Environmental Impact of Wood Products
We look at wood as a solution, not a problem
When making a material selection, neither design professionals, nor the general public recognize the efficient role wood has in reducing global warming, as well as the economic contribution it makes to our economy. Wood has many positive attributes in this regard over other common building materials. Besides being beautiful to look at, it is one of the greenest building materials we have available for furniture, construction, as well as other commodities. Looking at how much embodied energy is in a product is one of the best ways to measure how green a product is. Wood has very low embodied energy, and a very low carbon impact. Wood is both renewable and sustainable when good forestry practices are followed. While other materials may be recyclable, most are not renewable: wood is renewable. Processing wood requires less embodied energy than using either recycled metals or plastics. Much of our attention in the green movement has concentrated on reducing energy consumption through the use of insulation and more efficient appliances, and unfortunately, not on the use of more environmentally friendly materials. Recognizing that we can utilize materials that are positive for the environment has been somewhat overlooked. Wood products have very low embodied energy, and play a vital role in terms of carbon impact to the planet, and wood is renewable, not just recyclable. If it is burned for energy at the end of its useful life, it can be a substitute for fossil fuel. Burning wood produces 0.62 units of carbon for each unit of carbon in the wood less than natural gas. www.corrim.org/pubs/articles/2013/fpj-d-12-00093.pdf
In the United States, there is a general misconception that trees are being cut down faster than they are regenerating. In reality, trees in the United States are regenerating faster than they are being harvested. The Forest Inventory and Analysis (FIA) program implemented by the United States Forest Service is a Federal Government program administered by the USDA which regularly monitors the conditions of the nation’s forests. Their methodology is comprehensive and statistically verified. It is widely acknowledged to be a model for this kind of study. www.fia.fs.fed.us/library/bus-org-documents/docs/FIA_Annual_Report_2013.pdf the Forest Products Lab has studies going back to the 1950s, and has published the report: “National Measures of Forest Productivity” to support these claims. In their study; they showed that the current total forest growth is only slightly affected by the current harvesting because the trees being harvested are only a fraction of the total growing stock. The American hardwood living tree inventory is increasing with new growth exceeding removal by greater than a 2:1factor. The USDA Forest Products Laboratory in Madison WI has found that areas with active wood products industries had the least amount of deforestation. When properly managed, forests can yield durable and useful products indefinitely. Hard wood forests in the United States are growing faster than we are harvesting them, and we are under-utilizing one of the greenest materials available to us today.
For comparison, soft wood is more in demand than hard wood. Soft wood forests are also more productive because they are intensively managed. Hard wood forests are not being managed as well because the demand for hard wood is not great enough. The study notes that because hardwood timber stands are not being managed as actively as they could be; they are dense and mature and therefore; productivity has declined. If more select cutting were to take place, the forests would open up and new growth would continue. However, either way, our forests are growing.
Concerns have been raised about illegal harvesting of trees. To find out if this is a concern in the United States, the American Harwood Export Council (AHEC) commissioned a study to find out the extent of this problem. They published the results in the "Seneca Creek Study". The study was taken by a team of independent analysts and experts in the field of U.S. forest policy and forest certification and then subjected to a process of peer review. This report demonstrated that the amount of timber taken illegally in the United States is much less than 1% of the total hardwood production. The U.S. Government enforces the Lacy Act which bans the trade of illegally harvested timber. Forests that have mature trees harvested become more open and allow new trees to start growing and take the place of the ones that were removed. Because a mature forest has a very shaded floor, it is difficult for new growth to start. With little new growth, more decomposition takes place which accelerates the release of carbon back into the atmosphere.
There are countries that do have issues with deforestation and or illegal tree harvesting, but this is not true for all forests on the planet. One country where this is true is Thailand; there are reports that as much as 90% of the timber harvested in Thailand is harvested illegally. If there is an economic benefit to keeping a forest as forested land, then the forest is not as likely to be converted into grazing land, agricultural land, or other types of development like shopping malls or sub divisions. Ironically this land is often unsuited for either grazing or agricultural purposes and poses a much greater threat of soil erosion when the forest is completely removed. Converting forests into land for other uses is much more damaging to the environment than select cutting hardwood trees for furniture. Not only do we lose the trees but the wildlife that used to live there is displaced as well. The land would be better served for silviculture: the cultivation of forests and trees.
Embodied energy is the amount of energy required by a material to process it into a useable form. Wood requires far less embodied energy than other materials such as steel, aluminum, or plastic. Solid wood has the lowest embodied energy of all wood products; plywood and MDF have more embodied energy than solid wood because they require more steps in their manufacturing process; but still use far lower amounts of energy compared to many other materials. The sun provides the direct energy to grow the trees. Although electricity and fossil fuels are required for wood production; the wood industry is a leader in the use of bio-energy. The energy is created by utilizing tree bark, sawdust, and other wood waste (knots, planer shavings, and scrap). The U.S. wood products industry is both the nation’s leading producer as well as the consumer of bio-energy. Bio-energy is considered to be carbon neutral. Bio-energy makes up over 60% of the wood industries own energy needs. (see: Table 1-1). Many companies have been practicing this conservation for decades. Michigan Chair has been burning its wood waste in a boiler to provide heat for our dry kilns, steam for the bending process, as well as heat for the building during winter since 1972. Every time wood is substituted for either steel or aluminum, energy is saved, and emissions are avoided.
Our forests play a major role in the Earth’s carbon cycle. The process of photosynthesis removes carbon dioxide from the atmosphere and converts it into sugars for tree growth; it then releases oxygen back into the atmosphere. The standing trees, forest litter, and other woody debris in domestic forests have sequestered approximately 26 billion metric tons of carbon. The forest soils contain even more sequestered carbon contributing another 28.7 billion metric tons. Between 1995 and 2005 just the forests sequestered carbon at a rate equivalent to about 10% of our total national carbon emissions. The carbon in a wood product remains bound up for its useful life. The carbon is only released when it is used as a fuel, or sent to a landfill where the carbon is released during decomposition. The Consortium for Research on Renewable Industrial Materials found that different methods of forest management affect how much carbon is sequestered. They found that shorter rotations in harvesting sequester more total carbon than longer rotations in harvesting. More select cutting and forest management would increase the amount of carbon sequestered in wood, but demand for wood products needs to increase for this to happen.
Values are based on a life-cycle assessment and include gathering and processing of raw materials, primary and secondary processing, and transportation.
Source: EPA (2006)
From Bowyer and others (2008); a carbon content of 49% is assumed for wood.
The carbon in wood will eventually be emitted back to the atmosphere at the end of the useful life of the wood product, the same is true if the dead tree were to decompose in a forest.
With proper management, our forest resource is renewable, and the production of wood products can be maintained indefinitely. Plastic, which uses fossil fuels as feed stock, and metals cannot make the same claim. Our forests could be even more productive if they were actively managed by harvesting the mature trees. There are several programs that ensure that this is done in accordance with best land management standards. These include the Forest Stewardship Council (FSC), Sustainable Forestry Initiative (SFI), and the American Tree Farm System (ATFS). We purchase all our lumber from local sawmills within a 200 mile radius, and only from SFI certified saw mills.
The National Association of State Foresters in the USA passed a resolution in 2008 supporting all of the forest certification systems listed above. http://www.stateforesters.org/policy-statement-forest-certification-it-contributes-sustainable-forestry-oct-2008 Over 90% of American hardwood logs are sourced from private land owners. Primarily these are family owned wood lots of less than 25 acres (less than 10 Hectares). A limitation of the FSC certification is that to acquire their certification numerous biological profiles must be undertaken which can exceed the commercial value of the trees to be harvested on these small wood lots. These studies are only economically viable for large wood lots. FSC certification is also more expensive to acquire and maintain than some of the other certifications available. We find it lamentable that the United States Green Building Council does not recognize this reality and allow for other certifications to be admissible in their audit. Requiring FSC certification increases the cost of the harvested timber, increases the cost of manufacturing, and also increases the cost of the product to the end consumer. Studies have shown that deforestation is not a widespread problem in either the United States or Canada, and the Forest Stewardship Council is not the only responsible party.