Thermochemical Conversion of Biomass Storage Covers to Reduce Ammonia Emissions from Dairy Manure

Manure storages, and in particular those storing digested manure, are a source of ammonia (NH₃) emissions. Installing floating manure covers provide resistance to gas transfer from manure storage surface to air and reduces NH₃ emissions; however, performance can be limited to durability. Biochar and steam-treated wood have strong potential as manure storage covers as they are capable of repelling water, resistant to microbial degradation, and could be applied to crop acreage. An additional benefit of biochars as a cover is their capability of NH₃ sorption trapping TAN (total ammoniacal N) before it is volatilized resulting in further abatement. Installation of permeable manure storage covers is difficult and adding covers with agitators could facilitate implementation. This study measured NH₃ emissions from laboratory scale storages of digested manure with raw wood (white birch, Betula papyrifera), steam-treated wood, wood biochar, and corncob biochar covers. Additional treatments included mixing biomass treatments into manure storages to measure the reduction potential of incorporated biomass. All treatments reduced emissions of NH₃ from the control by 40 to 96%. The highest NH₃ emissions reductions of 96% were achieved with the wood biochar cover. The primary mechanism for treatment was resistance to gas transfer provided by the physical barrier of covers as NH₃ sorption did not correspond to reductions. Covering digested manure storages with any of the treatments can reduce NH₃ emissions; biochar covers are a more effective barrier to NH₃ emissions and are recommended to minimize NH₃ manure storage losses.