Biodiesel is used to extract automatic vegetable oil, which is widely used in tractors, trucks and ships. It refers to the renewable diesel oil that uses oil crops such as soybean, rape, cotton and palm to replace petrochemical diesel oil. , aquatic vegetable oil such as wild oil plants and engineering microalgae, animal oil and restaurant garbage oil as raw materials, through transesterification or thermochemical process. Biodiesel is a kind of biomass energy, and its physical properties are close to those of petrochemical diesel, but its chemical composition is different. Biodiesel is a mixture of complex organic components with extremely high oxygen content. These mixtures are mainly some high molecular weight organic compounds, including almost all kinds of oxygen-containing organic compounds, such as esters, ethers, aldehydes, ketones, phenols, organic acids, alcohols and so on. Composite biodiesel is synthesized by using waste animal and vegetable oil, waste engine oil and refinery by-products as raw materials, adding catalysts, special equipment and technology.