TEMPERATURE EFFECT ON ANAEROBIC-DIGESTION OF BEDDING STRAW IN A ONE-PHASE SYSTEM AT DIFFERENT INOCULUM CONCENTRATION

Simulated bedding straw was anaerobically digested in a one phase batch system. Two temperatures, 25-degrees-C and 35-degrees-C, and four compositions of bedding straw were tested (10.5-0.82% in VS). Digested pig manure was used as methanogenic inoculum. The higher biogas production rates and VS degradation were achieved, for a given time, at 35-degrees-C. At this temperature, higher biogas and methane final production were attained at higher cow inoculum contents. The digestion period was 110 days at 35-degrees-C and 240 days at 25-degrees-C. A deficient homogenization were observed in some digesters. A kinetic fitting was performed using a first order model with good results (k = 0.02 day-1). The operation at 25-degrees-C proved to be the more economical process.