Efficacy of Different Biochars in Removing Odorous Volatile Organic Compounds (VOCs) Emitted from Swine Manure

The potential of various biochars to remove 15 odorous volatile organic compounds emitted from swine manure were investigated via laboratory sorption experiments. Nine biochars made from pyrolyzing poultry litter, swine manure, oak, and coconut shell at 350 °C and 500 °C and a commercial coconut-shell activated carbon were evaluated for their sorption capacities toward the odorous compounds. These 15 odorous volatile organic compounds (VOCs) consisted of reduced sulfur compounds, volatile fatty acids, phenolic, and indolic compounds. The sorption capacities of these biochars were investigated using a laboratory-scale sorption column system. Among the 15 targeted VOCs, acetic acid was the most predominant compound in the emitted gas from swine manure; however, its contribution to the complex swine manure odor mixture was minimal. Dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) were the two most odor-causing VOCs in the swine manure emissions based on single compound odor active values. Livestock-manure-based biochars were poor sorbents for DMDS and DMTS. In contrast, plant-biomass-based biochars had considerably larger sorption capacity for DMDS and DMTS. Oak biochar pyrolyzed at 500 °C (OK500) showed high sorption capacities for both DMDS and DMTS. Although the sorption capacity of OK500 for DMDS is less than that of commercial activated carbon, it may provide additional income for users if the spent OK500 biochar can be sold as a soil amendment.