Consumption and Environmental Concerns

Jim Bowyer

Dovetail Partners, Inc. & University of Minnesota

 
Despite being ignored in environmental planning, both population and consumption continue to grow, and accompanying that growth is rising consumption of wood and other basic materials.  Globally, for the 35-year period from 1970 through 2005, the population increased 74 percent while consumption of steel, cement, alminum, plastics, and wood increased 83, 288, 221, 658, and 32 percent, respectively.  For the United States during the same period, the population increased 45 percent, while domestic consumption of cement, aluminum, plastics, and wood and wood products increased 34, 81, 78, 379, qnd 38 percent, respectively.   Thus, world-wide and even in the world’s highest consuming nation, consumption of a number of key materials is growing not only in absolute terms, but on a per capita basis as well. 
 
As population and consumption have grown, so too has concern about the environment.  Forests have been a particular focus of concern, in part because of their wide distribution and visibility, and in part because of the special significance of forests to people everywhere.   That concern is manifested in human behavior in a number of ways.  In the United States, for example, increasing regulation of forest land, both public and private, has served to moderate forest harvest activity in general, and to effectively halt harvest activity on federally owned land.  On the market side, programs have been developed to certify wood products and the forests from which the wood is harvested to ensure responsible harvesting and forest practices.  Also developed in recent years are green building systems that seek to reduce the environmental impact of building construction and operation; reflecting special concern for forests, the largest green building program in the U.S. requires environmental certification of only those building materials that are made of wood. 
 
 
Wood – a Key Material
 
The United States consumes massive quantities of raw materials each year.  Among these, wood stands out as a primary raw material.  In the U.S., roughly as much wood is consumed for industrial purposes each year as all metals, all plastics, and Portland and masonry cement combined! (Table 1).  Wood consumption is expected to grow more or less in step with population growth.

Table 1.  U.S. Consumption of Various Raw Materials, 2005

                                                       Million                  Million
                                                 Metric Tons         Cubic Meters

    Roundwood                              249                        560
    Industrial Roundwood              227                        516
    Cement                                     126                        114
    Steel                                          122                        154
    Plastics                                       39.1                       34.5
    Aluminum                                      6.8                         2.4

Source: Data for wood from USFS (2006), for cement, steel, and aluminum, from the U.S. Geological Survey (2006), and for plastics from the American Plastics Council (2006)

Thus while a broad range of initiatives are focused on reducing or moderating growth of consumption of wood, it is obvious that without attention to consumption in general, a reduction of wood use would require substitution of non-wood materials.  In addition, given the magnitude of wood use within the U.S., the substitution needed to achieve a significant reduction in wood use would be massive. 
 
 
Protecting the Environment – Should Wood Use be Reduced or Increased?
 

Current Trends in Environmental Activism
 
Environmental activists often note that per capita wood consumption in the United States is over 3 times that of the world average (3.3 times), using this as part of the justification for seeking reduction of wood use.  Completely ignored is the reality that per capita consumption of cement, steel, aluminum, and plastics in the U.S. is 1.5, 3.3, 6.0, and 5.6 times the world average.  Completely ignored as well are the environmental impacts of producing and using non-wood materials.   The thinking is apparently that the use of any other material is environmentally better than using wood.  Similar thinking is evident among leaders of the nation’s largest green building program.  Under this program a credit is awarded for the use of wood products certified under the FSC certification program.  Curiously, however, there is no requirement for certification of responsible and sustainable production of any material other than wood – not for products made of steel, of concrete, of vinyl, of bamboo, or of any other material.   Yet, the production and use of all of these materials is known to result in large and negative environmental impacts.  For instance, Brazilian pig iron (a source of U.S. imports) has been directly linked to significant tropical deforestation, the manufacture of cement to high energy consumption, the production of vinyl to release of highly toxic emissions and major end-of-product-life issues, and bamboo to substantial impacts across vast areas.  At present, all such impacts are completely ignored.  
 

In the pulp and paper arena there is a small but growing market for tree-free paper.  Websites promoting such paper appear to suggest that paper made of anything other than trees is environmentally preferable to paper made of wood fiber.  Raw materials such as hemp and kenaf are widely promoted as environmentally superior sources of fiber.  However, as in other environmentally-inspired initiatives there is a remarkable lack of careful, systematic analysis behind designation of materials as environmentally preferable.  When such analyses have been made, environmental superiority of non-wood materials has not been demonstrated.
 
 
Rethinking Wood
 

Research involving systematic examination of the environmental impacts of a product over its life is commonly referred to as life-cycle-assessment or simply LCA.  An LCA typically begins with a careful accounting of all the measurable raw material inputs (including energy), product and co-product outputs, and emissions to air, water, and land; this part of an LCA is called a life cycle inventory, or LCI. 
 

LCA studies have consistently found substantial differences in the environmental impacts associated with constructing and operating a wide range of building types; in virtually every study in which wood has been compared to other construction materials, wood has emerged as the material with the lowest environmental impact. For example, a 1992 New Zealand study found wood-frame construction of residential buildings with wood-framed windows and wood fiberboard cladding to require only 42 percent as much energy as brick-clad, steel-framed dwellings built on a concrete slab and fitted with aluminum-framed windows. When office and industrial buildings were considered, those constructed of timber were found to require only 55 percent as much energy as steel construction and approximately 66 to 72 percent as much energy as concrete construction.  A 1992 Canadian assessment of alternative materials for use in constructing a large research laboratory building showed all-wood construction on a concrete foundation to require only 35 percent as much energy as steel construction on a concrete foundation.  A comprehensive 2005 study that examined environmental impacts of residential building construction to existing code requirements in cold (Minneapolis) and hot (Atlanta) climates found fossil fuel consumption associated with steel framed construction to be 281 percent higher than for wood and 250 percent higher for concrete construction than for wood framing.  Differences in emissions of carbon dioxide were greater than suggested by differences in energy consumption, since substantial quantities of carbon are stored within wood.
 

Large differences in energy consumption tend to be linked to large differences in a number of emissions.  A 1994 study that examined not only energy and related emissions associated with wood and steel-framed construction, but also manufacturing effluents found emissions of a wide range of compounds associated with steel-framed construction to be 1.6 times to 41 times higher than for wood-framed construction.  Generation of solid waste was the only category in which wood construction ranked higher.  All more recent studies have supported these findings.
 

Most LCA studies to date have assumed the use of virgin materials (i.e. no recycled content).  One mid-1990s study that did consider incorporation of recovered material examined the use of recycled steel  in wall studs.  In this case, the manufacturing energy differences between wood and steel were found to narrow, but wood retained a significant advantage. As part of the wood vs. steel wall comparison, load-bearing wood and steel-framed walls, in which the steel contained 50% recycled steel content, were examined. In this case the steel-framed wall was found to be “some four times as energy intensive, and correspondingly ... at least that much more environmentally damaging, despite its recycled steel content.”
 

Many LCA/LCI studies have shown substantial differences in carbon liberation when comparing wood products manufacture and use with non-wood products.  For example, the New Zealand study that examined manufacturing processes, including raw material extraction and transportation, not only revealed large differences in net CO₂ emissions from material to material, but carbon emissions figures for lumber that are actually negative.  The negative values for wood are due to the fact that approximately one-half of the mass of wood is carbon, and that low energy consumption in manufacture results in far lower carbon emissions than the quantity of carbon stored in the lumber.  In view of these and other results, one author recently concluded that "The choice of building material has a huge effect on the carbon emissions to the atmosphere.  Timber used for framing, floor, and wall components of a house compares much more favorably than other common materials."
 

When trees are harvested, the carbon capturing ability of the trees harvested is lost.  However, if trees are replanted following harvest and much of the wood goes into long-term use, such as building materials, the overall impact on carbon storage is positive.  Much of the carbon contained within the trees harvested is stored or sequestered within wood products, wood residues used to generate power reduce the need for combustion of fossil fuels (and associated liberation of carbon), and the carbon removed from the forest in the form of wood is replaced by new growth. It is worth noting that LCA/LCI findings are not currently considered by green building program advocates.
 
 
Summary
 

Despite a pervasive anti-wood bias among many in the U.S. environmental community, wood stands alone among primary building materials as that generating the lowest environmental impact, a reality that is clearly indicated in findings of LCA/LCI studies from around the world.  And, wood is renewable.  While there are environmental impacts of wood harvesting, and harvest-related issues that are not addressed by LCA/LCI, there are also significant impacts associated with production of all other materials.  To date, there has been no effort by anyone to develop systems to monitor or promote responsible extraction of any material other than wood, despite widely known environmental problems associated with the production of many commonly used materials. 
 

In considering all of the evidence, a strong case can be made that wood is the most environmental benign material available to society today.  Thinking needs to be redirected to consider not how to reduce wood use, but rather how to increase its production and use while also ensuring forest sustainability for the long term.
 
 
References
 

Baird, G. and C.S. Aun. 1983.  Energy Costs of Houses and Light Construction Buildings.  Report No. 76.  New Zealand Energy Research and Development Committee, Auckland, New Zealand.
 
Cole, R., D. Roussau, and S. Taylor. 1992.  Environmental audits of alternate structural systems for warehouse buildings.  Canadian Journal of Civil Engineering 19: 886-895.
 
Garcia, J. Perez, B. Lippke, D. Briggs, and J. Wilson, J. Bowyer, and J. Meil. 2005.  The environmental performance of renewable building materials in the context of residential construction.  Wood and Fiber Science, 37 CORRIM Special Issue, pp. 3-17.
 
Garcia, J. Perez, B. Lippke, J. Comnick, and C. Manriquez. 2005.  An assessement of carbon pools, storage, and wood products market substitution using life-cycle analysis results.  Wood and Fiber Science, 37 CORRIM Special Issue, pp. 140-148.
 
Honey, B. G., and A.H. Buchanan. 1992.  Environmental impacts of the New Zealand building industry. Research Report 92-2. Dept. Of Civil Engineering, Univ. Of Canterbury-Christchurch, Canterbury, N.Z.
 
Meil, J. K. 1994.  Environmental measures as substitution criteria for wood and nonwood building products. In The Globalization of Wood: Supply, Processes, Products, and Markets, Forest Products Society Proceedings 7319, pp. 53–60.