**Abstract**

Gasification is an indirect combustion of solid and liquid biomass by converting them to combustive syngas. Gasification is an alternative process for the traditional combustion, in which the emission of dust and toxic gases can be minimized. In this chapter, a comparison of these two biomass-to-heat conversion processes applied on biomass is presented in term of environmental impacts and technological benefits with a hope to provide readers a basic view of choices. Gasification is classified as in term of gasification agents, non-catalytic and catalytic process, and plasma assisted process. Popular types of gasification equipment, aka gasifiers, are introduced with working principles, through which the advantages and weakness of technology are briefly discussed.

**Keywords:** gasification, gasifier, biomass, indirect combustion, direct combustion, syngas, plasma, updraft, downdraft, cross-draft, bridging, tar, charcoal, hydrogen, steam, carbon dioxide, flue gas
