Wood: The ‘Alpha Material’
August 14, 2011 | 9:07 pm CDT

By Margaret Fisher

Dig Deeper

Browse the resources that Margaret Fisher used to develop this article. Includes links and articles for a more in-depth understanding of the USGBC LEED program.

Woodworkers who deal with customers interested in sustainable building, especially architects and designers, often find themselves on the defensive, having to combat misconceptions about wood as a sustainable material. Yet, with a clear understanding about what wood is and what it does, such design pros should recognize that wood is a great material for the environment.

 To help spell out wood’s advantages for any customers who need convincing, Margaret Fisher shares some of the information she has gleaned from her research, as a follow-up to her column last month about the USGBC LEED program. Fisher, Market Development Manager of Saunders Wood Specialties in Park Walls, WI, is the AWI (Architectural Woodwork Institute) liaison to USGBC (U.S. Green Building Council).

It’s no secret that the reason we have the wood we have today is because of the great sustainable forestry practices that have been in place in this country for more than 100 years. We have about 25% more forest than we had even 45 years ago. As a grower of trees for paper production and dimensional lumber, and as a careful steward of the land and forests that provide our hardwoods, North America is doing just fine. In fact, this is something that we are gaining on.

Those of us in the industry have been “singing this song” for four decades and, on the popular front, we are having more success in getting society at large to sing along with us, to a certain extent. In the 1970s, people were alarmed when they saw trees harvested. But over time, we have become a more insightful and well-reasoned society. We realize that we rely heavily upon sustainable forestry to provide material for the 3 million-plus products we get from trees (the vast majority of which is paper) and that harvesting is a necessary step in the process.

Part of that realization is recognizing that carbon dioxide generation is what we really need to be concerned about, not whether or not we should use trees. Carbon dioxide and the release of greenhouse gases are playing the greatest role in changing our climate. The real questions are: Where does carbon dioxide come from? Where does it go? Can wood be carbon negative? What is the wood products industry’s role in this?

Let’s talk carbon

Decades’ worth of data has been compiled regarding the energy that is consumed and the carbon that is generated by the manufacture of building materials, including wood. Here is how it stacks up: Wood is from trees, which are produced naturally by solar power (the sun) and irrigated naturally (by rain). In addition, trees are often tolerant or resistant to pesticides, so they are rarely used during their growth.

The land which provides the trees is replanted with more trees. In many sustainable forest management programs, thinning is done in 30 and then 60 years, and even more carbon is stored in those trees. Unlike “rapidly renewable” crops with a life cycle shorter than 10 years, decades will go by before any power equipment will have to burn a fossil fuel to go back to that place to harvest more trees. Harvesting is quick and efficient — a tree is selected, cut, sectioned and stacked in just a couple of minutes.

Most important to remember is that trees and wood store carbon. The science we all learned in grade school hasn’t changed. Like other plants, trees take in carbon dioxide from the air as they grow and give us pure oxygen in return. No fossil fuels need to be drilled for, transported, sold, barreled or processed for this natural process to occur, creating a material that has a higher strength-to-weight ratio than steel.

Put wood up against concrete, aluminum, steel, iron, plastic, glass or even brick and, hands-down, the embodied energy of wood is lower than any of those non-renewable materials by a vast margin. Meanwhile, the carbon dioxide stays locked in the wood until the wood totally decomposes. So while there are still some people who think that using wood in construction is bad, in fact, the opposite is true.

Compared to other materials, like metals, concrete, gypsum or even brick, lumber also takes relatively little energy to produce in its desired sizes. In addition, if energy is needed to power up a wood production facility, only a small amount comes from fossil fuels. Bioenergy accounts for more than half (60%) of the energy consumed while producing secondary and primary wood products in the United States — bark, sawdust, broken twigs, etc., can all be used to generate power. It is not unusual to find facilities from furniture companies and architectural millwork firms, to lumber mills and veneer plants that use the waste of trees to fuel their plants.

Because of this, it has been suggested that wood products are not just “carbon neutral,” but “carbon negative.” If you combine the facts of high energy efficiency in creating the material, low or no fossil fuel consumption to process it, and that carbon accounts for half of wood’s dry weight, you find that no other building material can boast such a great environmental story.

A Lot of Carbon Out There

If we talk about wood construction products in general, knowing about how much wood has already been used in construction and how much debris potentially was taken to landfills, it is estimated that approximately 3.5 billion metric tons of carbon are standing in construction projects, with a fraction of that as landfill waste.

When it comes to the forests, the carbon in that wood (some of it standing; some of it fallen; some of it returned to the soil) stays there until it is removed. Since we know how much forest we have, we can figure out that there is about 170 million metric tons annually, or a total of 26 billion metric tons standing or laying on the forest floor, plus nearly 29 billion metric tons already back in the soil.

We can do a life cycle assessment of various building materials from the viewpoint of, “How many kilograms of carbon emissions are generated to create one metric ton of the material?” Then we can start making comparisons. When we include everything from preparing for and gathering up the material; processing the raw material; engaging in primary and secondary processing, and adding in the transportation required to move it all around from start to finish, wood comes out on top.

Here are the figures: One metric ton of framing lumber generates only 33 kilograms of carbon emissions (or about 72 pounds). One metric ton of MDF, which requires a little more facility processing, generates 60 kg of carbon (about 132 pounds). Contrast this with steel, 649 kg; concrete, 265 kg; brick, 88 kg, and aluminum, 4,532 kg of carbon (or about 9,970 pounds) per metric ton.

The results are even more favorable if you include the carbon storage factor in considering the net carbon emissions from lumber and MDF. Framing lumber is -457 kg and MDF is -382 kg. That is negative carbon.

As woodworkers, it can be frustrating to hear customers talk about reducing our carbon footprint and to see steel and concrete commonly suggested as better alternative materials to wood by some Environmental Building Standards and Building Rating systems. There is no apparent logic here. (It is even more frustrating to wonder why other building materials are not required to comply with a certification program like wood.)

I don’t think anyone should think twice about using wood of any kind, whether certified or not, in a sustainable construction project. The big discussion is about carbon, not forest certification. If society and the construction and design industries are going to get serious about real sustainable building and real environmental impact, the discussion has to include carbon comparisons of building materials, including sequestered carbon.

This is the point we need to emphasize whenever we participate in discussions about LEED or sustainability. When more people focus on carbon, it is going to change the way we talk about wood products, trees and forestry resources.

View links to several information sources used by Fisher to develop this article. They may be of interest to others wanting to delve further into this topic. If you have questions about this article or other LEED-related topics, direct them to hkuhl@vancepublishing, and we will address them in future issues as well.

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