Biodiesel Production from <i>Hevea brasiliensis</i> Seeds: A Systematic Review

ABSTRACT The Hevea brasiliensis (HB) species, also called the rubber tree, is currently cultivated worldwide for the extraction of latex, an input for rubber production. In addition, its seeds currently have few productive applications, despite their high oil content. As such, the HB seed oil is a potential feedstock for the biodiesel industry, which is currently dependent on oils from the food sector, including soybean oil. The HB seed oil, however, has a high acidity content (up to 84 mg KOH/g), which complicates transesterification. Therefore, there are several studies describing a variety of methods for the treatment of HB seed oil and for the subsequent biodiesel production. As such, this article presents a systematic review of the processes involving biodiesel production from HB seeds published between 2011 and 2024, as well as an analysis of patents published between 2001 and 2024. For this reason, 170 papers were analyzed, with 83 being selected, of which 36 were highlighted. In this context, the main conclusions were that acid esterification was the most reported method for treatment of HB seed oil, with acidity reductions of up to 99.77%. Moreover, heterogeneous catalyzed transesterification was the most reported method for biodiesel production, with yields of up to 99.52%. Furthermore, it was observed that few patents were published compared to the number of articles, indicating that research priorities remain heavily focused on publication rather than commercial intellectual property protection. Finally, recommended future research directions include the development of more efficient waste‐based heterogeneous catalysts and of methods that take advantage of HB seed oil's characteristics.