Biodiesel production from waste frying oil using waste animal bone and solar heat

A two‐step catalytic process for the production of biodiesel from waste frying oil (WFO) at low cost, utilizing waste animal‐bone as catalyst and solar radiation as heat source is reported in this work. In the first step, the free fatty acids (FFA) in WFO were esterified with methanol by a catalytic process using calcined waste animal‐bone as catalyst, which remains active even after 10 esterification runs. The trans‐esterification step was catalyzed by NaOH through thermal activation process. Produced biodiesel fulfills all the international requirements for its utilization as a fuel. A probable reaction mechanism for the esterification process is proposed considering the presence of hydroxyapatite at the surface of calcined animal bones.