Title : Anaerobic digestion of wood sector and sewage treatment plant wastes to produce biogas
One of the possible technological routes to compensate for the impacts caused to the environment by the wood sector and Sewage Treatment Plant is anaerobic digestion (AD) in biodigesters, transforming waste into energy. The objective of this work was to evaluate the increase in the biogas production, based on the mixture of hydrolyzed wood material (H) with sewage sludge (SS). The experiment consisting of anaerobic mono digestion (AmD) and anaerobic co-digestion (ACoD) and total solid (TS) and volatile solid (VS) analysis was conducted at the Laboratory of Rural Electrification and Alternative Energies. Indian model benchtop biodigesters were used, which were consisting of a "water seal" containment chamber, fermentation chamber, gasometer and U-tube manometer for the water column. The biodigesters were supplied in batches with 1.7 kg of influent at ratios of 100: 0, 75:25, 50:50, 25:75, 0: 100 H:SS. The product of the vertical displacement of the gasometer by its internal cross-sectional area determined the volume of biogas produced during 13 weeks of hydraulic retention time (HRT), being corrected by combined gas law. Biogas production profile and cumulative biogas yield were evaluated. Biogas production started in the first week, followed by peak production at 50:50, 75:25 and 0:100 H:SS. After the peak, a drop in production is observed until it remains null. The 25:75 and 100:0 H:SS ratios did not show peak production along the HRT. It can be seen that the ACoD process resulted in anticipation of the peak production when compared to AmD. ACoD with 75:25 H:SS caused 39.44% higher biogas production when compared to 0:100 H:SS. The ACoD process with 75:25 H:SS resulted in greater cumulative biogas yield, being 1.208 L kgadded-1, 0.174 L kgTSadded-1 and 0.235 L kgVSadded-1. Concluded synergy between the codigestants, mainly, by adopting a higher proportion of blend of hydrolyzed woody material.