Biomass moisture biomass is susceptible to mold growth

Biomass is described as all organic (plant and animal) matter of both live and dead biological organisms on the earth’s surface. It is considered as a form of stored solar energy, which is captured through the process of photosynthesis in plant growth. It also includes field and forest residues, waste products from the wood processing industries, animal manures and other sources. Biomass can substitute fossil fuels resulting in a net reduction in greenhouse gas emissions. This renewable energy can be recovered by combustion process or by conversion of biomass into usable form, for examples, ethanol, electricity, bio-oils or producer gases. The net energy available from biomass ranges from about 20 MJ/kg for dry plant matter to 55 MJ/kg for methane, as compared with about 27-32 MJ/kg for coal (Twidell, 1998; Demirbas, 1998b).          At the time of its collection, biomass may have a moisture content ranging from 10 to 75% (wb) depending on the type of biomass and harvesting time (Pordesimo et al., 2004). Transportation and storage of high moisture biomass are difficult for complete utilization. High moisture biomass is susceptible to mold growth and spoilage. The elevated moisture content in biomass not only reduces net energy but also increases the size of the equipment required to convert biomass energy into useful form (Kinoshita, 1998). Therefore, drying of biomass is an important operation of any biomass conversion process.          One of the major limitations of biomass is its low bulk density, typically ranging from 80–100 kg/m3 for agricultural straws and grasses and 150-200 kg/m3 for woody biomass, like wood chips (Sokhansanj and Fenton 2006; Mitchell et al. 2007). The low bulk densities of biomass often make the material difficult to store, transport, and use. Low bulk density also presents challenges for technologies such as coal cofiring, because the bulk density difference causes difficulties in feeding the fuel into the boiler and reduces burning efficiencies. Compaction is one promising option for overcoming these limitations. During compaction, biomass is mechanically compressed, increasing its density about ten fold. Commercially, compaction of biomass is performed using pellet mills, other extrusion processes, briquetting presses, or roller presses in order to help overcome feeding, storing, handling, and transport problems