Techno-economic analysis of biocrude, biogas, and fertilizer production from microalgae Coelastrella striolata cultivated in agroindustrial wastewater

Abstract

Coelastrella microalgae have gained attention due to their robustness, high lipid content, effective bioremediation agent, and ability to thrive in diverse environmental conditions. The objective of this study was to evaluate the economic feasibility of an integrated biorefinery of the unique original Coelastrella striolata var. multistriata strain 047 applied in agro-industrial wastewater, flue gases, and excess energy on a 1.2 ha open raceway pond (ORP). This study consists of three scenarios: (1) biocrude only (BO); (2) biocrude and biogas (BB); and (3) biocrude, biogas, and fertilizer (BBF). The findings indicated that the BB and BBF scenarios enhanced the financial feasibility and potential profitability of investment. This is reflected in the economic feasibility indicators for the BB scenario over a project lifetime of 20 years, which include a net present value (NPV) of $4,757,082, an internal rate of return (IRR) of 25.6%, a profitability index (PI) of 2.77, and a payback period of 3.75 years. Similarly, in the BBF scenario, financial viability is demonstrated with an NPV of $4,714,418, an IRR of 25.2%, a PI of 2.73, and a payback period of 3.79 years. Operational expenditures were identified as the most sensitive aspect of this study, particularly in the hydrothermal liquefaction (HTL) process for biocrude production. The utilization of effluent and excess energy from palm oil mill (POM) reduced the operational costs for energy and nutrients by up to 69% compared to the baseline, where palm oil mill effluent (POME) and excess energy were not utilized. Additionally, to achieve optimal results in the BO scenario, increasing the concentration of Coelastrella striolata var. multistriata strain 047 in POME proved to be the most effective approach for increasing biocrude oil production, reducing costs, and increasing economic sustainability.