Use of biochar and crude glycerin as additives in the composting of slaughterhouse waste in static piles

Abstract

This study is aimed to evaluate the efficiency of biochar and crude glycerin as additives in N retention throughout the composting of cattle slaughterhouse waste in static piles receiving forced aeration. There were five treatments (control, biochar accounting for 5 and 10%, and glycerin accounting for 5 and 10%, both at total solids) and four times (20, 50, 70 and 90 days of composting). The slaughterhouse waste was composted with a bulking agent at a ratio of 3:1, and the mixtures of waste and the tested additives were placed in nylon bags. The piles reached thermophilic temperatures soon after the process started and following turnings. The reductions of volatile solids, carbon, hemicellulose, cellulose and lignin were not influenced by the additives, resulting in averages of 69.1, 67.1, 62.1, 51.6 and 35.3%, respectively. The control showed greater N losses (58.38%), compared to the treatments with additives. The inclusions of biochar yielded an average loss of 48.47% N, while 10% of glycerin resulted in the lowest N losses (44.83%). The use of biochar and glycerin as additives in the composting of slaughterhouse waste is recommended in order to decrease N losses and improve the concentration of nutrients, without compromising the biodegradation of organic components.

Effects of aeration and season on the composting of hatchery waste

“…4,5 However, when the residues comprise animal leftovers, composting in static windrows and in some cases in composting cells with fully sealed walls must be adopted so as to promote the sanitary safety of the entire process. 6,7 The main challenge for composting such waste in static and fully sealed windrows is to maintain aeration conditions in the whole pile as the presence of anaerobic sites inside the windrows slows down the process and favors the proliferation of flies and foul smells. 8 In order to prevent this issue, the use of forced aeration inside the composting cells is recommended.…”

“…The composting technique can be employed as an effective alternative in the treatment and recycling of nutrients present in that waste, also yielding as final product an organic fertilizer rich in nutrients for later use in agricultural areas 4,5 . However, when the residues comprise animal leftovers, composting in static windrows and in some cases in composting cells with fully sealed walls must be adopted so as to promote the sanitary safety of the entire process 6,7 …”