Ajam Y. Shekh, Kannan Krishnamurthi,

Raju R. Yadav, Sivanesan S. Devi, Tapan Chakrabarti, and Sandeep N. Mudliar

CSIR-National Environmental Engineering Research Institute (NEERI)

Nagpur, India

Vikas S. Chauhan and Ravi Sarada

CSIR-Central Food Technological Research Institute (CFTRI) Mysore, India

Sanniyasi Elumalai

Presidency College Chennai, India

CONTENTS

11.1 Introduction…………………………………………………………………………………………….. 162

11.2 Microalgae for CO2 Sequestration: Concept and Recent Developments.. 162

11.3 Microalgae: Value-Added Products (VAPs)—Fuel-Based………………………. 163

11.4 Microalgae as a Source of Value-Added Food Supplements………………….. 168

11.4.1 P-Carotene………………………………………………………………………………….. 168

11.4.2 Astaxanthin………………………………………………………………………………… 169

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 (CO2) due to anthropo­genic interventions has led to several undesirable consequences, which include increas­ing 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 CO2 capture and storage technologies are being deliberated. Some of the CO2 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 effective­ness (Abu-Khader, 2006; Shekh et al., 2012). Therefore, there is an urgency to look for sustainable, economical, and replicable technologies for CO2 sequestration. Microalgae have attracted a great deal of attention for CO2 fixation because of their ability to convert CO2 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 P-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 CO2 sequestration technologies may be microalgal cultiva­tion integrated with CO2 sequestration and its conversion to value-added food and fuel — grade precursors/products. This chapter deliberates on some of these aspects.