13 March 2013
Straight from the Forest: The Life Cycle of Hardwood Flooring (Raw Materials)
Hardwood flooring is one of the most timeless options for flooring on the market, and with its long history and continued use into the 21st century, promises to thrive as a popular product in the years to come. It is considered a sustainable resource because of the renewability of forests, but consumers often forget to consider the many different processes and materials that go into the production of the lowly hardwood floor, taking it for granted that forests will grow back at unnatural speeds and be able to keep up with the demands of the world’s growing population. A closer look into the life cycle of this product offers consumers a chance to understand this process and will, hopefully, give them the ability to make more informed choices in the future. Studies on the subject are rather scarce, however, and most detailed information comes from companies involved in the production of hardwood flooring; it is assumed that the information they provide is generally true. Due to the scarcity of information on the processes within hardwood flooring manufacture, it is also assumed that hardwood flooring production practices are approximately similar both among companies in the United States and around the world. There are innumerable varieties of hardwood flooring, ranging from solid to engineered and, within solid hardwood, also types such as strip, parquet and plank. Many different species of trees are used for lumber as well; this particular study will cover the life cycle of general solid hardwood flooring with an emphasis on the more common strip variety. Strip hardwood flooring is generally classified as flooring with surface widths of 1.5, 2.25, or 3.25 inches while plank flooring is generally wider and parquet flooring is made up of one-foot-squares of thin wood strips. Life cycle boundaries will include tree cultivation, timber harvesting, log transportation – both from forest to sawmill and from sawmill to flooring mill – on-site sawmill and flooring mill production processes, pre-finishing as well as waste management.
The life of hardwood flooring begins in the forests; this can be a privately-owned woodlot or state-owned lands. Common domestic hardwood species used for solid flooring in the United States are red oak, white oak, sugar maple, red maple, ash, birch, walnut, cherry, beech, hickory and pecan, with red oak taking up almost 70% of the hardwood market (Hubbard et al.18). Trees are produced through photosynthesis and thus require sunlight or solar energy, soil, water and carbon dioxide. Most commercial forests are monitored closely during the growth process and, depending on the situation, may require planting, thinning, and soil-cultivating. Trees must then be re-planted to replace those harvested (Jonsson et al. 248). Different techniques employed by foresters to manage forests include prescribed burning, thinning, harvesting and planting. According to the North Carolina Forestry Association, prescribed burning, or controlled fires within the forest, is beneficial in that it removes the “litter layer” at the bottom of a forest floor composed of leaves, branches and dead trees that could potentially lead to a wildfire. It is assumed that fuel for igniting a fire and transportation for the foresters, as well as other machinery, would be needed. Thinning is usually done to lower the competition between trees for resources such as sunlight, nutrients and water so that the overall forest can grow healthier. Foresters will usually thin the forest periodically, presumably by trimming branches and other plants, or by cutting down portions of trees considered to be of “lower quality” (“Forest Management”). Timber harvesting methods include clear cutting, which completely removes all trees in an area; shelterwood, where mature trees are gradually removed within a period of 10 to 15 years; seed tree harvesting, in which a few trees are left scattered to provide seeds; group selection, which is basically a small-scale clear-cut, and single-tree selection where trees are individually selected and felled. Overall, the materials used in this step of the process involve the growth and harvesting of trees, and include water, sunlight, healthy or cultivated soil and electrically- or fuel-powered machinery for transportation and forest surveying.
Loggers then cut down the trees, using different harvesting equipment including tractors, cable-skidders, cable-yarders, chainsaws powered by gasoline or a hydraulic or electric motor, and primary movers such as horses. (Visser). Afterwards the felled timber is usually transported to the sawmill through the use of log-trucks fueled by diesel, where they are sorted by human operators based on species and length and either stored or put through a debarking machine to prepare for milling. The debarking process basically removes the bark from the logs, cleaning the surface of any debris and dirt; co-products of the process are bark and wood chips that are later turned into products like landscape mulch. Each log is run through a metal detector to protect against blade damage – presumably powered by electricity – then sawn to length with a bandsaw (“Sawmilling Process”). Transportation of the lumber within the premises of the sawmill is fueled by off-road diesel, propane and gasoline. The lumber is then either shipped to the flooring mill as green lumber – which has not yet been dried – or goes through solar or air drying before kiln-drying. Trucks are usually diesel-powered, with on-site transportation at the flooring mill assumed to be fueled by the same off-road diesel, propane and gasoline (“Wood Flooring.” 5-6). Materials used in the timber harvesting and sawmill stages are thus generally fuels such as diesel and gasoline, and electricity presumably generated from fossil fuels. Water is also used in sprinkling systems or holding ponds to control the dust in sawmills.
At the flooring mill, the actual production of the lumber into hardwood flooring takes place through a series of processes: sorting and organizing, kiln-drying for green lumber, planing, ripping, trimming, molding, another sorting, pre-finishing and packaging of the final product. When the lumber first arrives at the flooring mill, it is sorted into bundles based on species, dimension and grade through the use of manual labor and fork trucks. If the lumber has not yet been dried, it goes into a conventional kiln, following an optimized schedule depending on the wood species. Kiln-drying is the most energy-intensive process at the flooring mill, and can be fueled by thermal energy from burning wood waste with industrial boilers, which can include planer shavings, sawdust, edgings, trimmings and wood flour. After the lumber has been dried, it is unstacked and destickered with manual labor or specialized machinery, then run through a planer to be cut to uniform thicknesses. Dry planer shavings are produced as a by-product of this process. The now-smooth lumber then moves on to ripping, where they are cut to uniform widths with a rip-saw, producing dry sawdust and edge trimmings, which can also be used for fuel. Trimming comes next, cutting the lumber to length with either an automated chop saw or a manual operator who checks over the lumber for defects and executes cuts. Trim pieces are produced and often used as fuel for energy production. The next process, molding, consists of side- and end-matching; these essentially produce tongue-and-grooves along the length and ends of the wood flooring so that they can be joined together. Sometimes beveling is done as a part of molding, and can make strip flooring easier to install. Wood flour is produced as a waste, and is also used either as a fuel or “value added furnish” (Hubbard et al. 11). Once the lumber has essentially become unfinished flooring, it goes through a sorting process based on species and lumber grade, done by either human operators or scanning machines, conveyer systems and holding bins.
Electricity used throughout the mill is purchased or produced on-site; coal is the most widely-used source of fuel off-site, while thermal energy comes next, followed by the use of fossil fuels such as natural gas. In the Pacific Northwest region of the United States, much energy comes from hydropower, while the eastern region uses a combination of coal, nuclear, petroleum, natural gas and hydropower, with an emphasis on coal usage. Water is also used extensively in on-site industrial boilers (Hubbard et al. 18-20). Emissions control at the mill to capture wood dust and finishing gases – for pre-finishing of the flooring – consists of the usage of cyclones and bag houses; finishing lines have closed booths to capture extra furnish and volatile substances. These emissions control devices also need to be fueled, however, and generally use fossil fuels, wood waste, electricity and water. Certain captured emissions, such as wood waste, can often be reused as fuel for boilers.
Once the hardwood strips have been cut to size and equipped with tongue-and-groove features, they can be packaged and shipped from the flooring mill as unfinished flooring or go through another process called pre-finishing. Pre-finishing involves staining or coating the wood to protect the surface and act as a sealant; there are many different types of stains and sealants, as well as many different approaches to adding a finish, and this study is by no means comprehensive. One approach is through spray booths; the unfinished flooring is conveyed through enclosed chambers, where high-pressure air is used to spray the coating. Because the booths are closed, they can better capture any extra coating material as well as solvent emissions. Large rollers, such as those used in painting, can also be used to apply a finish. Vacuum coating is another method, using pressure differentials to force the coating into contact with the wood surface. Sensors and scanning equipment, powered by electricity, work in conjunction with these methods to distribute precise amounts of coatings at precise times. The finish must then be allowed to dry, often through a process called curing, where radiant heat, drying ovens or ultraviolet light is used. According to early results of a study conducted by Richard Bergman, pre-finishing consumes large amounts of electricity through processes such as drying the stains and coatings or controlling emissions (“Wood Flooring”). As for the finishes themselves, they can be split into two broad categories: penetrating and surface finishes. Penetrating finishes and seals soak into the wood and, according to manufacturers, create extremely durable flooring; examples are Danish oils, linseed oil and tung oil. Surface finishes stay on top of the surface of the wood and include varnishes, lacquer, shellac, French polish, wax, acrylic, epoxy or catalytic finishes and the more recent urethanes or polyurethanes. Most finishes are water- or solvent-based, with environmental concerns leading to a general rise in popularity of water-based coatings (Hawks). Due to the scarcity of information on the materials used for finish production, it is assumed that similar materials are used within each category of finish. Shellac comes from a natural resin – raw seed lac – secreted by the lac insect, and may be combined with an alcohol-based solvent such as ethyl, a volatile organic substance, or denatured alcohol, which appears to be more environmentally sound. It may also be tinted with dyes or bleach, in which case the shellac is dissolved in sodium carbonate and bleached with sodium hypochlorite (Bryk).
Wastes and emissions from solid hardwood flooring production are used to produce a variety of materials such as compost, animal bedding, plywood and wood pellets or burned for boiler fuel, “electricity generation in biomass-to-energy facilities or co-firing in coal power plants” (“Wood Flooring”). The final product, wood flooring itself, can also be deconstructed by equipment such as power saws or by hand and reused as reclaimed wood; larger support beams for buildings, for example, can be turned into recycled wood flooring (Nash). Deconstruction or dismantling is different from demolition; the purpose is to salvage materials instead of clearing the land as quickly as possible. This step involves the transportation of workers, dismantling by hand or machine – which requires electricity and fossil fuels – loading of the salvaged flooring onto trucks, and transportation to a storage facility. Fuels such as coal, crude oil, natural gas and uranium are generally used to generate electricity. The energy required to produce flooring from reclaimed wood, however, is much less than that required for virgin – that is, straight from the forest – wood. Therefore, reclaimed wood reuse has a significantly lower environmental impact as well (Bergman et al.). Wood waste can also be sent to the landfill, leading to emissions such as landfill methane and carbon dioxide, presumably from the biodegrading of the wood. High amounts of chemicals and toxins integrated into wood tend to render additional, recycled uses of the wood impossible.
Despite the common misconception that solid hardwood flooring is a sustainable, environmentally-friendly option, the processes involved in its manufacture – along with the materials used and emissions produced – contribute a significant part to environmental issues such as global warming. Much of this comes from forestry and timber harvesting; because trees release oxygen while consuming carbon dioxide, the depletion of forests will naturally lead to greater levels of carbon dioxide in the atmosphere. Greenhouse gases, including carbon dioxide, are also released in large amounts when wood is burned for fuel. Production of the electricity required to power machinery, transportation vehicles and other processes also utilize large amounts of fossil fuels such as coal and natural gas, adding to environmental burdens (Nebel et al.). While hardwood flooring is relatively sound compared to other options such as linoleum, many improvements can be made to reduce the wastes and emissions generated throughout the production process, as well as to cut down on fossil fuel use. Waste management is also a problem; much wood waste enters landfills unrecorded – that is, it is nearly impossible to distinguish wood waste from the rest of the waste in landfills, and thus difficult to establish the amount of wood waste that is thrown away. Foresters can investigate and improve on tree cultivation and harvesting methods to reduce the rapid depletion of forests worldwide. Therefore, although forests appear to be renewable, they are not necessarily a sustainable resource and, with current consumption levels, can quickly become a depleted resource.
Bergman, Richard D., Hongmei Gu, Robert H. Falk, USDA Forest Products Laboratory, Madison, Wisconsin, Thomas R. Napier, US Army Corps of Engineers, Engineer Research and Development Center, Construction Engineering Research Laboratory, and Champaign, Illinois. "Using Reclaimed Lumber and Wood Flooring in Construction: Measuring Environmental Impact Using Life-Cycle Inventory Analysis." Proceedings of International Convention of Society of Wood Science and Technology and United Nations Economic Commission for Europe -- Timber Committee October 11-14, 2010, Geneva, Switzerland. Web. <http://www.fpl.fs.fed.us/documnts/pdf2010/fpl_2010_bergman002.pdf>.
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Hubbard, Steven S., and Scott A. Bowe. Life-Cycle Inventory of Solid Strip Hardwood Flooring in the Eastern United States. Rep. N.p.: n.p., n.d. Nwfa.org. National Wood Flooring Association. Web. <http://www.nwfa.org/LCA_solid_wood_FINAL_REPORT.pdf>.
Jonsson, A., A-M Tillman, and T. Svensson. "Life Cycle Assessment of Flooring Materials: Case Study." Building and Environment 32.3 (1997): 245-55. ScienceDirect.com. Chalmers University of Technology, 6 May 1999. Web.
Jurgensen, M. F., A. E. Harvey, R. T. Graham, D. S. Page-Dumroese, J. R. Tonn, M. J. Larsen, and T. B. Jain. "Review Article: Impacts of Timber Harvesting on Soil Organic Matter, Nitrogen, Productivity, and Health of Inland Northwest Forests." Forest Science 43.2 (1997): 234-51. Ingentaconnect.com. Society of American Foresters. Web.
Nash, Jenny. "Unique Recycled Hardwood Floors." Hgtv.com. Scripps Networks, LLC, n.d. Web. <http://www.hgtv.com/kitchens/recycling-history-for-unique-earth-friendly- wood- floors/index.html>.
Nebel, Barbara, Bernhard Zimmer, and Gerd Wegener. "Life Cycle Assessment of Wood Floor Coverings - A Representative Study for the German Flooring Industry (11pp)." The International Journal of Life Cycle Assessment 11.3 (2006): 172-82. Link.springer.com. Ecomed. Web. <http://link.springer.com/article/10.1065/lca2004.10.187>.
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Visser, Rien, Dr. "Timber Harvesting (Logging) Machines and Systems." Timber Harvesting (Logging) Machines and Systems. Virginia Tech Forestry, Sept. 2007. Web. <http://web1.cnre.vt.edu/harvestingsystems/>.
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Embodied Energy in the Process of Hardwood Flooring
Hardwood flooring is one of the most common flooring in our life. The processes of produce hardwood flooring are very complex. Those processes from beginning to end of produce hardwood flooring embody different energy. My research is focus on the energy that embodied in the process of hardwood flooring.
From the article “Green Speak”, the embodied energy means “the sum of the energy necessary to make a product, from the raw material extraction to the manufacturing process to shipping it to its point of use. Embodied energy is part of Life Cycle Analysis, which follows the product’s environmental impact from raw material extraction all the way through its use and its ultimate disposal or reuse” (KEN 2008). The embodied energy of the hardwood flooring life-cycle is based on the flowing parts, the raw materials acquisition, the manufacturing, processing, transportation, recycle and waster management.
The primary raw material of the hardwood flooring is the wood from angiosperm trees. There are many kinds of hardwood species such as ash, pine, oak, maple and cheery. These primary raw materials can make two kinds of hardwood flooring, which are solid hardwood and engineered hardwood. Because of solid hardwood maintained properly and easily last a hundred years, it have been used for centuries. “They are a solid piece of milled hardwood which is precut in a tongue and groove shape which allows easy installation. They can be purchased in finished or unfinished condition. The main advantage of a solid wood floor is its life span” (MARC, 2013). Different from solid hardwood, engineered hardwood flooring is made of several layers of wood that are glued and compressed together and topped with a veneer. “A veneer is a decorative thin slice of wood applied to the core material which will provide you with the look of solid wood. The separately glued layers do provide certain advantages such as sound isolation, increased comfort level, and protection against moisture” (MARC, 2013).
The raw materials acquisition associated with the Greenhouse Gas (GHG) are GHG emissions from energy used during the raw materials acquisition and manufacturing processes. “Hardwood flooring manufacture is accomplished through a series of unit process. A unit process may be thought of as a machine center, a work cell or a specific operational task which both requires and modifies a material input in some way” (HUBBARD and BOWE 8). The manufacturing processes of hardwood flooring are fellow the flowing basic steps. First of all, harvested wood from forests and hardwood logs are transports to a sawmill. Then, at the sawmill, the first thing need to di is bucking the hardwood to length. The wood cutting machine will embodied the energy. And then limbing, transportation, decking and sawing. There are three major ways to sort the wood, head saw, head rig and primary saw. In this step, it use the kinetic energy. The same energy also shows in the next step, which called edging. The following steps are trimming, drying, planning smooth to the lumber and transportation to the flooring mill. The thermal energy from these processes is wood residue produce on-site used to fuel on-site boilers, and electricity is main source of energy. When flooring mill received the lumber, “manual labor and fork trucks are used in this process. The output of this unit process is stacked green lumber ready for kiln drying or kiln dried lumber ready for planning. (HUBBARD and BOWE 9). According to the figure in the article “Life-Cycle Inventory of Solid Strip Hardwood Flooring in the Eastern United States”, we will know that the process of flooring mill starts with stacked and stickered green lumber. This process called drying. The energies included in the drying process are “kiln and transportation maintenance, handling of kiln emissions, and transport of the newly dried lumber” (HUBBARD and BOWE 9 -10). The next step is called ripping. “Ripping involves feeding dry, planed, random width lumber along its length through a rip-saw to create stock of desired and uniform widths” ((HUBBARD and BOWE 10). After ripping is the process called trimming. “Trim pieces generated by the cuttings serve as a useful byproduct and are ofen sent to in house systems dedicated to energy production” ((HUBBARD and BOWE 10). When finished timing the wood, the next step is moulding. “Because it changes the profile of the wood stock so drastically, the moulding process is among the most critical value adding activities in secondaty wood processing” (HUBBARD and BOWE 10). The next step is sorting, this process may include manual labor, scanners, conveyer systems, and holding bins. The last step is packing. “Packaging provides a final chance to sort and grade the end product” (HUBBARD and BOWE 12). The embodied energy from is step is manual labor and transportation.
The hardwood manufacturing processes has been estimated that “a representative flooring operation realizes yields of roughly 50% of the original raw lumber input. Co-products associated with the process including trimmings, edgings, planer shavings, wood flour, and sawdust are considered useful and given careful attention. They may be sent to energy producing systems for use in the plant or serve as raw material furnishes for other value added wood products such as particleboard, animal bedding, or medium density fiber board” (HUBBARD and BOWE 8). The energy of Greenhouse Gas (GHG) emissions used to transport raw materials of hardwood flooring, and non-energy GHG emissions resulting from manufacturing processes. According to the article “Wood Flooring” estimated in Vanta and Nesbit, for virgin hardwood flooring, process energy GHG emissions result from wood harvesting, lumber production, planning ripping, trimming, and molding (WOOD 3).
In addition, the most prevalent form of energy used in the system boundary for hardwood flooring manufacture is electricity. “Purchased electricity is a key source and is used to operate conveyance and pneumatic equipment as well as saws, planers, matchers and emission control devices” (HUBBARD and BOWE 18). “The largest off-site energy source used to produce this electricity is coal. Thermal energy produced by combusting wood in on-site boilers is second followed by the fossil fuels natural gas and fuel oil #6. The eastern region produces most of its electricity through a variety of fuel sources. Unlike the Pacific Northwest region, little is produced by hydropower. The average composition of off-site electrical generation was determined for the eastern region by averaging United States Department of Energy values given for the North East/North Central region and those reported for southeastern states” (USDOE 2006).
According to the article “Life-Cycle Inventory of Solid Strip Hardwood Flooring in the Eastern United States” by Steven S. Hubbard and Scoot A. Bowe, the Major fuel sources used to produce the purchased electricity were coal, nuclear, petroleum, natural gas, and hydro. In addition, the energy sources of hardwood flooring manufacturing process also include “Energy use associated with kiln drying the hardwood lumber is accounted for in the cumulative system boundary through a hardwood lumber production model input” (Bergman & Bowe 2007a). “With the exception of one mill, all used industrial boilers to combust wood residue (hogged fuel) generated on-site to provide the thermal energy. On-site forklifts, trucks, and carriers relied on gasoline, diesel fuel, and liquid propane gas” (HUBBARD and BOWE 18-19).
After the manufacturing if hardwood flooring, transportation is the next step of the hardwood flooring’s life- cycle. Huge amount of energy embodied from this step. “Transportation emissions are generated from transportation associated with wood harvest, on-site transportation during lumber production and flooring manufacture, and transportation to the retail facility” (WOOD 3). The prime movers of transport hardwood flooring materials are human beings and animal power. There are many kinds of secondary movers, such as trucks, tractor, chain saw, cable yarder, skidder and so on. Some of these transportation use for transporting the hardwood materials after logging, and some of these transportation use for transporting the hardwood flooring after the manufacturing process. It is so called retail transportation. “The RMAM calculation in WARM also incorporates “retail transportation”, which includes the average truck, rail, water, and other‐modes transportation emissions required to transport wood flooring from the manufacturing facility to the retail/distribution point, which may be the customer or a variety of other establishments (e.g., warehouse, distribution center, wholesale outlet)” (WOOD 3). From the chart “Retail Transportation Energy Use and GHG Emissions” in article “Wood Flooring”, the energy of average miles per shipment is 250, the energy of retail transportation energy (million Btu per short of product) is 0.27, and the energy of retail transportation emissions (MTCO2 E per short ton of product) is 0.02. In addition, from the article “Life-Cycle Inventory of Solid Strip Hardwood Flooring in the Eastern United States” by Steven S. Hubbard and Scott A. Bowe, truck is mostly use for delivering hardwood lumber. “Delivery of the hardwood lumber from sawmills to the flooring mills was by truck. None of the mills reported delivery by rail. The averaged one-way delivery distance for the lumber was 283 km (176 mi). Mills reported that these trucks are empty on their backhaul. Burdens associated with this transportation are included in the cumulative system boundary but omitted from the on-site boundary analysis.” (HUBBARD and BOWE 17). And from the l hardwood flooring life-cycle, transporting waste is also part of the transportation step.
In every step of hardwood flooring’s life-cycle, it will produce waste. The energy is embodied from the waste and recycle of the hardwood flooring. The use of wood generates a large amount of waste. “In 2002. Nearly 63 million metric tons of solid wood waste was generated in the manufacture, use, and disposal of solid wood products in the United Stated” (FALK and McKEEVER 31). The wastes wood comes from a variety of sources and in a variety of forms. “Its principal sources are two waste streams: municipal solid waste (MSW) and construction and demolition (C&D) waste. Each generates distinctly different types of wood waste, with differing degrees and levels of recyclability” (FALK and McKEEVER 31).
The United States uses a large amount of wood waste produce is also large. “In the last decade, interest has been growing in utilizing this resource and millions of tons of solid wood waste are available for recycling into a myriad of products. Through the production of landscaping mulch and fuel are the dominant markets for recycled wood, reuse of solid lumber for structural use and for remanufacture into value-added products is also growing” (GALLIS 39).
The waste from the raw material of the hardwood flooring can be made into wood pallet. “About 50 percent of wood leaving the wood flooring manufacturing process was wood residue; therefore, the wood residue carries 50 percent of the burden from the wood flooring manufacturing process” (REED, BERGMAN, KIM, TAYLOR, HARPER, JONES, KNOWLES and PUETTMANN 282).
There are many methods of recycling the wood flooring. “Wood flooring that is in good condition at the end of a building’s life can be recycled by using deconstruction or hand demolition to remove the flooring, followed by de‐nailing, before reselling the wood for additional use” (WOOD 8). People often think Construction and demolition waste are similar because both of them are typically discarded together in landfills. But they are different. “ Since construction and demolition wasters originate from distinct types of activities, have different characteristics, and differ in their ease of separation, recovery, and recyclability, they are in fact different” (FALK and McKEEVER 34). For recycling the hardwood flooring, “large wooden support timbers recovered from buildings prior to demolition can also be re-manufactured into wooden flooring” (WOOD 8). According to the “Wood flooring” article, although hand recovery of wood flooring is the most common procedure, during deconstruction heavy equipment can also being used to recover good-quality timbers and other kinds of materials.
In addition, composting is another way to recycle the hardwood flooring waste. From the article “Wood Flooring”, wood flooring’s waste from C&D projects that has not been treated with chemical preservatives can be chipped or shredded for composting. Beyond that, combustion is also a useful method to recycle hardwood flooring’s waste. “Flooring and other wood wastes form a part of ‘urban wood waste’ that is recovered from demolition sites or at C&D material recovery facilities, sized using wood chippers, and used as boiler fuel or combusted for electricity generation in biomass‐to‐energy facilities or co‐firing in coal power plants” (WOOD 8). According the chart “Components of the Combustion Net Emission Factor for Wood Flooring”, there is non combustion emission factor of raw materials acquisition, manufacturing, CO2 from combustion and steel recovery. In the other hand, the largest combustion emission factor is transportation to combustion, which is 0.05a(MTCO2E/Short Ton). Similarly, the landfilling emission factor for wood flooring is also transportation to landfill.
From the life-cycle of the hardwood flooring, there are many kinds of energy embodied from the hardwood flooring process. These energies are inputs of the hardwood flooring life-cycle system.
Bergman, Richard D., and Scott A. Bowe. 2007a. NE/NC hardwood lumber model. University of Wisconsin, Madison. SimaPro Version 7.0.2.
Falk, Robert H.; McKeever, David B. 2004. Recovering wood for reuse and recycling : United States perspective. European COST E31 Conference : Management of Recovered Wood Recycling Bioenergy and other Options : proceedings, 22-24 April 2004, Thessaloniki. Thessaloniki : University Studio Press, 2004
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March 13, 2013
Wastes and Emissions of Hardwood Flooring
Many people may have the misconception that because hardwood flooring is dealing with trees, there aren’t major harmful emissions that are contributing to the Earth’s pollution. Of course, this is not the case at all. For many years, harmful greenhouse gases have been affecting the atmosphere, one of them being due to the production of hardwood flooring. The process of developing hardwood floors begins with the cultivation and harvesting of different types of trees, such as red oak or ash. The next step is to transport the lumber to sawmills. At the sawmills, the lumber is cut, trimmed, and smoothed. Often, the wood can be dried in the mill; if not, they are transported to flooring mills and dried there. It is there at the flooring mills that the hardwood floor is finished. In many ways, the process of hardwood flooring development is establishing ways to recycle wastes in order to make up for the environmental damage caused by emissions; however, it still continues to have its harmful effects.
In the development of hardwood floors, there is almost always waste produced through the cutting and shaping of the lumber. However, the waste does not remain waste; oftentimes, the wood waste is recycled for other uses. Some wastes include logging activities include used oil, tires, scrap metals, and soiled equipment, such as hoses and oily rags. (GEDEON 7). The use and maintenance of specialized machines creates wastes such as oil or other fluids, solvents and detergents, soil packaging and equipment, used tires and scrap metals. (GEDEON 2) Because these materials are not wood, they cannot be recycled. As for the wood products, there are many ways that they can be useful. For example, wood wastes can be used as “boiler fuel or combusted for electricity generation in biomass-to-energy facilities or co-firing in coal power plants” (Environmental Protection Agency 8). In the National Pollutant Inventory’s document, it states that “shavings, sawdust, and chips can be used in paper mills and reconstituted wood panel manufacturing plants, or used as fuel for boilers or for heat plants” (2). Figure 1 at the end of the essay illustrates this. Not only are these wood and chips are used in bio-mass and coal power plants, but they may also be used in utility boilers. This may seem better for the environment as it reduces fossil fuel emissions and also makes use of the scraps of unused wood; however, there are still emissions being released into the air. Other wood wastes include “chemically treated wood from railroad ties, telephone and utility poles, and pier and dock timbers, untreated wood from logging and silvicultural operations, chipped brush and limbs from utility right-of-way maintenance, and industrial waste wood,” in which parts of the material is often “reused, burned, or discarded in hazardous waste landfills but much is left on site” (Falk and McKeever 36). More and more manufacturers for hardwood flooring are trying to reduce waste by recovering their wood products. Recovered wood is “dominated by production of landscaping mulch and waste wood for fuel. Chipped or shredded wood is also used as a composting bulk agent, sewage sludge bulking medium, and animal bedding.” (Falk and McKeever 37) It also can be used to manufacturer value-added products, such as medium density particleboard and fiberboard. (Falk and McKeever 37) For instance, the Willard Brothers Woodcutters in Trenton, New Jersey recovered products that included “usable lumber (produced from logs), firewood (from large topwood), mulch (from branches), and sawdust, which is sold to local horse owners for use as bedding” (Solid Waste Association of North America 7). Through this, they are making use of all materials, which ultimately aims at helping the environment and economy.
In more specific terms, the Solid Waste Association of America sorts out the wood waste and its uses in its document Successful Approaches to Recycling Urban Wood Waste. In regards to lumber, it states, “A desirable option for wood waste management would be to reuse the structural or architectural elements, which include castings, banisters, and molding. Large timbers from older or unique structures can salvaged and reused as structural elements in new buildings” (Solid Waste Association of North America 2). Through this, the scraps are used in ways in which they initially were intended to be used. Another option for wood waste is “feedstock for engineered wood. Engineered wood is the term given to material derived from smaller pieces of wood that are bound together through a variety glues, resins, and other chemicals to make a wood-like product” (Solid Waste Association of North America 2). Examples of this include oriented strandboard, glue-laminated timber, laminated lumber, wood I-joists, particleboard, and finger-jointed studs. On in particular, particleboard, is made up from “wood particles of various sizes that are bonded together with a synthetic resin such as urea-formaldehyde” (National Pollutant Inventory 3). Most of this product is made up of wood residue, which “is ground into particles of varying sizes using flakers, mechanical refiners, and hammer mills” (National Pollutant Inventory 3). In addition, wood waste can be used as mulch or compost feedstock. The document states, “Chipped wood and bark are common mulches. Wood is an excellent bulking agent for composting, although a nitrogen source usually needs to be added.” (Solid Waste Association of North America 2). Importantly, the wastes can be used as biomass fuel. It states, “Ovendry wood produces about 9,000 Btu/lb when burned, and it can be converted to liquid or gaseous fuel. In addition, different forms of solid fuel such as charcoal are possible” (Solid Waste Association of North America 2). In this way, wood is used for power. Although it may seem better in comparison to fossil fuels used for energy, carbon dioxide is still released, contributing even more to global warming. Lastly, miscellaneous uses for waste wood include “alternative daily landfill cover, animal bedding, wood flour filler for plastic products, and a source of biofuels and chemicals” (Solid Waste Association of North America 2). It is vital that hardwood flooring manufacturers recycle wastes. Overall, wooden pallets seem to show the most success in the United Sates with wood recycling (Falk and McKeever 37). Not only can money be saved as landfill costs are avoided when recycling, but it also has many environmental and natural resource benefits. The environmental benefits are “most noteworthy when wood waste is used to displace coal for electricity or steam generation” (Solid Waste Association of North America 3). By recycling it this way, sulfur and carbon dioxide emissions are reduced. Because greenhouse gases, especially carbon dioxide, contribute to global warming, it is important to reduce any harmful emissions. As for the natural resource benefits, recycling the waste conserves the materials and puts them into other uses. New markets for wood waste, such as the pallet market, give forest owners “more opportunities to offset the costs of sustainable forest management and improve the overall health of the forests” (Solid Waste Association of North America 3). This ultimately helps maintain a stable environment.
As recycling continues to take place at the hardwood flooring mills, there are still emissions that are put out into the atmosphere. Many of the emissions are illustrated in Figure 2 in the end of the essay. In the National Pollutant Inventory’s document, it says, “In mills where chips or other furnish is generated on-site, operations such as debarking, sanding, chipping, grinding, and fibre separation generate particulate matter (PM10) emissions in the form of sawdust and wood particulate matter. Emissions to water include surface waters (eg. lakes, rivers, dams, and estuaries), coastal or marine waters; and storm water. (National Pollutant Inventory 6) Many of the emissions to land include “surface impoundments of liquids and slurries, unintentional leaks and spills” (National Pollutant Inventory 6). These instances are more likely to occur during the logging and transportation stages of the process. However, the majority of emissions from panel products come from the dryers and presses” (9). Based on this, most of the emissions come from the mills themselves. According to the National Pollutant inventory, “emissions from rotating drum wood chip dryers used in reconstituted wood panel facilities, are composed of wood dust, condensable hydrocarbons, fly ash, volatile organic compounds (VOCs) and products of combustion such as carbon monoxide and oxides of nitrogen if direct-fired units are used” (9). The organic portion of the emissions includes methanol, acetic acid, ethanol, and formaldehyde. The substances that are often emitted from saw-milling include volatile organic compounds (VOCs), oxides of nitrogen, carbon monoxide, sulfur dioxide; and particulate matter (PM10). (National Pollutant Inventory 9) These emissions are formed during the shaving, cutting, and drying process. In reference to the wood waste being used as fuel, the combustion of wood emits biogenic carbon dioxide and nitrous oxide emissions. (Environmental Protection Agency 8) These greenhouse gases being emitted into the air are harming the atmosphere and contributing to global warming. Other emissions, such as those that come from hot presses consist primarily of condensable organics. As described in the document, “When the press opens, vapors that may include resin ingredients such as formaldehyde, phenol, and other organic compounds, are emitted to the atmosphere. Formaldehyde emitted through press vents during pressing and board cooling operations is dependent upon the amount of excess formaldehyde in the resin, application rates, the nature of the specific resin formulation, as well as press temperature and cycle time” (National Pollutant Inventory 10). The emission being released into the atmosphere proves no good to the environment. Lastly, NPI-listed substances are likely to be emitted from wood preserving. Many of these substances include copper, chromium III, chromium VI, arsenic, ammonia, toluene, xylene, and polycyclic aromatic compounds (National Pollutant Inventory 10). In reducing the emissions that are put into the air, air emission control technologies are used. According to the National Pollutant Inventory, “Air emission control technologies, such as cyclones, electrostatic precipitators, fabric filters or baghouses, and wet scrubbers, are commonly installed to reduce the concentration of particulates in process emissions” (National Pollutant Inventory 10). This is used to lessen the harmful effects of the emissions that are being released. Unfortunately, it can only do so much, which only lets emissions to continue being released into the air and harming the atmosphere.
As a result, the waste that comes out of the hardwood floor process proves to be efficient; however, it does not fully prevent the harmful emissions that are contributing to global warming. Although it does not eliminate harmful emissions into being released in the atmosphere, recycling provides an option to reduce any harmful effects to the overall environment. There are so many types of substances that are being released that recycling wastes barely does anything to make up for it. Throughout this project, the most difficult part of my research was finding specifics on hardwood flooring’s wastes and emissions during its logging period. I was unable to find as many sources for it as I would have liked. I also would sometimes confuse myself in the overall processes of how the hardwood flooring is made. I was unsure as to where they would actually shape the wood or dry the wood. All in all, I was able to gain a good amount of information towards the topic. It gave me a broader perspective on how the making of a certain product can have such an impact on the whole world.
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