Water footprint in algaculture for advanced biofuels and high value products

Akwu-Ude, Allen Ude (2019) Water footprint in algaculture for advanced biofuels and high value products. PhD thesis, University of Glasgow.

Abstract

Other aspects of life and science as we know it have progressed over the past 50 years and no other sector of human existence has been as dependent on the breakthroughs of the past as with fossil fuels. Construction, medicine,agriculture, engineering technology have moved on immensely ever since the advent of petroleoum. Fossil fuels have thrived in mankind’s past, present and still plays a major role in the future, unlike any other technological trend in the 21st century in spite of revolutionary changes seen across all other spheres of human existence; their usefulness ought to have been limited in this era. Global carbon emmission and climate change originating from burning fossil fuels places a demand on the research community to discover newer and cleaner fuels like miroalgal biodiesel. Alternative energy sourcing has enjoyed some success in the forms of solar, wind, tidal energy and bioenergy however, a lot more needs to be done to improve the productivity efficiency of microalgae farming and limit mankind’s dependency and use of fossil fuels.
Current techniques employed in large scale microalgae cultivation to serve as a feedstock for biofuels and other high value products have proven to be unsustainable, this has been due to the high water and energy footprints required for their cultivation, harvesting and processing. This work is aimed at understanding the “flawed” conventional microalgae cultivation with growth experiments within the laboratory and subsequently experimenting on non-conventional methods capable of growth with significantly less water to establish profitable, sustainable and commercially viable alternative growth methods. The persistent use of unsustainable techniques in microalgae farming has proven that microalgae based fuels cannot successfully compete with fossil fuels until these challenges are mitigated, or at best alleviated.
The major bottlenecks associated with the future of biofuels from microalgae are associated with the enormous volumes of water used in their cultivation as well as the amount of time and energy required to dewater the algal culture during harvest. In excess of 27,000 litres of water is required to produce 5 litres of algal bio-oil32, that represents a colossal water footprint and needs to be lessened considerably to stand a chance of sustainability and commercialization. Certain microalgae species are known to be capable of growing wildly and thriving on walls, fences and other external surfaces without human intervention, supervision or nourishment. This wild growth
phenomenon can be exploited scientifically and influences the research into microalgae cultivation and the possibility of achieving attached growth with considerably lower water footprint within the laboratory.
The materials and methods used in the experiments were of a conventional nature in most cases with asceptic cultivation of homogenous cultures a major focus. In the cases of preliminary non-conventional experiments, new experimental setups are designed and fabricated to achieve the desired goals.
During laboratory cultivation of microalgae, the initial salt water culture (Nannochloropsis oculata) experienced severe water losses during growth leading to salt crystallization. This challenge led to the search for alternative fresh water strains, capable of quick growth as well as high in biomass productivity with Euglena gracilis the prefered choice. E. gracilis scores lower than N. oculata in lipid content with up to 20% and 29% dry weight biomass respectively, however E. gracilis compensates for this deficiency with a superior volumetric productivity of biomass with 7g/L/day compared to N. oculata’s meagre 0.5 g/L/day returns.
At the end of the experiments, the growth setups recorded up to 400% growth in some cases over a week’s growth based on conventional growth techniques and with additional CO2 .The carbon supplied sample recorded a higher initial concentration on day one and recorded a similar growth trend as the non-carbon sample which recorded a growth of 144% at the end of experiment. The carbon cultivated sample on the other hand logged a 247% growth over the same period. This proves that the carbon supplied sample was more productive in terms of biomass generation over the same time.
The impact of nutrient water produced 46.7% higher cell density in a sample with more dilution than that lower nutrient water dilutions thus suggesting that this strain of microalgae, grown under these laboratory conditions prefer more nutrient-water for their growth.
When water dilutions were compared between four samples A,B,C,D having dilution percentages of 1000%, 750%, 500% and 100% and the same nutrient volume a 15 day period. Over the 15 day experiment period, sample D (lowest dilution) recorded the highest growth and at the end of the experiment, sample B showed the least biomass
accumulation . All the samples recorded their highest average densities in the following decreasing order D,A,C,B.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Bioenergy, biofuels, microalgae, biodiesels, E. gracilis, Photobioreactors, lipids, cultivation, fossil fuels, water footprint.
• Subjects: L Education > L Education (General); Q Science > QR Microbiology; T Technology > TD Environmental technology. Sanitary engineering; T Technology > TJ Mechanical engineering and machinery; T Technology > TL Motor vehicles. Aeronautics. Astronautics
• Colleges/Schools: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Supervisor's Name: Watson, Dr. Ian
• Date of Award: 2019
• Embargo Date: 4 May 2023
• Depositing User: Dr Allen Akwu-Ude
• Unique ID: glathesis:2019-81340
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 05 May 2020 11:29
• Last Modified: 05 May 2020 11:34
• URI: https://theses.gla.ac.uk/id/eprint/81340