Assessment and mitigation of ammonia, nitrous oxide and methane emissions from a straw flow system for fattening pigs.

Animal welfare and environmental protection are increasingly important. Housing systems must be found that offer animal welfare and emit little NH3 and greenhouse gases. Often, a contradiction is seen between animal welfare and environmental protection. Emissions from slurry based pig houses have intensively been researched. Data on emis-sions from straw based houses are limited. Straw bases systems often are assigned higher emission factors than slurry based systems. This, however, has up to now not been scien-tifically proven. More research is needed into straw based systems for pigs. Mitigation op-tions for NH3, and greenhouse gases must be proposed. The straw flow system is an animal friendly housing system for fattening pigs. It can be operated economically efficiently on commercial farms. It was to be investigated, if the straw flow system emitted less ammonia and greenhouse gases than a conventional fully slatted floor system. The research project was carried out in close cooperation with the Federal Research Institute for Agriculture in Alpine Regions. Emissions of NH3, N2O, CH4, and VOC were measured at a commercial farm in Upper Austria from June 2003 to April 2004. Gas concentrations were measured with high resolu-tion FTIR spectrometry. VOC were analysed by a flame ionisation detector. The ventilation rate was continuously recorded in the central exhaust fan. From May 2004 to June 2005 emissions were followed from storage of pig slurry received from a straw flow systems. The slurry was stored with and without a solid cover. Measurements were carried out at the research station "Gross-Enzersdorf" of the University of Natural Resources and Applied Life Sciences, Vienna. Emissions of CH4, N2O, NH3, and greenhouse gases from the straw flow system were al-ways lower than default values for forced ventilated fully slatted floor systems. From the straw flow system CH4 emissions of 1.24 (dung channel system) respectively 0.54 (daily manure removal system) kg CH4 per pig and year were lost. The default value for fully slat-ted floor systems is 4.00 kg CH4 per pig and year. N2O emissions from the straw flow sys-tem amounted to 39.95 (dung channel system) respectively 24.54 (daily manure removal system) g N2O per pig and year. Fully slatted floor systems are estimated to emit 100 g N2O per pig and year. NH3 emissions from the straw flow system were 2.10 (dung channel sys-tem) respectively 1.91 (daily manure removal system) kg NH3 per pig an year. The default value for fully slatted floor systems is higher: 3.00 kg NH3 per pig and year. The straw floor system emits less ammonia and greenhouse gases than a conventional fully flatted floor system. When the dung channel system is additionally equipped with a scraper and the pig manure is daily removed to the outside storage, then emissions from the straw flow system can further be reduced. A solid cover placed on the pig manure store was an efficient means to reduce ammonia and greenhouse gas emissions during pig slurry storage. It is recommended to store pig slurry in covered stores. When stored under cool climatic conditions, pig manure emitted less NH3 and GHG than when stored under warm climatic conditions. It is recommended to set up the national emission inventory by applying separate emission factors for slurry storage in the cooler and in the warmer half of the year. This would improve the inventory quality and would reduce net total agricultural emissions. The straw flow system for fattening pigs is an animal friendly system that can be operated economically efficiently on commercial farms. NH3, CH4 and N2O emissions are lower than from conventional fully slatted floor systems. Stores for pig slurry should be equipped with a solid cover. The straw flow system combines recommendations of animal welfare and environmental protection.