The main objective in this research is to explore two separate approaches for improving the growth of microalgae that can be potentially used for producing fuels and chemicals. One approach was to use optical light filters, which selectivity filter natural light allowing certain wavelengths into the culture systems. The other study is to use an algal growth system with different bio-renewable materials being used as attachment materials. Both studies demonstrated increased biomass productivity and the ability to scale-up.

In the first part of the study, the research involving the use of optical light filters for microalgal growth in different cultivation systems included flask culture systems, flat panel photobioreactors, and rotating algal biofilm (RAB) systems. The optical light filters allow a specific range of wavelengths to pass through, while reflecting harmful wavelengths such as UV and IR. Two thin film light filters were fabricated for this research. One light filter allows both red and blue wavelengths to penetrate through (termed as blue filter) while the other allows the penetration of wavelengths in the red spectrum (termed as red-filter). Both filters resulted in increased biomass productivities when microalgae were grown in the flat panel photobioreactors and the RAB systems. When the blue filter was used for the culture, the biomass productivity increased 31.9% in flat panel photobioreactors and 99.8% in RAB systems; while the red filter resulted in an increase of 34.1% in the continuous operation of the flat panel photobioreactor. These results provide evidence that the use of these filters have the ability to enhance algal yield.

The second part of this study used different bio-renewable materials as an attachment substrate for algal growth. An initial test was performed to screen the material that can result in the highest amount of attached biomass. It was found that the soy protein based sheet showed the greatest amount of algal attachment. Compared to the suspended cell growth of the control, the biomass productivity from the soy protein based sheets increased by 294%. However, significant deterioration was observed from the soy protein based sheet after 20 days. To alleviate the dissolving of materials and enhance the integrity, poly-lactic acid was integrated into the soy protein based sheet. After this integration the attachment material displayed a significant amount of rigidity allowing for a longer duration of experimentation. However, the productivity from the PLA integrated soy protein based sheet displayed a certain degree of decreasing biomass yield compared to the 100% soy protein based sheet. Collectively, the PLA integrated sheet still demonstrated adequate performance in terms of cell growth improvement and material longevity.

In summary, this study shows that the use of the optical light filters and bio-renewable based sheets for attached algal growth are two viable approaches for enhancing algal growth performance. However, these two approaches need to be further optimized in order to be implemented at a large scale.