Maneesha Pande and Ashok N. Bhaskarwar

Rapid depletion of fossil fuels, compounded by the accompanying environmental hazards, has prompted the need for alternative sources of energy. Energy from biomass, wind energy, solar energy, and geothermal energy are some of the most promising alternatives which are currently being explored. Among these, biomass is an abundant, renewable, and relatively a clean energy resource which can be used for the generation of different forms of energy, viz. heat, electrical, and chemical energy. There are a number of established methods available for the conversion of biomass into different forms of energy which can be categorized into thermochemical, biochemical, and biotechnological methods. These methods have further been integrated into the concept of a biorefinery wherein, as in a petroleum refinery, a variety of biomass-based raw materials can be processed to obtain a range of products including biofuels, chemicals, and other value-added products. We present here an overview of how biomass can be used for the generation of different forms of energy and useful material products in an efficient and economical manner.

1.1 Introduction

The current major source of energy/fuel is fossil fuel, which, for all practical purposes can be considered to be nonrenewable. Fossil fuels are all petroleum derivatives and the use of these fossil fuels leads to the generation of greenhouse gases such as CO2, CH4, N2O. The transportation sector is responsible for the

M. Pande • A. N. Bhaskarwar (H)

Department of Chemical Engineering, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India e-mail: anbhaskarwar@gmail. com

C. Baskar et al. (eds.), Biomass Conversion,

DOI: 10.1007/978-3-642-28418-2_1, © Springer-Verlag Berlin Heidelberg 2012

highest rate of growth in greenhouse gas emissions (GHG) among all sectors. This concern as well as the current concern over the rapid depletion of fossil fuel, accompanied by the ongoing price increase of fossil resources and uncertain availability, combined with environmental concerns such as global warming has propelled research efforts toward generating alternative means of energy produc­tion using renewable resources. The solution to this problem seems to emerge in the form of bioenergy, i. e., energy generated from biomass.

Biomass is the only renewable organic resource. It is also one of the most abundant resources. It comprises all biological materials including living, or recently living organisms, and is a huge storehouse of energy. The dead biomass or the biological waste can be used as a direct source of energy like heat and elec­tricity or as an indirect source of energy like various types of fuels. The living biomass, or components thereof, like microorganisms, algae, and enzymes can be used to convert one form of energy into another using biofuel cells. Figure 1.1 gives the various sources of biomass which can be used for biomass conversion into energy. In the entire process of conversion of biomass into energy, a dual purpose of energy generation and environmental clean-up is achieved.

Sunlight is an infinitely abundant source of energy on this earth and all energy on this planet, in principle, is renewable. However, considering the factor of time frame, the present sources of energy such as coal, oil, and natural gas take mil­lennia to renew. Therefore, it is imperative that research in the field of energy generation should focus on reducing this time frame by cutting short the time required to turn sunlight into usable energy. Biomass is an excellent source of renewable energy and serves as an effective carbon sink. Plants and trees which constitute biomass can be considered as perpetual powerhouses capable of con­tinuously tapping the energy from sunlight and converting it via photosynthesis

Atmospheric carbon dioxide, water and sunlight

through photosynthesis

Plant material is harvested
ana burnt

Fig. 1.2 Renewable nature of biomass conversion into energy into carbon-rich compounds. These carbon-rich compounds which constitute the biomass can then be exploited as and when required to release the energy trapped from sunlight (Fig. 1.2).

It can be seen from Fig. 1.2 that the carbon which is released into the atmo­sphere as a result of burning biomass, returns to the biomass by way of photo­synthesis, which is again converted into carbon-rich compounds for reconversion into energy. This, process can thus be considered to be carbon neutral unlike fossil fuel, which is carbon positive, i. e., burning fossil fuel releases CO2 into the atmosphere which remains in the atmosphere, thus increasing the amount of CO2 indefinitely.

The current technology of biomass to energy conversion is at the most, carbon neutral but the amount of CO2 already present in the atmosphere as a result of use of fossil fuel for so many years, is so high that it cannot be absorbed by con­ventional sinks such as trees and soils. Thus there is a dire need to reduce the global CO2 emissions by energy generation technologies that are carbon negative in nature. These technologies, which are commonly termed as ‘‘Bioenergy with Carbon Capture and Storage’’ (BECCS) are expected to achieve the goal of cre­ating a global system of net negative carbon emissions. This carbon capture and storage (CCS) technology, serves to intercept the release of CO2 into the atmo­sphere and redirect it into geological storage locations. A similar alternative to achieve carbon negativity lies in fourth-generation fuels which are those fuels based on high solar efficiency cultivation. This chapter gives an overview of conversion of biomass into energy with special reference to the biorefinery con­cept. The recent developments in the area are also highlighted.