Life cycle assessment (LCA) of marine microalgae cultivation and harvesting process for the Indian context

Abstract

Microalgae cultivation is one of the emerging CO2 mitigation technologies and converting it into valuable products. The present study evaluates the environmental impacts of marine microalgae's cultivation and harvesting process with a cradle-to-gate approach from an Indian context. The algal cultivation site of 1000 acres is assumed to be located near the Indian coastal area. The life cycle inventory (LCI) data related to the site was assumed based on the literature. The functional unit (FU) for the present study was one kg of dried algae. The evaluation showed that the algal-based technology could mitigate about 1.28 kg CO2 eq./kg algae produced. Among all the impacts, marine aquatic ecotoxicity potential (MAETP) was found to be the most significant one, at 612 kg 1,4-dichlorobenzene (DCB) eq./kg algae. The major contributor to MAETP was the source of electricity. To take into account the uncertainties in the LCI, a scenario analysis was performed with the lower and higher possible process data. The global warming potential (GWP) for 35 g/m2 day productivity was −1.34 kg CO2 eq./kg algae, and for 15 g/ m2 day was −1.11 kg CO2 eq. against −1.28 kg CO2 eq. for the base case. For harvesting the feed concentration of 0.25 g/L, GWP was −0.98 kg CO2 eq./kg algae, and for 0.75 g/L, GWP was −1.39 kg CO2 eq./kg algae. For the consumption change of ±50% in electricity, the change in GWP was ± 13.85%. Further, a scenario analysis based on the source of electricity was evaluated. Replacing 25%, 50%, and 100% of Indian mixed grid electricity with solar-based electricity resulted in improvement in CO2 mitigation by 6%, 12%, and 24%, respectively. Additionally, a significant improvement in MAETP and human toxicity potential (HTP) was observed, with a reduction in MAETP by 20%, 40%, and 80% and HTP by 17%, 35%, and 70% for 25%, 50%, and 100% solar-based electricity respectively.