Biomass, as a renewable energy source, is the organic matter of vegetable or animal origin and is used in combustion processes or converted in systems for the production of heat or electricity related energy (Dodic et al., 2012). In other words, according to the definition of the EU, Directive 2003/30/EC, biomass is biodegradable fraction of products, wastes and residues from agriculture (including plant and animal substances), forestry and the wood processing industries as well as the biodegradable fraction of municipal and industrial wastes which is permitted for use in energetics, in accordance with relevant regulations for the environment protection. In short, any organic matter sources can be considered as biomass such as agricultural and forestry wastes, aquatic plants, animal waste and garbage, and the availability of these sources varies depending on the region, climate, ground type, geography, population density, productive activities, etc. (Rosua & Pasadas, 2012).
Biomass may have different origins. Biomass of plant, for example, is a product of photosynthesis in plant organisms; while biomass of animal origin is produced as a product – the rest is in the process of feeding of animals. Biomass is consumed and renewed continuously, in the cycle of circulation of material and energy in the nature. Man, with his activities, increases the amount of biomass circulating in the environment (Dodic et al., 2012).
Biomass has traditionally been an important source of energy and is particularly attractive nowadays owing to its wide distribution, low negative environmental impact and sustainable utilization (Xingang et al., 2012). Hence, it is regarded as one of the major energy sources today, contributing approximately 14% of the annual energy consumption of the world in comparison to 12% from coal and 15% from gases (Seneca, 2007).
The growing interest towards biomass all over the world in recent years can also be explained through its availability of feed stocks including agricultural and forestry residues and wastes (Shen et al, 2009).