ABSTRACT
Depletion of fossil fuels, climate change, concern over energy securities, volatile energy costs, and negative impact on the environment, particularly greenhouse gas emissions, ignited efforts for nding renewable fuel alternatives. The concern over fossil fuel supply is clearly reected by an increase in crude oil price from US$80 per barrel in 2006 to US$108.01 per barrel in 2013. As an initiative, the European Commission set a goal to substitute 5.75% of fossil fuels with alternate fuels in 2010 and subsequently aimed the same at 20% substitution by 2020 (Hahn-Hagerdal et al. 2006). Similarly, United States has also attained 10% blend of ethanol in gasoline in 2011 and is steadily planning to increase the blend to E15. Ethanol is the most widely used transport biofuel across the globe and showed a signicant increase in production from less than a billion liters in 1975 to more than 86 billion liters in 2010, and it is expected to reach 170 billion liters by 2020 (Licht 2006; ISO World Fuel Ethanol Outlook 2012). The United States, Brazil, and the European Union (EU) are the pivotal markets for bioethanol production and consumption and accounted for 90% of the world’s ethanol market share (Table 11.1). The rise in transport fuel demand globally has made it mandatory for other countries also to think over other alternatives like bioethanol. Canada, Colombia, China, Thailand, and India are among other countries involved in ethanol production currently at a small scale but with rise in the future. Bioethanol is largely derived from starch/cellulose-based
CONTENTS
11.1 Introduction ........................................................................................................................ 197 11.2 Biofuel .................................................................................................................................. 199 11.3 Seaweeds as Renewable Source of Biofuel .....................................................................200 11.4 Proximate Composition of Seaweeds .............................................................................. 201 11.5 Status of Bioethanol Production from Seaweeds .......................................................... 202
11.5.1 Conversion of Seaweed Carbohydrate to Fermentable Sugars ....................... 203 11.5.2 Fermentable Sugars to Bioethanol ....................................................................... 207
11.6 Research Activities on Seaweed Ethanol across the Globe ......................................... 209 11.7 Challenges and Future Plans in Seaweed Fuel ............................................................. 210 11.8 Conclusion .......................................................................................................................... 211 Acknowledgment ........................................................................................................................ 211 References ..................................................................................................................................... 212
biomass, that is, plants, crops, and agricultural wastes. The world leaders United States, Brazil, and EU utilize two major sources, namely, corn and sugarcane, as raw materials for ethanol production (Chiaramonti 2007). As an estimate, 70% of the world’s ethanol has been produced from corn and sugarcane. The high cost involved in the production of ethanol from sugarcane and the food versus fuel debate over corn ethanol give a negative perception in governing bodies leading to a search for new feedstock for ethanol production. The lignocellulose-based feedstocks are nowadays looked as an alternative to food crops in most of the bioreneries to produce ethanol and other high-value chemicals (Cherubini 2010). Agriculture waste and fast-growing nonedible terrestrial plants such as Populus and Eucalyptus constitute the major lignocellulosic biomass. Another concern on availability of arable lands for agriculture limits the propagation of aforementioned trees for fuel purposes. It is therefore necessary to shift our focus from terrestrial to marinebased renewable biomass such as macroalgae (John et al. 2011; Subhadra and Grinson 2011; Kraan 2013). Marine macroalgae are a group of large photoautotrophic multicellular, sessile, benthic plants commonly called as seaweeds and consist of as many as 25,000 species worldwide with considerable morphological and functional diversity (Holdt and Kraan 2011). The continuous exploration of seaweeds for chemicals has resulted in a spurt of seaweed production from 3.8 million tons in 1990 to whopping 15.8 million tons fresh in 2008, ranking them as one of the major mariculture crops with a market value of over US$7.4 billion (FAO 2010). Macroalgae have wider industrial applications from conventional food, feed, and hydrocolloids to recently explored sources of fertilizer, bioactive compounds, and energy molecules (McHugh 2003) (Figure 11.1). Seaweeds are a rich source of easily depolymerizable polysaccharides with little or no impregnation of lignin, which have better potential as renewable biomass for bioethanol production over terrestrial resources. This chapter discusses the potential of seaweeds as renewable feedstock for bioethanol production with an overview on seaweed biomass characteristics, its saccharication, and fermentation. Further, global initiatives on seaweed bioethanol production and the challenges faced are also summarized.
