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Life Cycle Analysis

What other environmental benefits are provided by American hardwoods?

American hardwoods have many environmental advantages over alternative materials:

• The trade in U.S. hardwoods creates an incentive for the long term management of U.S. hardwood forest for sustainable timber production, primarily achieved through low intensity harvesting followed by natural regeneration by small-scale non industrial family foresters. In addition to providing economic and social benefits, this form of management contributes to soil and water protection and bio-diversity conservation.
• Long term management of U.S. hardwood forests for sustainable timber production makes a significant contribution to carbon sequestration. Each year for the last 50 years American hardwood forests stored around 110 million tonnes of CO2 (excluding all harvested material). That’s enough to offset about 10% of U.S. annual residential emissions, or 6% of U.S. annual transport emissions.
• This direct contribution of America’s hardwood forests to carbon sequestration excludes the carbon held in long term storage as a component of American hardwood products. With useful lives spanning generations, furniture, flooring, cabinetry and trim crafted of American hardwoods act as an additional carbon store for many decades.
• The U.S. wood products industry is efficient and has a strong waste-minimization record. Over the last 50 years, throughout the U.S. there has been a 39% increase in the amount of wood and paper products produced per cubic foot of wood input[1].  The application of a set of the internationally recognised NHLA grading rules, established more than 100 years ago has made a major contribution to waste-minimization in the American hardwood lumber sector.
• The process of converting timber into usable building products requires considerably less energy than most other materials. Research in Australia provides an indication of the scale of the energy savings to be derived by using timber in place of other materials (Tables 1 and 2). For example, the embodied energy of a typical wood flooring assembly requires less than half of the energy to manufacture and install than a typical concrete floor assembly[2].
• Low energy during manufacture combined with the carbon sequestration properties of timber products mean that these are the only mainstream construction products that can actually contribute to overall reductions in carbon dioxide concentrations through their increased use (chart 1)[3].
• The durability of American hardwood products means that they tend to outlast their synthetic counterparts. Hardwood floors can last 50 years or more. Broadloom and tile carpeting, on the other hand, has a four- to-six-year life span. After 15 or 20 years of use, hardwood flooring can gain a fresh, new appearance with refinishing for roughly half the cost of replacing carpet or other flooring options.
• Low-VOC finishes can be used to protect the aesthetic appearance and performance of American hardwoods.
• American hardwoods are easy to maintain with non-toxic cleaners and they don’t trap dust, dirt and other allergens. Simple regular maintenance such as dust mopping, sweeping and vacuuming keeps the environment allergen-free. For this reason, they are recommended for chemically sensitive individuals, or those who suffer from allergies or asthma.
• At the end of a building’s life span, many hardwood components are re-useable and recyclable.
• Hardwood components needing to be disposed are biodegradable and non-toxic.

Life cycle assessment

The evolving science of life-cycle analysis (LCA) assesses environmental effects at all stages of a product's life including resource procurement, manufacturing, building service life and de-commissioning at the end of the useful life of a building. Recent LCA studies have confirmed that when originating from well managed forests, wood products are a good environmental choice. For example:

• In their 2006 study of the flooring industry in Germany, Nebel, Zimmer, and Wegener examined the whole life cycle of four wood floor coverings, including solid parquet, multilayer parquet, solid floor boards, and wood blocks[4]. The authors point out that, compared with all German volume domestic products, wood flooring contributed significantly less (factors of 5 to 50 lower) to impact categories including climate change, acidification, eutrophication, photo-oxidant formation, and ozone depletion. Storage of carbon inherent in wood flooring coupled with energy production alternatives to fossil fuels realized by residual wood and post-consumer wood streams represent significantly reduced, perhaps even negative, global warming potential for these products.
• In 2004 research, the Consortium for Research on Renewable Materials (CORRIM), a U.S. non-profit corporation of 15 research universities, concluded that steel framing used 17 percent more energy than wood construction for a typical house in Minnesota, while concrete construction used 16 percent more energy than a wood construction house in Atlanta. In both situations, the consortium found that the use of steel had 26 percent more global warming potential than wood, and concrete had 31 percent more[5].
• The Athena Model, developed by the non-profit Athena Sustainable Materials Institute, compares the cradle-to-grave ecological quotient of wood, steel and concrete across the six stages of a material’s life expectancy: resource extraction, manufacturing, on-site construction, facility occupancy, and demolition and ultimate reuse or recycling. The Athena Model found wood to have the lowest environmental impact in each of these categories, and that wood exceeds the other materials in terms of environmental soundness and energy use; production of greenhouse gases; air and water pollution; production of solid waste; and overall ecological resource use[6].
• In a study entitled “Environmental and energy balances of wood products and substitutes” commissioned by the United Nation’s Food and Agriculture Organisation (FAO) in 2002,  the University of Hamburg undertook a comprehensive review of LCA work during the previous decade. The authors concluded “The results of the comparative LCA studies clearly indicate that wood products and products systems show advantages in most environmental impact categories. The subjective impression that wood products are better than competitive products with respect to environmental aspects can be scientifically proved.”[7] 
• Also in 2002, the UK Building Research Establishment (BRE) published results from the study, ‘Environmental Profiles of Building Materials, Components and Buildings’. BRE scored timber highly in the 13 environmental impacts studied - from climate change, pollution to air and water, waste disposal, and transport pollution and congestion. Timber was recognised as the only building material to have a positive impact on the environment due to trees’ ability to absorb carbon dioxide. BRE concluded that “timber and wood based materials have excellent environmental performance…often better than that of alternative materials. Timber and wood-based materials can make an important contribution to achieving more sustainable production.”[8] 

Source: Lawson Buildings, Materials, Energy and the Environment (1996)

Source: Lawson Buildings, Materials, Energy and the Environment (1996)

Chart 1: Net life cycle emissions of major construction materials in tonnes of C02 per cubic meter of product - typical figures for Finland

¹Ince, P.J. 2000, Industrial Wood Productivity in the United States, 1900–1998. Research Note FPL-RN-0272, USDA Forest Service, Forest Products Laboratory

²Bill Lawson, Building Materials Energy and the Environment, 1996, Red Hill, Australia, Royal Australian Institute of Architects, 1996

³RTS Building Information Foundation, Finland, Environmental Reporting for Building Materials, 1998 - 2001

⁴Nebel B, Zimmer B, Wegener G (2006): Life cycle assessment of wood floor coverings – A representative study for the German flooring industry. Int J LCA 11 (3) 172–182

⁵Consortium for Research on Renewable Industrial Materials (CORRIM), summary report from Forest Products Journal, June 2004, Vol 54, No. 6. Available at http://www.corrim.org/reports/

⁶Full details of this and other LCA studies by ATHENA, are available at the Canadian Wood Council website: http://www.cwc.ca. See http://www.cwc.ca/NR/rdonlyres/FBEC3574-62E5-44E0-8448-D143370DCF03/0/EnergyAndEnvironment.pdf. Details about the ATHENA Sustainable Materials Institute are available at: www.athenasmi.ca/

⁷Dr Mohammad Scharai-Rad and Dr Johannes Welling, 2002, Environmental and energy balances of wood products and substitutes. Department of Wood Technology, University of Hamburg and the Federal Research Centre for Forestry and Forest Products, Hamburg. Results published by the FAO, Rome, 2002. A full copy of their report is available at: http://www.fao.org/docrep/004/y3609e/y3609e00.htm

⁸Building Research Establishment, 2002, Digest 470: Life cycle impacts of timber. A review of the environmental impacts of wood products in construction. Details of BRE and their publications are available on their website: http://www.bre.co.uk