De la Hoz Siegler, HectorDemirkaya, Cigdem2023-05-112023-01-25Demirkaya, C. (2023). Development of a Cyanobacterial Biorefinery:Integration of Autofermentation and AnaerobicDigestion for Maximal Value Generation and Reduced Energy Inputs (Doctoral thesis). University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca .http://hdl.handle.net/1880/116351https://dx.doi.org/10.11575/PRISM/dspace/41195Cyanobacteria are ideal bio-factories for diverse biotechnological applications owing to their capacity to use solar energy and fix carbon dioxide into valuable bioactive compounds such as proteins and pigments. However, the economic viability of large-scale cyanobacteria cultivation is hindered by low volumetric productivity due to the slow mass transfer rate of CO2 into the culture media and significant CO2 losses. High pH (>10) and high alkalinity (>>10000 ?Eq L-1) can be used to improve CO2 delivery efficiency, as alkalinity enhances buffering capacity and improves CO2 mass transfer rates. Another important factor is the high cost associated with harvesting and energy intensive downstream processing methods. Thus, there is a need to develop integrated biorefinery strategies to maximize product recovery and value creation. To develop an economically viable cyanobacterial biorefinery, an alkaline cyanobacterial biomass production system was integrated with an autofermentation step, and a low temperature anaerobic digestion. Integration of these processes increase biomass productivity, trigger the release of valuable products, and enable multiple product recovery, nutrient recycling, and maximum energy production.Autofermentation was investigated as an energy-efficient and low-cost method to reduce pH to an optimal level (6.8–7.2) for the successful conversion of biomass to biogas and enable the production of hydrogen and organic acids simultaneously. High value-added products, hydrogen, and phycocyanin were also recovered from the process. Maximum total organic acid yield (60 % C mol/ C mol biomass) and hydrogen yield (326.1 ?mol/g AFDM) were obtained at the lowest biomass concentration after natural settling with no additional energy requirement.Three different inocula including digested manure, digested sewage sludge, and soda lake sediment were evaluated for energy efficient anaerobic digestion of cyanobacterial biomass at a low temperature (21 °C). Low temperature semi-continuous anaerobic digestion of fermented cyanobacterial biomass was carried successfully over 800 days with an average methane yield of 476 ml/ g VS by using soda lake sediment in duplicate 2 L digesters operating at 21 °C. Techno-economic assessment of the integrated process showed that phycocyanin is an important parameter for the economic value of this proposed alkaline cyanobacterial based biorefinery.EnglishBiorefineryAutofermentationAnaerobic DigestionAlkaliphilesCyanobacteriaHydrogenOrganic acidsCarbon CaptureEngineering--ChemicalEngineering--EnvironmentalEnergydoctoral thesis