Thermal environment in commercial swine nursery heated with biogas heat exchanger

Abstract

The study of alternative heating systems, notably those that demonstrate energy sustainability, are currently imperative for piglets in the nursery phase, since, at this stage, the animals cannot maintain homeothermy, resulting in a high energy cost. There are different heating systems on the market. However, the literature shows a lack of studies concerning the use of heat exchangers supplied with biogas for piglets. This research aimed to analyze the thermal environment in the nursery phase of a commercial confined system during the winter and the response of piglets through weight gain. Biogas generated by biodigesters is the energy source of the heat exchange system. Part of the biogas produced is converted into thermal energy, which is carried to the warehouses and heat the nursery rooms through heat exchangers. The nursery room evaluated in this study has a total area of 183.14 m2, a ridge orientation in the East-West direction, eight pens, and an average density of 0.20 m2 per piglet. The parameters of the black globe humidity index (BGHI) were recorded daily at every fifteen minutes during the 35 days spent in the nursery in order to analyze the thermal comfort. To evaluate the weight of F1 piglets (Large White vs Landrace), 20 chemically castrated male piglets and 20 female piglets, both randomly chosen, were monitored. After separating the sexes in symmetrically opposite pens, the records on the first day and at every seven subsequent days of 5 piglets per pen were recorded, totaling 240 observations. The expected tendency of different weight gains between both sexes presented an average of 24.95 kg for males and 19.32 kg for females, favoring 28.87% for males. The highest values (p < 0.05) were found for male piglets housed in pens located on the south side of the room from the weight gain records. The thermal comfort intervals from the values obtained from the BGHI presented a mean value (p < 0.005) of 67.11 between 5 am and 8 am and an average of 73.97 between 2 pm and 5 pm, for the periods with daily minimum and maximum ambient temperatures, respectively. The results submitted to analysis of variance, using the Sisvar statistical software and a 95% level of confidence, confirmed that even in the winter the studied system maintained acceptable BGHI averages, at intervals found in the literature for this phase. The biogas heating system proved to be efficient for managing the thermal comfort for confined piglets, being an interesting alternative in the search for energy sustainability in pig production.