General Process Information
The simplest way to obtain energy from wood is through a process called “direct combustion” (in other words, by burning it). Energy from burning wood can produce power, electricity, or heat. To produce power, wood can be burned in a boiler, a large combustion chamber, to heat water and generate steam. In some cases, this steam is used directly to power machines or to heat buildings.
In addition, steam can be used to turn large, rotating engines called turbines, which generate electricity. This electricity can be used onsite by industries to power machinery, or it can be sold to the power grid. Some facilities do both—steam first turns a turbine and then is used for heat. This is called co-generation because two forms of energy are generated from one process.
When wood is used in power plants, it can be burned alone or in combination with coal or other fuels; burning two fuels together is called co-firing. Because it is more efficient to burn wood pieces that are the same size and have similar moisture content, most facilities use wood chips, wood pellets, or saw dust . Wood chips are typically 5 to 50 millimeters (mm) long, and longer than they are thick or wide; wood pellets, made from compressed sawdust, range from 5 to 30 mm long; and sawdust is the smallest at 1 to 5 mm.
Combustion systems can use different forms of wood, including split fuel wood (traditional firewood), whole trees, wood chips, wood pellets, waste wood from forest product production processes, and charcoal briquettes. Some of the wood-burning units can also use other types of fuel such as oil or natural gas in combination with wood or electricity from the power grid. Wood can also be burned to produce heat using woodstoves, fireplaces, pellet stoves, or boiler systems. These systems can be located inside or outside buildings. Converting Wood into Gas
Woody biomass can be converted into a synthesis gas (syngas) through the process of gasification. It can be made into biogas through the process of anaerobic digestion.
Gasification: exposing wood to extremely high temperatures (900-1,200°C) and pressure in a low oxygen environment can produce syngas—a gas made up of carbon dioxide, carbon monoxide, and hydrogen. Syngas is combustible and can be used as a fuel source.
Anaerobic digestion: exposing wood to certain bacteria in the absence of oxygen and under other controlled conditions can produce biogas, a type of fuel produced from biomass materials.
In both processes, a gas is produced as the cellulose is broken down. Syngas and biogas can be used like natural gas for cooking