Content excerpted from "Carbon Benefits of Wood-based Products and Energy" on the USFS Climate Change Resource Center and the USFS report Considering Forest and Grassland Carbon in Land Management (WO-GTR-95).
Management activities can have a substantial effect on greenhouse gas mitigation that extends beyond the carbon contained within forest ecosystems. Harvested wood goes into diverse forest products that continue to store carbon for the duration of their useful life (1, 2). Forest management activities can also supply wood directly for energy, and waste materials from wood products manufacturing and processing can be recovered to produce power.
Carbon Storage in Harvested Wood Products
A substantial amount of carbon is stored in wood products. Differences in the type of wood product, its production, its use, and its disposal have substantial influences on the amount and duration of carbon storage. Where the goals of forest management include carbon benefits, product use and disposal is an important consideration. Standard methods are available for estimating the carbon that is sequestered in harvested wood products (3), and life-cycle assessment approaches can be used for more in-depth analysis of carbon gains and emissions (4-6).
There are some ways that forest management can help to increase carbon storage in the harvested wood products pools. Emphasizing “durable” or “long-lived” wood products, such as lumber used for building construction can help to increase the overall lifespan of the product in use, as well as shift the mix of products toward those that decay less in landfills (2). Wood products can also be used as substitutes for other materials that require greater fossil fuel inputs to produce, such as steel or concrete (8, 9). For example, one study that compared the life-cycle emissions needed to build a single-family home using primarily wood, steel, or concrete construction materials found that the wood house had the least embodied energy, particularly compared to steel construction (10, 11). Although forest management can influence the species and size of trees available for wood products, larger-scale policies and markets will largely drive the demand for particular products.
Forest management to promote woody biomass
Recent concerns regarding climate change and rising energy costs have dramatically increased interest in the use of renewable and alternative energies, including wood-based energy. While energy consumption from wood sources in the United States is currently greater than it was during much of the 20th century, the contribution of wood to the overall energy portfolio is small. In 2015, nearly 5 percent of U.S. energy consumption was from biomass sources (12), about two-thirds of which is derived from forests (13). The major sources of wood used for energy, including electricity, heat, and transportation fuel, include fuelwood (29 percent of forest biomass consumption), residues and pulping liquors from the forest products industry (60 percent), and wood municipal solid waste (10 percent) (13). Wood sources may account for a greater portion of energy in the future; for example, one study evaluated the potential for the use of biomass feedstocks from forests to increase by 175 percent by 2030, with the majority of the increase coming from additional utilization and production of fuelwood (13).
Forest management can be used to increase the amount of woody biomass that is available for energy use in a few different ways. One option is to increase the removal of logging residues—the woody material generated during forest harvest operations. These materials can include tree tops, branches, and stems that are unsuitable for use in the production of traditional forest products but can be used to generate energy as a replacement to fossil fuels (13). One study identified that additional logging residues could displace as much as 17.6 million tons of carbon emitted from coal-fired power plants, or about 3 percent of total carbon emissions (14). While several studies point to the potential to use logging residues for bioenergy, the availability of these materials is heavily influenced by the financial costs of production relative to the sale price of biomass (13, 15). There are also concerns about the ecological effects of more intensive biomass removal from forests (16-18).
There is also the potential to implement forest management activities for the purpose of generating wood for energy in addition to meeting other management goals. Biomass markets, where they exist, can provide additional opportunities for fuel reduction treatments, noncommercial thinnings, and other silvicultural activities that do not contribute to the traditional forest-products industry. Fuel reduction treatments may reduce the risk of large, high-intensity wildfires, thereby reducing the potential for emissions from wildfire and creating opportunities to substitute renewable forest-based energy for fossil energy (8, 19).
Wood-based bioenergy is often compared favorably to fossil fuels and several renewable energies due to a relatively low amount of fossil fuel inputs and a smaller “carbon footprint” (Malmsheimer et al. 2008). Wood energy is sometimes talked about as being “carbon neutral” based upon the idea that any carbon that is released by the burning or use of wood for energy is recaptured through the sequestration of the forest as it regrows (20). The reality is more complex: The carbon effects associated with bioenergy production need to be evaluated to include the entire life cycle of energy production, as well as the longer term use and growth of the land used to produce the energy, relative to the business-as-usual use of fossil fuels (21-24). While many studies support the idea that woody bioenergy produced from sustainably managed forests can have carbon benefits over the long term, the degree of benefit is heavily influenced by factors that include the initial forest conditions, forest productivity, fossil energy from harvest operations and transportation, and the type of fossil fuel that is replaced by wood (25, 8, 26, 27). A full accounting of the greenhouse gas benefit of forest bioenergy would include comparisons of forest carbon stocks for bioenergy versus a no-bioenergy scenario, as well as a full life-cycle assessment of the emissions used to produce forest bioenergy and for the displaced fossil fuel emissions (21, 15).
Associated Topic Pages at the USFS Climate Change Resource Center
- Global Carbon
- Forest Soil Carbon
- Forest Management for Carbon Benefits
- Grassland Carbon and Management
Content originally prepared by the following authors for the USFS Climate Change Resource Center:
- Maria Janowiak, Northern Institute of Applied Climate Science, US Forest Service, Houghton, MI.
- Chris Swanston, Northern Institute of Applied Climate Science, US Forest Service, Houghton, MI.
- Todd Ontl, Northern Institute of Applied Climate Science, US Forest Service, Houghton, MI.
This content was drawn from the USFS Climate Change Resource Center (CCRC) topic page "Carbon benefits of wood-based products and energy", and the report Considering Forest and Grassland Carbon in Land Management (WO-GTR-95).
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