KINETICS OF BIOMETHANATION OF SOLID TANNERY WASTE AND THE CONCEPT OF INTERACTIVE METABOLIC CONTROL

Anaerobic digestion of calf skin collagenous waste was optimized for a batch process based on accelerated maximal methane yield per gram of input volatile solid. A kinetic analysis with respect to changes in th e levels of volatile solid, collagen, amino sugars, amino acids, hydro xyproline, ammonium ions, and volatile fatty acid were followed for a period of 80 d. Distinct metabolic phases included an initial high rat e collagenolysis for 4 d, with 50% degradation and was followed by an acidogenic phase between 4-12 d with volatile fatty acids levels incre asing to 215 mmol/L. Subsequently methanogenesis ensued and was maxima l between 12-24 d when volatile fatty acids attained steady state leve ls. During the period of 80 d, the overall decrease in volatile solid level was 65%, whereas the collagen level declined by 85% with 0.45 L of methane yield/g of volatile solid degraded. Based on the levels of various metabolites detected, the concept of interactive metabolic con trol earlier proposed has been validated.