Biochemical methane potential of raw and pre-treated meat-processing wastes

Raw and pre-treated greaves and rinds, two meat-processing wastes, were assessed for biochemical methane potential (BMP). Combinations of temperature (25, 55, 70 and 120 °C), NaOH (0.3 g g−1 waste volatile solids) and lipase from Candida rugosa (10 U g−1 fat) were applied to promote wastes hydrolysis, and the effect on BMP was evaluated. COD solubilisation was higher (66% for greaves; 55% for rinds) when greaves were pre-treated with NaOH at 55 °C and lipase was added to rinds after autoclaving. Maximum fat hydrolysis (52–54%) resulted from NaOH addition, at 55 °C for greaves and 25 °C for rinds. BMP of raw greaves and rinds was 707 ± 46 and 756 ± 56 L CH4 (at standard temperature and pressure) kg−1 VS, respectively. BMP of rinds improved 25% by exposure to 70 °C; all other strategies tested had no positive effect on BMP of both wastes, and anaerobic biodegradability was even reduced by the combined action of base and temperature.