Direct Transesterification: From Seeds to Biodiesel in One-Step Using Homogeneous and Heterogeneous Catalyst

Biodiesel is a renewable alternative biofuel and is an option to diversify the conventional fossil fuels. Moreover, biodiesel is nontoxic, biodegradable, and biomass renewable diesel fuel and its combustion produces low amount of CO, CO2, hydrocarbon, and particulate matter. It can be produced through transesterification reaction. The most common method is homogeneous transesterification process using basic catalyst as NaOH. However, this route has drawbacks as long timespans, saponification reaction, a large amount of solvent, and a large amount of water to neutralize the methyl esters to eliminate the catalyst. This chapter presents the direct transesterification as a green and sustainable alternative method to improve the benefits of conventional transesterification. The direct transesterification is a one-step process to obtain biodiesel from seed crops in presence of a catalyst. Jatropha curcas L. and Ricinus communis have been evaluated as non-edible seeds feedstocks. Also, various acid and basic homogeneous and heterogeneous catalysts have been investigated. Results shown that heterogeneous direct transesterification yields ~99% with 5 wt% catalyst in 4 h without n-hexane for oil extraction or water for purify the biodiesel. Heterogeneous direct transesterification is a promising method of obtaining biodiesel as methanol acts as a reactant and as a solvent.