Greenhouse gas emissions of an on-farm swine manure treatment plant - comparison with conventional storage in anaerobic tanks

This study aims to estimate greenhouse gas (GHG) emission reduction over a five-month period due to the implementation of a swine manure treatment plant, installed as an alternative to conventional manure storage in anaerobic tanks. The treatment plant, located in Segovia (Spain), was installed in a farrow-to-finish farm with approximately 300 sows, and was based on solid-liquid separation using screw pressing followed by coagulation-flocculation and nitrification-denitrification of the liquid fraction. Information collected during the study of the on-farm treatment plant together with the guidelines proposed by the Intergovernmental Panel on Climate Change (IPCC) was used to quantify GHG emissions for each scenario. Implementing the manure treatment plant led to a total annual GHG emission reduction of 62% (from 1204 t CO2-equiv to 456 t CO2-equiv). CO2 and CH4 emissions fell by 72% and 69%, respectively, whereas N2O emissions were similar in the two scenarios studied. It should be pointed out that only CO2 emissions from fossil fuel use were considered in the estimation. In addition, the contribution made by each of the treatment plant units to GHG emission was calculated. Carbon credit exchange might translate to a direct benefit of 0.21 € per m3 of treated manure. Reducing GHG emissions should thus be considered as a complementary factor in the development of cleaner systems for manure management, yielding both environmental as well as financial advantages.