Optimization of microwave intensified slaughterhouse sludge pretreatment method to enhance anaerobic digestion process by response surface methodology

Slaughterhouse sludge is a highly polluting waste generated by the meat processing industry. Its disposal poses significant environmental challenges due to its high organic content, unpleasant odour, and potential contamination risks. However, this waste can also be an excellent source of renewable energy in the form of biogas through anaerobic digestion. Microwave pretreatment is a promising technology to improve the biodegradability of slaughterhouse sludge and maximize biogas yield. In this study, we optimized the microwave pretreatment conditions by using response surface methodology (RSM) for slaughterhouse sludge to enhance sCOD value and hence biogas production. The results showed that microwave pretreatment enhances the maximum sCOD value by up to threefolds in the selected design space. Optimal microwave pretreatment conditions were a temperature of 59.8 °C, a treatment time of 4.9 min, and a power level of 343.8 W, which increased sCOD value by 2.13-folds. Biogas production of slaughterhouse sludge increased from 90 Nml/g-VS (untreated) to 490 Nml/g-VS (microwave pretreated) after microwave pretreatment. With a 5.44-fold increase in specific biogas yield production of microwave-pretreated sludge compared to untreated sludge, the microwave pretreatment method proved to be a suitable method for the enhancement of biogas production.