The catalytic pyrolysis of food waste by microwave heating

•Microwave pyrolysis with catalysts was a feasible method to handle food waste.•MgO, Fe2O3, MnO2, CuCl2 and NaCl can lower bio-oil yields and enhance gas yields.•The optimal microwave power to maximize bio-oil yield during pyrolysis was 400W.•Chloride salts promoted formation of acidic compounds in the bio-oil’s lower layer.•CuCl2 was the most effective among the tested catalysts, followed by MnO2. This study describes a series of experiments that tested the use of microwave pyrolysis for treating food waste. Characteristics including rise in temperature, and the three-phase products, were analyzed at different microwave power levels, after adding 5% (mass basis) metal oxides and chloride salts to the food waste. Results indicated that, the metal oxides MgO, Fe2O3 and MnO2 and the chloride salts CuCl2 and NaCl can lower the yield of bio-oil and enhance the yield of gas. Meanwhile, the metal oxides MgO and MnO2 can also lower the low heating value (LHV) of solid residues and increase the pH values of the lower layer bio-oils. However, the chloride salts CuCl2 and NaCl had the opposite effects. The optimal microwave power for treating food waste was 400W; among the tested catalysts, CuCl2 was the best catalyst and had the largest energy ratio of production to consumption (ERPC), followed by MnO2.