Precast concrete is a popular building material that is cast in a mold or form. This process is done off-site from a project to control the product quality and reduce waste. The material is used in both indoor and outdoor projects for wall panels, flooring, and even kitchen countertops. Gray is often the color choice for concrete products, but there are several color options available that are achieved through the use of dyes, pigments, and acid stains.

Some of the ingredients in precast concrete are natural materials, such as coarse and fine aggregates, cement, water, and admixtures. The concrete industry has made efforts to reduce their significant environmental impact by substituting some of these ingredients with fly ash, a byproduct of coal production. Because they are achieving a reduction in the embodied carbon with this strategy, they often market their products as “green.” There are a few sustainable characteristics to precast concrete including its thermal mass. The factory environment uses less material than concrete created on site and often the materials come from local sources, which can reduce transportation costs and emissions. However, as you can see from the manufacturing process outlined below, the multi-step and energy intensive processes involved in manufacturing precast concrete create a much larger environmental footprint than natural stone.

A precast concrete wall panel with a repeating pattern. Photo Credit: Wikimedia Commons/ Acabashi

Manufacturing Precast Concrete vs. Natural Stone

To manufacture precast concrete, raw materials are required to first make cement. Minerals are mined out of the ground and then transported to a cement manufacturer or plant. The minerals are heated at extremely high temperatures to create the cement which requires the use of a lot of energy and produces a significant amount of harmful emissions including sulfur dioxide, nitrogen oxide, and carbon monoxide. A mold and steel reinforcement are also needed for the precast concrete. The mold must be created and the steel must be acquired and transported to a steel manufacturer, where it is melted and cast into reinforcing rods. Aggregates are also required, which must be mined, crushed, and sorted. There are other additives and products required depending on the desired finish. The materials are mixed with water, put into molds, and cured into the final product. Polishing, sealing, and/or waxing may also be necessary, depending on the end use of the precast concrete.

In contrast, natural stone requires only quarrying, fabricating, finishing, and transporting. No additional materials or chemicals are required to create natural stone. The Earth naturally forms the material over time. This means natural stone really is a natural material and has many other attributes, including its durability, recyclability, and wide range of aesthetics. Natural stone can be used in many different indoor and outdoor applications as well and contains no Volatile Organic Compounds (VOCs), meaning it does not emit any harmful gases, making it a healthy material.

Sustainability Concerns

From an overall sustainability perspective, natural stone has a lower environmental footprint than precast concrete. This is due to the minimal resources used to quarry, fabricate, finish, and transport natural stone.  As the graph below demonstrates, precast concrete has a higher global warming potential (GWP) than natural stone. Every step in the precast concrete manufacturing process requires the use of a lot of energy, which contributes to their total GWP. The larger the GWP, the more that a given gas warms the Earth compared to carbon dioxide (CO2) over the same timeframe. The natural stone industry is often criticized for utilizing raw materials that are not rapidly renewable. However, natural stone is abundant within the Earth. Other industries also utilize the supply of natural stone as it is a significant ingredient in concrete, porcelain, and other manmade products.

The impacts of these processes have been documented and systematically compared against other materials using the same environmental criteria. This information is a valuable resource when selecting a sustainable material for a project.

The embodied carbon quantities displayed were estimated based on the following:
Unite of Measure: Global Warming Potential (kg CO₂ eq)
Functional Unit: 1m²
Scope: Raw Material Extraction, Transportation, Manufacturing (A1-A3)
Natural Stone: Industry-Wide EPDs for Cladding, Flooring & Countertops
Pre-Cast Concrete Cladding: Industry-Wide EPD for Architectural Precast Panels, 150 lbs per ft3, 4” thick
Engineered Quartz: Average of three individual manufacturer EPDs
Terrazzo: Average of three individual manufacturer EPDs

These characteristics and attributes also make natural stone a great choice when seeking a green building rating certification within the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) or the International Living Future Institute’s Living Building Challenge (LBC). The different manufacturing processes and impacts of building materials are being documented in product labels such as Environmental Product Declarations (EPDs) and Health Product Declarations (HPDs). These labels make it even easier to qualify for points and credits within LEED and other green building rating systems using natural stone. The labels document and quantify environmental information on the life cycle of a product and allow you to make comparisons and informed decisions on materials that fulfill the same function. The product labels are also intended to demonstrate that the health and environmental claims are transparent, accurate, and meet defined standards. Industry-wide EPDs are available for natural stone cladding, flooring/paving, and countertops. HPDs are available for common natural stone types used in the dimension stone industry including granite, limestone, marble, quartzite, onyx, sandstone, slate, travertine, and more.  (See also: Environmental and Health Product Labels for Natural Stone.)

To further advance these issues, the natural stone industry has been working diligently over the years to make continuous improvements in each area and step of the process. This includes reducing water use, energy use, improving the efficiency of the transportation of natural stone, properly managing and adaptively reusing quarry sites, and many others.

Technology advancements in the natural stone industry have led companies to create zero waste strategies that use every part of a stone block. Photo Credit: Coldspring

Stone wall designs can be quickly and easily fabricated using computer numerically controlled machinery, with any waste being used in stone byproducts. Photo Credit: Stephanie Vierra

The natural stone industry has created a certification system that determines if a quarry or fabricator meets defined sustainability standards in key areas of importance. This makes it easier to find and use natural stones that meet the standard, simplifying the process of choosing the right material that not only looks and performs well, but also has the least amount of impact on the environment. The standard is also accepted within the LBC, further ensuring its use in sustainable building projects. The metrics of the Natural Stone Sustainability Standard can be used to vet stone suppliers even if they have not yet achieved certification.  More information is available via the Natural Stone Institute or NSF International.

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Sintered surface, also known as ultra-compact surface, is an engineered product that is dense, durable, and resistant to stains, heat, and scratches. The material can be used in many different applications including interior kitchens and bathrooms, and exterior applications such as wall cladding and countertops. This is due to the material’s various thicknesses and durability, and because it has a low porosity and does not fade from UV exposure. The intended design gets printed on the surface but typically does not go all the way through the material. This means that the ends and edges may not have the same color or pattern as the rest of the surface. Sintered surface has an increased risk of chipping due to its denseness and hardness. The edges are especially prone to damage if impacted and can be difficult to repair.

Sintered surface is sometimes marketed as sustainable because it contains natural materials. But as you will see from the manufacturing process described below, the use of an energy intensive manufacturing process gives sintered surface a larger environmental footprint than natural stone.

A sintered stone slab with an interesting texture ready for use as a countertop. Photo Credit: Wikimedia Commons/JonSmith37341.

Manufacturing Sintered Surface vs. Natural Stone

Sintered surfaces are created with several natural materials including kaolin, feldspars, silico-aluminates, and clays, which are first mined out of the ground. The raw materials are then transported to a manufacturing plant, where they must then undergo a complex, energy intensive process that simulates, or mimics, hundreds of years of metamorphic change. To manufacture a sintered surface requires several different stages of processing including grinding, mixing, reacting, stabilizing, separating, and drying. This resulting mixture is then subjected to immense pressure and extreme heat—more than 2,000^o F—to fuse the materials together, all of which requires a lot of energy.

In contrast, natural stone requires only quarrying, fabricating, finishing, and transporting. No additive materials or chemicals are required to create natural stone. Stone is formed naturally by the Earth over time. Several types of natural stone, including marble and gneiss, undergo metamorphoses within the Earth’s crust where extreme pressure and heat transform the deposit from a more porous material to a harder and denser material. This process happens over millions of years in the ground. This means natural stone really is a natural material and has many other attributes, including its durability, recyclability, and wide range of aesthetics. Natural stone can be used in many different indoor and outdoor applications as well and contains no Volatile Organic Compounds (VOCs), meaning it does not emit any harmful gases, making it a healthy material. 

Sustainability Concerns

From an overall sustainability perspective, natural stone has a lower environmental footprint than a sintered surface. This is due to the minimal resources used to quarry, fabricate, finish, and transport natural stone. Each step in the sintered surface manufacturing process requires the use of energy, which contributes to the total GWP. The larger the GWP, the more that a given gas warms the Earth compared to carbon dioxide (CO₂) over the same timeframe.

These characteristics and attributes also make natural stone a great choice when seeking a green building rating certification within the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) or the International Living Future Institute’s Living Building Challenge (LBC). The different manufacturing processes and impacts of building materials are being documented in product labels such as Environmental Product Declarations (EPDs) and Health Product Declarations (HPDs). These labels make it even easier to qualify for points and credits within LEED and other green building rating systems using natural stone. The labels document and quantify environmental information on the life cycle of a product and allow you to make comparisons and informed decisions on materials that fulfill the same function. The product labels are also intended to demonstrate that the health and environmental claims are transparent, accurate, and meet defined standards. Industry-wide EPDs are available for natural stone cladding, flooring/paving, and countertops. HPDs are available for common natural stone types used in the dimension stone industry including granite, limestone, marble, quartzite, onyx, sandstone, slate, travertine, and more.  (See also: Environmental and Health Product Labels for Natural Stone.)

To further advance these issues, the natural stone industry has been working diligently over the years to make continuous improvements in each area and step of the process. This includes reducing water use, energy use, improving the efficiency of the transportation of natural stone, properly managing and adaptively reusing quarry sites, and many others.

An example of a stone fabrication plant recycling and reusing water in the polishing stage, saving thousands of gallons of water annually. Photo Credit: Dennett Tile & Stone

The natural stone industry has created a certification system that determines if a quarry or fabricator meets defined sustainability standards in key areas of importance. This makes it easier to find and use natural stones that meet the standard, simplifying the process of choosing the right material that not only looks and performs well, but also has the least amount of impact on the environment. The standard is also accepted within the LBC, further ensuring its use in sustainable building projects. The metrics of the Natural Stone Sustainability Standard can be used to vet stone suppliers even if they have not yet achieved certification.  More information is available via the Natural Stone Institute or NSF International.

Manufacturing Impacts Series: Read More

Porcelain is a hardwearing material that is suitable for both indoor and outdoor design projects. Porcelain slabs or tile are often used for kitchen and bathroom counters, flooring, stairs, and windowsills. It is a fairly thin material, typically manufactured to be only ½” thick. The basic ingredients that go into the process of manufacturing porcelain are clays, sands, and different feldspar minerals. Because it contains some natural materials, porcelain is often marketed as a sustainable material. Porcelain is also produced to emulate the beauty and veining of marble. But as you will see from the manufacturing process outlined below, the use of many materials and additives and the energy intensive processes involved in its manufacturing create a larger environmental footprint for porcelain than natural stone.

Manufacturing Porcelain vs. Natural Stone

Raw materials like clay, feldspar, and other materials must first be mined out of the ground and then transported to a manufacturing plant. The next step in the process is the intake, storage, and sorting of the required raw materials. Additives such as inks and glazes must also be transported to the manufacturing plant, where they undergo further sorting, mixing, forming, drying, and pressing. Images and glazes are applied to the porcelain surface at this stage. Then, extreme heat is required to fire and glaze the materials into the final porcelain product.

Manufacturing impacts of porcelain.

In contrast, natural stone requires only quarrying, fabricating, finishing, and transporting.  No additional materials or chemicals are required to create natural stone. The Earth naturally forms the material over time.  This means natural stone really is a natural material and has many other attributes, including its durability, recyclability, and wide range of aesthetics. Natural stone can be used in many different indoor and outdoor applications as well and contains no Volatile Organic Compounds (VOCs), meaning it does not emit any harmful gases, making it a healthy material.

Manufacturing impacts of natural stone.

Sustainability Concerns

From an overall sustainability perspective, natural stone has a lower environmental footprint than porcelain due to the minimal resources used to quarry, fabricate, finish, and transport it.  All of the steps in the manufacturing process of porcelain require the use of a lot of water and energy which contribute to the total GWP. The larger the GWP, the more that a given gas warms the Earth compared to CO₂ over that same timeframe.

These characteristics and attributes also make natural stone a great choice when seeking a green building rating certification within the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) or the International Living Future Institute’s Living Building Challenge (LBC). The different manufacturing processes and impacts of building materials are being documented in product labels such as Environmental Product Declarations (EPDs) and Health Product Declarations (HPDs). These labels make it even easier to qualify for points and credits within LEED and other green building rating systems using natural stone. The labels document and quantify environmental information on the life cycle of a product and allow you to make comparisons and informed decisions on materials that fulfill the same function. The product labels are also intended to demonstrate that the health and environmental claims are transparent, accurate, and meet defined standards. Industry-wide EPDs are available for natural stone cladding, flooring/paving, and countertops. HPDs are available for common natural stone types used in the dimension stone industry including granite, limestone, marble, quartzite, onyx, sandstone, slate, travertine, and more.  (See also: Environmental and Health Product Labels for Natural Stone.)

To further advance these issues, the natural stone industry has been working diligently over the years to make continuous improvements in each area and step of the production process. This includes reducing water use, energy use, improving the efficiency of the transportation of natural stone, properly managing and adaptively reusing quarry sites, and many others.

Halibut Point State Park in Massachusetts is a former granite quarry reclaimed into a public park. Photo courtesy of Mass.gov.

The natural stone industry has created a certification system that determines if a quarry or fabricator meets defined sustainability standards in key areas of importance. This makes it easier to find and use natural stones that meet the standard, simplifying the process of choosing the right material that not only looks and performs well, but also has the least amount of impact on the environment. The standard is also accepted within the LBC, further ensuring its use in sustainable building projects.  Even if a natural stone is not yet certified to the standard, the information can be used to vet stone suppliers and ask important questions to help choose the optimal natural stone for your project. More information is available via the Natural Stone Institute or NSF International.

Manufacturing Impacts Series: Read More

There are many building materials to choose from when designing or remodeling a project.  Engineered quartz is one material that is often used in interior projects, especially for countertops. It comes in a variety of colors, patterns, and textures. The product is made by combining natural and manmade materials including quartz, resins, pigments, and other ingredients.  It is a hard, dense, and nonporous material but can only be used on interiors because the resins are not UV stable for outdoor use. Engineered quartz is often manufactured to mimic popular natural stones, especially white marble, but tends to have less variation or veining than natural stone. Engineered quartz is sometimes marketed as a sustainable, natural material because of the quartz in it. However, as the process of manufacturing engineered quartz below demonstrates, that is not the case.

Manufacturing Process for Engineered Quartz

The manufacturing process for engineered quartz includes many energy and resource intensive steps, resulting in a greater impact on the environment. First, quartz is quarried or mined out of the ground, then crushed. Several other additives are required, such as polyesters, resins, acids, alcohols, styrene, peroxide, and other chemicals to create a series of chemical reactions. These additive materials all have to be manufactured and then transported to a manufacturing plant where they will be mixed and put into molds, compacted, and often heated and cured to create slabs. Depending on the manufacturer, the resulting slabs will vary in size, thickness, and appearance. Since engineered quartz is manufactured and installed in slabs, the seams will be visible in a large countertop application. Also, while engineered quartz is manufactured to be somewhat heat resistant, it is not as heat resistant as natural stone. For example, it cannot be used as flooring over radiant heat because of possible damage from the long-term heat exposure.

Manufacturing impacts of engineered quartz.

Sustainability Concerns

Comparatively, natural stone can be used in most applications and requires only quarrying, fabricating, finishing, and transporting. No additional materials or chemicals are required to create natural stone. The Earth naturally forms the material over time. This means natural stone really is a natural material and has many other attributes, including its wide range of aesthetics, durability, and recyclability. Natural stone contains no Volatile Organic Compounds (VOCs), meaning it does not emit any harmful gases, making it a healthy material.

Manufacturing impacts of natural stone.

The materials used and the multi-step process required to manufacture engineered quartz also result in a higher global warming potential, as shown below. From an overall sustainability perspective, natural stone has a lower environmental footprint than engineered quartz due to the minimal resources used to quarry, fabricate, fabricate, finish, and transport it. The impacts of these processes have been documented and systematically compared against other materials using the same environmental criteria. This information is a valuable resource when selecting a sustainable material for a project.

Global Warming Potential

The embodied carbon quantities displayed were estimated based on the following:
Unite of Measure: Global Warming Potential (kg CO₂ eq)
Functional Unit: 1m²
Scope: Raw Material Extraction, Transportation, Manufacturing (A1-A3)
Natural Stone: Industry-Wide EPDs for Cladding, Flooring & Countertops
Pre-Cast Concrete Cladding: Industry-Wide EPD for Architectural Precast Panels, 150 lbs per ft3, 4” thick
Engineered Quartz: Average of three individual manufacturer EPDs
Terrazzo: Average of three individual manufacturer EPDs

These characteristics and attributes also make natural stone a great choice when seeking a green building rating certification within the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) or the International Living Future Institute’s Living Building Challenge (LBC). The different manufacturing processes and impacts of building materials are being documented in product labels such as Environmental Product Declarations (EPDs) and Health Product Declarations (HPDs). These labels make it even easier to qualify for points and credits within LEED and other green building rating systems using natural stone. The labels document and quantify environmental information on the life cycle of a product and allow you to make comparisons and informed decisions on materials that fulfill the same function. The product labels are also intended to demonstrate that the health and environmental claims are transparent, accurate, and meet defined standards. Industry-wide EPDs are available for natural stone cladding, flooring/paving, and countertops. HPDs are available for common natural stone types used in the dimension stone industry including granite, limestone, marble, quartzite, onyx, sandstone, slate, travertine, and more.  (See also: Environmental and Health Product Labels for Natural Stone.)

To further advance these issues, the natural stone industry has been working diligently over the years to make continuous improvements in each area and step of the process. This includes reducing water use, energy use, improving the efficiency of the transportation of natural stone, properly managing and adaptively reusing quarry sites, and many others.

The natural stone industry also created a certification system that determines if a quarry or fabricator meets defined sustainability standards in key areas of importance. This makes it easier to find and use natural stones that meet the standard, simplifying the process of choosing the right material that not only looks and performs well, but also has the least amount of impact on the environment. The standard is also accepted within the LBC, further ensuring its use in sustainable building projects. Even if a natural stone is not yet certified to the standard, the information can be used to vet stone suppliers and ask important questions to help choose the optimal natural stone for your project. For more information, see the Natural Stone Institute’s website at: www.naturalstoneinstitute.org/sustainability.

Manufacturing Impacts Series: Read More