Bentonite as an additive in the composting of wastewater sludge from the poultry agroindustry

Abstract The objective of this work was to evaluate the use of bentonite as an additive in the composting of wastewater sludge from the poultry agroindustry regarding nitrogen conservation, carbon degradation, and nutrient content increase. The experimental design was completely randomized with five treatments with bentonite at 0, 0.5, 1.0, 3.0, and 6.0%, with three replicates. The organic compost used in the treatments consisted of pine sawdust and wastewater sludge from the treatment plant. During and after the composting process, the following were analyzed, respectively: pH, dry matter, temperature, and C, N, NH4+, NO2-, and NO3- contents; and P, K, Ca, Mg, Cu, and Zn contents and humic and fulvic acid concentrations. Bentonite at 6.0% increased C degradation, N losses, Mg content, and humification, but decreased Zn content and humidity. Bentonite, as an additive in the composting of sludge from the poultry agroindustry, promotes humification, decreases Zn content and humidity, but does not affect pH and P, K, Cu, NH4+, NO2-, and NO3- contents.