The Screening, Fabrication and Production of Microalgae Biocomposites for Carbon Capture and Utilisation

Abstract

The use of microalgae for carbon dioxide sequestration and as a feedstock for biodiesel production has been a topic of active research since the late 1950s. It has not been adopted as a technology due to the difficulties in growing the microalgae, harvesting it and the excessive cost of the fuel produced via this route. This research work focuses on a novel idea of attached microalgae growth method to cultivate different species of freshwater and marine microalgae on a solid substrates to sequester carbon dioxide and use the biomass to produce biofuel. Initially, we undertake a study to prove the concept of nourishing microalgae cells attached to filter paper via capillary. The initial results indicate a good survivability of the immobilised cells with limited nutrients for 8 weeks. The average cumulative CO2 fixation of C. vulgaris cells (3.33 mmol g-1 day-1 ) attached to the paper was more than twice the suspended culture cultivation (0.924 mmol g-1 day-1 ) using 5% CO2/air mixture. The next stage in this research work investigated the use of binders for cell immobilisation on a biodegradable substrate. A binder screening protocol which took into account toxicity and adhesion strength was developed to produce a biocomposite using the best combinations of microalgae species and binders upon different substrates. We subsequently developed an experimental system to continuously sequester carbon dioxide for 6 weeks using biodegradable microalgae bio composites made from loofa sponge and latex binders. D. salina cumulative CO2 fixation of 5.96 mmol/g day-1 when immobilised with latex binder Baymedix CH-120 polyurethane resin dispersion was 15 times higher than the 0.40 mmol/g day-1 recorded for suspended culture. This also translate to reduction in land and water usage when compared to open pond algae cultivation or photobioreactor. The immobilised cells lipid content production improved for two of the algae species (C. vulgaris and D. salina) that were tested. The lipid content was 69.38% and 66.22% biomass dry weight for C. vulgaris and D. salina respectively. This novel research work has the potential to substantially reduce the cost associated with biological carbon capture and biofuel production using microalgae when compared with the open ponds and photobioreactors.