Abstract
The impending danger of climate change and pollution can now be seen on the world panorama. The concentration of CO2, the most important Green House Gas (GHG), has reached to formidable levels. Although carbon capture and storage (CCS) methods have been largely worked upon, they are cumbersome in terms of economy and their long term environmental safety raises a concern. Alternatively, bio-sequestration of CO2 using microalgal cell factories has emerged as a promising way of recycling CO2 into biomass via photosynthesis which in turn could be used for the production of bioenergy and other value-added products. Despite enormous potential, the production of microalgae for low-value bulk products and bulk products such as biofuels, is heretofore, not feasible. To achieve economic viability and sustainability, major hurdles in both, the upstream and downstream processes have to be overcome. Recent technoeconomic analyses and life-cycle assessments of microalgae-based production systems have suggested that the only possible way for scaling up the production is to completely use the biomass in an integrated biorefinery set-up wherein every valuable component is extracted, processed and valorized. This article provides a brief yet comprehensive review of the present carbon sequestration and utilization technologies, focusing primarily on biological CO2 capture by microalgae in the context of bio-refinery. The paper discusses various products of microalgal biorefinery and aims to assess the opportunities, challenges and current state-of-the-art of microalgae-based CO2 bioconversion, which are essential to the sustainability of this approach in terms of the environment as well as the economy.
Highlights
The increased concentration of Green House Gases (GHGs) are causing dramatic climatic changes as a result of wellknown phenomenon “Global Warming” (Alexander et al, 2006; Church and White, 2006; Rignot and Kanagaratnam, 2006; Meinshausen et al, 2009; Rockstrom et al, 2009; Solomon et al, 2009; Dawson et al, 2011)
Recent technoeconomic analyses and life-cycle assessments of microalgae-based production systems have suggested that the only possible way of realizing the potential production is to completely use the biomass in an integrated biorefinery set-up wherein every valuable component is extracted, processed and valorized (Chew et al, 2017)
As reviewed by Mata et al (2010), the lipid content of common microalgae such as Chlorella, Dunaliella, Isochrysis, Nannochloris, Nannochloropsis, Neochloris, Phaeodactylum, Porphyridium, and Schizochytrium, varies between 20 and 50% of cell dry weight, that can be augmented to higher levels by manipulating environmental and other growth factors, process optimization and genetic modifications of the production strain
Summary
The increased concentration of Green House Gases (GHGs) are causing dramatic climatic changes (rise in temperature, changes in the distribution, intensity and pattern of rainfall, rising sea levels, floods, droughts and increased occurrence of extreme climatic phenomena) as a result of wellknown phenomenon “Global Warming” (Alexander et al, 2006; Church and White, 2006; Rignot and Kanagaratnam, 2006; Meinshausen et al, 2009; Rockstrom et al, 2009; Solomon et al, 2009; Dawson et al, 2011). Many research studies have come up showing the positive impact of growing microalgae under high concentrations of Ci in the form of pure gaseous CO2, real or simulated flue gas, or soluble carbonate (bicarbonate), reporting increased carbon bio-fixation and biomass productivity (Ho et al, 2010; Sydney et al, 2010; Yoo et al, 2010; Tang et al, 2011; Singh et al, 2014; Aslam et al, 2017; Kuo et al, 2017).
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