Removing Odorous Volatile Organic Compounds Emitted from Swine Manure Using Biochar

The potential of various biochars in removing swine manure odorous volatile organic compounds were investigated via laboratory sorption experiments. Nine biochars made from pyrolyzing poultry litter, swine manure, oak, and coconut shell at 350 and 500 ⁰C and a commercial coconut-shell activated carbon were evaluated for their sorption capacities toward odorous compounds. These odorous volatile organic compounds (VOCs) consisted of 15 reduced sulfur (S) compounds, volatile fatty acids (VFAs), phenolic and indolic compounds emitted from swine manure. The sorption capacities of these biochars were investigated using a laboratory-scale sorption column system. Among the 15 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 (SCOAVs). Animal-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 ^oC (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 be more economically advantageous if the spent biochar can be applied as a soil amendment.