Use of biochar for the sorption of volatile organic compounds (VOCs) emitted from cattle manure

The ability of biochar to be used as filter or as additive for the adsorption of volatile organic compounds (VOCs) emitted from cattle manure is investigated. The employed biochar was produced from cattle manure after slow pyrolysis at 550 °C (under nitrogen). Towards this, in-house-made glass emission reactors were filled with fresh cattle manure samples and a thin layer of biochar (10% w/w) was placed on the top of the manure layer. The mixture was left for 24 h to equilibrate and air samples were collected from the headspace air. The samples were then analyzed using the headspace solid-phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) method. Cattle manure emissions are considered unpleasant and odoriferous. The respective changes in the emitted cattle manure VOCs were reported; these included mainly reduction in sulfur- (thiols and sulfides) and oxygen-containing VOCs (alcohols, ketones, phenolics), showing a promising application of biochar for the removal of such compounds from manure wastes. Also, five VOCs were selected as sorbents for further laboratory studies: hexane, dimethyl trisulfide, phenol, p-cresol, and 2-methyl-3-pentanone. The results of cattle manure-derived biochar, revealed a reduction in their emitted concentrations (low ppbv). The present application highlights a straightforward example of cyclic economy, where a waste product is reused after being processed; its re-usage as odor adsorbent serves again the agriculture sector.