Techno-Economic Analysis of an Integrated Membrane-Based Harvesting and Effluent Recycling Strategy for Microalgal Biomass Production in Raceway Ponds

Microalgae-based systems offer a sustainable route for biomass production and carbon dioxide (CO2) capture; however, their economic feasibility remains scale-dependent. This study presents a techno-economic analysis (TEA) of Monoraphidium sp. KMC4 cultivated in open raceway ponds (ORPs) using low-cost kaolin-based ceramic membranes integrated with a three-batch effluent recycling system. Four scenarios (S1–S4) were evaluated to assess the influence of production scale (1–100 ha) and electricity subsidies. Capital expenditure (CAPEX) and operating expenditure (OPEX) were quantified, and a sensitivity analysis was conducted for plant life, discount rate, biomass selling price, and utility and labor costs. Results show that small-scale systems with subsidies (S1) yield marginal profitability (net present value, NPV: $0.28 million), while unsubsidized small-scale systems (S2) remain unviable. Industrial-scale production (S4) demonstrated favorable economics with a unit biomass cost of $7.50 per kilogram, a payback period of 5.3 years, and an NPV of $145.78 million. The sensitivity analysis confirmed that the biomass selling price and utility costs are the most influential parameters that affect economic viability. Overall, the findings emphasize that economies of scale, process optimization, and resource recovery are key to widespread adoption and the feasibility of algae-based systems.