The effect of magnesium sulfate addition on volatile solid destruction and chemical oxygen demand reduction of food waste anaerobic digestion

Process instability often occurs in anaerobic digestion (AD) due to inhibitors, such as the high sodium content in food waste. Recent studies have reported that magnesium can reduce the sodium ion's toxicity towards methanogens. This study aimed to analyze the effect of magnesium addition to Volatile Solids Destruction (VSD), Chemical Oxygen Demand (COD) reduction, and biogas production in AD of food waste. The experiment consisted of two phases, the control phase and the experimental phase, without and with MgSO₄, respectively. The control phase results were: average COD reduction, VSD, and methane yield up to 80.9%, 87.6%, 340 mL CH4/gr VS/day, respectively. The experimental phase results were: average COD reduction, VSD, and methane yield up to 78.5%, 83.9%, 125 mL CH4/gr VS/day, respectively. Overall, the study's results showed that MgSO₄ had a negative impact on VSD and methane yield. The addition of MgSO₄ seemed to cause instability in the AD system, which resulted in a decrease in the VSD value and a decrease in the methane concentration.