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Keywords: Applied Sciences
Agriculture & related technologies
Issue Date: 2016
Abstract: Biofuel production is widely deliberated to be one of the most sustainable alternatives to the non-renewable petroleum fuels and used as feasible means for environmental and economic sustainability. Biological capture of carbon dioxide by photosynthetic unicellular microalgae is an attractive technology because it is scalable and efficient mean to yield renewable energy source i.e. biodiesel. Microalgae, a third generation feedstock for biofuel, can be grown on non-arable land in fresh, brackish or saline water and with higher areal productivities than any other land-based crops. In particular high productivities are achieved during cultivation when coupled with an additional carbon dioxide supply; for every kilo grams of dry biomass approx. 1.83 kg of CO2 is required. In this study five industrial cities of Punjab were selected to identify microalgae strains from industrial areas which provide opportunities to achieve significant reductions in carbon dioxide emissions. Microalgae have been considered for biological carbon capture and sequestration to offset carbon emissions from fossil fuel combustion. Series of factors for carbon sequestration like tolerance of CO2 source (i.e. flue gas), cultivation conditions, inhibiting compounds that come with the CO2 source (e.g. SOx & NOx) and physiochemical parameters such as pH, nutrients, temperature and light, had been studied in this research. The adapting ability of mixed consortia of microalgae was used to tolerate growth in 100% flue gas from an unfiltered coal-fired power plant that contained 11% CO2. Challenges existed in particular around the high SOx and NOx emissions that caused a rapid decline in pH when added to cultures. This required slow adaptation of microalgae over many months, with step-wise increases from 10% to 100% flue gas supplementation, and the maintenance of high phosphate fertilizer levels in the form of 50mM phosphate buffer for flue gas at and above 50%. Concurrently, this led to a selection of microalgae that seem to be particularly well adapted to low pH and high level flue gas supplementation. For two different microalgal consortia, 18S rRNA community profiling and microscopic analyses revealed that, after a rapid decline in biodiversity over the first few months, in particular Desmodesmus sp. was the dominant genus (-79-90%). This novel study demonstrates that upto 100% unfiltered flue gas from coal-fired power generation can be used for algae cultivation. While it is clear that large areas are needed to xviii offset flue gas emission through microalgae, direct comparisons to other carbon sequestration technologies should be made once upscaling, cost reductions and process optimizations are in place. With the implementation of serial passages of over a range of open or closed PBRs this process may contribute towards the development of microalgal-mediated carbon capture and sequestration processes.
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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