Exploration of agricultural residue ash as a solid green heterogeneous base catalyst for biodiesel production

Biodiesel is an economical and nonpolluting green fuel produced from the transesterification of oil and alcohol in the presence of a catalyst. Transesterification of vegetable oils with conventional (homogeneous) catalysts for biodiesel production is considered to have a promising future but they are nonrenewable and hazardous. The major setback is the increase in cost of production. High production cost, in terms of feedstock oil and catalyst acquisition is one of the major challenges facing the global commercialization and acceptance of biodiesel. Heterogeneous solid catalysts are currently replacing homogeneous catalysts because of their ability to overcome hurdles associated with homogeneous catalysts. This study discussed the development and feasibility of calcined ash from agricultural residues as a solid green heterogeneous base catalyst for biodiesel production without chemical degradation. Solid-calcined ash based catalysts are being developed primarily via calcination at suitable temperatures and have been used as catalysts without mixing with carrier compounds. The various agricultural residues used and the corresponding biodiesel yields were also discussed. The study also looked at some agricultural residues that could be targeted for high catalytic output. It was found that high biodiesel yields (80%–98%) were achieved with most of the crude oil raw materials used. The catalyst could be reused at least five (5) times. From the discussed literature, it was found that the current state of biodiesel production can be improved by using heterogeneous base catalysts made from agricultural residue calcined ash.