American hardwoods low on carbon footprint

New study confirms they are among the world’s most environment-friendly building materials

Converting wood into usable building products requires less energy than most other materials, and much of that energy is bio-energy.

A life cycle assessment (LCA) study commissioned by the American Hardwood Export Council (AHEC), the leading international trade association for the American hardwood industry, reveal the strong environmental performance of American hardwoods – underpinned by an expanding forest resource, sustainable management and low carbon emissions.

According to the study, the carbon footprint of kiln-dried American hardwood lumber shows that sequestration of carbon during the growth of the tree more than offsets total carbon emissions during extraction, processing and shipment to India.

It also underlines how ocean transport is a relatively minor factor in the overall carbon footprint of American hardwoods. In addition, the heavy dependence on bio-mass (rather than fossil fuel) energy during processing is a particularly important factor in keeping the overall carbon footprint of American hardwoods low.

Sustainable design

In embracing sustainability, designers are not simply responding to a new fashion. Nor are they only seeking to minimise the direct impact of their own creations on the environment.

They are promoting desirable visions that compel people to want to live sustainably. And, by doing so, designers are becoming a key part of the process to move towards a more sustainable future.

The choice of materials is a key component of sustainable design. By using American hardwoods, designers are assured that they are minimising their impact on the environment throughout all the stages of the product life cycle, from extraction, through processing, use, reuse and final disposal.

At the same time, through their choice of particular species and grades of American hardwoods, designers have a central to play to reduce waste and maximise utilization of this valuable natural resource.

American hardwoods have a low impact on the environment at all stages of their life cycle, right from the point of extraction. Forest management in the sector is not intensive, one outcome of the fact that most American hardwood forests are owned and managed by individuals, families, or small companies rather than large timber corporations.

Forest holdings are relatively small, mostly under 10 hectares, limiting the size of harvesting operations. The primary motivation for owning the land is usually not timber production or economics, but simply the enjoyment of forest ownership!

Expanding resource

Because timber production and economic return to shareholders are not primary objectives, the owners of American hardwood forests tend to manage less aggressively and to grow their forests on longer rotations. Selection harvesting is typical, involving removal of only a few trees per hectare, rather than clear-felling.

After harvesting, forest owners usually rely on natural regeneration, which is abundant in the deep fertile forest soils of the United States. There is little need or incentive for addition of chemical fertilisers. No non-native ‘exotic’ or genetically modified species are used.

Regular forest inventories undertaken by the US federal government every 10 years clearly demonstrate that American hardwoods are not only renewable, but are an expanding resource. The latest data from the US Department of Agriculture was published in 2009 in preparation for the 2010 inventory report.

It shows that between 1953 and 2007, the volume of US hardwood growing stock more than doubled from 5 billion cubic metres to 11.4 billion cubic metres. Hardwood growing stock volumes have continually increased for the past 50 years, even in times when timber harvesting was most intensive.

The survey also shows that forests are aging and more trees are being allowed to grow to size before being harvested. The volume of hardwood trees with diameters 48 cm or greater has tripled.

Positive impact

While other industries – such as steel, concrete and plastic – often emphasize efforts to reduce their negative environmental impact, American hardwoods are one of the very few materials that make a positive environmental impact.

Long-term management of US hardwood forests for sustainable timber production makes a significant contribution to carbon storage. Each year for the last 50 years American hardwood forests stored around the equivalent of 165 million tonnes of carbon dioxide (excluding harvested material).

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 process of converting wood into usable building products requires considerably less energy than most other materials. Furthermore, much of the energy needed to produce American hardwood products is bio-energy.

A 2007 study of 20 hardwood sawmills in north-eastern US revealed that 75% of the energy required to manufacture kiln-dried lumber was derived from bio-mass (tree bark, saw dust and wood off-cuts). As a result, even less carbon dioxide is emitted when producing American hardwood lumber than when producing many recycled materials.

Carbon footprint

Assessment of the carbon footprint of American hardwoods from forest to European distributors indicates that carbon sequestration during forest growth of the tree more than offsets the total carbon emissions resulting from harvesting, processing and transport. In fact, transport is a relatively minor factor in the overall carbon footprint.

This is particularly true of ocean transport. Transporting American hardwoods by ship across the Atlantic, a journey of over 6,000 km, requires little more energy than an overland journey of 500 km. In fact, even a complete circumnavigation of the world by sea (40,000 km) would be readily offset by the carbon sequestered in the wood product.

The health risks associated with a natural material like American hardwood, which requires no glues or other chemical treatment during processing, are minimal. Where needed, a wide range of 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 vacuum cleaning keeps the environment allergen-free. For this reason, they are recommended for chemically sensitive individuals, or those who suffer from allergies or asthma.

Commercial ‘afterlife’

A key principle of sustainable design is that products, processes, and systems should be designed for performance in a commercial “afterlife”. This is allied to a new trend towards bio-mimicry, involving the re-design of industrial systems on biological lines and enabling the constant re-use of materials in continuous closed cycles.

The most direct way to achieve bio-mimicry is through use of natural organic renewable materials like American hardwoods. Because they are untarnished by mixing with other materials and chemicals, American hardwoods are readily reusable and recyclable at the end of a building’s life span.

Those American hardwood components needing to be disposed of are bio-degradable and non-toxic. They may also be safely incinerated, providing a carbon-neutral source of energy.

The US wood products industry has a strong waste minimisation record. Over the last 50 years, throughout the US there has been a 39% increase in the amount of wood and paper products produced per cubic metre of wood input. Longer lasting and better functioning products have to be replaced less frequently, reducing the impacts of producing replacements. Hardwood floors can last 50 years or more. Broadloom and tile carpeting, on the other hand, has a life span of up to 6 years!

When sourcing American hardwoods, you can be assured that these issues are comprehensively dealt with through a fully-enforced regulatory framework in the US. This is the story of a natural organic product derived from rural families and communities in the US that have been managing forests for generations and are guardians of the world’s largest renewable hardwood resource.

AHEC represents these committed exporters among US hardwood companies and hardwood production trade associations. It runs a worldwide programme to promote American hardwoods in over 50 export markets, and also produces a full range of technical publications.  

(www.americanhardwood.org).

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