Co-digestão anaeróbia de dejetos de suinos com adição de batata doce e mandioca em diferentes relações C/N

Abstract

Due to the high growth of intensive swine production, we observe the large amount of residues generated during this process, which must be recycled before being disposed of in the environment. Thus, the objective of this work was to evaluate if the adjustment of the C / N ratio with food residues alter the reductions of total solids (TS), volatile solids (VS), hydrogen ionic potential (pH) and biogas production from co-digestion of swine manure with addition of sweet potato and cassava. Twenty batch type biodigestors were used, supplied with substrates containing swine, sweet potato and cassava slurry, differentiated into five treatments with four replicates each, two treatments were added with sweet potato to reach the C/N ratios of 23 and 28/1, two other treatments followed the same increased ratios of manioc and one treatment contained only swine manure. The results were submitted to analysis of variance and, in the case of statistical difference, were submitted to a test of average (Tukey) at 5% of probability using software R (version 3.1.0 for Windows). The treatments evaluated did not present high values for TS and VS reductions, nor for biogas production. The pH demonstrated that during the process the substrates acidified rapidly, falling from a pH average of 6 to 3, directly interfering in the biogas production. The best values found for all analyzes were treatment 1, which used only swine manure as control, presenting reductions of 52.03% and 54.87% for TS and VS, respectively. The addition of food materials to balance the C/N ratio was not beneficial to the process, so it is recommended only the treatment using swine manure, since it excelled in the results achieved.