Composting and evaluating a pulp and paper sludge for use as a soil amendment/mulch

Abstract

Composting could be used in the pulp and paper industry to treat primary sludges as an alternative to landfilling. The objective of this project was to compost and evaluate a pulp and paper sludge for use as a soil amendment/mulch. Primary sludge, tailings, wood ash (0, 5 or 10 percent by volume), and paunch (cattle stomach contents and tissue) from a slaughterhouse were composted in a 91 m windrow that was turned one to two times per week. The pile moisture content and temperature were controlled at 50 percent and 57–63°C during 14 weeks of composting. The compost was then cured for 4 weeks for a total treatment time of 18 weeks. Sludge dry mass decreased by approximately 50 percent, pH increased slightly to 8.2 to 8.5, and carbon-nitrogen ratio decreased from 270:1 to 14–67:1 after composting and curing. Electrical conductivity of all final composts was over 4 dS/m. Shoot biomass of tomato plants grown in a compost-amended medium (50 percent compost, 25 percent sand, 25 percent perlite by volume) improved with composting time but was still only 35–65 percent that of plants grown in a peat moss-amended medium (control). Shoot weight and height of poplar plants grown in soil amended with aged compost were unaffected by compost application rate (incorporated or as a mulch) at less than or equal to 180 Mg/ha. In summary, this study demonstrated that a pulp and paper sludge and wood ash mixture yielded a compost that could be used as a low quality mulch or soil amendment for poplar. © Taylor & Francis Group, LLC.