Life cycle assessment: heterotrophic cultivation of thraustochytrids for biodiesel production

This study provides a life cycle assessment of the energy balance and the potential greenhouse gas impacts of heterotrophic microalgal-derived biodiesel estimated from the upstream biomass production to the downstream emissions from biodiesel combustion. Heterotrophic microalgae can be cultivated using a by-product from biodiesel production such as glycerol as a carbon source. The oils within the algal biomass can then be converted to biodiesel using transesterification or hydroprocessing techniques. This approach may provide a solution to the limited availability of biomass feedstock for production of biorefined transportation fuels. The life cycle assessment of a virtual production facility, modeled on experimental yield data, has demonstrated that cultivation of heterotrophic microalgae for the production of biodiesel is comparable, in terms of greenhouse gas emissions and energy usage (90 g CO₂e MJ⁻¹), to fossil diesel (85 g CO₂e MJ⁻¹). The life cycle assessment identified that improvement in cultivation conditions, in particular the bioreactor energy inputs and microalgae yield, will be critical in developing a sustainable production system. Our research shows the potential of heterotrophic microalgae to provide Australia’s transportation fleet with a secure, environmentally sustainable alternative fuel.