Biodegradation Assessment of Woolscour Sludge and Fellmongery Sludge

Sustainable land application of agricultural and industrial wastes requires an understanding of factors likely to limit waste decomposition and the release of plant‐available nitrogen. This paper describes the biodegradation of a woolscour sludge and a fellmongery sludge and suggests a biodegradation assessment strategy suitable for agricultural and industrial wastes. After 50 d of decomposition in microcosms, the woolscour sludge mineralized 18% of initial C and 9% of initial N, while the fellmongery sludge mineralized 37% of initial C and 53% of initial N. Net N mineralization from woolscour sludge was principally constrained by the recalcitrant behaviour of the wool fiber component, whereas elevated temperature (43°C) or anaerobic conditions constrained fellmongery sludge decomposition. Two negative consequences of soil amendment were identified. First, soil amended with fellmongery sludge leached up to 39% of applied sludge N as mineral N during 100 d of decomposition. Second, both sludges caused a reduction in microbial blomass (MB) after 1 yr of soil amendment. Our data indicated that the woolscour sludge was a substrate of low quality for soil microbial metabolism and that chemical parameters are a poor predictor of biodegradation. On the other hand, the fellmongery sludge was a substrate of moderately high quality for which chemical characteristics permitted relatively consistent prediction of N mineralization.