Life Cycle Assessment of Algal Derived Biodiesel

Microalgae biofuels are considered to constitute a promising alternative for fossil fuels and are being intensively investigated from a life cycle perspective. The present work focuses on the life cycle assessment of microalgae-derived biodiesel production according to a cradle-to-gate approach using the conventional technology. Moreover, many scenarios are proposed and studied, which aim to improve overall performances. The impact 2002+ is used to evaluate the impact categories. The main environmental impacts assessed are, in particular, carbon balance and net energy ratio. The main obtained results show that microalgae cultivation and biomass drying are the most important contributors to the studied impact categories, which represent a share of 57% and 38%, for GHG emissions and Net energy ratio, respectively. Furthermore, using the spent biomass as energy source for biomass drying combined with CO2 recycling for the cultivation phase has been found to be the most effective process, among other scenarios such as the use of wastewater as a culture media and anaerobic digestion of the spent biomass. This process was found to improve the overall energy balance, which a value of 1.9 is obtained. Using life cycle assessment tool shows that microalgae-derived biodiesel could be a promising alternative for fossil diesel and for CO2 sequestration. However, the sustainability of microalgae production needs more insights on CO2 source and energy requirement during the cultivation phase and biomass conversion to biofuels.