RESTON, VA -- The American Hardwood Export Council (AHEC) has published a comprehensive report on the environmental life cycle of delivering U.S. hardwood lumber into overseas markets. An equivalent report on U.S. hardwood veneer is currently undergoing critical review and will be published soon. Fully ISO conformant and receiving high praise from independent LCA experts, the reports are being used as the basis for innovative tools to integrate sustainability into product design.

If sustainability is ever to become more than a mere aspiration in design, manufacturing and construction, decisions need to be made based on hard facts. New tools are needed which bring in data from numerous sources covering a huge range of environmental impacts. These tools must be flexible enough to accommodate widely different materials and contexts, and yet accessible so that environmental information can be readily integrated into the design process without adding excess cost.

That’s a very tall order – but a widening range of scientists, industry groups, specifiers, government and consumer interests have been chipping away at the problem now for several years. Their efforts are beginning to show results. Central to this process has been the development of Life Cycle Assessment (LCA), a scientific method involving collection and evaluation of quantitative data on all the inputs and outputs of material, energy and waste flows associated with a product over its entire life cycle so that the environmental impacts can be determined.

The LCA process is now covered by international standards, the ISO14040 series, to ensure results are scientifically rigorous and not subject to manipulation by different industrial sectors. The standards require, for example, that data collection and analysis is undertaken by independent third parties and subject to critical review by a panel of independent experts.

AHEC, which represents the interests of exporters of hardwood lumber and veneer from the United States, is actively promoting an LCA based approach to sustainable material use and design to help overcome widespread misconceptions about the environmental credentials of hardwood products. It is often assumed, for example, that because hardwoods are usually derived from managed natural forests and “slow to grow”, their use contributes to forest degradation or deforestation. Another common assumption in Europe is that because American hardwoods have to be transported across the Atlantic, they must have a higher carbon footprint than locally produced materials.

This led AHEC to embark on a comprehensive LCA project with two major objectives: first to ensure full conformance to ISO14040 to ensure the credibility of the data; and second to ensure that the LCA data is made available in such a form that it is useful to decision-makers in material specification and product design.

PE International, an independent company, was engaged to undertake the work due to its experience of LCA in a wide range of business sectors and ability to offer innovative LCA tools. These include PE’s proprietary Gabi software, which facilitates collection and analysis of LCA data, and an “i-report” system to make this data accessible and useable by designers and manufacturers. PE has also been heavily engaged in efforts to develop a global standardised framework for reporting of LCA data in Environmental Product Declarations (EPDs).

At the start of the process, AHEC and PE International assembled a high-powered Critical Review Panel chaired by Dr Matthias Finkbeiner, a professor at Berlin University who also chairs the ISO committee developing international LCA standards. By involving the Panel in the project early on, rather than simply seeking their endorsement at the end, methodological issues could be dealt with as they arose. When the final LCA report on U.S. hardwood lumber was published in July 2012, the Panel not only confirmed its compliance to the ISO standard, but also “found the overall quality of the methodology and its execution to be excellent.”

The report provides a comprehensive analysis of U.S. hardwood lumber’s profile across a wide range of environmental impacts. In technical terms it is a “Cradle-to-gate plus transport” study, covering all impacts associated with extracting the wood in the forest, transporting, sawing and kiln-drying the material in the United States, and then delivering the lumber to the importers yard in major overseas markets.

Benefitting the forest environment

The report includes a qualitative assessment of land use and land use change, biodiversity, water resource and toxicity impacts associated with supply of U.S. hardwood lumber, indicating very low environmental impact across all these categories. On land-use change, it observes "in the system under investigation the main material – wood – comes from naturally re-grown forests. The harvested areas had undergone several iterations of harvesting and re-growth. After harvesting, the land is returned to forest so there is no direct land use change to account for in the timeline of few hundred years".

On biodiversity impacts, the study concludes that: "Conversion of any other commercial land into the hardwood forest would most probably be a positive impact on the land quality including biodiversity and associated ecosystem services". On toxicity it notes that: "In the production of hardwood lumber there are no fertilisers or wood treatment chemicals or any other known substances of particular toxicity concern". On water resources it comments: "hardwood lumber is expected to have very low impacts”.

While some impacts are treated qualitatively in the LCA report, others are dealt with quantitatively. The report provides numerical data on Global Warming Potential (GWP – better known as carbon footprint), Acidification Potential (AP), Eutrophication Potential (EP), Photochemical Ozone Creation Potential (POCP), and Ozone Depletion Potential (ODP). It also identifies which processes along the supply chain (forestry, sawing, kilning, transport) are most important in determining each of these impacts. It includes a sensitivity analysis to show how environmental impacts vary according to key factors such as species, lumber thickness, and transport distance and mode.

Wide variation between U.S. hardwood species

A key conclusion from this number crunching is that variation in environmental profile is at least as dependent on species and thickness as it is on transport factors. Providing average results for “sawn hardwood lumber” can be very misleading and data needs to be reported separately for each individual hardwood species and board thickness. This is mainly because the kiln drying process consumes a surprisingly large share of the energy needed to produce and deliver hardwood lumber. The time lumber spends in the kiln also varies widely between species and by thickness. For example, for 1” lumber, oak typically needs to be kilned at least three times longer than tulipwood. And 3” lumber requires more than 4 times as long in the kiln as 1” lumber.

While kiln drying has more of an impact than might be expected, the global warming impact of transport is less. Even very large changes in transport distance result in relatively minor changes in carbon dioxide emissions. For example, for 1” white oak lumber, the carbon footprint of delivering into London (shipping distance 720 km by road and 6300 km by sea) is little different from that of delivering into central Poland (1265 km by road, 7735 km by sea). Even transporting lumber all the way from the Eastern United States to Australia, via Suez and Singapore (2205 km by road, 25000 km by sea), results in a carbon footprint no more than 50% greater than that of delivery into the UK.

What about wood’s carbon storage?

Like all wood products, close to 50% of the dry mass of U.S. hardwood lumber comprises carbon which has been absorbed as the tree grows through photosynthesis. In fact, the data gathered by PE shows that the amount of carbon stored in U.S. hardwood lumber almost always exceeds the emissions required to extract, process and transport that lumber into any export market worldwide. However, all the above observations about carbon footprint ignore this storage benefit of the lumber. That’s because the scope of this particular LCA report is restricted in that it ends at the point of delivery - unavoidable since it’s not possible for producers to know how their material will be used. Treatments, fixings, further processing, life-span and method of disposal all have an influence on carbon storage. These need to be fully accounted for in future ‘cradle-to-grave’ studies of manufactured products containing U.S. hardwood – before it is appropriate to make far-reaching claims about the “carbon neutrality” of the raw material. The AHEC study facilitates this next step by providing conservative estimates of the amount of carbon stored in U.S. hardwood lumber products. This treatment of the carbon properties of wood products, which aligns with international best practice, was singled out for particular praise by the Critical Review Panel:

Another commendable aspect of the study is the conservative approach taken with regard to modelling biogenic carbon removals from the atmosphere. The study quantifies the biogenic carbon uptake in forestry, and reports this separately from the cradle-to-gate result. This transparent and unbiased treatment of the biogenic carbon issue supports proper use of the data for future assessments of the complete life cycle of American hardwood based products”.

The data provided on carbon storage in U.S. hardwoods again highlights that there are significant variations between U.S. species that need to be taken into account during the design process. Denser species like oak and hickory store more carbon for each cubic meter than less dense species like tulipwood and willow.

Bringing LCA into design with U.S. hardwoods

The next stage of the project, and the most challenging, aims to integrate life cycle thinking into all stages in the design, manufacturing and delivery of products containing U.S. hardwoods. To achieve this aim, AHEC is exploring opportunities to develop PE’s on-line ‘i-report’ system so that LCA data on American hardwoods is made readily available in a useable form at various supply chain stages.

PE’s draft ‘i-report’ system for U.S. hardwood lumber enables specific LCA data to be generated for individual species, lumber thickness, processing parameters (such kiln efficiency and energy sources), transport distances and modes (truck, ship, rail). The system is now being adapted so that all AHEC members will have the option of providing a comprehensive American Hardwood Environmental Profile with every individual consignment of product delivered to any market in the world. Each Environmental Profile will combine the LCA data (GWP, AP, EP etc.) with other credible information on the legality and sustainability of U.S. hardwood products required, for example, by EU importers to demonstrate conformance to the EU Timber Regulation (EUTR).

AHEC is also working with PE and a range of other partners to encourage wider use of LCA in design and manufacturing. During 2012 AHEC undertook the joint “Out of the Woods” project with PE, the Royal College of Art in London, and British furniture producer Benchmark. This involved pilot development and practical demonstration of an ‘i-report’ system for furniture designers. As part of the project, 12 teams of RCA students were each asked to design and construct a functional chair out of American hardwoods. Using the American hardwood data and PE’s ‘i-report’ system, the environmental impact of each chair was assessed on a full LCA basis. Each chair together with its LCA profile was show-cased at a high-profile exhibition in the Victoria and Albert Museum during the London Design Festival in September 2012. The project demonstrated to a wider audience the power of new LCA tools to assess genuine sustainability credentials during the design and manufacturing process.

Drawing on experience gained in the “Out of the Woods” project, AHEC is now exploring with PE the potential to adapt the furniture i-report system so that it can be applied to a wider range of manufactured wood products. 

AHEC is also engaging in on-going efforts at national and European level to integrate LCA into the construction sector through various green building initiatives such as a DGNB in Germany, BREEAM in the UK, and HQE in France. Delivery of LCA data to these systems increasingly is required in the form of formal Environmental Product Declarations prepared in accordance with the EN 15804 standard for construction product EPDs. AHEC will soon commission EPDs covering U.S. hardwood lumber and veneer in line with several national programmes including the ECO-EPD developed by the Institut Bauen und Umwelt (IBU) in Germany.

Meanwhile, the LCA data is being systematically introduced into AHEC’s existing technical species guides and project case studies, which have long provided guidance and inspiration for use of American hardwoods in construction, interiors and furniture manufacturing.

About the American Hardwood Export Council:

The American Hardwood Export Council (AHEC) is the leading international trade association for the U.S. hardwood industry, representing the committed exporters among U.S. hardwood companies and all the major U.S. hardwood product trade associations. AHEC concentrates it efforts on providing architects, specifiers, designers and end-users with technical information on the range of species, products and sources of supply.

The ISO-conformant LCA report on U.S. hardwood lumber is available at:

AHEC produces a full range of technical publications, which are available free of charge by visiting

Source: AHEC

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