Abstract: Under the background of “dual carbon”, the preparation of biodiesel from kitchen waste oil would play an important role in achieving “turning waste into treasure”and the green and low-carbon transformation of energy. The energy consumption and greenhouse gas emissions of kitchen waste oil throughout its lifecycle from production to the production of biodiesel were analyzed. And it was compared with the entire process of petrochemical diesel production. The greenhouse gas emissions contribution of each stage in the preparation of biodiesel from kitchen waste oil, as well as the energy consumption and CO2 emissions comparison of biodiesel production between enzymatic and traditional ester exchange methods were analyzed. The results showed that compared with petrochemical diesel, the energy consumption of biodiesel produced by enzymatic method was reduced by 71.43%, and the GWP of CO2 and greenhouse gas were reduced by 60.09% and 59.79%, respectively. The pre-treatment of trench oil and frying oil, as well as the deep processing of waste oil and fat, were the main stages of energy consumption and greenhouse gas emissions throughout the entire life cycle of waste oil and fat. The greenhouse gas emissions caused by methanol and steam production was the main reasons. Compared with the ester exchange method, the energy consumption of biodiesel process using bioenzyme method was reduced by 4.58%, and the GWP of CO2 and greenhouse gas were reduced by 38.53% and 38.52%, respectively. It was recommended to develop a biodiesel processing technology using kitchen waste oil as raw material in China, to prevent kitchen waste oil from flowing back to the dining table, save fossil energy consumption, and reduce greenhouse gas emissions.

Key words: kitchen waste oil and fat, greenhouse gases, carbon emissions, full life cycle, biodiesel