WHEAT STRAW COVER FOR REDUCING AMMONIA AND HYDROGEN SULFIDE EMISSIONS FROM DAIRY MANURE STORAGE

Abstract

Analysis of the use of a wheat straw cover for reducing ammonia and hydrogen sulfide emissions from liquidmanure was conducted in both a laboratory and a pilot system. Two straw covers with different thicknesses (5 cm and10 cm) were evaluated for their effectiveness in reducing odorous gas emissions. The rates of ammonia and hydrogensulfide emissions from the treatments were monitored; concentrations of ammonia, dissolved sulfide, chemical oxygendemand (COD), and pH of the liquid manure were measured. Additionally, the overall mass transfer coefficients ofammonia and hydrogen sulfide were calculated for the conditions of the experiment. The results demonstrated that boththe 5-cm and 10-cm straw covers were effective in reducing ammonia and hydrogen sulfide emissions from manurestorage. In the laboratory tests, when a crust formed on the manure surface within three to four weeks after the strawapplication, ammonia emissions were reduced by up to 95%. A similar trend was observed in the pilot experiments in thefield. Hydrogen sulfide emissions were suppressed by 95% with the wheat straw cover. The mass transfer coefficients ofhydrogen sulfide with the straw covers were significantly lower than those of the control, which indicated the effectivenessof a straw cover as a physical barrier for reducing hydrogen sulfide emissions. Reduced pH and decreased ammoniaconcentrations in the liquid surface layer beneath the straw cover, both of which were observed during the tests,suggested that biological reactions might also be a factor contributing to the emission reductions.