Towards sustainable continuous co-production of biodiesel and ether from wet microalgae- a review

Microalgae are possible biodiesel feedstocks whose potentials are yet to be realized. The increased ethanol-to-oil molar ratio required by in situ transesterification makes it more water tolerant. The necessity to remove unreacted ethanol (> 95%) from product streams, on the other hand, necessitates a higher distillation heat load, which raises the operational cost. This review provides guidance on how to execute in situ transesterification for the production of sustainable algal biodiesel. It pinpoints obstacles to the commercialization of algae biodiesel. In situ transesterification of wet microalgae, co-production of diethyl-ether and biodiesel from the same wet microalgae, and two-step transesterification for biodiesel were examined for energy and cost. Energy consumption by cell disruption, biomass drying, and transesterification steps largely contributes to the high biodiesel production cost by two-step transesterification. This should be minimized for sustainable production. The excessive ethanol (or methanol) to oil ratio of in situ transesterification of microalgae to produce biodiesel can be overcome by continuous co-production of biodiesel and diethyl ether from wet microalgae as it has a lower production cost compared to two-step and in situ transesterification of wet microalgae. The blend of diethyl ether with biodiesel also improves fuel quality and lessens its emission characteristics. [GRAPHICS] .