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Liquid hatchery waste improves the breakdown of volatile solids and increases methane production in co-digestion with bovine waste

Ana Carolina Amorim Orrico ; Walter Renato Teixeira Lopes ; Marco Antonio Previdelli Orrico Junior ; Rodrigo Garófallo Garcia ; Jorge de Lucas Junior ; Débora Maurício Manarelli ; Luana Pael Costa ; Juliana Dias de Oliveira
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Abstract: Hatcheries of broiler and laying chickens are responsible for generating high large amounts of waste. It is estimated that between 1.3 and 1.6 metric tons of waste are generated daily in Brazil with the incubation of 100 thousand eggs. The liquid fraction of that waste has great polluting potential mainly due to the contents of lipids and N in its composition, which keeps it from being used alone as a substrate for anaerobic biodigestion. When bovine waste is digested, on the other hand, it produces medium amounts of methane mainly due to its high fiber content and limited N concentration. Hence, the co-digestion of these waste products can improve the medium conditions and, thus, favor the breakdown of the organic components with higher methane production. This study aimed to assess the ideal inclusion of liquid hatchery waste in the co-digestion with bovine waste by assessing the reductions in volatile solids (VS) and the specific methane production according to the amounts of total solids (TS) and (VS) added. This trial was developed at the School of Agricultural Sciences of the Federal University of Grande Dourados, Brazil, and employed a completely randomized design with seven treatments (corresponding to the ratios between hatchery waste and bovine waste at 0:100, 5:95, 10:90, 15:85, 20:80, 25:75, and 30:70) and five repetitions for a total of 35 batch biodigesters. The maximum reduction in VS was 49.6% for the inclusion of 16% of liquid hatchery waste, a value 56.2% higher compared to the control treatment. The higher specific methane productions were 120.1 and 151.8 L.kg-1 of added TS and VS, respectively, when 17.5% and 18.0% liquid hatchery waste were added. These values were 105.8% and 97.6% higher than the productions in biodigesters with no such inclusion. It is concluded that adding liquid hatchery waste at up to 16% benefited the co-digestion process with bovine waste by improving the reduction in VS and increasing the specific methane production.