March 13, 2013
The Raw Materials of Eco-Friendly Cork Flooring
In the 21st century, everyone has the mindset of being “eco-friendly.” But what exactly does eco-friendly mean? Recycling? Sustainable? Reusing? Green? Literally, it means not harmful to the environment and earth friendly. Eco-friendly products and practices help to conserve resources like water and energy and prevent pollution to air, water, and land. A very popular idea in today’s world is producing goods made from recycled materials. Goods that are originally made from materials such as glass, wood, metal, or plastic can be reused to produce something new. One such eco-friendly product is eco-friendly flooring. There are many types of eco-friendly flooring that are sustainable and made from natural or recycled materials. Cork, bamboo, reclaimed hardwood, biohaus carpeting, etc. are all great options for eco-friendly flooring. This paper takes an in depth look at the raw materials used in the making of eco-friendly cork flooring. Find out just how eco-friendly cork flooring is and why it is a better choice than typical flooring from the past.
Cork, a material that has been used for 5,000 years, is a natural, environmental, and renewable raw material that is very versatile. It is light, impermeable to liquids and gases, elastic and compressible, a thermal and acoustic insulator, fire retardant, and highly abrasion resistant. These factors make cork a unique product that humans have been unable to imitate. Since it is such a useful and versatile material, it is used in products such as stoppers for wine, insulators, insoles, boards, and of course, flooring.
Cork is a combination of cells (about 42 million per cubic centimeter) with a closed cell structure, which gives cork its uniqueness. As seen in the image provided, the cells are joined together in a honeycomb fashion. These cell shapes are about 40 to 50 micrometers in height, which translates to thousandths of a millimeter. The composition of cork cells consists of about 50% of gas. This gas is responsible for cork’s impermeability to liquids and gases. Cork also consists of a variety of other different compounds including suberin (45%), lignin (27%), polysaccharides (12%), tannins (6%), ceroids (5%), and mineral water, glycerine, and others making up the remaining 4%. Suberin is responsible the elasticity of cork, lignin acts as the binding compound (more binding substances will be discussed later), polysaccharides make up the texture of cork, tanins provide cork’s color, and ceroids guarantee the impermeability of the cork.
The life cycle of cork begins in the Mediterranean, primarily in the countries of Algeria, Spain, Morocco, France, Italy, and Tunisia, and in the coast of Portugal. Portugal contains about 60% of the world’s cork tree area and produces about 50% of the world’s cork supply. The cork oak trees are “open, savannah-like cork oak forests” that cover approximately 5.4 million acres around the world. The location of the cork forests are ideal to the versatility of the cork bark. Over time, the cork bark evolved to provide protection against brush fires, droughts, and temperature fluctuations. The versatility of cork allows the material to be used for a variety of products.
To retrieve the cork from the cork oak tree, the bark is stripped from the tree. The stripping process of this versatile material begins when the cork oak tree is stripped of its outer layer of bark, called Quercus suber, in large slabs. The cork oak trees are not cut down to harvest the bark, making it an environmentally friendly process. Instead, the bark is stripped from the entire tree and then left to regrow. Harvesting the bark happens on a periodic basis, normally every nine or ten years, allowing the bark enough time to grow back.
There are two main types of tools that are used in the harvesting of cork. One is a Machada and another is a knife. The Machada is a multi-functioning ax that is used to strip the bark away from the tree. The knife is then used to cut the bark into smaller pieces. This is actually where my research stopped for the tools. There was surprisingly very little information about the tools used in the process of manufacturing cork.
The stripping of cork requires a lot of manual skill and experience so as not to harm the tree. The process entails many steps and demands the work of two men. The first step is the opening of the bark. Using the knife, a vertical cut is made in the cork. At the same time, the ax is wedged into the space and twisted, separating the outer bark from the inner bark. The separating and removal of the bark is the second step. In the third step, the large slab of bark is carefully removed from the tree so that it does not split. These steps are then repeated until the tree is removed of the usable cork bark.
After the slabs of bark are harvested, the cork production process begins. The slabs are treated by being cleaned, boiled and stripped from the rough outer surface. The planks are boiled to soften them, making them flatter and easier to work with. Once the planks are cut into manageable sizes, holes are punched through the slabs to make bottle stoppers (also known as wine corks). This leaves the cork plank full of holes. However, the plank is still useful. Another aspect of the eco-friendly process is how the leftover bark is used. The remainder of the slab of bark is ground into small particles and mixed with a binder. After the binder is mixed with the small cork particles, it is molded into larger chunks and baked in specialized ovens to produce cork for its many other uses.
Today, there are two ways to form cork after it has gone through all the necessary preparations: the use of chemicals as a binder and the method of not using any binders at all. Typically, a binder is required to hold the particles of cork together. Depending on the final product, different binders are chosen to accommodate flexibility, softness, resistance to wear, etc. In the past, urea formaldehyde was used but it’s popularity fell in the 1980’s due to rising health issues within the homes it was used in. Today, manufacturers have created binders like urea melamine, phenol formaldehyde and natural proteins that are non-toxic and are healthier and better for the environment. To make the blocks of cork for the rest of the cork based products, a rectangular mold is filled with the crushed cork and the binder. The volume is pressed to about 60%, held while compressed, and then heated in a kiln to allow the form of the cork to set.
One of the major cork manufacturers, Amorim (which will be discussed later), recently developed a method of binding the cork together without using any urethanes or formaldehydes. They use a process that is “heated, pressurized expansion to produce insulation blocks that are free of binders altogether.” The cork is sent to steel autoclaves that are heated with steam to 300 degrees Celsius. The cork mixture begins to explode like popcorn and presses against the sides of the oven, eventually quadrupling in size. When finished, it is injected with cooled water vapor to thwart the deformation of cork.
Cork continues to be eco-friendly with the waste management of the raw materials during the production process. The cork forming process produces almost no waste emissions. Cork is naturally prone to be moisture, mold and rot resistant and does not let off any form of gas. Corks’ sustainable harvesting practices have a relatively low impact on the environment because of how the trees are reused on a periodic basis. Many cork manufacturers use the unusable cork that is either too fine or has become dust and convert it into biomass. For example, the Amorim manufacturer burns the cork at over 900 degrees Celsius and uses it as 63% of the power needed to run its factories.
Amorim is a cork manufacturing company based in southern Portugal. It is the world’s largest producer of cork products. As a pioneer and leader in the cork industry since the 19th century, the company’s goal is to “reutilise, recycle, and reinvent entirely natural and organic materials.”
Now that we’ve covered the life cycle of cork, let’s discuss cork flooring. Cork flooring is low-maintenance flooring that is easy to care for and beautiful to look at. It is extremely durable and comfortable and insulates sound, noise, and temperature change. “Cork’s low thermal conductivity combined with a reasonable compressive strength makes it an excellent material for thermal insulation purposes.” Not only is cork flooring good for the environment, but it is great for the average household. The cork’s anti-microbial properties reduce allergens and act as a natural insect repellent.
Cork flooring has a 50 year estimated lifetime. It is made up of 93% recycled cork waste and 7% binder (for those companies that do use binders). To produce the floor tiles, the compressed cork is cut into sheets that are either 5 mm of 8 mm thick. Once the cork is sliced into pieces, it is ready to install. Most manufacturers recommend a polyurethane adhesive. The down side to this adhesive option is that it could release potentially dangerous chemicals during the installation process. However, another installment option is DriTac Flooring Adhesive. This adhesive, unlike the polyurethane, is water-based, contains low volatile compounds, and is latex adhesive. After installed, the cork is coated with a water-based varnish. This option is a much more environmentally friendly choice than the harmful polyurethane adhesives.
From a design perspective, cork is a preferred flooring option. Like wood, cork can be finished in a variety of different paints and stains to fit any design style or color scheme. To produce the variations in color often seen in styles of cork flooring, manufacturers don’t use dyes or additives. Instead, the cork is baked at different temperatures to produce cork in the shades of light, medium and dark.
Cork flooring is clearly a great flooring option in terms of being eco-friendly and positive for the environment. A downside, however, is the price. Cork is an expensive flooring material. The least expensive cork flooring options start at about $1.50 /ft, plus installation. Some cork flooring can even cost as much as $3.00 - $3.50 /ft, plus installation. Builders and contractors have to order the cork flooring directly from the manufacturers because of the lack of distribution networks in the United States for cork flooring.
“Going green” and “saving the environment” is the common thought of producers and manufacturers in the 21st century, especially when it comes to flooring. Cork flooring in particular is getting more popular as more people become fascinated by the idea of eco-friendly flooring. Cork is the style of eco-friendly flooring that reaps the most benefits and is the most eco-friendly. Not only are the raw materials of cork flooring considered to be eco-friendly, but the process of manufacturing cork requires little energy and almost no waste emissions, which is great for the environment. The process of extracting cork from the cork oak trees is ideal because the trees can be reused every nine to ten years. Using leftover particles of cork to be heated and used as power to run the manufacturing companies, completes the reuse cycle in the cork making process. These eco-friendly processes while extracting and making the cork add to the already great appeal of cork flooring. Cork flooring has become a popular item that lures homeowners. The flooring is comfortable to walk on, as it has a cushioning effect when you walk on it. It traps heat, is sound resistant and fire resistant, and reduces allergens in the household. These facts and more prove that cork flooring is the best option for your eco-friendly needs, not only to the environment but to your health and household as well.
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8 See “Cork Composites: A Review.” 1.
10 See “Cork, Culture, Nature, Future.” 4.
12 See image 1.
14See “Cork Composites: A Review.” 5.
16 Note: The statistics for the actual percentage of the amount of cork Portugal produces varied so, I went with the most common percentage from my research.
18 See “Cork Flooring.”
20 See image 2.
22 See image 3.
24 See “Cork, Culture, Nature, Future.” 6-7.
26 See images 4 and 5. Image 4 is before the slabs have been boiled and softened and image 5 is after.
 See image 6.
28 See “How Products Are Made.”
 See “Core77.”
 See “Core77.”
 See “Core77.”
 See “About Us.”
 See Gil, Luis. 777.
 See Bowyer, Jim. 3.