Composting of de-inking paper sludge with poultry manure at three nitrogenlevels using mechanical turning: behavior of physico-chemical parameters

De-inking paper sludge (DPS) is rich in carbon (C) but poor in nitrogen (N) . Thus, it has a high C:N ratio which limits the composting process. Accord ingly, the goal of this study was to investigate the effect of three N trea tments on DPS composting. Compost piles of 100 m(3) were formed by mixing r aw DPS with poultry manure and chicken broiler floor litter, giving on aver age 0.6%, 0.7% and 0.9% total N. The changes in physico-chemical parameters , total weight and fiber losses, and maturity of composting piles of DPS. w ere monitored during 24 weeks. The compost piles had a neutral to alkaline pH throughout the study. Inorganic N decreased whereas organic N increased over time for all treatments. These changes in magnitude were different amo ng N treatments resulting in a final total N content of 0.9% for the 0.6% N treatment whereas final total N contents of 0.7% and 0.9% N were measured for the 0.7% and 0.9% N treatments. The total weight, cellulose and hemicel lulose losses were higher in 0.6% N treatment giving the lowest C:N ratio a fter 24 weeks of composting. However, none of the 24 week-old composts of D PS were mature based on their final C:N ratio and colorimetric test of matu rity. Except for copper, their final total trace element contents meet most known standards or guidelines for organic soil conditioners. Overall, 0.6% N treatment was the best to enhance DPS composting using mechanical turnin g, but a period of more than 24 weeks was required to reach compost maturit y. Crown Copyright (C) 2001 Published by Elsevier Science Ltd. All rights r eserved.