Biomass of various types is being used as coal substitute in power generation and industrial usage around the world. Significant investments have been made in Europe and elsewhere to accommodate the use of dried and pelleted biomass materials in various power plants. Substituting biomass for coal in coal-based boiler systems without degrading boiler capacity requires pretreatment to make its properties similar to the coal that it is displacing. The pretreatment technologies currently under active development include: torrefaction, steam explosion, and hydrothermal carbonization (wet torrefaction). Power plant trials have shown that the pretreated materials can be used as a direct replacement for coal up to 100 percent. The factors associated with biomass pretreatment and the use of the advanced biomass-based fuels in power plant trials are reviewed in this chapter.