Crusting of Stored Dairy Slurry to Abate Ammonia Emissions
2005
Misselbrook, Tom H. | Brookman, Siobhan K. E. | Smith, Ken | Cumby, Trevor | Williams, Adrian G. | McCrory, Dan F.
Storage of cattle slurry is a significant source of ammonia (NH₃) emissions. Emissions can be reduced by covering slurry stores, but this can incur significant costs, as well as practical and technical difficulties. In this pilot-scale study, slurry was stored in small tanks (500 L) and the effectiveness of natural crust development for reducing NH₃ emissions was assessed in a series of experiments. Also, factors important in crust development were investigated. Measurements were made of crust thickness and specially adapted tank lids were used to measure NH₃ emissions. Slurry dry matter (DM) content was the most important factor influencing crust formation, with no crust formation on slurries with a DM content of <1%. Generally, crusts began to form within the first 10 to 20 d of storage, at which time NH₃ emission rates would decrease. The formation of a natural crust reduced NH₃ emissions by approximately 50%. The type of bedding used in the free stall barn did not influence crust formation, nor did ambient temperature or air-flow rate across the slurry surface. There was a large difference in crust formation between slurries from cattle fed a corn (Zea mays L.) silage–based diet and those fed a grass silage–based diet, although dietary differences were confounded with bedding differences. The inclusion of a corn starch and glucose additive promoted crust formation and reduced NH₃ emission. The maintenance of a manageable crust on cattle slurry stores is recommended as a cost-effective means of abating NH₃ emissions from this phase of slurry management.
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