and odorless compost. This study investigates the composting of four frequently discarded municipal and industrial wastes (brewery sludge and solid waste from potato chips factory) around Debre Berhan city and Tulefa town, Ethiopia, examining the change in key physicochemical properties. Experimental wastes were blended with powdered cow dung in a 3:1 ratio and composted in four triangular-shaped piles using the windrow technique under shade. The original physicochemical characteristics of all wastes and the resulting final compost underwent analysis for temperature change, volume reduction, pH, total Kjeldhal nitrogen( TKN), total potassium( TK), total phosphorous( TP), total organic carbon (TOC), and carbon to nitrogen ratio (C:N). All treatments (T1 = brewery sludge + cow dung, T2 = solid waste from potato chips factory + cow dung) demonstrated significant volume reduction, ranging from 60% to 70%. The final pH of the compost in all treatments shifted towards neutral (7-7.4). Additionally, all treatments achieved thermophilic temperatures within 15-28 days. The thermophilic phase persisted for 15 to 35 days across treatments, followed by a cooling phase that occurred between 49 and 77 days later. The cessation of further temperature rise was observed between 77 and 99 days. Across all windrows, significant changes were observed in key parameters such as TKN, TK.TP, TOC, and C:N ratio. These findings suggest that windrow composting is a viable alternative for effectively reducing substantial quantities of solid organic waste from residential areas and agro-processing industries, while also producing organic soil amendments that support sustainable agriculture.