Producing lipids, biogas and fertilizer from microalgae – conceptual design and technoeconomic analysis

Biological CO2 capture by microalgae is seen as a promising technology and has the advantage of producing biofuel/biomass simultaneously. The combination of biofuel/biomass production, CO2 fixation and bio-treatment of wastewater underscore the prospect and potential of microalgae. This work concerns the optimal use of microalgal biomass, focusing on carbon capture and economic feasibility. Microalgal products are briefly reviewed as well as the carbon capture from industrial flue gas. Conceptual level techno-economic analysis is erformed
for four concepts that produce lipids, biofuels and/or fertilizer. The evaluated processes include open pond cultivation with industrial flue gas, harvesting, rying, cell wall disruption, extraction of lipids and anaerobic digestion. Process parameter and economic evaluation data, such as prices, specific power consumptions and the yields of unit operations, have been obtained mainly from literature. The results of this study indicate that microalgae-based production of selected products would be unprofitable with the assumptions used. Sectorial literature shows similar performance. The most significant factors affecting the profitability were high investment costs and other fixed costs, as well as the cost of heat in concepts where biomass was dried.