Co-digestão anaeróbia dos dejetos de suínos com batata doce ou mandioca em diferentes relações C/N

Abstract

This work was carried out with the objective of evaluating the best anaerobic co-digestion condition of swine waste (SW), sweet potato (SP) and cassava (C) in biodigestors batch model and semi-continuous feed (second stage) to establish the best C/N ratios for these substrates. A batch model was used to evaluate the specific biogas production during the biodigestion process in different C/N ratios (10/1, 13/1, 17/1, 22/1), conducted in a completely randomized design, a control treatment containing only SW, four treatments with addition of SP and four treatments with addition of C, all with four replicates. The reductions of TS and VS and specific biogas productions were measured for the evaluation of the results. The treatments SP 10/1; 13/1; 17/1; 22/1 and C 10/1 obtained the highest TS reductions and for VS reductions, Control, SP 10/1 and C 10/1 treatments were higher. The highest specific biogas productions by TS added (286 and 270 L kg-1) were obtained by SP10 / 1 and C10 / 1 and for added VS (331, 323, 304 and 301 L kg-1) for SP10 / 1, C10 / 1, Control and SP 13/1 respectively. Among the studied parameters the treatments SP 10/1 and C 10/1 presented the best results and consequently were selected to compose the second stage. A completely randomized design with three treatments (control, SP 10/1 and C 10/1) and five replications were used. The efficiency of the treatments was evaluated by means of the reduction of constituents TS and VS and specific productions of biogas, as well as their composition (CH4 and CO2), alkalinity and volatile acidity. The control treatment differed from the others (P <0.05) and presented lower performance. Co-digestion treatments did not differ (P> 0.05) for the biogas yield (0.968 and 0.948 L g-1 VSadic), methane (0.633 and 0.586 L g-1 VS) and TS reductions (75.7 and 76.0%) and VS (85.7 and 85.7%) for the SP and C treatments respectively. Thus, the co-digestion of SW with SP or C, in semicontinuous feed biodigesters, in addition to promoting an increase in biogas production, provided a better quality of this, adding the content of CH4.