Solid acid-catalyzed biodiesel production from microalgal oil—The dual advantage

The major challenges facing the commercialization of biodiesel are: readily available and profitable feedstock and cost-effective production process. Although conventional oilseed feedstocks provided biodiesel yields of more than 98%, sufficient land for cultivating such feedstocks is a major challenge. Moreover, the use of refined feedstocks is uneconomical because of refining costs and priority as food. Algae (including macro- and microalgae) are the focus of many current research interests because they have the potential to provide sufficient fuel for global consumption. Beside their high lipid contents and fast growth rate, microalgae have the potential to mitigate the competition for land-use and food-for-fuel conflicts. They are also able to reduce the greenhouse effects via CO2 sequestration. Critical survey of the literature suggests that microalgal oil has the potential to produce higher biodiesel yields with about 25% reduction in production costs. However, the oil from microalgae contains high free fatty acids which require pretreatment if conventional homogeneous catalysts are employed. Heterogeneous base catalysts are also not suitable due to soap formation and post-production processes, hence the need for solid acid catalysts. Therefore, this article provides a review on solid-acid catalysts used in processing microalgal oil for biodiesel production. Also discussed in details are the challenges and prospects of the production process. With more advances in technology and long-term commitment to investments, heterogeneous acid-catalyzed microalgal-biodiesel can become the ideal process for the future.