Manure storage and its effect over N-related compounds emissions

Abstract

Agricultural sector is particularly important in Spanish economy, being one of the main European distributors of pork, with a consumption of 1 kg-pork/week per inhabitant (Faostat 2007). However, it has some negative environmental impacts that clearly affect the global warming. According to data available from 2006 in the National Greenhouse Gas Emissions Inventory, GHG emissions from pig sector in Spain amount to 8.8 million tonnes of equivalent CO2 per year. This has led to several regulations which demand the treatment of surplus. Some mitigation strategies might be implemented at farm-level. Consequently, the main objective of this work was to evaluate two mitigation strategies during storage: acid addition and methanogenic activity inhibitors. To that purpose, a state of the art was carried out to establish the different storage strategies and to select the suitable additive. Manure was characterized and an experimental set-up was performed to simulate anaerobic storage conditions. NH3 and GHG emissions were calculated according to the IPPC Directive tables and a comparison regarding tabulated values of IPPC (European Directive), of attained NH3 and GHGs emissions with these strategies was made. As a secondary objective, an open chamber was designed and set-up to measure NH3 and GHG emissions. Therefore, a decrease of pH to 5.5 H2SO4 contributed to reduce CH4 emissions in a 60% and completely inhibit NH3 but hardly increased SO42- concentration to dangerous levels for planted soils. Thus, organic acids were suitable being less harmful and most effective than strong in reduce GHG emissions, in the case of cow slurry mixture, particularly acetic acid. Related to pig manure, lactic acid showed the same mitigation effect as H2SO4. RY modulate CO2 and NH3 production in the case of the acidification strategy