Real-Time Control Technology for a Bio-Liquor Circulation System in a Swine Barn with Slurry Pit: Pilot Scale Study

SIMPLE SUMMARY: The high intensity of odor emitted from swine production facilities is the biggest complaint from local residents and hinders the development of the swine industry. Furthermore, the odor of swine farms is a core concern of the global swine industry, and various efforts have been made to develop odor reduction technology. Although the bio-liquor circulation system (BCS) as an odor reduction technology has been popular among Korean farmers, the odor reduction effect of BCS has often not been fully obtained because of the lack of an appropriate operating strategy, dependent on each different condition of individual farms. To overcome this limitation, in this study, the bio-reactor was operated in a real-time manner based on a diagnosis of ORP and pH(mV) time-profiles in a pilot scale. From the results of this study, the BCS control strategy using the time-profile of ORP and pH (mV) showed a successful performance for detecting the biochemical changes of nitrogen, achieving self-operation of the bio-reactor and effective odor reduction. ABSTRACT: The livestock industry, especially swine production, has been pressurized by vicinity complaints about odor in Korea. Therefore, a lot of effort has been undertaken regarding reducing the odor emissions from pigsties, widely carried out and the washing out manure in slurry pit by liquid-phase compost has particularly been spotlighted with outstanding performance of odor reduction. However, such a washing out manure called bio-liquor circulation system (BCS) has been controlled by a timer with designated reaction time, which cannot guarantee the system performance. This research proposes an effective real-time control technology for BCS, which circulates bio-liquor to the slurry pit of swine barns. The real-time control system was operated through accurate detection of the designated control points on the oxidation reduction potential (ORP) and pH time profiles for the nitrate knee point (NKP) and nitrogen break point (NBP) in anoxic and aerobic conditions with 100 and 99.6% performances, respectively. The duration of the anoxic and aerobic phases was also automated and noticeably lowered the concentration of nutrients in the manure in the slurry-pit, which served as a source of malodor. The real-time control strategy may be an innovative way to reduce odor and simultaneously produce liquid fertilizer, and provides a reference for the optimization of the industrial scale.