Evaluation of simplified covering systems to reduce gaseous emissions from livestock manure storage

Ammonia, methane, and carbon dioxide are the primary atmospheric emissions from cattle and pig farms. A significant part of these emissions is produced by the decomposition of slurry organic matter during manure storage and treatment phases. Present solutions to contain emissions from storage lagoons generally involve reducing the free surface of the slurry by covering it either with permanent fixed structures or temporary floating ones. This study investigated the effectiveness of five simple floating covers in reducing emissions from pig and cattle slurry. The coverings included vegetable oil (a mixture of rapeseed and soybean oil), expanded clay, chopped maize stalks, chopped wheat straw, and chopped wood chips. All were tested at two different thicknesses: 70 and 140 mm for solid coverings, and 3 and 9 mm for liquid. Slurry samples covered with the above-mentioned materials were placed in nine stainless steel airtight cylinders measuring 190 dm 3. Gaseous and odor concentrations in the headspace were monitored using a Bruel & Kjaer 1302 multi-gas monitor and a T07 olfactometer. The flotation aptitude of the different coverings was also tested. Results revealed substantial differences in ammonia emission reduction efficiency (1% to 100%) and odor abatement (0% to 90%), and high levels of reduction efficiency were achieved by all the tested covers at the higher thickness. However, equally valid results were not obtained for methane emissions reduction. In regard to flotation aptitude and cover deterioration on slurry, expanded clay and wood chips demonstrated long-term resistance to both deterioration and sinking.