Abstract
Simple SummaryOdor emission from swine production facilities can irritate the people living in surrounding areas, although the farmers consider odor emission as a part of farming practice. Despite the governmental and institutional efforts, odor-related complaints from the neighborhood communities around the swine farms are rapidly increasing and have been identified as a key concern to sustaining progress of the swine industry globally. Bio-liquor circulation systems (BCSs) in swine farms have become popular among the farmers as an odor reduction technology in Korea. However, due to the lack of appropriate operating strategies, the odor reduction capacity of BCSs is often depleted. In this lab-scale study, a real-time control strategy based on oxidation–reduction potential (ORP) and pH (mV) time profiles was developed and applied for BCS operation. This study shows the potential effectiveness of using ORP and pH (mV) time profiles as operational parameters for the BCS to improve swine manure properties in slurry pits and thus reduce odor emission.In this study, an attempt was made to develop a real-time control strategy using oxidation–reduction potential (ORP) and pH (mV) time profiles for the efficient operation of bio-liquor circulation system (BCS) in swine farms and its effectiveness in reducing odor emission through improving manure properties in the slurry pit was evaluated. The lab-scale BCS used in this study comprised a bioreactor and a slurry pit. The bioreactor was operated in a sequence of inflow of swine manure → anoxic phase → aerobic phase → circulation to the slurry pit. The improvement in swine manure properties was elucidated by comparing the results of the BCS slurry pit (circulation type, CT) and conventional slurry pit (non-circulation type, NCT). The results revealed that the ORP time profile successfully detected the nitrate knee point (NKP) in the anoxic phase. However, it was less stable in detecting the nitrogen break point (NBP) in the aerobic phase. The pH (mV) time profile showed a more efficient detection of NBP. Compared to the NCT slurry pit, concentrations of ammonium nitrogen (NH4-N) and soluble total organic carbon (STOC) and other analyzed swine manure properties were much lower in the CT slurry pit. In the aspect of odor reduction, around 98.3% of NH3 was removed in the CT slurry pit. The real-time controlled BCS can overcome the drawbacks of fixed time-based BCS operation and therefore can be considered as a useful tool to reduce odor emission from intensive swine farming operations. However, further studies and refinement in control algorithms might be required prior to its large-scale application.
Highlights
Intensive livestock farming systems inevitably result in numerous environmental concerns in many parts of the world [1]
All the combinations of first drop in ORP (FDO), APP, and second drop in ORP (SDO) trigger values were effective in controlling the anoxic phase in the bioreactor, regardless of oxidation– reduction potential (ORP) values, and resulted in successful detection of nitrate knee point (NKP) during bioreactor operation using the ORP time-profile
The time was delayed by approximately 4.8 h, the complete stop of the bioreactor operation was prevented by using the ORP lower limit
Summary
Intensive livestock farming systems inevitably result in numerous environmental concerns in many parts of the world [1]. Complaints regarding odor emission from livestock farms have been increased significantly worldwide and become the prime concern for livestock industries [2,3]. In 2010, there were around 462 articles related to odor emission from livestock farms, whereas it reached 5566 in 2018 [4]. According to the Ministry of Environment (MoE) and the Ministry of Agriculture, Food and Rural Affairs (MAFRA), 3061 (about 46%) out of 6712 cases of odor complaints in Korea between November 2009 and October 2013 were related with livestock farms [5]. Another report mentioned that 2838 out of 10,753 odor complaints were associated with the livestock industries in 2015, which was the highest among all the 18 surveyed sectors, and the majority (46.0%) of the odor-related complaints were associated with swine farms [6]. Social conflicts related to odor emission are expected to intensify gradually and urgent countermeasures are required to reduce odor emission from swine farms
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