7.7.1 Introduction ......................................................................................................... 244
7.7.2 Biorefineries........................................................................................................ 244
7.7.3 Synthetic Biology ............................................................................................... 246
7.7.4 Conversion of Lignocellulosic Biomass into Value-Added Products .............. 247
7.8 Conclusion ...................................................................................................................... 248
References................................................................................................................................ 249
7.1 Introduction
Constant increase in oil prices, possible depletion of oil reserves, and climate
change concerns are the main reasons to search for sustainable oil substitutes. In
most parts of the world, oil is the leading source of energy and provides the main
part of chemical precursors used to manufacture a large variety of products, from
plastics and composites used in almost all aspects of our lives to food and fine
chemicals (Howard et al. 2003; Waltz 2008). While energy requirements may be
covered at least partially by alternative raw sources as solar, wind power,
hydrogen, and tidal energy, chemical commodities require a renewable source of
chemical precursors that can be produced in a sustainable way (Lynd et al. 2003).
Lignocellulosic biomass as agriculture, forestry, paper pulp, and food wastes is
the best potential alternative source for the production of both biofuels and fine
chemicals with the potential to cover our most important needs (Kerr and Service
2005; Kumar et al. 2008). Energy or chemical precursors obtained from lignocellulosic biomass by-products or agricultural waste and forest activities cannot
compete with food production, as is the case of biofuel production from sugarcane
or maize starch, or even indirectly for crop lands and resources, as is the case of
oils used for biodiesel production (US Department of Energy; Turner et al. 2007;
Bhatia et al. 2012).
Some crops are more suitable for certain uses than others, for example, banana
and pineapple are two fruit crops whose wastes are very suitable for biofuel
production, but many more agricultural wastes may be used for the production of
fine chemicals or energy, and those potentially useful materials are treated as waste
in most countries, increasing the chance of litter accumulation with the potential to
produce environmental harm (Isitua and Ibeh 2010; Bahtia and Paliwal 2010;
Bahtia et al. 2012).
Lignocellulosic biomass is a heterogeneous material formed mainly by long
chains of cellulose; any fiber is made of thousands of beta 1,4 linked glucose
residues, every two residues forms a cellobiose-repeating unit. Cellulose chains are
produced in tightly packed crystalline and amorphous regions. Smaller molecules
of hemicellulose formed by D-mannose, D-galactose, D-xylose, and D-arabinose
as well as 4-O-methyl-D-glucoronic acid are scattered in the cellulose fibers; while
lignin, a complex three-dimensional structure formed by aromatic monomers
forms a matrix around the fibers (Lynd et al. 2002). Cellulose can be hydrolyzed to
236
S. de J. Romero-Gómez
7.7.2 Biorefineries........................................................................................................ 244
7.7.3 Synthetic Biology ............................................................................................... 246
7.7.4 Conversion of Lignocellulosic Biomass into Value-Added Products .............. 247
7.8 Conclusion ...................................................................................................................... 248
References................................................................................................................................ 249
7.1 Introduction
Constant increase in oil prices, possible depletion of oil reserves, and climate
change concerns are the main reasons to search for sustainable oil substitutes. In
most parts of the world, oil is the leading source of energy and provides the main
part of chemical precursors used to manufacture a large variety of products, from
plastics and composites used in almost all aspects of our lives to food and fine
chemicals (Howard et al. 2003; Waltz 2008). While energy requirements may be
covered at least partially by alternative raw sources as solar, wind power,
hydrogen, and tidal energy, chemical commodities require a renewable source of
chemical precursors that can be produced in a sustainable way (Lynd et al. 2003).
Lignocellulosic biomass as agriculture, forestry, paper pulp, and food wastes is
the best potential alternative source for the production of both biofuels and fine
chemicals with the potential to cover our most important needs (Kerr and Service
2005; Kumar et al. 2008). Energy or chemical precursors obtained from lignocellulosic biomass by-products or agricultural waste and forest activities cannot
compete with food production, as is the case of biofuel production from sugarcane
or maize starch, or even indirectly for crop lands and resources, as is the case of
oils used for biodiesel production (US Department of Energy; Turner et al. 2007;
Bhatia et al. 2012).
Some crops are more suitable for certain uses than others, for example, banana
and pineapple are two fruit crops whose wastes are very suitable for biofuel
production, but many more agricultural wastes may be used for the production of
fine chemicals or energy, and those potentially useful materials are treated as waste
in most countries, increasing the chance of litter accumulation with the potential to
produce environmental harm (Isitua and Ibeh 2010; Bahtia and Paliwal 2010;
Bahtia et al. 2012).
Lignocellulosic biomass is a heterogeneous material formed mainly by long
chains of cellulose; any fiber is made of thousands of beta 1,4 linked glucose
residues, every two residues forms a cellobiose-repeating unit. Cellulose chains are
produced in tightly packed crystalline and amorphous regions. Smaller molecules
of hemicellulose formed by D-mannose, D-galactose, D-xylose, and D-arabinose
as well as 4-O-methyl-D-glucoronic acid are scattered in the cellulose fibers; while
lignin, a complex three-dimensional structure formed by aromatic monomers
forms a matrix around the fibers (Lynd et al. 2002). Cellulose can be hydrolyzed to
236
S. de J. Romero-Gómez