Corresponding to a 32% increase, from around 280 ppm to 400 ppm, since the industrial revolution ( De Silva et al., 2015). The concentration of CO 2, the most important GHG and the major contributor to global warming, has reached to formidable levels. The temperature of the planet has risen by 0.85☌ from 1880 to 2012 and it has been forecasted that by the end of this century, a rise of 1.4–5.8☌ would be witnessed ( De Silva et al., 2015). 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 well-known 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). The paper discusses various products of microalgal biorefinery and aims to assess the opportunities, challenges and current state-of-the-art of microalgae-based CO 2 bioconversion, which are essential to the sustainability of this approach in terms of the environment as well as the economy. This article provides a brief yet comprehensive review of the present carbon sequestration and utilization technologies, focusing primarily on biological CO 2 capture by microalgae in the context of bio-refinery. 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. To achieve economic viability and sustainability, major hurdles in both, the upstream and downstream processes have to be overcome. Despite enormous potential, the production of microalgae for low-value bulk products and bulk products such as biofuels, is heretofore, not feasible. Alternatively, bio-sequestration of CO 2 using microalgal cell factories has emerged as a promising way of recycling CO 2 into biomass via photosynthesis which in turn could be used for the production of bioenergy and other value-added products. 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. The concentration of CO 2, the most important Green House Gas (GHG), has reached to formidable levels. The impending danger of climate change and pollution can now be seen on the world panorama. Centre for Conservation and Utilisation of Blue Green Algae, Division of Microbiology, Indian Agricultural Research Institute, New Delhi, India."I think there's a tremendous amount of potential. Its working to increase that amount and, meanwhile, larger facilities, including the one in Texas, are now being built as well. "Every ton of CO2 that's removed is a ton that's actually helping fight climate change and not contributing to global warming," said Climeworks' Chief Marketing Officer Julie Gosalvez.īut it can only remove about 4,000 of the nearly 40 billion tons of CO2 humans are pumping into the atmosphere every year. However, these DAC facilities can only remove a fraction of the CO2 emissions released annually. It captures CO2 from the air, separates it and injects it into rock formations for permanent storage. The ClimeWorks plant in Iceland, operated by Swiss company ClimeWorks, is the world's largest DAC facility. While skeptical of CCS, Harvey believes that direct air capture, also known as DAC, which extracts CO2 from the atmosphere, could play a role in combating climate change. "We have the technology to do that right now and I don't think we should be distracted from that." "The frustrating thing is that there is an easy solution and that is to stop using fossil fuels," Harvey said. He argues that carbon capture allows the industry to continue relying on fossil fuels, and even the captured carbon from the Petra Nova plant was used to extract more oil from the ground in a process called enhanced oil recovery. "A dollar spent in renewable technologies will avert a lot more emissions than CCS will," said Harvey.
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