Techno-economic analysis of microalgae biorefinery in arid environments for co-production of biofuels and value-added compounds

Abstract

Depletion of fossil fuel resources and climate change are among the biggest challenges that humanity will face in the next decades. Historically, development of countries was closely linked with cheap and reliable sources of energy. Liquid biofuels derived from first generation feedstocks are considered to be unsustainable, and second generation biofuels are often economically or energetically unfeasible. Microalgae – small unicellular photosynthetic organisms inhabiting aqueous environments – are regarded as a promising solution to these challenges. In this thesis, feasibility of producing algal biofuels in arid environment of United Arab Emirates has been investigated. Chlorella vulgaris was used as a model organism to determine the potential of co-production of lipids for fuels and proteins using biorefinery concept. It has been demonstrated numerically that incorporation of higher-value products is necessary to shift the negative economic balance of producing lipids only. For the purpose of perspective microalgae biorefinery in the UAE, screening for local strains was performed, resulting in isolation of two marine strains – Synechococcus and Picochlorum, with former one displaying stable growth in wide range of temperature (22-37°C) and salinity (20-42 ppt). Strain was cultivated in two media of different nutrient composition, harboring as much as 22% of dry weight as lipids when grown in F/2 medium, and 54% of dry weight as proteins when grown in ASW/BG medium. Strain was investigated for flocculation using sodium hydroxide, ferric chloride, and chitosan; as well as for cell disruption using alkaline, hydrothermal, sonication, and enzymatic treatments. Resulting numbers were incorporated into processing model. Based on the current state of knowledge, processing local Synechococcus strain for lipids and proteins is unfeasible unless final products are upgraded into higher-value commodities. Furthermore, application of proteins as isocyanate substitutes in production of sustainable polyurethane-like biomaterials has been explored. Optimal formulations have been established and processing cost model was created. Finally, the manual on how to approach microalgal biorefinery design has been created, in order to serve as instruction for future investigations.

Date of Award	May 2017
Original language	American English
Supervisor	Jens Schmidt (Supervisor)