Biomass Utilization for Bioenergy in the Western United States

Forest Products Journal, Jan/Feb 2008 by Nicholls, David L, Monserud, Robert A, Dykstra, Dennis P

Wildfires, hazardous fuel buildups, small-diameter timber, wildland-urban interface zones, biomass. These are some of the terms becoming familiar to communities throughout the Western United States after the record-breaking fire seasons of the past decade. Although small-diameter stems are generally expensive to remove and often have limited utilization options, the need to reduce wildfire hazard has become increasingly important with the expansion of the wildland-urban interface across the Western United States. An estimated 73 million acres of national forest land in western states (397 million acres across all ownerships) have been identified as high-priority treatment areas (USDA Forest Service 2000). Nearly 3,800 communities near federal lands in western states are considered to be at high risk of wildfire (USDA and USDI 2001).

The increased risk of forest fires as a result of overstocked stands has created strong incentives to use biomass material for energy or other purposes, often resulting in thinned stands that can be sustainably managed at lower risk of wildfire. While prescribed burning represents one relatively low-cost option for reducing stem densities, mechanical removals may be preferred when prescribed burning is not a viable option. For example, in forests located near residential areas, prescribed fires could cause unacceptable wildfire risks or create smoky conditions.

Often, mechanically removed stems must be reduced in size or bundled, transported to a market destination, and used within a relatively short period of time. These costs are often several times the final value of any products obtained from biomass. A key challenge for natural resource managers, therefore, is to find markets and products that will recover at least a portion of these costs while providing other benefits such as reducing fire risk. For example, thinning costs typically range from $150 to $550 per acre, and the average thinning on Forest Service land costs about $70 per ovendry ton (ODT) of recovered biomass (LeVan-Green and Livingston 2001). This is roughly twice the market value of biomass for the energy and chip markets, which typically ranges between $25 and $35 per ODT.

Biomass may be used for energy at different scales, including large-scale electrical power generation at standalone facilities, cogeneration to produce process steam and electrical power, or smaller scale thermal heating projects at governmental, educational, or other institutions. However, barriers that tend to inhibit bioenergy applications in western states include accessibility, terrain, harvesting costs, and capital costs. The availability of government incentives has the potential to stimulate new technologies and new uses of biomass material when private investors may not be willing to provide investment capital.

National and regional perspectives on bioenergy from woody biomass

Electrical energy generation from wood is based largely on mature technologies, which include direct combustion boilers with steam turbines. Stand-alone wood energy plants average about 20 megawatts (MW) in size, ranging up to about 75 MW (Bain and Overend 2002). However, these plants are relatively inefficient as compared with competing technologies such as hydropower or wind energy, typically resulting in biomass electricity costs of 8 to 12 cents per kilowatt-hour (kWh). Even so, biomass energy production is currently the second most widely used form of renewable energy in the United States (Table 1).

Power costs for stand-alone wood energy electrical facilities are approaching a point where they will become competitive with fossil fuel systems (Table 2). However, generally declining energy costs in the 1990s as well as loss of state incentives (e.g., in California) and a limited supply of biomass available at low cost have made wood less competitive, resulting in some plant closures. Adoption of new wood-burning technologies, use of wood in cofiring applications, and use of low-grade and/or diverse biomass sources could help create favorable trends for biomass fuels, particularly in light of recent energy cost increases. Nationally, bioenergy use is expected to grow at a slower rate than biobased transportation fuels or biobased products (Table 3).

Renewable energy portfolios in western states

Renewable energy standards, or portfolios, are state policies requiring a certain percentage of electrical needs to be met with renewable energy resources by a specified date. Currently, 20 states and the District of Columbia have developed renewable energy standards-collectively accounting for more than 42 percent of U.S. electricity sales (US DOE 2005). Renewable energy electric standards typically include goals of up to about 30 percent of total electrical use, with target dates typically set for about 2020 or sooner (US DOE 2005).

Western Governors' Association

The Western Governors' Association, serving the governors of 19 western states, has adopted a resolution to examine the feasibility of developing 30 gigawatts (GW) of "Clean and Diverse Energy" by 2015, of which half (15 GW) is expected to be obtained from biomass (Western Governors' Association 2006). Energy sources considered include not only biomass, but also advanced coal, natural gas, solar, and wind.