Deodorization of swine manure using minced horseradish roots and peroxides

Public concerns about offensive odors from livestock manures are on the rise and so is the pressure to develop practical ways to reduce the odors. The use of minced horseradish (Armoracia rusticanaL) roots (1:10 w/v plant tissue to swine slurry ratio), with calcium peroxide (CaO2 at 26 or 34 mM) or hydrogen peroxide (H2O2 at 34, 52, or 68 mM) for the deodorization of swine manure, was evaluated through a series of laboratory experiments. The principle underlying this deodorization method is the oxidation of odorants by the concerted action of horseradish peroxidase (present in the plant tissue) and peroxide that serves as an electron acceptor, followed by polymerization of phenolic odorants with a possible copolymerization or adsorption of other odorant compounds. The deodorization effect was assessed by a human panel and gas chromatography (GC). In the case of the GC method, 12 compounds commonly associated with malodor (7 volatile fatty acids or VFAs, 3 phenolic compounds, and 2 indolic compounds) were used as odor indicators. Malodor assessment of the treated slurry by a human panel indicated a 50% reduction in odor intensity. GC results showed 100% removal of all phenolic odorants without reoccurrence for at least 72 h. In view of these data, using plant materials as enzyme carriers and peroxides as electron acceptors emerges as an effective approach to phenolic odor control in animal manure.