Bio- Meta- Nasi ?

Biomethanation is a formation of methane and a decomposition process of organic matter by microorganism in the absence of oxygen (Ward et al., 2007; Romana et al., 2000). Biodegradation of cellulosic crop residues, agricultural solid wastes and municipal solid wastes in the absence of oxygen can be used to reduce pollution and produce biomethane as a fuel (Romana et al., 2000). Biomethane or biogas is generally composed of 48% - 65% methane, 36% - 41% carbon dioxide, up to 17 % nitrogen, < 1% oxygen, 32 -169 ppm hydrogen sulphide, and traces of other gases (Rani et al., 2007). The methane and carbon dioxide are potent greenhouse gases which affect the global warming phenomenon. Therefore, controlled biodegradation of organic material is environmentally beneficially. By containing the decomposition processes in a sealed environment, methane is prevented from entering the atmosphere and subsequent burning of the gas will release carbon- neutral carbon dioxide is back to the carbon cycle. The energy gained from combustion of methane will be substituted fossil fuels, reducing the production of carbon dioxide that is not part of the recent carbon cycle (Moller et al., 2004).



Lignocellulosic waste is a promising feedstock for biomethanation. Grasses, including straws from wheat, corn, sugar beet leaves; alfalfa and horse bean are plentiful supply of lignocellulosic waste. The methane yield are typically high from these feedstocks, although recaltritrant materials such as lignocellulosic materials often requires pre-treatments to fully realize the potential yield. Lignocellulose is the most abundant material available for the feedstock. It is composite material of rigid cellulose fibers embedded in a cross-linked matrix of lignin and hemicelluloses. There are almost 40% - 60% cellulose, 20% - 40% hemicelluloses and 10% - 20% of lignin contained in lignocellulose. Banana stem waste is softwood lignocellulose and it may contain of 41% - 57% cellulose, 8% - 12% hemicelluloses and 24% - 27% lignin (Scurlock et al., 2004). Harvesting time can also significantly affects the biogas yield of plants especially softwood lignocellulosic, as demonstrated by Amon et al., (2007); Mari et al., (2008).




The microorganism such as microbacteria and fungi can release the enzyme which can be use to degrade the lignocellulose. In hydrolysis process, the microorganism can be use to degrade the lignocellulose into simpler monomer such as glucose which later can be use as their substrate to produce energy for themselves (anaerobic microorganism) especially during anaerobic environment. Some of anaerobic microorganism is facultative anaerobic where, they can live in both environment either in aerobic environment (with oxygen) or in anaerobic environment (without oxygen). The mesophilic bacteria is the bacteria that live in moderate temperature typically between 15-40oC while, thermophilic bacteria live in high and extreme temperature between 45- 100oC. Few of them, may live in psycrophilic environment which live in -15-10oC.