Dynamics of the co‐composting of barley waste with liquid poultry manure

Co‐composting of barley waste with liquid poultry manure was assessed by monitoring several chemical and biological parameters related to compost stability/maturity throughout a 103 day period. A compost of solid poultry manure was used as the control, because a compost could not be obtained from the liquid manure. The materials composted reached thermophilic stage temperatures within 4 days, lasting for more than 10 days; thereafter the temperature decreased rapidly to around ambient levels. The initial pH value was around 9 for both mixtures and, despite an initial decrease, high values were maintained over the entire co‐composting process. Electrical conductivity increased with composting time, while the opposite behaviour was observed for total carbon content. Organic matter loss in the co‐composting of barley waste with liquid poultry manure was 35%. In general, the final products showed physicochemical characteristics considered normal for such materials, but pH and ammonia content values were high. The results of a bioassay test performed with seeds of three plant species (ryegrass, wheat and barley) indicated that the co‐compost could be considered mature from a biological point of view, since phytotoxicity was absent for ryegrass and barley. Comparison of these data with those obtained for solid poultry manure indicated that barley waste notably improved the composting efficiency as well as the quality of the final product. © 2003 Society of Chemical Industry