Abstract The transformation of the lipids extracted from duck tallow into biodiesel was achieved using activated alumina and CO2 under ambient pressure (1bar). Crude fatty acids (∼98% assay) were also esterified to help us understand and validate the noncatalytic biodiesel conversion mechanisms. Its conversion efficiency was nearly 93.5(±0.5)%. The transformation of crude fatty acid into biodiesel proves that this newly developed technology for the production of biodiesel combines esterification of free fatty acids and transesterification of triglycerides into a single process that has a 98.5(±0.5)% conversion efficiency to biodiesel within 1min at 350–500°C. This paper addresses the simplest methodology for the production of biodiesel. Herein, it is confirmed that the main driving force of biodiesel conversion in the noncatalytic transesterification reaction is temperature rather than pressure. Noncatalytic biodiesel transformation can be achieved in the presence of a porous material via a thermochemical process in a continuous flow system. This noncatalytic biodiesel transformation was enhanced under the presence of carbon dioxide (CO2).