Envinronmental Life Cycle Analysis of Algal Biorefineries for Biofuel Production under the Circular Economy Concept

Algal biofuels can be a potential alternative as a source of fuel while it alleviates greenhouse gas emissions that causes climate change. However, the feasibility of these is still a challenge. Hence, a biorefinery concept introduced, where the system can produce the main product such as biofuel and can cater various co-products. However, limited studies look at the environmental impact of the system. This study uses life cycle assessment (LCA) to assess the proposed algal biorefinery under the circular economy concept. The results of the LCA reveal that the transesterification and cultivation processes were the environmental hotspots of the system, while dewatering and biochar production contributed the least. Additionally, sensitivity analysis on the process inputs of the system revealed that the heat usage of transesterification most significantly influenced the global warming potential of system, indicating that improvements to the system should focus on reducing the heat requirement of transesterification to improve the global warming potential of the system the most. Lastly, the results of the scenario analysis show that incorporating biochar production, combined heat and power (CHP), and anaerobic digestion (AD) to the conventional microalgae-to-biofuel process chain will not be environmentally beneficial. Instead, system managers should only focus on integrating biochar production and either CHP to AD to the conventional system to achieve the lowest environmental impact.