Manufacturing Impacts: Natural Stone vs. Engineered Quartz

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.

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