A variety of biomass resources can be used for energy by conversion process.

They can be divided into four categories:

• Crops: woody energy crops, industrial crops, agricultural crops, and aquatic crops (Ra et al. 2012; Ignaciuk and Dellink 2006; Paine et al. 1996; El-Shinnawi et al. 1989)

• Agricultural wastes: crop waste and animal waste like cow dung and chicken manure (Ren et al. 2010; Abouelenien et al. 2010)

• Forestry waste and residues: mill wood waste, logging residues, trees, and shrub residues (Alich and Witwer 1997; Gomez et al. 2010; Malinen et al. 2001)

• Industrial and municipal wastes: municipal solid waste (MSW), sewage sludge, and industry waste (Dent and Krol 1990; Manara and Zabaniotou 2012; Nges et al. 2012)

Hydrogen is a prosperous source of energy for the future. New ways of hydrogen production have been made in the last decades. One of the promising processes is biomass gasification.

Biomass gasification using supercritical water is a new way to produce hydrogen gas. Besides producing hydrogen, however, this method has a possibility to release heteroatomic compounds. It is therefore important to clarify the mechanisms for obtaining hydrogen gas. An online system of mass spectrometer and a reactor cell has been developed for analysis of the sulfur heteroatom compounds generated from L-Cysteine, as a standard substance and durian fruit as a practical sample, which contain sulfur at high levels. In this study, effects of Ca(OH)2 an alkaline additive on the formation of heteroatom compounds were also studied in detail, in conjunction with suppression of toxic emission.