The term “biomass” means any plant derived organic matter available on a renewable basis, including dedicated energy crops and trees, agricultural food and feed crops, agricultural crop wastes and residues, wood wastes and residues, aquatic plants, animal wastes, municipal wastes, and other waste materials. It can be in solid or liquid form.
“Biomass power” or “biopower” is the use of biomass to generate electricity, or heat and steam required for industrial operations or space heating. Biopower system technologies include direct-firing, co-firing, gasification, pyrolysis, and anaerobic digestion.
Most references to burning woody biomass to produce electricity refer to the use of hog fuel or conventional wood pellets, which have different energy content and handling than torrefied biomass briquettes:
- Hog fuel is very bulky and heavy to transport and is generally used in smaller power plants close to the hog fuel. Facilities dedicated to burning hog fuel are ideally located within 50 to 75 miles of the woody biomass used as fuel.
- Conventional wood pellets are shipped long distances to be used in power plants with dedicated biomass boilers; however, they are not water-proof, so must be shipped and stored under cover.
- Neither hog fuel nor conventional wood pellets can be co-fired with coal without extensive investment in the coal power plant. Coal boilers are designed to blow pulverized coal into the combustion chamber, where specific operating parameters are controlled. Wood ground even as small as sawdust cannot be readily co-fired without plant modifications. Besides, none of these fuels are water resistant, like coal, so shipping and handling would involve great expense to add cover.
Torrefaction changes the chemical composition and traits of biomass so it can be shipped economically in open rail cars for long distances (like coal) and stored without cover. Torrefied biomass properties allow it to be handled much like coal and easily pulverized prior to feeding. It does not require plant modifications because of these torrefied biomass properties.
Here is a glossary of biomass power terms, courtesy of the Biomass Power Association.