Research status on particulate reduction technology in livestock houses

Abstract: With the development of large-scale intensive animal husbandry, a large amount of Particulate Matter (PM) originated from livestock houses has become an important source of atmospheric particles PM10 and PM2.5. The dust of the livestock houses mainly originates from the feed, manure, dander, hair, etc., and carries various types of microorganisms, including bacteria, fungi, viruses, and harmful gases such as ammonia and hydrogen sulfide. No doubt that livestock related PM can seriously threaten not only the health of livestock farm workers and animals, but also the surrounding atmospheric environment. Applicable technologies of PM emission reduction are the important methods to maintain the comfortable indoor air quality as well as the ambient environment. This review firstly overviewed the emission sources, characteristics, and hazards of PM in livestock houses. Then, major focuses were put into the research status and problems of state-of-the-art reduction technologies of PM in livestock houses. In this part, the reduction technologies were classified into three groups: source reduction methods, process reduction methods, and terminal reduction methods. According to literature review, the source control of PM in livestock houses was generally done by changing either the form of feed or adding feed additives (e.g., animal fat, tallow). Source emission reduction included optimization of feed, manure removal technology, and breeding mode, etc. However, reports showed that both modification of feed form and usage of feed additives might negative affect the growth of animals, and affect animal welfare to a certain extent. Process control includes spray technology, optimization of ventilation system, and electrostatic precipitator technology, which were designed to reduce the particulate matter suspended in the barn air. The spray technology was relatively mature, low in cost, and high in efficiency. But it was easy to breed bacteria, which affected the health of animals, and it was also not suitable for low temperature season. Dust removal via ventilation was the most widely used and efficient way for removing PM in livestock houses, and requirements of ventilation and dust reduction in livestock houses should be taken into comprehensive consideration. Electrostatic precipitator technology was divided into three categories: Electrostatic Space Charge System (ESCS), Dry Electrostatic Precipitator (DESP), and Wet Electrostatic Precipitator (WESP) according to different structures, which had no interference to humans and animals, but their efficiency were needed to be further optimized. Terminal control included scrubber technology and filter technology, aiming to reduce the harm to the ambient environment. Scrubber technology could effectively remove multiple pollutants in the air by means of chemical and biological methods, but such equipments were more susceptible to corrosion. Filter technology was a cheap method and had a good dust-reducing performance on large particles. However, it was easy to clog, resulting in an increased air resistance and decreased efficiency of dust reduction. By comparing and analyzing the research status of various emission reduction technologies, hopefully, it could serve as a reference for the future development of high-efficiency, energy-saving, economical, and environment-friendly reduction technologies of particulate matter in livestock houses.