The influence of using different types of modified vermiculite cover on ammonia mitigation from animal slurry storage: The role of sulfuric acid.

Animal slurry storage is an important ammonia (NH) emission source. Sulfuric acid (HSO)-modified vermiculite coverage is a new promising technology for controlling NH emission from slurry storage. However, the underlying mechanisms in controlling the mitigation effect remain unclear. Here, a series of experiments to determine the effect of HSO on the modified vermiculite properties, floating persistence, and NH mitigation effect was conducted. Results showed that abundant HSO and sulfate remained on the outer surface and in the extended inner pores of the vermiculite with acidifying H concentrations higher than 5 M. An initial strong instantaneous acidification of surface slurry released rich carbon dioxide bubbles, strengthening cover floating performance. An acidification in the vermiculite cover layer and a good coverage inhibition interacted, being the two leading mechanisms for mitigating NH during initial 40-50 days of storage. The bacterial-amoA gene dominated the conversion of NH to nitrous oxide after 50 days of storage. Vermiculite with 5 M H modification reduced the NH emissions by 90 % within the first month of slurry storage and achieved a 64 % mitigation efficiency throughout the 84 days period. With the development of the aerial spraying equipment such as agricultural drones, acidifying vermiculite coverage hold promise as an effective method for reducing NH emission while absorbing nutrients from liquid slurry storage tank or lagoon. This design should now be tested under field conditions.