Evaluating composting and co-composting kinetics of various agro-industrial wastes

Purpose Agro-industrial wastes are posing serious challengesfor the agro-industries. Composting and co-compostingof such wastes will lead to converting such wastesinto a useful product that will serve as a soil conditioner.The present research investigated the kinetics of compostingand co-composting of several agro-industrialwastes.Methods Seven pilot scale composting and co-compostingpiles of substrates from grain dust (GD), coffee-processingwaste (CPW) and olive mill waste (OMW) were tested.Temperature and moisture content of the piles were monitoredduring the composting process and adjusted whenevernecessary.Results The biodegradation kinetics was found to be offirst order for all composting and co-composting piles. Asjudged by the value of the reaction rate constant, and thetemperature of the piles, the biodegradability of the graindust was the highest among all composting piles, followedby the coffee-processing residue and finally the fresh olivemill waste. As for the co-composting, the highest degradabilitywas noticed in the pile that was composed of graindust and coffee-processing waste followed by that of graindust mixed with dry olive mill waste, and then followed bycoffee-processing waste and dry olive mill waste andfinally by grain dust with fresh olive-processing waste.Conclusions Composting and co-composting of agro-industrialwastes is a low cost and an environmentallyfriendly waste management option for solving the problemof the disposal of such waste. The study revealed that allpiles followed first-order kinetics with differentbiodegradability rates.