Abstract
The objective of this study was to investigate the ability of an ammonia (NH3)-recovery device to recover NH3 over a full year from a closed vertical composting facility (CVCF), and the possibility of using the recovered ammonium solution as fertilizer. A 600-L NH3-recovery device fi lled with phosphoric acid solution was connected to a CVCF belonging to a pig farmer in Fukushima (S Farm, 200 head of mother pigs). There were four periods of 10-day experiments: November 2017 and January, April and July 2018. The concentration of NH3 of exhaust changed from 1833–3222 ppm at the device inlet to 117–149 ppm at the outlet, and average NH3 removal rate was 94.7 %. The recovery solution contained 6.06–6.60 % of nitrogen and 18.6–20.5 % of phosphoric acid. Inclusion of 150 kg of phosphoric acid was suffi cient to capture about 30 kg of nitrogen in one batch. The mass of solution increase that consisted of recovered nitrogen and water from dew condensation was relatively small in summer, suggesting the possibility of obtaining high ammonium phosphate concentrations depending on conditions. In addition, no harmful components according to the Fertilizer Regulation Act were detected, and the recovered ammonium solution had the same effect as the control fertilizer on seedling growth. Thus, the recovered ammonium solution can be used alone or as raw material for mixed compost compound-fertilizer.
