430
1 Introduction
The global industrialization has changed the picture of the world’s energy consumption. Most of the energy needs of the people are globally catered by fossil fuel
resources. The market worth of world’s energy is about 1.5 trillion dollars and still
directed by fossil fuels. The World Energy Outlook (WEO) states that energy produced through fossil fuels will remain as the chief source and is projected to meet
~84% of energy requirement up to 2030. Crude oil, gas and coal are the leading
supplies for energy. Ever-increasing consumption of these resources led to the carbon dioxide emissions and depletion of the fossil fuel reservoirs. The continuous
consumption leads to the dwindling of the resources [1–3]. All over the globe, the
fossil fuel reserve depletion times for coal, gas and crude oil are nearly 109, 54, and
53 years, respectively [4]. These reports are alarming for the energy demands of the
future generations.
The quest to produce transportation fuels and chemicals from resources other
than fossil resources switched over the ongoing research activities towards renewable resources. The main theme is to produce clean energy, transportation fuels and
chemicals in a sustainable approach from biomass, wind, nuclear, solar and hydroelectric resources. Except biomass, other renewable resources are familiar for the
production of electricity. To compete with the fossil fuel resources in terms of the
production of transportation fuels and chemicals, biomass is the outstanding renewable resource as it is carbon rich and the most abundant feedstock. Moreover, the
carbon dioxide released during the consumption of biomass-derived transportation
fuels can be utilized for the production of feedstock via photosynthesis and thereby
maintain the carbon neutrality.
2 Lignocellulosic Biomass
During the past decades, researchers tried to produce biofuels and chemicals from
sugars, starches and vegetable oils. These are called first-generation biofuels and
have created several problematic issues. The competition between food and fuel
arises due to the need of fertile land and high economic inputs for the cultivation
and conservation of the crops. Both the economic and environmental (eutrophication and acidification) complications are associated with the production of firstgeneration biofuels [5, 6]. However, the production of biofuels and chemicals from
biomass is still encouraging due to utilization of the most abundant lignocellulosic
biomass. The major sources for the lignocellulosic biomass are from agricultural,
forestry and dedicated energy crops. These are second-generation biofuel feedstocks [7, 8]. Figure 1 shows the first- and second-generation feedstocks for biofuels. The global production of plant biomass amounts to about 200*10
9
tons/year, of
that over 90% is lignocellulose, in which potentially accessible biomass remains
only about 8–20*10
9
tons.
B. S. Rao et al.
1 Introduction
The global industrialization has changed the picture of the world’s energy consumption. Most of the energy needs of the people are globally catered by fossil fuel
resources. The market worth of world’s energy is about 1.5 trillion dollars and still
directed by fossil fuels. The World Energy Outlook (WEO) states that energy produced through fossil fuels will remain as the chief source and is projected to meet
~84% of energy requirement up to 2030. Crude oil, gas and coal are the leading
supplies for energy. Ever-increasing consumption of these resources led to the carbon dioxide emissions and depletion of the fossil fuel reservoirs. The continuous
consumption leads to the dwindling of the resources [1–3]. All over the globe, the
fossil fuel reserve depletion times for coal, gas and crude oil are nearly 109, 54, and
53 years, respectively [4]. These reports are alarming for the energy demands of the
future generations.
The quest to produce transportation fuels and chemicals from resources other
than fossil resources switched over the ongoing research activities towards renewable resources. The main theme is to produce clean energy, transportation fuels and
chemicals in a sustainable approach from biomass, wind, nuclear, solar and hydroelectric resources. Except biomass, other renewable resources are familiar for the
production of electricity. To compete with the fossil fuel resources in terms of the
production of transportation fuels and chemicals, biomass is the outstanding renewable resource as it is carbon rich and the most abundant feedstock. Moreover, the
carbon dioxide released during the consumption of biomass-derived transportation
fuels can be utilized for the production of feedstock via photosynthesis and thereby
maintain the carbon neutrality.
2 Lignocellulosic Biomass
During the past decades, researchers tried to produce biofuels and chemicals from
sugars, starches and vegetable oils. These are called first-generation biofuels and
have created several problematic issues. The competition between food and fuel
arises due to the need of fertile land and high economic inputs for the cultivation
and conservation of the crops. Both the economic and environmental (eutrophication and acidification) complications are associated with the production of firstgeneration biofuels [5, 6]. However, the production of biofuels and chemicals from
biomass is still encouraging due to utilization of the most abundant lignocellulosic
biomass. The major sources for the lignocellulosic biomass are from agricultural,
forestry and dedicated energy crops. These are second-generation biofuel feedstocks [7, 8]. Figure 1 shows the first- and second-generation feedstocks for biofuels. The global production of plant biomass amounts to about 200*10
9
tons/year, of
that over 90% is lignocellulose, in which potentially accessible biomass remains
only about 8–20*10
9
tons.
B. S. Rao et al.