292
approaches made and process tools deployed, in particular for γ-valerolactone,
LA-based plasticizers, HMF and FDCA. Challenges on these approaches and possible strategies to overcome them will also be discussed.
Keywords Biomass valorization · Levulinic acid derivatives · γ-Valerolactone ·
Furan compounds · 5-Hydroxymethylfurfural · 2,5-Furandicarboxylic acid
1 Introduction
At present, the world’s energy and chemical requirements are largely met through
fossilized sources like petroleum, coal and natural gas. The improvement in the
quality of life and, consequently, the increasing demand for energy necessitate the
search for alternate and sustainable solutions to energy crisis. Sustainability, arguably the “word of this century,” has been instrumental in stimulating scientists and
technologists to explore alternative options in making fuels, chemicals and polymers that facilitate our daily lives. Carbon-rich biomass is the only renewable source
that could be explored with significant potential for producing chemicals including
polymers. This is de facto an attractive option considering the balance between the
availability and consumption patterns. The approach also has an intrinsic advantage
of reducing indispensability on fossil fuels to an extent besides reducing CO 2 emission, thereby benefitting our environment. Researchers all over the world have
enthusiastically contributed to the value addition of biomass for producing chemicals. Many countries with strong roots in agriculture, availability of extensive forest/agro-resources and vast coastline for marine macro−/micro-algae are likely to
generate non-edible/waste biomass which can potentially be harnessed to produce
chemicals sustainably in the years to come.
Generally, lignocellulosic biomass consists of 38–50% cellulose, 23–32% hemicellulose and 15–25% lignin, which constitute about 80–90% of the total biomass.
Cellulose is a non-branched water-insoluble polysaccharide consisting of several
hundreds to tens of thousands of glucose units linked through 1,4-β-glycosidic ether
bonds. Cellulose is the most abundant biopolymer synthesized by nature; its amount
is estimated at approximately 2 × 10
9
tons/year [1]. Hemicellulose is a polymeric
network connecting lignin and cellulose. Although lower in molecular weight than
cellulose, hemicellulose consists of C6 sugars (glucose, mannose and galactose)
and C5 sugars (arabinose, xylose and so on). Lignin is a complex three-dimensional
cross-linked amorphous polymer consisting of three major methoxylated phenylpropanoid units (coumaryl alcohol, coniferyl alcohol and sinapyl alcohol) connected by strong C–O (~60–70%) and C–C (~25–35%) linkages [2, 3]. Thus, the
primary components have great potential for the production of diverse chemicals [4].
The Department of Energy (USA) with NREL (National Renewable Energy
Laboratory) and PNNL (Pacific Northwest National Laboratory) have conducted an
extensive study to identify valuable sugar-based building blocks [5]. Of the 300
S. Gundekari et al.
approaches made and process tools deployed, in particular for γ-valerolactone,
LA-based plasticizers, HMF and FDCA. Challenges on these approaches and possible strategies to overcome them will also be discussed.
Keywords Biomass valorization · Levulinic acid derivatives · γ-Valerolactone ·
Furan compounds · 5-Hydroxymethylfurfural · 2,5-Furandicarboxylic acid
1 Introduction
At present, the world’s energy and chemical requirements are largely met through
fossilized sources like petroleum, coal and natural gas. The improvement in the
quality of life and, consequently, the increasing demand for energy necessitate the
search for alternate and sustainable solutions to energy crisis. Sustainability, arguably the “word of this century,” has been instrumental in stimulating scientists and
technologists to explore alternative options in making fuels, chemicals and polymers that facilitate our daily lives. Carbon-rich biomass is the only renewable source
that could be explored with significant potential for producing chemicals including
polymers. This is de facto an attractive option considering the balance between the
availability and consumption patterns. The approach also has an intrinsic advantage
of reducing indispensability on fossil fuels to an extent besides reducing CO 2 emission, thereby benefitting our environment. Researchers all over the world have
enthusiastically contributed to the value addition of biomass for producing chemicals. Many countries with strong roots in agriculture, availability of extensive forest/agro-resources and vast coastline for marine macro−/micro-algae are likely to
generate non-edible/waste biomass which can potentially be harnessed to produce
chemicals sustainably in the years to come.
Generally, lignocellulosic biomass consists of 38–50% cellulose, 23–32% hemicellulose and 15–25% lignin, which constitute about 80–90% of the total biomass.
Cellulose is a non-branched water-insoluble polysaccharide consisting of several
hundreds to tens of thousands of glucose units linked through 1,4-β-glycosidic ether
bonds. Cellulose is the most abundant biopolymer synthesized by nature; its amount
is estimated at approximately 2 × 10
9
tons/year [1]. Hemicellulose is a polymeric
network connecting lignin and cellulose. Although lower in molecular weight than
cellulose, hemicellulose consists of C6 sugars (glucose, mannose and galactose)
and C5 sugars (arabinose, xylose and so on). Lignin is a complex three-dimensional
cross-linked amorphous polymer consisting of three major methoxylated phenylpropanoid units (coumaryl alcohol, coniferyl alcohol and sinapyl alcohol) connected by strong C–O (~60–70%) and C–C (~25–35%) linkages [2, 3]. Thus, the
primary components have great potential for the production of diverse chemicals [4].
The Department of Energy (USA) with NREL (National Renewable Energy
Laboratory) and PNNL (Pacific Northwest National Laboratory) have conducted an
extensive study to identify valuable sugar-based building blocks [5]. Of the 300
S. Gundekari et al.