Energy is one of the most basic and indispensable elements of industry, production, improvement and development in the world and in our country. The energy requirement is increasing due to industrialization, technological developments and population growth. Thus, the limited reserves of fossil fuels from traditional energy sources and the fact that they will be depleted in the near future, environmental pollution and destruction of nature have led to the importance of new and renewable energy sources. Thus, it is biomass that does not pollute the environment, is one of the low-cost new and renewable energy sources, and offers a wide application area for developing and developing countries. The components that make up biomass resources have a complex and heterogeneous structure. The physical and chemical differences in the structures of these components cause these components to behave differently with the conversion of biomass sources to fuels. herefore, in this section, the importance of the thermal properties of the components of biomass, which is a renewable, safe and continuous energy source that is less harmful to the environment, will be discussed by using appropriate technologies and methods.