The valorization of organic waste through biodiesel synthesis was investigated to explore the concept of hazardous waste-to-energy. Fish waste (mackerel waste) was chosen as a case study because of the growing concern regarding the treatment of food waste, which is potentially hazardous to the environment. This study focused on the thermally-induced transesterification of fish waste for the production of biodiesel (Le., fatty acid methyl esters (FAMEs)). This process requires a porous material that allows for the collision between reactants (fish waste and methanol) to increase inside its pores at high temperatures. Therefore, commercial clay (montmorillonite) was used as the porous material in this study. The optimal temperature for the thermally-induced transesterification of unpurified mackerel oil was 380 degrees C, and the FAME recovery reached up to 72 wt.%. This study also proved that thermal cracking of polyunsaturated FAME species was initiated at temperatures >= 390 degrees C, and that fish waste is a promising feedstock for biodiesel when it is produced via thermally-induced transesterification over clay as a porous material.