After the energy crisis, researchers in developed countries have developed technologies for converting energy trees to take the place of mineral fuel because biomass is abundant and renewable, and it contains less sulfur and ash but more hydrogen than coal and accordingly it is cleaner. If it is changed into gas or liquid fuel, it is not only clean, but also convenient. Furthermore, in the course of burning, mineral fuel gives out CO₂, which keeps accumulating in the atmosphere. In the beginning of the industrialization, the density of CO₂ in man's breath took up 0.28% of the volume of air. But in 1980 the density rose to 0.34%. It is estimated that by the beginning of the next century, it will reach 0.56%. The ever increasing density of greenhouse gases in the atmosphere leads to a warmer climate. As biomass is a low-carbon fuel and absorbs CO₂ in its production, it becomes a sink for the greenhouse gases. So for the cooperation with the universally united action to eliminate the greenhouse gases, it is of great significance to devote major efforts to exploit biomass energy resource for the improvement of the fossil-dominated energy structure, especially for the supply of a clean and convenient energy in line with the local conditions in rural area.

The use of biomass energy can be roughly classified as the technology of direct burning, physical conversion technology, biological conversion technology, liquefaction technology, and conversion technology for solid waste (see figure for details).

Gasification Technology               Biogas Technology     Landfill Technology