ABSTRACT:The purpose of this study was to evaluate the production of biogas, as well as the biogas production potential resulting from the anaerobic biodigestion of dairy cattle manure under organic (CMOS) and conventional (CMCS) production system. Also, the concentration of thermotolerant coliforms was evaluated after the biodigestion process. Therefore, bench biodigesters prototypes were supplied with CMOS and CMCS for 30 weeks. The experimental design was completely randomized with four repetitions for each treatment. Analysis of total solids (TS), volatile solids (VS), biogas production potential, most probable number (MPN) of thermotolerant coliforms were made. The cumulative biogas production was 6.18 L and 11.15 L, when using the CMOS and CMCS, respectively. Average biogas production potential of CMCS were 0.2; 2.6 and 2.9 L kg -1 substrate, ST and SV added, respectively and for CMOS 0.1; 1.4 and 1.9 L kg -1 substrate, ST and SV added, respectively. After the anaerobic biodigestion process of CMOS and CMCS, it was observed that the concentrations of thermotolerant coliforms were well below than the limit established by law.

Abstract:The objective of this study was to evaluate the agronomic potential of the biofertilizer resulting from the anaerobic biodigestion of milk cattle, under organic system (DBSO) and conventional (DBSC) of production. Eight prototypes of biodigesters supplied with bovine waste were used. The experimental design was completely randomized, with 4 replicates for each treatment. After the process of anaerobic biodigestion of wastes, chemical, physical and biological analyzes were performed, in accordance with CONAMA Legislation 375/06. DBSO and DBSC biofertilizers presented a minimum carbon content to be considered as organic fertilizer, with values of 392.4 and 411.9 g kg -1, respectively. The Mg, K and Fe contents were higher in DBSO biofertilizer and Ca, Mn, Cu, Zn and Ba contents were higher in DBSC biofertilizer. DBSC biofertilizer had Cd content above that allowed by law for organic fertilizers. Therefore, milk production systems influence the biofertilizer chemical and physical characteristics. The manure produced by cattle under organic system of milk production showed greater potential of use as organic fertilizer when compared to the manure from conventional management.Keywords: Bovine manure; organic fertilizer; biodigester; agricultural waste; animal waste treatment. ResumoObjetivou-se avaliar o potencial de utilização como adubo orgânico do biofertilizante, resultante da biodigestão anaeróbica de dejetos de bovinos de leite, sob sistema orgânico (DBSO) e convencional (DBSC) de produção. Utilizaram-se oito protótipos de biodigestores abastecidos com os dejetos de bovinos. O delineamento experimental foi o inteiramente casualizado, com 4 repetições para cada tratamento. Após o processo de biodigestão anaeróbica foram realizadas análises químicas, físico-químicas e biológicas, de acordo com a Resolução CONAMA 375/06. Os biofertilizantes oriundos de DBSO e DBSC apresentaram um teor de carbono mínimo para serem considerados fertilizantes orgânicos, com valores de 392,4 e 411,9 g kg -1, respectivamente. A biodigestão anaeróbica elevou o pH e reduziu a condutividade elétrica (CE) no material efluente, apresentando diferença estatística entre os dois tratamentos. Os teores de Mg, K e Fe foram superiores nos biofertilizantes de DBSO e os de Mn, Cu, Zn e Ba foram maiores nos biofertilizantes de DBSC. No biofertilizante oriundo de DBSC o teor de Cd ficou acima do permitido por lei para fertilizantes orgânicos. Portanto, os sistemas de produção de leite influenciam nas características químicas e físico-químicas do biofertilizante produzido. O esterco produzido por bovinos sob sistema orgânico de produção de leite demonstrou maior potencial de uso como adubo orgânico quando comparado ao esterco oriundo do manejo convencional.Palavras-chave: Adubação orgânica; biodigestor; resíduos agrícolas; tratamento de dejetos animais.

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