Biomass as a source of energy

Before the dawn of fossil fuel based economy in the 19th century, biomass was a major contributor to energy. However, the energy ability in transforming biomass was less. So, fossil fuel energy grew as a more cost-effective and customary alternate for biomass. Recently, the demand for energy has increased because of an increase in population and industrialization worldwide. It has reached a point where fossil fuel energy will not be able to satisfy the supplies of persistent growth of the world economy in the forthcoming ages. The environmental problems by releases of greenhouse gases (GHG), mainly CO2 (Yu et al., 2007), unbalanced market prices and limited availability (Boldor et al., 2004; Fischer and Schrattenholzer, 2001; Huber et al., 2006; Krewitt et al., 2007; Okkerse and Van Bekkum, 1999) are other drawbacks of the fossil fuels based energy. As a result, a shift back to the biomass-based economy is compulsory because only biomass from existing renewable energy resources can be converted into suitable solid, liquid and gaseous fuels (Demirbaş, 2001a, 2001b).

Biomass is a rich source of the energy coming from agriculture, forests and energy crops (Saxena et al., 2009). Annual growth of dry biomass on a contingent basis is 118x109 tons (Bobleter, 1994). The international energy agency (IEA) states that entire oil use of the world in 2007 was 3.53x109 tons, equal to 148.26x1018 J of energy. This amount is less than 10 % of yearly worldwide production of biomass in the energy content (Guo et al., 2012). One investigation by the United Nations Conference on the environment and development (UNCED) evaluates that biomass might possibly supply about 50 % of the existing principal energy need through 2050 globally (Ramage and Scurlock, 1996).
Biomass is a biological matter including all living materials on the earth. Biomass mainly consists of cellulose (C6H10O5)x, hemicelluloses (C5H8O4)m, lignin [C9H10O3(COH3)0.9-1.7]n, small extractives (Duku et al., 2011; Fatih Demirbas et al.,2011), fats, proteins (Verma et al., 2012), sugars, arrowroots, water and ash. The largest fraction of biomass is cellulose (35-50 % of biomass weight). Hemicellulose represents 20-35 % of biomass weight and lignin shares 15-20 % of biomass weight, while remaining 15-20 % includes proteins, fats, extractives and ash content (Haghighi Mood et al., 2013). Biomass is characterized by physical properties, proximate analysis, and ultimate analysis (Unz et al., 2010). These properties may change in every substance (Christian et al., 2006) with growing environment (Xiong et al., 2010), and time or age (Lewandowski and Heinz, 2003; Pordesimo et al., 2005).
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