Raw materials and other materials used in the production of Skis.
Max Connor, group member #1
There are many approaches to manufacturing skis in the U.S. The use of materials, methods of production and distribution vary widely with each company. Our group chose to base our production methods off of Skibuilders.com, a website that group member Brian Wang is affiliated with because a friend of his co-founded the site. Skibuilders.com is a resource that demonstrates how to produce skis for small-scale production like personal use, work orders and niche market demographics. The site provides a breakdown of the materials used in skis and how they are layered, processed and produced to form a pair of skis. My research chronicles the raw materials and secondary materials that are processed into skis. There is limited material on the reuse, recycle and waste of these materials because of the undeveloped methods of disposal. Because the information and resources of disposal are very limited I will center my research on the materials used and gain insight into their derivatives and how their properties are beneficial to the ski.
The base layer, epoxy, composites, wood core, top sheet, and metal edges combined together in this order form a ski. Each of these elements of the ski is unique in their function and properties. When their unique qualities are combined together the result is a highly durable and flexible pair of skis ideal for their use on the snow.
The production of the ski begins with the construction of the base layer. The base material of the ski is a thin sheet of plastic made from sintered or extruded UHMWPE. UHMWPE or ultra-high molecular weight polyethylene in powder form is derived from a “virgin polymer manufactured from a homopolymer of ethylene, while the fabricated forms are manufactured from the same UHMWPE powder but without any stabilizers or processing aids.” A chain of UHMWPE consists mainly of hydrogen and carbon molecules. The material derives its name from the properties high molecular weight. While the weight of the material is dependent on the grade of the material, there are typically 40,000 atoms on its molecular chain. This long chain allows for large load capacities because the weight of an active force is distributed/transferred along the chain or polymer , which makes the material highly durable and impact resistant. Furthermore, the properties characteristics are a “low coefficient of friction, high wear resistance, good chemical resistance, resistance to environmental stress cracking, dimensional stability over a wide temperature range and high energy absorption at high stress rates.” The structures simple molecular construction makes it resistant to water and ideal for maintaining the materials integrity on snow. Due to the materials wetness resistance not any type of glue can be used to bind the elements of the ski together.
Epoxy resin is the glue like substance that is used in the production of skis to bind parts together. The substance is formed when epoxy and a polymer are combined. The epoxy resin consists of the two chemical properties epichlorahydrin and bisphenol-A. The resin is the material that provides the qualities epoxy is known for, water and heat resistance, while the polymer is the compound that activates the resin. When the two substances are combined the polymer latches on to both ends of the epoxy and makes the resin harden. “In most epoxy resins the polymer is a smaller molecule called diepoxy. Some epoxy groups can have up to 25 polymer groups, but the common household adhesive usually has one.” The consistency of the polymer is dependent upon the amount of polymers used, the more polymers the harder the substance becomes. These chemicals must maintain separated until their application because they will harden when combined (See Image 1). This process takes a quite a while and is referred to as curing.  When the two solutions are done curing you’re left with epoxy, a substance that is commonly used to form molds, bind skis, fiberglass, and minerals composites on circuit boards. 
Composites are synthetic fabrics that are placed above and below the ski’s wood core to provide torsional support to the ski. The synthetic materials that are most commonly used in ski production are Kevlar, fiberglass and carbon dioxide. Because the wood found in the core of skis have a one directional grain and are placed vertically they have no lateral support. Carbon dioxide, Kevlar and fiberglass are the synthetic composites that provide the lateral support skis need because they are not one directional. Their synthetic fabrics are woven into multi-directional patterns to provide lateral support to the ski; the more directions in the synthetic weave the more lateral support the ski has. There are two, three and four directional composites (see image 2). When combined with epoxy the material cures into a strong material along the direction of the fabric’s fibers, which augments the strength of the bind. Kevlar is most commonly used in small production skis; it was registered for copyright by Dupont in 1965. The properties of its molecular formula is “[-CO-C6H4-CO-NH-C6H4-NH-]n”. This formula is synthesized by a solution of the “the monomers 1,4-phenylene-diamine and terephthaloyl chloride”. This chemical process causes a condensation reaction that yields hydrochloric acid as a byproduct. The result of this process is Kevlar, a material that is five times stronger than steel and is more malleable and versatile because of its plastic properties.
Sandwiched in between the composites is the core of the ski. The core is typically composed of wood or foam. However, today wood is the preferred material because it provides more durability, flexibility and response. This is the only raw material used in the production of the ski and is far cheaper and beneficial than its synthetic counterpart (foam). The amount of wood necessary for the construction of the wood core is one and a half times the combined width of the skis plus the length. You need 150% more wood than the combined width because when sawing the shape of the ski it is important to have excess room for efficient production.
The most common tree species for core production are: ash, maple, birch, spruce, aspen, fir, and poplar. When choosing the species it is important to account for the woods “stiffness (modulus of elasticity), strength (modulus of rupture), and weight (density)” because each species produces different results and is reflective of personal preference and sport (downhill, slalom and freestyle skiing). The wood is composed of vertical strips of laminated wood to increase consistency by reducing directional grains and knots found within the wood. This process allows for customization because you are allowed to incorporate multiple species of woods for different results. For instance, a core may be constructed with sweet birch in the center and black ash on the outside. Sweet birch has a density of .714, which allows for maximum energy transfer from underneath the bindings while the black ash on the edges of the board has a high elasticity of 1126 kg/mm2, which provides flexibility for carving. On the outside and between each layer of wood there is an epoxy that forms the cores laminate. Because epoxy is twice as dense as wood, there are multiple approaches to the ratio of these materials that are used in ski construction. A core with thins strips of wood has reduced deficiencies within the wood but a larger weight because of the epoxy. The thicker wood strips weigh less but are not as torsionally stiff. The different affects of these ratios provide different results that are tailored to different styles of skiing.
The next step in the production process is the top layer of the ski. This layer serves as a platform for graphics and protection against UV radiation. The top sheet is made out of Ptex, which is a plastic composite patented in the 1960’s specifically for the use of ski production. At the time of its patent, foam ski cores were the industry standard and they had a chemical memory. This caused them to revert to their production state (flat) over time and whenever pressure was released from the ski, i.e. the bindings being released. The Ptex encapsulated the foam core and caused the ski to maintain its bent shape, specifically at the tips. Since their invention, skis have returned to wood cores and no longer need Ptex to completely encapsulate the whole ski. However, today Ptex can still be found on the layer for skis. Ptex is a highly dense polyethylene that binds well with epoxy. Combining many multiple of monomers of etherene until they combine and break down millions of times on the atomic level makes Polyethylene. This process is called polymerization and is a quick process once all of the materials are combined properly.
The edges of skis are rimmed with steel to allow the ski to penetrate the snow with ease and increase the radius of the turns a ski is able to make. Mixing a multitude of metal composites with oxygen in high heat forms molten steel. The steel is carried across the production line in a ladle where it is sent to pretreatment, where a blast furnace is used to treat the metal’s impurities: phosphorous, sulfur, and silicon. In desulfurising, pretreatment powdered magnesium is added to the molten iron and it reduces the sulfur into magnesium sulfide. The magnesium sulfide is released through the steam and what’s left rises to the top of the iron where it is extracted. This treatment increases the strengths of the metal by increasing the purity of the metal. Similar treatment is used to treat the phosphorous and silicon by using iron oxide and lime as reagants. When the steel is done cooling it is fabricated into a chain of teeth that allow the metal to clench to the ski (See Image 3). The steel and the ski are then lined with epoxy and pressed together to form a finished ski.
The ski has a multitude of layers of materials that provide it with a multitude of functions. These functions are derived from the chemical compositions found within the materials. These functions can be altered and transformed to suit certain desires, like Ptex. On the other hand, raw materials like wood are still used in the construction process. Despite its raw form its properties offer more than its chemical counterpart. To the blind eye the difference in these materials may seem minute, but they are not. They are as complex as the layers of snow underneath the skis. There is a base level, a core and a top layer. Without this understanding, you are restricting your potential as a skier because you are unobservant of your surroundings. This project has opened up my eyes to the many levels beneath the surface and the complexities that form them.
Image 1: http://upload.wikimedia.org/wikipedia/commons/5/5e/FiveMinEpoxy.jpg
1 "F648-10a Standard Specification for Ultra-High-Molecular-Weight Polyethylene Powder and Fabricated Form for Surgical Implants." ASTM F648 - 10a. N.p., n.d. Web.
2 "Ultra-high-molecular-weight Polyethylene." Wikipedia. Wikimedia Foundation, 03 July 2013. Web. 11 Mar. 2013.
3 Allen, Mark. "UHMWPE Processing: Techniques and Problems." Perplas Medical, United Kingdom, n.d. Web.
4 Bartleson, Becca. "Properties of Epoxy Resins." EHow. Demand Media, 24 May 2009. Web. 11 Mar. 2013.
5 Dooley, Keith. "How Is Epoxy Resin Made?" EHow. Demand Media, 06 July 2009. Web. 11 Mar. 2013.
6 "Kevlar." Wikipedia. Wikimedia Foundation, 03 Feb. 2013. Web. 11 Mar. 2013.
7/8/9 "SkiBuilders.com: Howtorequired Materials." SkiBuilders.com: Howtorequired Materials. N.p., n.d. Web. 11 Mar. 2013.
10 "Google." Google/patents. N.p., n.d. Web. 13 Mar. 2013.
11 "How Is Polythene Made?" WikiAnswers. Answers, n.d. Web. 13 Mar. 2013.
12 "Basic Oxygen Steelmaking." Wikipedia. Wikimedia Foundation, 25 Feb. 2013. Web. 13 Mar. 2013.
Analysis of Embodied Energy in the Production of Skis
Skiing is one of the most popular winter pastimes the United States. Naturally, skis are an integral part of the sport. 47 million pairs of skis were sold nationwide during the 2011/12 monitoring period . In order to create enough skis to keep Americans on the slopes, large amounts of raw materials are harvested and refined, resulting in the consumption of energy and the generation of waste. The entire life cycle of skis impact the environment around them. One of the methods of measuring this impact is by calculating the embodied energy of the skis. The embodied energy represents the total amount of energy needed to produce a set of skis, including everything from the initial extraction of materials to the eventual disposal of the used pair. By analyzing the entire life cycle of a pair of skis, it was found that their equivalent embodied energy was over 146,000 MJ.
There are many different ski production companies across the US, and each company has their own designs and production techniques. In general, skis are made by layering multiple different materials over each other to combine their properties and produce an end product that is both durable and flexible enough to be used as a ski. These layers include a core sandwiched between two [strength making] layers, with a base and surface layer of [slippery thing]. The different layers are held together by an epoxy resin that is applied throughout the production process. The exact components and material composition of each ski varies drastically between companies, and even between ski models. There are no standards in the ski industry, and each year designs change and evolve in pursuit of a lighter, stronger ski.
The variability of ski designs make it difficult to generalize the embodied energy in the production process. When purchasing skis, skiers care more about the style of skiing the ski is intended for and the size, weight, and skill level for the intended application. These factors are determined mainly from the shape of the ski, not from the materials the ski is made from. Because of this, raw materials are not commonly provided for commercial skis. For this analysis, the ski design used was based on instructions from www.skibuilders.com, which provided more detail on exactly what materials can be used in a ski than typical ski companies. The assumption is made that the skis to be analyzed will be assembled and used by residents of Davis, California, and all transportation analyses will reflect this assumption.
The life cycle of a ski includes five major phases: material gathering, transport, production, use, and disposal. In the material gathering phase, raw materials are brought together from sources all over the country and prepared for inclusion in a ski. Once all of the materials are fabricated, they are brought together in the production phase, creating a completed ski. When the ski is complete, the transport phase then brings the ski to the consumer for use. The ski is then in the use phase, where over the course of its life it will be utilized by the consumer. This is where the majority of the embodied energy occurs, as skis require regular transport to the snow in order to be used. Finally, the ski ends its life in the disposal phase when it is brought to the dump.
The refined materials needed to create a ski include plywood, Ultra-High Molecular Weight Polyethylene (UHMWPE), fiberglass, ash wood, ABS plastic, steel, and epoxy. Each of these materials must be obtained by processing raw materials through multiple stages, which require varying amounts of energy. The final material that goes into the ski contains embodied energy from all of the development that came before it, including the extraction, transport, and processing needed to create the refined material. The materials in a ski are tabulated below, showing the embodied energy of each one. Totaling the results yields a total embodied energy in the materials of 386.5 kJ.
Table 1 - Embodied Energy of Refined Materials. Material properties from , volume from 
In most life cycle analyses, the embodiment of energy from transportation is most prominent in the shipment of the finished product. The skis in this analysis are assumed to be manufactured by the consumer, so there is no need to ship them elsewhere before they are used. Nevertheless there is still the need to ship all of the materials needed to craft the ski to the home of the consumer, so this will be the focus of the transport phase of the analysis.
Finding the original source of materials used to manufacture skis is not easily done. The materials for skis are common in many products, and factories that make these materials are scattered throughout the country. The assumption cannot always be made that the materials will come from the closest factory, since not all materials are produced in every factory, and the specific products made in each factory change based on the overall demand for each material. The best approximation for the average travel distance for any given material is to assume that the factory of origin is randomly selected. With a sufficiently large number of skis in consideration, the distance traveled is equal to the distance to the center of all the factories. This reasoning has been used to calculate the average embodied energy needed to complete the transportation phase.
The polyethylene, ABS, and epoxy resin all most likely come from Dow Chemical. Dow is the largest petrochemical company in the United States , and while there are many other sources that could provide the synthetic plastics for the skis, it is a reasonable bet that many skis are made solely from Dow products. Dow has production facilities located across the eastern United States, and the approximate average location falls in Kentucky, 2400 miles from the final destination of Davis, CA.
The largest fiberglass producer in the world is Owens Corning , which has its production centers located mainly in the northeast in the Great Lakes region. This makes the average origin of fiberglass very easy to determine, and places it on the eastern border of Ohio. Ash wood is also likely to come from Ohio, courtesy of Industrial Timber and Lumber. ITL is one of the largest hardwood suppliers in the United States, and owns the largest commercial ash forest regularly used for industrial purposes. This forest runs along the Ohio River Valley, and can be assumed to be the origin of many wooden ski cores .
Steel is assumed to be generated close to the ski assembly facility. Steel working takes place across the entire country, and is done by over 350 distinct companies , each with multiple steel plants. Due to the sheer size of the steel industry, most places in the country are no farther than 300 miles from a steel mill that regularly produces steel fit for use in skis.
To calculate the embodied energy in transporting these materials, it is assumed that each company providing supplies ships their contribution in a large semi-trailer to the final destination. This requires four shipments: one from Dow, one from Owens Corning, one from ITL, and one from a local steel plant. These shipments total approximately 7500 miles, and can carry enough material to produce over 18000 ski pairs. This works out to 0.052 gallons of diesel fuel for each pair, given the average hauling fuel consumption ration of 8 mpg. 0.052 gallons of diesel contains 9.45 MJ of energy. The embodied energy of this phase can theoretically skyrocket depending on how much material is actually sent with the shipment. Shipping only enough material for a few pairs of skis quickly brings the embodied energy into the thousands of MJs, which is enough to significantly impact the total embodied energy of the skis.
After all of these materials are prepared and gathered together, the production phase combines the different processed materials together to produce a finished ski. Skis are made by layering each of these materials in a specific order, pressing the stacked elements until the epoxy cures, then cutting away excess material. The layering portion of the manufacturing process is done by hand and is assumed to include no direct embodied energy. The energy is supplied by the worker laying up the ski, and cannot be directly quantified.
A ski press is used to hold the ski together while the epoxy cured. One of the most common types of ski press is a hydraulic press, which utilizes water pumped into an expanding bladder to apply a uniform pressure to the skis while they are held in a mold. The pressure exerted by the hydraulic press can vary, but is typically in the range of 25 to 30 psi . The weight of water to be pressurized also depends on the specific press, but is approximately 240 lbs. Once the bladder is filled and sealed off, the press can be left to sit for the duration of the curing process. Therefore, the energy required to operate a hydraulic press is equal to the energy needed to pressurize the bladder. The energy needed to pressurize water can be computed by the equation 𝐸𝑛𝑒𝑟𝑔𝑦=𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒∗2.31 𝑓𝑒𝑒𝑡/𝑝𝑠𝑖 ∗𝑤𝑒𝑖𝑔ℎ𝑡 . The average hydraulic press therefore requires 30 psi x 2.31 feet/psi x 220 lb = 16632 ft-lbs, or 22.6 kJ.
Excess material is then removed with jigsaws, routers, and files. The energy used in this process depends on the specific tools used and how long the worker takes to clean the edges of the ski. Typical jigsaws draw 720 watts of power, routers draw 600, and files are hand powered and draw no consistent power. Because fiberglass is a brittle composite material, a low speed cutting rate of about 5 feet per minute is recommended. Given a ski's circumference of about 25 feet, this would result in 5 minutes of cutting time per tool for a pair of skis. Combining the power usage of a jigsaw and router, a total of 396 kJ would be required to machine the edge of the ski to the desired shape.
When the ski is finally used by the skier, it does not directly consume any more energy. It instead requires energy both for maintenance and to be brought to a location where it can be used. According to multiple online ski forums, a well maintained ski can be expected to last around 100 days on the slopes before it is to be replaced. Davis skiers will commonly ski at Lake Tahoe, making about 2 trips to the mountains each season. At this rate, well maintained skis can be expected to last up to 50 years before they require a replacement set.
The primary form of maintenance that must be done on skis is to wax the bottom of each ski once every ski season. This process involves melting ski wax onto the skis, then pressing the wax into the base with a ski iron, and takes about 15 minutes for both skis. Ski irons draw roughly 850 watts of power . Over 50 seasons, this requires a total of
900 𝑠𝑒𝑐∗850 𝑤𝑎𝑡𝑡𝑠∗50 𝑠𝑒𝑎𝑠𝑜𝑛𝑠=38.25 𝑀𝐽 of energy.
In addition to waxing, energy is needed to move the skis and the skier to the slopes. It is a 120 mile trip each way from Davis to Lake Tahoe. Assuming a typical 22mpg SUV  is driven, 5.5 gallons of gasoline are used each leg of the trip. Over the life of the skis the total gas usage becomes 1100 gallons. The embodied energy of one gallon of gasoline is 133 MJ , resulting in a total of 146,300 MJ of energy needed to transport the skis to and from the mountains over the course of their lifetime.
The current technology to recycle skis does not exist, which means that at the end of their lives all skis are simply thrown into the dump. Municipal solid waste is handled through various methods across the country. In Yolo county, the only publicly available method of disposal is the landfill. The embodied energy in the disposal of the skis is limited to the energy needed to operate the landfill. Landfills require careful planning and organization in order to properly keep the waste contained, and this upkeep is typically done with large machinery and a lot of manpower. It takes approximately 26 kJ of electrical energy and 7.4 kJ diesel energy to properly landfill 1 kg of waste. A set of skis weighs approximately 5.5kg, requiring a total of 183.7 kJ of energy to dispose of in a landfill. 
Another common method of waste disposal is incineration with energy recovery. In this process, waste is used as fuel to heat water meant to turn steam turbines. There is no public incinerator near Davis, however there are commercial incinerators that will burn industrial waste for a fee. 36 kJ of natural gas is needed as fuel to burn each kg of waste, however an additional 2.42 MJ of energy can be recovered from the material burned. Disposal by incineration would result in a net gain of 13.112 MJ of energy produced by each set of skis. Both incineration and land filling release CO, CO2, NOx, and SO2 into the atmosphere, and when the two disposal methods are compared it is found that incineration is better for the environment. 
The total embodied energy from all of these phases is 146,350 MJ. This number seems amazingly large, and deserves some deconstruction. 146,338 MJ of the total came from the assumed 100 trips to and from a ski resort required to actually make use of the skis. That is over 99.99% of the total embodied energy, rendering the entire refinement, production, transport, and disposal of skis irrelevant when it comes to embodied energy. This serves to emphasize just how much energy is used by automobiles, especially over an extended period of time. Even a big rig hauling freight cross country can't come close to the energy needed to make 100 trips to Tahoe. If the gasoline for use is removed from the calculations, the embodied energy is instead equal to 10.44 MJ. Again, over 90% of this energy is derived from the shipping fuel needed to transport the raw materials across the country. The next highest amount of energy comes from the production cycle, and is 1/20th the amount needed to ship the raw materials. While some materials in skis may be difficult to produce, and others may generate significantly toxic waste after their disposal, it is clear that the largest impact the skis have on the environment stems from the fossil fuels that drive them across the country.
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Skis Wastes and Emissions
It is difficult to properly assess the waste and emissions produced by a modern ski. As a sport and industry, freeskiing has evolved from its 21st century humble beginnings under the shadows of snowboarding to the mainstream status it holds today. It has infiltrated popular culture with the approval of halfpipe and slopestyle competitions for Sochi 2014 by the International Olympic Committee.1 This momentum has caused a growth in participation, thereafter influencing many new companies to enter the market. As industry competition increased, companies both new and old tried to innovate their products to differentiate themselves. In addition, brands attempted to vary their range of models depending on a skier’s intended riding style with vastly diverse designs. Each pair of skis found on the market can be constructed from completely dissimilar materials, from bamboo to titanium to foam. They can be assembled in unthinkable ways like being horizontally laminated similarly to a skateboard (Line Afterbang model) or having wavy edges mimicking a serrated knife (Lib-tech NAS model).
For the purpose of waste and emissions research, we standardized the design and construction of the ski to a basic, yet modern, form. This ski will be made with an ash core, with layers of fiberglass, a base consisting of ultra-high-molecular-weight polyethylene (UHMWPE), steel edges, sandwiched between acrylonitrile butadiene styrene plastic (ABS plastic) sidewalls, and all held together with epoxy. There were no reliable in-depth resources of waste and emissions from a ski factory, only rudimentary overview videos of an assembly line more for entertaining and marketing rather than educating. In this case study, the ski will be manufactured in a personal press at home parallel to what many ski enthusiasts do at www.skibuilders.com. The materials and resources used could not be at located at the same plants and factories that ski manufacturers source from. In fact, it was difficult to find information overall on the waste and emissions of ski resources. This study will do its best to follow the life cycle of a ski built from one’s home, assuming the ski press is already made, and sourcing common materials.2
To begin, ski builders need to determine the shape of a ski they want to build. Ski shape is the most important factor determining what type of skiing the skis were intended for. Before the modern ski, skis were very long and completely straight to encourage stability and speed. However, they were difficult to turn and cumbersome to ski. Skis eventually evolved into shorter planks with wider tip and tails, a thinner waist, making it a side cut that made turns on a dime. Many manufacturers have even adopted a reverse side cut where the tip and tails of the skis were thinner than the waist. The idea is that in heavy snowfall, the normal side cut would cause the waist to sink while the tip and tails would initiate turns by themselves, causing a hook effect and less control, especially if there was a layer of crust on top of the deep snow. With this knowledge, ski builders cut a template to determine the shape of their ski bases, which also determine the entire ski’s shape. Plywood is generally used for these templates and it is composed of two veneers glued together with their wood grains at right angles from each other. The wood harvested can be from a variety of woods, but it is cut from a tree cylindrically like pieces from a roll of toilet paper. It is then dried and baked at 140 °C (284 °F) and 1.9 MPa (280 psi). The glue used is urea-formaldehyde and they emit formaldehyde, which is known to be carcinogenic in high concentrations. Companies have low formaldehyde-emitting glue systems that reduce or eliminate these emissions and rate their products on an E# scale with the lowest E0 representing 0 formaldehyde emissions.3
On top of this plywood template lays the base of the ski, the surface that glides on the snow. It is slick and durable, but requires periodical maintenance from the friction caused by sliding over ice crystals and unfortunately sometimes the hazardous rock. Bases are all made from UHMW polyethylene, but they can either be extruded or sintered. Extruded bases are made from melting UHMWPE pellets together under extreme heat. They are easier to maintain, absorbing less wax, more durable, and cheaper to manufacture. Sintered bases are found on high price-point skis since they require extreme pressure to press UHMWPE pellets together. The result is that they are very porous and absorb lots of wax, making them faster if properly maintained. Since manufacturing utilizes pellets, companies can decide on how much they want to use and put them in molds. There are no excess wastes in the production process and the process is less labor intensive than machining other parts. Pure polyethylene burns fairly cleaning into H2O and CO2, but if oxygen is insufficient for complete combustion, carbon monoxide poisoning can occur.[4 ]
To aid structure and rigidity, fiberglass is layered on top of the base. Fiberglass is plastic polymer infused and reinforced with glass. Silica sand, a valuable ingredient for glass is widely extracted causing carbon emissions. A British company recognized the wastes produced and focused on reducing their carbon footprint by 17,000 tons by 2010. They have reduced their emissions by 25,000 tons to date.6
Steel edges are wrapped around the base of the ski. Steel is made from heating iron ore, magnesium, and oxygen. Iron ore is a widely extracted resource and causes two forms of wastes. There is the non-ore bedrock in the mine known as mullock and the unwanted minerals from the ore called gangue. The mullock is dumped in waste areas while the gangue is separated during a beneficiation process and removed as tailings. Tailings are of the taconite variety and consist of mostly mineral quartz and are safe for the environment. They do not leak and are not reactive chemically. Mineral quartz is stored in regulated water settling ponds. When making steel, the outcomes are steel, carbon dioxide, carbon monoxide, and slag. Slag is a mixture of metal oxides or in other words, oxygen plus metals that are not iron.
The foundation of the ski resides in the ash wood core. Ash is commonly harvested in the Ohio River Valley Region and requires sawmills and drying kilns. The forest products sector used 12% of the total energy input for the U.S. manufacturing industry. In 2002, sawmills consumed 127 trillion BTU.8 Twenty million BTU’s use about a ton of coal. Therefore, in 2002 sawmills consumed about 6.35 million tons of coal. Coal produces carbon dioxide emissions 1.87 times its weight. In 2002, sawmills emitted about 11.9 million tons of carbon dioxide.9 The lumber drying kiln process uses about 1.7 million BTUs. Doing the necessary conversions, a drying kiln uses .086 tons of coal and emits .16 tons of carbon dioxide gas.10
After laying another piece of fiberglass on top of the wood core, sidewalls need to be put in place to protect the wood from the elements. ABS plastic consists of acrylonitrile, butadiene, and styrene. It is commonly used for sidewalls as it is stronger than other plastics and has rubber-like qualities from the butadiene. The energy required for 1 kg of ABS plastic is 95.34 MJ or 26.48 kWh. One pound of coal contains sixteen million joules of energy, so 5.96 pounds of coal is used when making 1 kg of ABS plastic. Therefore 11.1 pounds of carbon dioxide is emitted for 1 kg of ABS plastic.11
Finally, the epoxy used to put all this together is made of two parts. They are sold in separate containers and require mixing to activate their sticking potential. Once epoxy is mixed and cured it is very difficult to take apart. The first part of epoxy consists of sodium hydroxide, bisphenol a, and epichlorohydrin. The byproducts of sodium hydroxide are mercury, chlorine gas, and hydrogen gas. The output of bisphenol a is bisphenol a and water. BPA itself is a very toxic material.12 The second part of epoxy is made of ammonia, ethylene dichlorid, and sodium hydroxide again. The outputs of ammonia are ammonia, carbon dioxide, zinc sulfide and the outputs of ethylene dichloride are ethylene, hydrochloric acid, and water.
Much of the waste and energy use of the lifetime of a ski comes from the actual use of the ski. Skiing itself doesn’t use any outside energy besides the kinetic energy and power of the human and the gravitational energy from going down the slope. However getting to the mountain requires a mode of transportation that exhausts fuel resources. For example, to get to Lake Tahoe from Davis requires a commute of 116 miles. A round trip would be 232 miles and consume 10.5 gallons of fuel for a fairly efficient common sport utility vehicle. For this trip, .094 metric tons of carbon dioxide would be emitted from just the drive.13 Another factor needed to include would be the chairlifts that take you up the mountain. Common power usages from the motors of chairlifts require 670 kw as used at Breckenridge and Sugarbush. That is about 603 pounds of coal and 1128 pounds of carbon dioxide emissions. 14
There are no programs or systems to recycle skis. Normally they are sold and resold on the secondhand market. However if one breaks their ski, there is nothing else to do but to discard them. The epoxy bounding the materials together prevents ski components from being able to disassemble easily. Each pair of skis contributes about 12kg of municipal sold waste and requires 185 KJ or to handle them. Skis are resorted to sitting in the landfill waiting to degrade or they can be incinerated with other wastes and release carbon monoxide, carbon dioxide, nitrogen oxide, and sulfur dioxide.15
The waste and emissions induced by skiing is complex and hard to find. Looking at various conversion values, an efficient way to find the carbon dioxide emitted from skis was to find the embodied energies of each material, convert that to how much a common fuel type has of that energy, and convert its carbon dioxide emissions to the amount produced in one pair of skis.
As can be seen, the total amount of carbon dioxide emissions per pair of skis does is not significant at all. On the contrary, the ride up to the mountains produces much more amounts of CO2.
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