Drying of Woody Biomass for Bioenergy: Drying Technologies and Optimization for an Integrated Bioenergy Plant

The heavy reliance of mankind on fossil fuels has caused serious consequences, such as global warming and potential energy crisis. Biomass originating from plants has been recognized as the most promising alternative source for energy and fuels in the future. The biomass, in the forms of wood chips, sawdust, bagasse, grass, and agricultural residues, contains moisture from 50 to over 150% and must be dried in order to increase energy efficiency, improve energy product quality, and reduce emissions during energy conversion. A number of dryer types and drying technologies can potentially be used for biomass drying. Selection of the dryer and optimization of drying conditions requires in-depth understanding and quantification of the biomass material, requirements of energy conversion, and the drying process. This review article focuses on woody biomass; it first discusses the characteristics of woody biomass and thermochemical energy conversion technologies in industrial applications. Then, promising drying technologies and fundamental studies are reviewed and evaluated to examine their suitability and optimization for different forms of the biomass. The dryer types considered include a packed moving bed dryer (conveyor dryer), a rotary dryer, and a pneumatic dryer. Issues involved in biomass drying and possible solutions are addressed.