Production of Bioethanol Using <i>Chlorella vulgaris</i> Cake: A Technoeconomic and Environmental Assessment in the Colombian Context

In this paper, fuel ethanol production from <i>Chlorella vulgaris</i> cake was evaluated by experimental and conceptual design techniques. Enzymatic hydrolysis and fermentation with <i>Saccharomyces cerevisiae</i> was performed to quantify the reducing sugars and ethanol from microalgae cake. Extractive distillation and molecular sieves were evaluated as alternative technologies for the dehydration of ethanol. The mass and energy balances were solved using the Aspen Plus software. The total ethanol production costs were evaluated using the Aspen Process Economic Analyzer software, and the Waste Reduction algorithm (WAR) was used to calculate the environmental impacts. Additionally, the effect of energy integration was included in the economic analysis and environmental assessment. The yields obtained for reducing sugars and ethanol were 0.55 and 0.17 g per g of cake, respectively. The global yield of ethanol was 211.9 L per tonne of cake, and the total production cost was 0.76 and 0.91 USD per liter using molecular sieves and extractive distillation, respectively. The most promising technology to produce ethanol from microalgae cake was dehydration by molecular sieves with full energy integration. For this technology, the production cost was 0.76 USD per liter, which resulted in an economic margin of 19.15%. From the environmental point of view, the potential environmental impact was 0.84 PEI/kg products. Additionally, bioethanol from microalgae was shown to be less harmful than bioethanol from corn and sugar cane.