Biomedical Engineering Reference
In-Depth Information
11.4.3 Other Value-Added Products (VAPs) ............................................... 170
11.5 Future Needs ................................................................................................. 171
References .............................................................................................................. 173
11.1 INTRODUCTION
The increase in the atmospheric concentration of carbon dioxide (CO 2 ) due to anthropo-
genic interventions has led to several undesirable consequences, which include increas-
ing Earth temperature, violent storms, melting of polar ice sheets, and sea level elevations
(Shekh et al., 2012). In the global effort to combat and mitigate climate change, several
CO 2 capture and storage technologies are being deliberated. Some of the CO 2 abatement
processes currently in use include the use of chemical/physical solvents, adsorbents onto
solids, membranes, cryogenic/condensation systems, and geological and deep ocean
sequestration (Abu-Khader, 2006; Shekh et al., 2012; Yadav et al., 2012). In practice,
the above-mentioned approaches are questionable with respect to their cost effective-
ness (Abu-Khader, 2006; Shekh et al., 2012). Therefore, there is an urgency to look for
sustainable, economical, and replicable technologies for CO 2 sequestration. Microalgae
have attracted a great deal of attention for CO 2 fixation because of their ability to convert
CO 2 into biomass via photosynthesis at much higher rates than conventional terrestrial
land-based crops (Chisti, 2007; 2008). Microalgae are able to grow on agriculturally
nonproductive arid lands, in saline water, and in domestic and industrial wastewaters,
and consequently do not compete with conventional food crops grown on agricultural
land and thus pose no threat to food security issues (Sheehan et al., 1998).
Similarly, Dunaliella is gaining popularity as a source of β-carotene. Haematococcus
is being grown for the production of the ketocarotenoid Astaxanthin. Further,
Botryococcus species are a promising renewable energy source as they accumulate very
large quantities of hydrocarbons (30% to 73% of dry weight) and also have a high octane
rating as a fuel source because of their highly branched structures. Therefore, one of the
most promising future-proof CO 2 sequestration technologies may be microalgal cultiva-
tion integrated with CO 2 sequestration and its conversion to value-added food and fuel-
grade precursors/products. This chapter deliberates on some of these aspects.
11.2 MICROALGAE FOR CO 2 SEQUESTRATION:
CONCEPT AND RECENT DEVELOPMENTS
The urgent need for substantive net reductions in CO 2 emissions into the atmosphere
can be addressed via biological CO 2 mitigation (Ramanan et al., 2009a, b; Fulke et al.,
2010; Shekh et al., 2012; Yadav et al., 2012), coupled with a transition to value-added
products (VAPs) such as biofuels (Fulke et al., 2010; Kumar et al., 2010). Microalgae
can fix CO 2 from the atmosphere, from flue gases, or directly as soluble carbonates by
the process of photosynthesis using solar energy (Wang et  al., 2008). Concurrently,
biomass is produced with 10 to 15 times greater efficiency than terrestrial plants, which
has application in carbon credit programs (Lam and Lee, 2011). Microalgal cells con-
tain approximately 45% to 65% carbon, wherein 1 kg dry biomass is produced by
fixing approximately 1.8 kg CO 2 (Chisti, 2007). CO 2 from the external atmosphere (air/
extracellular surroundings of microalgae) can be dissolved as bicarbonates and made
Search WWH ::




Custom Search