Produção de metano a partir da codigestão de soro de leite e resíduos de caprino

Abstract

Lignocellulosic biomass and agricultural residues rich in carbohydrates, lipids and proteins are promising sources for the production of renewable energy that are currently growing in the area of biofuel production. Goat waste (RC) is an excellent raw material for anaerobic digestion due to its high total nitrogen content and stability during fermentation, but its use has a low biogas production yield. An increase in this yield can be achieved by co-digestion of animal manure with co-substrates such as whey. The objective of this study is to perform the co-digestion of whey (SL) and goat waste (RC) to produce methane. With this, in a first stage (E1) Simplex Lattice experimental planning was applied in bench reactors (300 mL) in batch mode. Different mixture proportions (SL100/RC0, SL75/RC25, SL50/RC50, SL25/RC75, SL0/RC100) were evaluated through adjustments to linear and quadratic models. In E1, the results showed COD removal efficiency between 40.07 and 63.73%, and Total Volatile Solids (SV) between 22.87 and 58.99%. Codigestion was favorable for the production of CH4 in relation to goat waste, in addition, maximum values of 319.89 mL of CH4/gDQOapl and 303.34 mL of CH4/gSVapl were obtained, both observed in the SL75/RC25 condition. The quadratic model had the best fit (R2 equal to 0.983 for methane yield). A second stage (E2) was carried out with the SL75/RC25 reactor, aiming to produce methane, based on an experimental design 23 with the objective of evaluating the effect of the variables initial substrate concentration (COD), agitation and percentage of inoculum in methane yield. The highest yield in relation to the applied biomass was achieved in the reactor with an initial COD concentration of 10g/L, without agitation with 10% inoculum, resulting in 939.45 mL of CH4/gSVapl. Finally, a third stage (E3) was carried out using a 5L reactor with the conditions adopted in the Rp5 reactor, which presented the best performance in E2. The results showed a yield of 648.03 CH4/gSVapl.