Its density may be increased by milling and compressing dried residues. The resulting briquettes or pellets are also easier to handle, store, and transport. Compression has been used with a variety of materials including crop residues, herbaceous native plant material, sawdust, and other forest wastes. Solid fuels are not as convenient or versatile as liquids or gases, and this is a drawback to the direct use of biomass. Fortunately, a number of techniques are known for converting it to liquid or gaseous forms.
Partial combustion is one method.
In this procedure, biomass is burned in an environment with restricted oxygen. Carbon monoxide and hydrogen are formed instead of carbon dioxide and water. Syngas may also be converted to methanol, a one carbon-alcohol that can be used as a transportation fuel. Because methanol is a liquid, it is easy to store and transport. Anaerobic digestion is another method for forming gases from biomass.