Microbial Biogas Production From Pork Gelatine.

Abstract Dark fermentation of collagen (gelatine) results are shown in this research. The concentrations of applied gelatine were of VSS (volatile suspended solids) from 10 g VSS/L to 30 g VSS/L. The initial process pH was 5.5, depending on concentration reached pH values from 7.5 to 7.8 after 55 days. Although inoculum was heat-shocked in the case of 30 g VSS/L of collagen the process was hydrogenotrophic anaerobic digestion. In collagen concentration below 30 g VSS/L, hydrogen production was dominant only in the first 5 days of experiments. Then there also changed from dark fermentation into hydrogenotrophic methane production. In the case of optimal biogas production was due to accumulative production for a concentration of collagen 20 g VSS/L: 147.2 mL of hydrogen and 57.23 L of methane. In the case of optimal biogas production was due to accumulative production for a concentration of collagen 20 g VSS/L: 147.2 mL of hydrogen and 57.23 L of methane. The optimal hydrogen and methane yields were for concentration 10 g VSS/L (7.65 mL H2 /g VSS, and 3.49 L CH4/ g VSS). In 10 g VSS/L was also the lowest accumulated emission of hydrogen sulphide (10.3 mL of H2S), while the lowest yield was for 30 g VSS/L (0.44 mL H2S /g VSS). After a lag time, the hydrogen production and hydrogen sulphide grew with a specific ratio depending on concentration. Collagen, a protein with known amounts of sulphur allowed determining the origin of hydrogen sulphide in biogas. The hydrogen sulphide emission and sulphur added analysis proved that hydrogen sulphide origins in biogas from bacteria remains more than from substrate.