Energy Integration of Bioethanol Production Process Topology from Microalgae Biomass: Evaluation of SSCF, SSF, Acid Hydrolysis and Product Purification Alternatives

Abstract

An increasing interest exists in the use of ethanol as substitute of fossil fuels which can be obtained from renewable resources, microalgae are a promising source for third generation bioethanol due to the high percentage of carbohydrates/polysaccharides presents in some species and thin cellulose walls. Ethanol can be produced from either microalgae biomass before lipid extraction or from microalgae cake after cell disruption and oil extraction. Second option gives the interesting possibility of producing both biodiesel and ethanol from the same biomass. Energy analysis can be used for evaluation of the performance and efficiency of a process based on the first law of thermodynamics. In this work, third generation bioethanol production process was evaluated using the methodology of energy integration with the software Aspen Plus, the microalgae genera used was Chlorella sp. and technologies evaluated were Simultaneous Saccharification and Co-fermentation SSCF, Simultaneous Saccharification and Fermentation SSF, and Separate Saccharification and Fermentation using acid hydrolysis (SHF). Results shows that technology of Simultaneous Saccharification and Co-fermentation SSCF (route 1) presents the highest bioethanol yield 24.1 %, and the lowest energy requirements after energy integration. Separated hydrolysis and fermentation SHF (route 3) presents the lowest efficiency, ?Tmin was defined in 9 °C for SSCF, 4 °C for SSF, and 8.5 °C for SHF, the use of molecular sieves technology for bioethanol dehydration represents lower energy requirements respect to extractive distillation.