Ecofuel conversion technology of inedible lipid feedstocks to renewable fuel

The main obstacle in the global commercialization of biodiesel is the high production cost. In general, biodiesel feedstock depends on crops amenable to regional climates. The use of refined edible oils for the production of biodiesel accounts for 60%–80% of the biodiesel production cost. Utilization of alternative feedstocks that are cheap, abundant, and inedible can decrease that production cost. Besides that, the optimization of the synthesis and purification processes and the utilization of byproducts can also reduce the total biodiesel production cost. This chapter discusses the advantages and drawbacks of catalytic and noncatalytic technologies to convert inedible feedstocks, such as rice bran, microalgae, and spent coffee grounds. For rice bran, the noncatalytic in situ trans(esterification) using a subcritical water-methanol mixture seems to be the most promising method as it requires no preliminary steps to extract oil from feedstock and to remove impurities. For microalgae and spent coffee grounds, the in situ trans(esterifications) using a subcritical water-methanol mixture with an acid catalyst and supercritical methanol/ethanol, respectively, seem to be the most promising methods. Besides that, these feedstocks are rich in carbohydrates and bioactive compounds (γ-oryzanol in rice bran, carotenoids in microalgae, and chlorogenic acid in spent coffee grounds). The purification processes are also discussed, particularly the ones that can isolate a small fraction of high-value bioactive compounds. The utilization of these byproducts according to the biorefinery approach can further reduce the overall biodiesel production cost.