Current Status of Biomass in the US
The United States is covered by approximately 595 million acres of forestlands. Using only trees that are currently considered to be pre-commercial, non-merchantable, and residues from timber harvesting operations and "healthy forest and fire hazard reduction" operations, these forestlands can produce a total of approximately 368 million dry tons of biomass annually (Perlack and others 2005). Approximately 36% (214 million acres) of the total forestland is located in the thirteen southern states. In the South, about 55 million tons of pre-commercial, non-merchantable, and residue forest biomass are potentially available annually for the production of bioenergy and other bio-based products. For specific information on the supply of biomass, refer to the Sources and Quantity of Supply section. When the demand for more wood energy and bio-product feedstocks increases, trees now being harvested for traditional products such as pulp and paper, can be used. This transition of using commercial trees for energy will be a logical change, since demand for roundwood pulpwood in the South has decreased significantly over the last decade.
Yet, even with such a large available resource in the United States, only 9% of our domestic energy production is in the form of renewable energy. Forty-seven percent of that energy is from biomass (EIA 2004). While wood-based biomass is not as highly publicized as other forms (corn, sugarcane, etc.), it accounts for 72% of the source material for biomass generated energy. Our consumption of renewable energy is even lower, with only 6% of our total consumption being from renewable sources. Biomass accounts for approximately 47% of the renewable energy consumed in the U.S. (see Energy Benefits of Biomass).
The forest products industry is probably the largest user of forest biomass, generating more than 50% of its energy in-house - most of which comes from by-products (black liquor from the papermaking process, bark, hogged fuel, and dirty chips) of its manufacturing process.
The process of merchandising wood products from the forest is a well-developed process. As trees are harvested they are accumulated at a central location and sorted into the highest value products. These products are then transported to manufacturing facilities for processing into the targeted products (at left). Primary products include lumber, paper, fiber board, oriented strand board, pulp, and other wood composites. Chips, bark, and other by-products created from these processes are used to produce boiler fuel for the manufacturing processes. "Clean" chips and wood flakes can be used to produce such commodities as paper, oriented strand board, particle board, etc. "Dirty" chips are used to produce energy for the facility, mulch, etc.
In some cases, residual logging debris, under-sized trees, and other woody biomass are converted into wood chips by an in-woods chipper. These residue materials can be used for the production of electricity, dyes, inks, adhesives, fuels, chemicals, and many other bio-based products. However, this material is most frequently left on site and unutilized because of handling and transportations costs as well as the lack of markets. Efficient systems for harvesting and transportation systems can increase the utilization of this biomass while protecting the productive potential of the forest site. See the Harvesting module for more detailed coverage of this topic.
Dirty chips (at right) are another by-product used to generate energy for the forest products industry. According to the U. S. Department of Energys Energy Efficiency and Renewable Energy Office (2004), the U. S. forest products industry is among the top 10 manufacturing industries in 46 states. It is also among the nine most energy intensive industries in the U. S., ranking third behind petroleum and chemical industries. Energy accounts for 15-25% of the operating expense of the forest products industry.
Across the nation, projects utilizing wood-based biomass are beginning to gain a foothold. Many of these projects are in the Northeast and West. A 25 MW plant in St. Paul, MN, uses urban tree waste to produce electricity (LeVan-Green 2005). Wood chips are used as heating fuel in Montana and Vermont. In Colorado, small modular gasifiers (at left) are being used to generate electricity. And in Arizona, wood from forest fuel treatments is being used to generate electricity.
The South has relatively few wood-based biomass energy projects. Santee Cooper in South Carolina announced in August 2005 that they would begin co-firing wood with coal in one of their facilities. Wood for the facility would be from fuel treatments and thinnings from the forests of the USDA Forest Service National Forest System (Stock 2005). According to company news releases and conference presentations, Southern Company has done limited studies, with varying degrees of success, of co-firing wood with coal, and switchgrass with coal at its Gadsden, Alabama coal fired plant.
Yet, for a number of reasons logging residues and small diameter trees do not comprise a significant component of energy production. Approximately 16% (by weight) of softwood and 26% of hardwood volume harvested is left in the forest as residue (Smith and others 2004) because it is currently not economical to utilize this material. Continued research in harvesting, utilization, and efficiency along with education will help move the industry forward into the future. When demand for energy, bio-fuels such as cellulosic ethanol, and bio-chemicals requires it, the value for these uses exceeds the value from traditional markets such as wood pulp, and conversion technologies are in commercial use, the United States, particularly the South, can produce enormous volumes of energy and bio-chemical feedstocks that are renewable, sustainable, and expandable to meet the countrys needs. This can be done without compromising air or water quality, wildlife habitat, or recreational opportunities on the land producing the wood feedstocks. One way to accomplish this is to integrate an energy/bio-chemical harvest in the silvicultural practices for forests located within an economical distance from energy and bio-chemical markets.
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