Impact of a retrofit in-house slurry acidification on ammonia and methane emissions from a fattening pig barn

Abstract

Acidification of slurry is known to reduce ammonia emissions. In some European countries, for example Denmark, this method is already in use. At present, the system is only integrated in the construction of new barns with flat slurry channels. The aim of this study is to investigate whether acidification technology can also be retrofitted in existing barns with slurry storage under the floor. Furthermore, it is to be investigated whether ammonia and methane emissions are reduced with this method. Therefore, a trial compartment with 32 fattening pigs was retrofitted with the new acidification technology. The pH value of the slurry stored under the floor was reduced to 5.5. For this purpose, part of the slurry was mixed with sulfuric acid in an external process tank and then pumped back into the slurry channels. In the identical reference compartment (partially slatted floor, 4 pens with 8 animals each), the fattening pigs were housed simultaneously. The air volume flow was recorded with measuring fans in the exhaust air ducts. The ammonia and methane concentration in the inlet and outlet air were measured using photoacoustic infrared spectroscopy. In this way, the emission mass flow of ammonia and methane from the respective compartment could be quantified during the entire fattening period. Three fattening periods were carried out. The ammonia and methane emissions rose with increasing animal weight. Compared to the reference compartment without acidification, ammonia emissions were reduced by about 40% through slurry acidification. Furthermore, a reduction of methane emissions by about 67% was observed. The pH value in the slurry channels had to be below pH 5.5 to ensure a considerable reduction in emissions. In-house slurry acidification can thus contribute to environmental and climate protection. In addition, it is possible to still use the slurry channels as storages.