Water Footprint of Biodiesel Production from Microalgae Cultivated in Photobioreactors

Based on experimental data, this study determined the water footprint of biodiesel production from freshwater microalgae cultivated in photobioreactors. The findings highlighted the necessity of recycling harvest water and applying undiluted wastewater to grow microalgae in efforts to save freshwater resources. Without water recycling, approximately 3,494 kg freshwater was required to produce 1 kg microalgal biodiesel. By contrast, recycling harvest water at the degree of 50 and 100% to regrow microalgae could reduce the water utilization by 39.4 and 93.0%, respectively. The results also showed that using undiluted wastewater to grow microalgae could decrease the usage of freshwater by 93.7%, reaching as low as 219 kg water/kilogram microalgal biodiesel produced. Factors that affect the water footprint of microalgal biodiesel production were also discussed in this study.