Integrated Microalgae Cultivation for Sustainable Wastewater Treatment and Carbon Dioxide Bio-Fixation in Milk Factories

Abstract

Technologies have been developed to reduce CO2 emissions, including CO2 bio-fixation by microalgae. This study evaluates carbon reduction by integrating milk factory wastewater treatment with microalgal biomass production, including its sustainability aspects through life cycle assessment (LCA) and techno-economic assessment (TEA). The microalgae species used were a consortium of Chlorella sp. and Scenedesmus sp. Five levels of carbon dioxide were provided to microalgae cultures: 0%, 5.5%, 6.2%, 8.1%, and 10.3%. Observed variables included CO2 uptake, absorption efficiency, and microalgal biomass production. The results showed that the CO2 sequestration efficiency by indigenous microalgae reached 0%, 9.2%, 98.8%, 96.2%, and 93.2% with average CO2 level loadings of 0%, 5.2%, 6.2%, 8.1%, and 10.3%, respectively. Chlorella sp. exhibited greater tolerance to high levels of CO2 concentration than Scenedesmus sp. TEA analysis revealed that CO2 bio-fixation and wastewater utilization significantly increased microalgal biomass production while also reducing environmental pollution. Furthermore, LCA indicated that the initial biomass production method (scenarios 1 and 2) had a higher environmental impact than the advanced method using wastewater treatment (scenarios 3 and 4). In conclusion, coupling microalgae-based wastewater treatment with CO2 bio-fixation offers promise for CO2mitigation, enhanced biomass production, and reduced operational costs.