Sustainable Biodiesel Production Using Wastewater Streams and Microalgae in South Africa

Abstract

The diminishing petroleum reserves in the world call for sustainable use of cheaply and readily available substrates such as wastewater streams for biomass and lipid production by microalgae. Treated wastewater is rich in macronutrients, such as nitrates and phosphates, and can therefore be used as a substrate for microalgal cultivation in open raceway ponds. The chemistry and composition of treated wastewater is of significance since it is made up of a wide range of compounds that support microalgal growth. The use of raceway pond technology utilizing wastewater streams feed is a new phenomenon that provides much needed phytoremediation of the wastewater as well as facilitating microalgal mass production. Macronutrient utilization by the microalgae justifies the application of treated wastewater as a sustainable raw material for renewable bioenergy production. The operational parameters in the raceway pond such as light intensity, photoperiod, pH, nutrients, salinity, and temperature are carefully optimized for maximal biomass and lipid yield. The biomass and lipid produced using the raceway pond system undergoes downstream processing in order to get the final product. The lipids are converted via transesterification to produce algae biodiesel. Other biologically active compounds and novel phytochemicals can also be derived from microalgae.