Effect of manure separation on ammonia emission during storage and subsequent field application.

Emission of ammonia from agriculture is a problem due to the negative effects on human health and natural ecosystems. Additionally, ammonia is a precursor for production of N₂O in the atmosphere and is therefore an indirect greenhouse gas. A large part of ammonia emissions from agriculture originate from manure handling, which also reduces manure fertilizer value. Therefore, more knowledge on emissions from different types of manure and the effect of manure treatments are necessary to develop new measures to reduce ammonia emissions. Separating liquid manure (slurry) into a liquid and solid fraction can be used as a reduction technique for field application. The lower dry matter content of the liquid fraction may increase infiltration and decrease emission. Because separation might influence emissions during the storage period, this period must be considered along with the potential increased emissions from field application of the fiber fraction, when assessing the ammonia mitigation effect of separation. Here, data on ammonia emissions from storage and field application of raw and separated manure is presented. The manure types investigated were anaerobically digested manure and pig manure. Ammonia emissions from storage were measured with 1 m³ tanks constructed as dynamic flow chambers, and emissions after field application were measured with wind tunnels. Online measurements of ammonia concentrations were done with cavity ring-down spectrometry.   
    How the fiber fraction from the manure separation is utilized is important for the overall ammonia loss. Fiber can be stored in a pile and subsequently spread in the field. Another way to treat the fiber is to pyrolyze it into biochar which can be incorporated into the field as a strategy for long term carbon sequestration. It has been suggested to mix the biochar and manure prior to field application to limit operating costs with field driving. Therefore, during the field application experiments, a treatment with biochar added to the liquid fraction of manure was also investigated.