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Corvallis, OR, United States

Caputo J.,SUNY College of Environmental Science and Forestry | Balogh S.B.,SUNY College of Environmental Science and Forestry | Volk T.A.,SUNY College of Environmental Science and Forestry | Johnson L.,Leonard Johnson and Associates | And 3 more authors.
Bioenergy Research

To estimate fossil fuel demand and greenhouse gas emissions associated with short-rotation willow (Salix spp.) crops in New York State, we constructed a life cycle assessment model capable of estimating point values and measures of variability for a number of key processes across eight management scenarios. The system used 445.0 to 1,052.4 MJ of fossil energy per oven-dry tonne (odt) of delivered willow biomass, resulting in a net energy balance of 18.3:1 to 43.4:1. The largest fraction of the energy demand across all scenarios was driven by the use of diesel fuels. The largest proportion of diesel fuel was associated with harvesting and delivery of willow chips seven times on 3-year rotations over the life of the crop. Similar patterns were found for greenhouse gas emissions across all scenarios, as fossil fuel use served as the biggest source of emissions in the system. Carbon sequestration in the belowground portion of the willow system provided a large carbon sink that more than compensated for carbon emissions across all scenarios, resulting in final greenhouse gas balances of -138.4 to -52.9 kg CO2 eq. per odt biomass. The subsequent uncertainty analyses revealed that variability associated with data on willow yield, litterfall, and belowground biomass eliminated some of the differences between the tested scenarios. Even with the inclusion of uncertainty analysis, the willow system was still a carbon sequestration system after a single crop cycle (seven 3-year rotations) in all eight scenarios. A better understanding and quantification of factors that drive the variability in the biological portions of the system is necessary to produce more precise estimates of the emissions and energy performance of short-rotation woody crops. © 2013 Springer Science+Business Media New York. Source

Lippke B.,University of Washington | Puettmann M.E.,WoodLife Environmental Consultants LLC
Forest Products Journal

Using wood wastes provides an opportunity to avoid fossil carbon emissions from the combustion of natural gas or other fossil fuels. Using a life-cycle assessment, a new biomass boiler sourced by forest residuals, sawmill residuals, and clean demolition material (CDM) was compared with an existing natural gas boiler for supplying heat to a large-scale district heating system. Potential alternative uses of these feedstocks, such as recycled or reprocessed products, and landfill alternatives were also evaluated for their relative impact on carbon emissions. We found a reduction in emissions from natural gas of 0.62 unit of carbon for every unit of carbon in the wood combusted. Temporary losses of forest carbon after initiating the collection of forest residuals were minimal over a short interval. These losses were more than offset by the joint production of wood products displacing fossil emissions. Carbon mitigation in the Pacific Northwest was increased from 5.5 metric tons/ha/y from the production of forest products with no collection of forest residuals to 6.5 metric tons/ha/y after completing the first rotation, an 18 percent reduction in fossil emissions per hectare of forest. The potential to recycle CDM into wood products may ultimately raise the efficiency in avoiding carbon emissions by 40 to 60 percent, although available wood quality and logistics currently favor use of CDM as biofuel feedstock. In the absence of any "incentives" or value for carbon mitigation, feedstock collection costs relative to low-cost fossil fuel will substantially limit the use of waste woods for biofuel or recycling alternatives. © Forest Products Society 2013. Source

Puettmann M.E.,WoodLife Environmental Consultants LLC | Lippke B.,University of Washington
Forest Products Journal

The use of wood waste for heating in urban settings provides an opportunity for communities to reduce annual fossil emissions by directly reducing the amount of fossil fuel used. Life-cycle assessments (LCA) comparing the environmental impacts of alternative processes or products provide the essential information to better understand opportunities for improvement. An LCA was performed on a Seattle, Washington, district heating system that provides thermal energy to a large number of buildings in downtown Seattle. This study presents annual impacts in terms of carbon emissions for heat production generated using a new boiler design fuel mix including wood wastes as well as natural gas. Results are compared with the results from the 100 percent natural gas boiler that was previously used. The LCA includes results from both a lifecycle inventory of all inputs and outputs and a life-cycle impact assessment comparing alternatives. Results show that global warming potential (GWP) was reduced by 57 percent for the mix fuel design boiler compared with an all natural gas boiler. When 100 percent woody biomass is used, the reduction increases to 104 percent. Transportation and collection of feedstocks contributed minimally (8%) to the overall impact, while the combustion life-cycle stage accounted for 92 percent of the total GWP. © Forest Products Society 2013. Source

Bergman R.,U.S. Department of Agriculture | Puettmann M.,WoodLife Environmental Consultants LLC | Taylor A.,University of Tennessee at Knoxville | Skog K.E.,U.S. Department of Agriculture
Forest Products Journal

Wood products have many environmental advantages over nonwood alternatives. Documenting and publicizing these merits helps the future competitiveness of wood when climate change impacts are being considered. The manufacture of wood products requires less fossil fuel than nonwood alternative building materials such as concrete, metals, or plastics. By nature, wood is composed of carbon that is captured from the atmosphere during tree growth. These two effectssubstitution and sequestration are why the carbon impact of wood products is favorable. This article shows greenhouse gas emission savings for a range of wood products by comparing (1) net wood product carbon emissions from forest cradletomill output gate minus carbon storage over product use life with (2) cradle-to-gate carbon emissions for substitute nonwood products. The study assumes sustainable forest management practices will be used for the duration of the time for the forest to regrow completely from when the wood was removed for product production during harvesting. The article describes how the carbon impact factors were developed for wood products such as framing lumber, flooring, moulding, and utility poles. Estimates of carbon emissions saved per unit of wood product used are based on the following: (1) gross carbon dioxide (CO2) emissions from wood product production, (2) CO2 from biofuels combusted and used for energy during manufacturing, (3) carbon stored in the final product, and (4) fossil CO2 emissions from the production of nonwood alternatives. The results show notable carbon emissions savings when wood products are used in constructing buildings in place of nonwood alternatives. © Forest Products Society 2014. Source

Katers J.F.,University of Wisconsin - Green Bay | Snippen A.J.,University of Wisconsin - Green Bay | Puettmann M.E.,WoodLife Environmental Consultants LLC
Forest Products Journal

This study summarizes environmental impacts of "premium" wood pellet manufacturing and use through a cradle-tograve life-cycle inventory. The system boundary began with growing and harvesting timber and ended with use of wood pellet fuel. Data were collected from Wisconsin wood pellet mills, which produce wood pellets from a variety of feedstocks. Three groups of manufacturers were identified, those who use wet coproduct, dry coproduct, and harvested timber. Pellet mill data were weight averaged on a per unit basis of 1.0 short ton of "premium" wood pellets, and burdens for all substances and energy consumed were allocated among the products on a 0 percent moisture basis. Wood pellets produced from dry coproduct required 60 percent less energy at the pellet mill. However, when considering all cradle-to-gate energy inputs, producing wood pellets from whole logs used the least energy. Pellets from wet coproduct and dry coproduct used 9 and 56 percent more energy across the life cycle, respectively. This study also compared environmental impacts of residential heating fuels with wood pellet fuel. Environmental impacts were measured on net atmospheric carbon emissions, nonrenewable energy use, and global warming potential (GWP). Assuming "better than break-even" forest carbon management, cordwood and wood pellet fuels emitted 67.3 and 26.6 percent less atmospheric carbon emissions per megajoule of residential heat across the life cycle than natural gas, the best fossil fuel alternative. Cordwood and wood pellets consumed fewer nonrenewable resources than natural gas, which consumed fewer resources than petroleum-based residual fuel oil. However, wood pellet fuels had a smaller GWP and effect on respiratory health because they have more efficient combustion. © Forest Products Society 2012. Source

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