Naveen Kumar Mekala1, Ravichandra Potumarthi2’*,

1 3

Rama Raju Baadhe 1, Vijai K. Gupta 3

^Department of Biotechnology, National Institute of Technology, Warangal, Andhra Pradesh, India,
^Department of Chemical Engineering, Monash University, Clayton, Victoria, Australia, 3Molecular Glycobiotechnology
Group, Department of Biochemistry, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
*Corresponding author email: ravichandra. potumarthi@monash. edu; pravichandra@gmail. com

OUTLINE

Introduction 1

Different Forms of Bioenergy 3

Biopellets 3

Bioethanol 3

Feedstock for Bioethanol 3

Pretreatment of Lignocelluloses 4

Biological Pretreatment 5

Physical Pretreatment 6

Chemical

Pretreatment 6

Bioethanol Fermentation 7

Molecular Biology Trends in Bioethanol

Production Development 8

Bioreactors in Ethanol

Production 8

Immobilization of Cells for Ethanol

Production 9

Biodiesel 9

Feedstocks for Biodiesel 10

Biodiesel from Pure Vegetable Oil 10

Biodiesel from Animal Fat Wastes 11

Other Waste Cooking Oils 12

Algae as a Biodiesel Source 12

Bioreactors for Biodiesel Production 13

Biogas 14

Biogas Feedstock 15

Household Digesters for Biogas 15

Fixed Dome Digesters 15

Floating Drum Digesters 16

Social and Environmental Aspects of Biogas Digesters 17

Conclusion 17

References 18

INTRODUCTION

Modern world is facing two vital challenges, energy crisis and environmental pollution. Energy is a key component for all sectors of modern economy and plays an elementary role in improving the quality of life (US DOE, 2010). In current situations, approxi­mately 80% of world energy supplies rely on rapidly exhausting nonrenewable fossil fuels. At the current
rate of consumption, crude oil reserves, natural gas and liquid fuels were expected to last for around 60 and 120 years, respectively (British Petroleum Statisti­cal Review, 2011). An additional challenge with fossil fuel consumption is emission of greenhouse gases (GHGs). In 2010, an average of 450 g of CO2 was emitted by production of 1 kWh of electricity from the coal (Figure 1.1) (International Energy Agency Statis­tics, 2012). It is also clear that coal’s share of the global

Bioenergy Research: Advances and Applications http://dx. doi. org/10.1016/B978-0-444-59561-4.00001-2

Energy production FIGURE 1.1 Global energy production chart signifies the growing demand for energy. Source: IEA, 2012. (For color version of this figure, the reader is referred to the online version of this book.)

energy continues to rise, and by 2017 coal will come close to surpassing oil as the world’s top energy source. China and India lead the growth in coal consumption over the next 5 years. Research says China will surpass the rest of the world in coal demand during the outlook period, while India will become the largest seaborne coal importer and second largest consumer, surpassing the United States (IEA, 2012).

Growing global energy needs, release of environ­mental pollutants from fossil fuels and national security have finally tuned the attention in clean liquid fuel as a suitable alternative source of energy. The alternative bio­energy sources, not only cut the dependence on oil trade and reduce the doubts caused by the fluctuations in oil price, but also secure reductions in environmental pollu­tion due to their high oxygen content (Huang et al., 2008; Boer et al., 2000).

In this context, the availability of bioenergy in its two main appearances, wood and agro energy can offer cleaner energy services to meet basic energy require­ments. This century could see a remarkable switchover from fossil fuel-based energy to bioenergy-based econ­omy, with agriculture and forestry as the main sources of feedstock for biofuels such as wood pellets, fuel — wood, charcoal, bioethanol, and biodiesel (Agarwal,

2007) . Moreover, energy crops can be part of highly specialized and various agricultural production chains and biorefineries, where a variety of bioproducts could be obtained besides bioenergy, which are important for their economic competitiveness (United Nations Envi­ronment Program, 2006).

The exploitation of currently unused by-products and growing energy crops can address other existing environmental concerns. Perennial energy crops and plantations are generally characterized by higher biodi­versity compared with conventional annual crops. By providing more continuous soil cover, they reduce the impact of rainfall and sediment transport, thereby pre­venting soil erosion. The introduction of annual energy crops into crop systems allows for diversification and expansion of crop rotations, replacing less favorable monocropping systems (Kheshgi et al., 1996). Defor­ested, degraded and marginal land can be rehabilitated with bioenergy plantations, thus helping to combat desertification and hopefully reducing market and geo­social pressures on high-quality arable land.

Biofuels can be obtained in bulk when they are derived from agricultural crops, crop residues and processing wastes from agroindustries, forests, etc. Despite this immense potential, existing biofuel policies have been very costly; they produce slight reductions in fossil fuel use and increase, rather than decrease, in GHG emissions (Wuebbles and Jain, 2001). However, recent volatility and rise in international fossil fuel prices, make biomass increasingly competitive as energy feedstock.

Current bioenergy research around the globe should direct us toward reduced production cost, higher energy conversion efficiency and greater cost- effectiveness of biofuels. After all we are aware of a fact "use of biomass as a potentially large source of energy in the 21st century will have a significant impact in rural, agricultural and forestry development" (UNEP, 2006).