When it comes to material sourcing, Life Cycle Assessments (LCAs) can help designers identify and specify green products with greater confidence. Here’s what you need to know about the process.
The late Finnish architect and designer Alvar Aalto once said, “Modern architecture does not mean the use of immature new materials; the main thing is to refine materials in a more human direction.” His insight from more than 40 years ago echoes with revived relevance as the architecture and design community has re-focused much of the dialogue about sustainable design in recent years around materials and their relationship to both people and the planet. Without a doubt, one of the most pressing and talked-about environmental issues today is climate change, and how the spaces we create can mitigate the impact they have on natural resources as well as human health. The reason is simple: buildings—their construction and their operation—could affect the climate.
According to the U.S. Green Building Council (USGBC), 2016 was the hottest year since recording began in 1880, and the third year in a row to set that record. The USGBC also notes that the international scientific community is nearly certain that human activity is a driver of global warming, citing a 95 percent probability that human actions over the past 50 years have warmed our planet, per the Intergovernmental Panel on Climate Change’s “Fifth Assessment Report.”
Further, buildings account for more than one-quarter of all greenhouse gas emissions (GHGs). “Add in other infrastructure and activities, such as transportation, that are associated with buildings, and that number jumps,” said Christina Huynh, LEED GA, content specialist for the USGBC. “However, by building green, we can reduce the impact our buildings have on contributing to climate change while also building resilience into our homes and communities.”
As a result, LEED v4—the latest iteration of the USGBC’s highly successful Leadership in Energy and Environmental Design rating system—acknowledges the significant impact buildings have on the environment and gives special consideration to climate change with its “Reverse Contribution to Global Climate Change” impact category. But outside of energy efficiency strategies for buildings, how can architects and designers reduce the impact their projects have on climate change? One way is to look at the carbon footprint of products being specified for a project. While these pieces of data are still not readily available for many products, more and more manufacturers are recognizing the need to measure the carbon footprint of their goods; some are even disclosing this information to their customers.
“One thing is for sure, we have entered a new age of market transparency, and it has changed the conversation about building materials for good,” wrote Bill Walsh, founder and executive director of Washington, D.C.-based Healthy Building Network, in a blog post. “We are now having the right conversation about how to better understand the products we build with; how to make better, more informed decisions; and how to catalyze the resources of the building industry to promote the best environmental health outcomes and societal well-being for all.”
In short, the carbon footprint of a product represents the total amount of carbon emissions produced throughout the entire life cycle of the product, as measured by a Life Cycle Assessment (LCA). Given that flooring represents an important portion of building construction projects, with total flooring sales in 2016 reaching $21.174 billion and representing 19.13 billion square feet of space, according to research from Floor Covering News, the impact of this category on reducing a building’s carbon footprint is significant.
This CEU will focus specifically on the life cycle of rubber flooring, the steps involved in its manufacture (including raw materials), and improved processes that have catapulted this category into the forefront of sustainable building solutions. Additionally, this learning module aims to help specifiers understand the role that Life Cycle Assessments play in making informed and responsible material-sourcing decisions, as well as in society’s effort to mitigate the effects and continue resilience through climate change.
Rubber Production: A Brief History
To better understand both the metamorphosis of rubber as a building material and its life cycle impacts, it’s important to understand its history, and how the use of rubber to make flooring is tied to rubber production around the world. The story of rubber manufacturing is well documented by the Rubber Division of the American Chemical Society and other international sources, and includes inventions, discoveries, and industry changes over time. From the use of natural rubber in South American ball games to the development of synthetic rubbers for myriad uses during wartime shortages, as well as the housing booms of middle classes around the world, one thing is clear: the world of rubber continues to evolve.
But how important is rubber in the grand scheme of things, really? The short answer is, a lot more than many people may realize. Writer Charles Mann has written extensively about the history of rubber and recently contributed an article to National Geographic about developing trends in this product category. Mann noted that what makes rubber such an interesting and vital material is precisely because it largely goes unnoticed. He wrote:
Because rubber is so common, so unobtrusive, so dull, it may not seem worth a second glance. This would be a mistake. Rubber has played a largely hidden role in global political and environmental history for more than 150 years. You say you want an industrial revolution? If so, you need three raw materials: iron, to make steel for machinery; fossil fuels, to power that machinery; and rubber, to connect and protect all the moving parts. Try running an automobile without a fan belt or a radiator hose; very bad things will happen within a minute. Want to send coolant around an engine using a rigid metal tube instead of a flexible rubber hose? Good luck keeping it from vibrating to pieces. Having enough steel and coal to make and drive industrial machinery means nothing if the engines fry because you can’t cool them.
Currently, Mann explained, economic and industrial development globally is increasing the demand for tires for passenger cars and for industrial use. In Southeast Asia, for example, jungles are being clear-cut in order to generate rubber plantations. Ecologists are warning that the destruction caused by the clearing of older forests and jungles, as well as the rubber trees’ need for high volumes of water, will cause continued ecosystem damage. At the same time, development of new industries and products is helping families across Southeast Asia, which makes for a very challenging situation in terms of balancing economic prosperity with environmental preservation.
As a result, some conscientious rubber flooring producers have announced they will no longer use natural rubber in the manufacturing of their products. Refusing to accelerate global ecological destruction and climate change, many manufacturers have equipped their plants to process both natural and synthetic rubber (more on the production process later on). Flooring products of the highest quality can be created with either natural or synthetic rubber, and environmentally responsible manufacturers are increasingly relying on synthetic products to help protect our natural resources. To that end, rubber flooring suppliers are turning to tools such as Life Cycle Assessments and Environmental Product Declarations (EPDs) to both measure and disclose the effect their products have on the environment.
To those who may be unfamiliar with the term, a Life Cycle Assessment can be defined as a holistic approach to quantifying the carbon footprint of a product because it takes into account every stage in the product’s life cycle, including the carbon emissions produced during the extraction and manufacturing of raw materials, the manufacturing of the product itself, the use of the product, and its end-of-life disposition. An LCA uses input data based on the various phases of the project life: information from the installation such as adhesive, energy and water used, waste generated; information from the use phase of the product, including service life, maintenance methods, and frequency; amounts of chemicals, water, and energy used; and information from the End of Life (EoL) phase, including type of reuse or disposal.
The International Standards Organization (ISO) 14040 series of standards provides the framework and guidelines for how an LCA must be conducted. When paired with the requirements specified in Product Category Rules (PCRs), which industry sectors create for their products, the LCA can be used as a tool to compare the environmental impacts of two products in the same category. The LCA process identifies and measures a product’s inputs, outputs, and environmental impacts across its lifespan, from sourcing through end-of-life, whether disposed of (cradle-to-grave) or disassembled for reuse (cradle-to-cradle).
The LCA employs scientifically based methods to analyze a product’s:
- Raw material selection and production
- Packaging and distribution
- Disposal, reuse, or recyclability
Additionally, the life-cycle impact assessment phase of an LCA evaluates a product’s impact relative to end points, including:
- Climate change
- Ozone layer depletion
- Land and water acidification
- Eutrophication, i.e. water pollution due to high concentrations of phosphates and nitrates
- Formation of photochemical oxidants
- Depletion of fossil energy resources
- Depletion of mineral resources
- Hazardous and non-hazardous waste
Six Steps of Rubber Flooring Life Cycles
For the purposes of this CEU module, the types of products described in the process of rubber product production and distribution include rubber flooring, stair treads, and cove bases. This life cycle process for these flooring products includes six phases:
- Mixer (raw materials)
- Production (manufacturing plant)
- Transport (warehouses, trucking)
- Installation (contractors, adhesives used)
- Use (cleaning, detergents, water, electricity)
- End of Life (disposal, reuse, recycle)
As illustrated in the flow chart above, the first step in the process flow is material mixing, which considers rubber’s environmental emissions, water use, and energy use associated with the raw materials incorporated into the product. The production phase includes all energy and water used, as well as the waste generated in the manufacturing process to make the product. The distribution phase includes moving the product to a warehouse, where it is packaged, then moved to a distribution center, and finally transported to the installation site. The installation phase takes into account the use of adhesives, water, and waste generated during installation. Maintenance of the product after installation is completed takes place during the entire life of the product, which in the case of most rubber flooring products averages 40 years. Finally, the EoL phase is how the product is used or disposed of after it is removed from the installation site, whether salvaged, recycled into a new product, or disposed to landfill.
In LCAs, data from combined emissions, energy use, water use, waste generated, and other input from all six product life phases is collected and entered into computer models which estimate impacts to the environment. From the LCA, summary reports are then created to describe the impacts of specific products. These summary reports, designed to be informative for designers and general consumers making purchasing decisions, are called Environmental Product Declarations. According to third-party product certification provider SCS Global Services, an EPD is “an objective report based on Life Cycle Assessment. It is used to communicate information about the potential environmental and human health impacts of a product. It’s like a nutritional label, stating what a product is made of and how it impacts the environment across its entire life cycle, from raw material extraction to disposal.”
In other words, an LCA must be conducted before an EPD can be produced, critically reviewed by an independent expert for conformance to the ISO Standards, and then published by a manufacturer that wants to voluntarily disclose the environmental makeup of its product(s).
In this article, we will concentrate primarily on the first two steps of the life cycle process for rubber flooring—Mixer/Raw Materials and Manufacturing—as these categories encompass the manufacturing process, which is the focus of this CEU. We’ll also touch briefly on the remaining four steps in the flooring production process in context of LCAs.
STEP 1: MIXER
The graph below illustrates a very simple outline of how polymer chemists think about compounding raw materials. The majority of the ingredients in the base materials for rubber include a binder and a filler. Every polymer needs a material to act as the “glue” for the mixture as well as a material to be “glued.” (Note: These are not scientific terms that chemists use.)
In rubber flooring manufacturing, binders are the polymers—natural rubber or synthetic rubbers, such as styrene butadiene rubber (SBR) and ethylene propylene diene rubber (EPDM). Common fillers used in the manufacturing process are limestone or clay, which are used to improve properties of the final product and to add bulk, as well as to reduce costs. In addition, chemicals are added to the mixture to improve the process, to accelerate the chemical reactions, or to eliminate overheating of product.
Chemicals are also added to improve the final product by reducing degradation from ultraviolet (UV) light and indentation from heavy furniture or equipment resting on floors. Performance and long-term durability of rubber flooring is a result of the manufacturer’s choice of raw material ingredients. For example, linoleum and bio-based flooring can break down with water exposure; rubber products are resistant to water spills. Carpeting can use dyes, but rubber products are free of dyes and avoid the “upstream” and “downstream” environmental impacts of manufacturing dyes containing heavy metals. In addition, rubber flooring can be recycled into mulch chips for a second life—not disposed in landfill. (More about this last point in the next sections.)
The majority of the compounding mixture is made from base materials. In general, chemicals added for process and product improvements are minority ingredients. As mentioned previously, due to the environmental challenges that current worldwide demand for natural rubber production poses to the environment, many manufacturers have chosen to use only synthetic rubber in their flooring products—and that is not the only principled decision made by conscientious flooring suppliers. A number of these companies have also been actively working to remove chemicals of concern to their customers.
Most recently, the question being posed throughout the design and manufacturing community—“What are our products made of?”—has led to the concept of “material health.” This term relates to the effect of materials on human health within the built environment, and it has seen widespread adoption due in large part to the launch of the Health Product Declaration (HPD) and the Declare label—standard formats for reporting product content and associated health information for building products and materials—over the past five years. Further, the inclusion of Material Health reporting into LEED v4 as a formal credit under the Materials & Resources (MR) category has further shed light on material and human health, a move by the USGBC that is encouraging market transformation.
To that end, many flooring manufacturers continue to look at chemicals of concern and experiment with substituting safer chemicals for those that customers are inquiring about and asking for in their design specifications.
When changing formulations for a processed material like rubber, the laboratory teams run hundreds of trials, first in the laboratory and then on production equipment. Concentrations are adjusted and additional trials were conducted. Throughout this process, the performance (durability, indentation, resistance to UV light) of the resulting products needed to be checked against stringent quality standards as well. After many months of work, changes can be made and products introduced to the marketplace.
STEP 2: PRODUCTION
The second of the six phases of life cycle assessment for rubber flooring products is Production. This step involves the myriad activities that take place within the manufacturing plant and the resources required to produce the end product.
As illustrated by the chart above, the manufacturing process begins with raw materials and ends with a finished product, as shown in blue. Between the starting and ending state, a variety of operations are performed, which represents the metamorphosis of rubber from its natural state to the finished product. The first step involves pouring the dry mixture into giant mixing equipment. Once the mixture is blended thoroughly, it undergoes “calendaring,” a process in which rubber compound is formed to a continuous sheet or coated on a fabric. This is done by feeding the rubber compound to one or several layers onto each other following roll gaps.
Calendering is a popular process because of its ability to precisely adjust the thickness of the product, according to Goodyear Rubber. Another benefit of the process is that finishing textures and coatings can also be applied to the product.
Next, the sheets of rubber undergo vulcanization, “a chemical process by which the physical properties of natural or synthetic rubber are improved; finished rubber has higher tensile strength and resistance to swelling and abrasion, and is elastic over a greater range of temperatures,” according to Encyclopedia Britannica. In its simplest form, vulcanization is brought about by heating rubber with sulfur. Once vulcanized, the finished products are then sanded (in the case of rubber tiles), and the molded pieces are trimmed and packaged for shipment.
A helpful analogy for understanding the production process of rubber wall base products is making pasta from scratch. Dry ingredients like flour and salt are mixed in a bowl with eggs, and then flattened and further mixed by rolling before being placed in a pasta machine. In the case of wall base production, the final step (the pasta machine) is a process known as extrusion, in which long, flat pieces of wall base (or “dough”) are formed. Finally, the pasta is heated by the process of boiling—or in the case of rubber, vulcanized, to form a chemically stable product.
Likewise, in the process of manufacturing rubber tiles and treads, an analogous example is baking cookies or cupcakes. Ingredients are mixed at a high speed, and the raw dough is placed in the same quantity in cupcake tins, and then baked. With rubber (and not in baking, of course), the final product is then sanded and trimmed.
Products such as stair tread, flooring, or wall base are new materials after the chemical process of vulcanization, not just “a bit of flour and a bit of salt,” or a bit of synthetic rubber and a bit of clay. Understanding the difference between the characteristics of the raw materials and the characteristics of the final vulcanized or cured product is key to discerning its use. Resistance to water and ultraviolet light are properties of the final product provided by the component parts. Similarly, any potential health risks of products are different from the potential hazards of component materials. For example, a chemical could be used in preparation of the product and not be present in the final product, or could be held in the final product’s polymer matrix and not be available for human exposure. This is the “metamorphosis” of rubber products.
Quality checks are made at regular steps along the production process. Ingredients are carefully weighed before mixing, then calendared material is heated and cooled, and samples of the raw rubber are analyzed in the laboratory—a crucial step in the process. After vulcanization, the rubber will be a different chemical entity and cannot be returned to the mixer to try again. Just as finished cake does not go back into batter for mixing, the finished rubber cannot be changed after vulcanization. Checking the mixture after calendaring for color and properties prior to vulcanization is important for reducing waste and maintaining high quality. If problems are found, additional elements such as pigments for color matching or process aids can be added, and the raw rubber can be re-calendared.
After vulcanization or molding, the process operators check the molded rubber products, which may be a visual or touch test. Products that do not meet quality criteria are put to the side for recycling. If a large batch of tiles is affected, machine settings can be re-adjusted. During trimming and packaging, further visual checks of the final products are made to ensure consistent, high quality.
STEPS 3-6: DISTRIBUTION, INSTALLATION, USE & END OF LIFE
As with any product or furnishing produced today, once a material has been manufactured, it must be packaged and then housed in a distribution center awaiting transportation to either a retailer or its final destination in a building project. Each of these steps contributes to a product’s LCA, and its impacts across a number of factors are considered and calculated.
Packaging can play a significant role in the environmental effect of a product/packaging combination. The material used, the packaging weight, and its manufacturing methods are all factors that can increase or decrease a product’s environmental footprint. “The environmental impact of a packaging can be quantified in terms of air, water, and ground emissions, as well as in terms of a final waste product that must be eliminated,” explained Bernard De Caevel, managing director of Intertek-RDC. “An LCA takes all of these aspects into account, as well as the raw material, water, and energy consumption that is required at each stage of the lifecycle.” In addition, an LCA enables the identification of the stages at which actions can be implemented to lower repercussions on the environment.
Similarly, transportation of goods can also contribute to the reduction of greenhouse-gas-emission goals as part of a comprehensive LCA. According to the Journal of Industrial Ecology, “Using uni- and multi-modal freight movements by truck, rail, and ocean-going vessels […] long-run average per tonne-km results show that ocean going vessels emit the fewest emissions, followed by rail, then trucks,” and that the differences in energy use and GHG emissions between ocean going vessels and trucks can be up to 30 percent on average.
When it comes to installation, rubber flooring’s impact is measured in terms of the amount adhesives used as well as packaging waste. For the average rubber floor tile, for example, approximately 250 g/m2 of adhesive is required for installation. During installation, approximately 4.5 percent of the total material is cut off as waste. Though some of this waste could be recycled, this scrap, as well as installed product waste and packaging waste, are assumed to be sent to a landfill (although packaging material is often recycled in local systems). Landfill emissions from paper, plastic, and wood packaging are also allocated to installation. It’s important to note that following installation procedures correctly is critical to meeting the health and safety of workers during installation.
During the use phase, the service life of rubber flooring will vary depending on the amount of foot traffic, furnishing type and use, and the equipment used for floor maintenance and frequency of use. The level of maintenance is also dependent on the actual use and desired appearance of the floor. For a typical rubber flooring tile product, the defined Reference Service Life (RSL) is 40 years. This means that the product will meet its functional requirements for an average of 40 years before replacement.
The recommended cleaning regime is also highly dependent on the use of the premises where the floor covering is installed. In high traffic areas, more frequent cleaning will be needed compared to areas where there is low traffic. In general, rubber flooring is a low-maintenance product that does not require waxes or finishes. Additionally, low-VOC cleaning materials for use in maintaining rubber flooring are available through most manufacturers.
Finally, based on current best information from sustainability consultant thinkstep inc., a small amount of construction waste from rubber flooring is typically incinerated or recycled; however, the majority of all flooring removal waste is disposed of in a landfill. To lessen the negative impact on the environment, many flooring manufacturers take part in rigorous recycling programs in-house to improve the overall LCA of their products. For example, one manufacturer sends scrap rubber from its manufacturing plant to another local manufacturer of rubber truck flaps, resulting in more than 500,000 pounds (250 tons) annually diverted from the landfill. Additionally, through the IMPACT program, one manufacturer has recycled more than 26,180,000 pounds of rubber in the past five years. IMPACT accepts demolition and renovation waste from projects around the country to make municipal mulch for use in playgrounds, flower beds, etc.
THE BOTTOM LINE
As is evident by now, there are numerous factors that contribute to a product’s sustainable characteristics, and specifiers should be cautious when manufacturers of products—be it of rubber, wood, concrete, glass, metal, tile, or any other building material or furnishing—make environmental claims based on single attributes alone, such as recycled content or low-VOC emissions. Clearly, LCAs help paint a far more complete picture of a product’s total ecological footprint, and when compared with like products using the same Product Category Rules, specifiers have a much more accurate baseline from which to make responsible material sourcing decisions.
Before the input-output model for life cycle assessment was developed, two brothers proposed a novel way to measure environmental impacts in process and product life cycles. The Odum brothers, Eugene Odum (1913-2002) and Howard Odum (1924-2002), each made myriad contributions to ecological engineering, ecological economics, and energy systems theories during their scientific careers. Together, they wrote the popular ecology textbook "Fundamentals of Ecology,” published in 1953 (and now in its fifth edition). In many ways, the environmental movement of the 1960s and 1970s was based on their integrative or holistic ecological thinking. One of their contributions to life cycle thinking was energy systems, or “Emergy,” which was measured in units of “sols.” This unit was designed to measure the geological, environmental, and current use of solar energy as a basis of life on earth. Although limited in quantifying effects to different environmental systems – water, land, air, biological – the sol unit allowed for more holistic thinking about use of fossil fuels, which has led to innovations in other fields like space travel. In the discussions about life cycle assessment procedures, the input-output model won over the Odum Emergy model. The input-output model, summarizing multiple effects on multiple environmental media, describes effects using different units (e.g., kilogram carbon dioxide equivalents, joules, etc.). This model is employed today in the life cycle assessments being conducted in thousands of locations around the world.
Source: “Ecologically-Based Life Cycle Assessment (Eco-LCA)” (accessed Sept. 2017).
Impact Categories for life cycle assessment show the effects of product manufacture, use, and disposal on a wide range of environmental media. Of course, which environmental media are of interest changes over the decades, from land, to water, to air, and so on. Here are a few of the most widely discussed:
The impact category “global warming” considers the potential contributions of different air emissions to global climate change.
Earth receives a constant influx of solar radiation, which provides it with heat. Some of this heat is reflected back into space, while some of it is radiated from the earth back into space. Since the industrial revolution, there has been a rapid accumulation of carbon dioxide and other greenhouse gases in the atmosphere. These greenhouse gases absorb and re-radiate heat, thereby trapping it in the atmosphere. This is known as the greenhouse effect, and its implications include potential sea level rise, more frequent and severe storms, changes in global precipitation patterns, and many other adverse consequences. Emissions of carbon dioxide from fossil fuel combustion account for the vast majority of global warming emissions, but emissions of methane, nitrous oxide, and various process chemicals are also significant contributors.
The impact category “acidification” refers to the potential for emissions to increase the acidity of water and soil systems. The most well known of these effects is acid rain, which can corrode the built environment, damage forests, and acidify soils and waterways, which has deleterious effects on plants and aquatic life. Additionally, acid chemicals can also be incorporated into dust or smoke in the air, which then gets deposited on the ground, in buildings, and so on, which eventually washes off into waterways. The major contributors to acidification are sulfur dioxide and nitrogen oxides from fossil fuel combustion.
The impact category “eutrophication” refers to the addition of chemical nutrients to surface waters, which promotes the excessive growth of plant life in those waters, such as algae. The decay of these plants and algae can deplete the water of its available oxygen, which leads to the death of other aquatic life, such as fish. The major drivers of eutrophication include excessive runoff of phosphorus and nitrogen compounds from fertilizers used for agriculture, and pollution from septic systems and sewers. For example, in the United States, we have an ongoing problem with excessive fertilizer runoff into the Mississippi River, which causes a so-called “dead zone” of eutrophication in the Gulf of Mexico. Similar “dead zones” exist in other parts of the world, too.
“Ozone depletion” refers to the thinning of the stratospheric ozone layer, which protects Earth from harmful ultraviolet radiation. The major causes of ozone depletion are emissions of chlorofluorocarbons and hydrofluorocarbons, which were commonly used in refrigerants, propellants, solvents, and insulating foam. Fortunately, nearly every country in the world has agreed to phase out the production and use of these and other ozone-depleting substances. However, because some of these chemicals are still being phased out, they can still be found in many products and production chains.
The demand for fresh water resources is accelerating, and competition for fresh water is increasingly of concern to planners and policy makers. There is enough freshwater on the planet for seven billion people, but it is distributed unevenly and too much of it is wasted, polluted, and unsustainably managed, resulting in water scarcity.
Source: Thinkstep, c 2017. Used with permission.
- Huynh, Christina (April 19, 2017). “How green buildings can help fight climate change,” U.S. Green Building Council
- Walsh, Bill, (Nov. 6, 2013). “Options? Rivals? Imitators? Transparency Market Has Them All,Healthy Building News
- Mann, Charles, C., . “W
- International Living Building Institute, (2017). “Red List”
- “Scoring flooring: Industry stats for 2016,” (June 26, 2017). Floor Covering News, Vol. 32, Iss. 1
- “What Is an EPD?” (Aug. 2017). SCS Global Services
- “Rubber Calendering Process,” (May 31, 2016). Goodyear Rubber
- “Vulcanization: (accessed Aug. 2017). Encyclopedia Britannica
- Nahlik, M. J., Kaehr, A. T., Chester, M. V., Horvath, A. and Taptich, M. N. (2016), “Goods Movement Life Cycle Assessment for Greenhouse Gas Reduction Goals,” Journal of Industrial Ecology, 20: 317–328.