Refining

Specialized processing (or refining) is required to recover/extract methyl ester from feedstock raw materials (e.g., algae, soy bean oil, yellow grease, chicken fat, beef tallow, and other animal fat and plant oil sources). This process must meet certain environmental legislation and ASTM requirements already in place to monitor the biodiesel industry.

Purification of methyl esters is typically accomplished by vacuum distillation from a crude biodiesel stream, which includes impurities such as water, methanol, glycerin, mono-glycerides, di-glycerides, tri-glycerides, and other high boilers. Different procedures may be necessary depending on the type of raw materials. For example, soy bean scrubbers are used to minimize methanol emissions.

Biodiesel purification plants are being built in North America and elsewhere to accommodate the growing need. As of June 2007, there were approximately 150 commercial biodiesel production plants in the U.S. alone.