Control of hydrogen sulphide, ammonia and odour emissions from swine barns using zinc oxide nanoparticles

Abstract

Application of zinc oxide (ZnO) nanoparticles was evaluated as a possible measure to mitigate the levels of hydrogen sulphide (H2S), ammonia (NH3) and odour in swine facilities. Two deployment techniques were investigated: direct mixing of zinc oxide nanoparticles into the slurry, and filtration with nanoparticles as filtering media for the manure gases. The overall goal of this work was to determine the impact of the treatments on hydrogen sulphide, ammonia and odour emissions, pig performance and manure characteristics as well as to assess the feasibility of the application of this technology in a typical swine barn.

Semi-pilot scale tests were conducted to evaluate operational factors in open system conditions, the results of which showed that the mixing method required a particle-to-slurry ratio of 3 grams of zinc oxide per litre of slurry to control hydrogen sulphide and ammonia levels. Using the air filtration technique, a fluidized bed filter design with a 0.28 g/cm2 loading rate and rated at 0.5 m/s face velocity was found to be the most effective combination for controlling gas levels. Room-scale experiments were conducted in specially designed chambers to assess the effectiveness of the treatments under conditions that represent commercial swine production. The addition of zinc oxide nanoparticles into the manure achieved more than 95% reduction in hydrogen sulphide levels while no significant effects on ammonia concentrations were observed. Zinc oxide nanoparticles were persistent in maintaining low hydrogen sulphide levels up to 15 days after treatment application. On the other hand, the ventilation air recirculation system with a zinc oxide filter achieved significant reduction in both hydrogen sulphide and ammonia concentrations at the animal- and human-occupied zones. Neither treatment had any significant impact on pig performance and manure nutrient characteristics. Estimates of the cost of application of the treatments in a 100-head grow-finish room showed that employing the air filtration method amounted to around 3.8% of the average total cost of production, which was economically more feasible than the mixing method; however, various options can be pursued to further reduce the cost of application of both treatments.