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June 30, 2020
Look around you: how much of your surrounding environment was built using concrete? For many of us, the answer is most of it.
Concrete is the most widely used construction material in the world. It is also a long-standing source of environmental degradation and human health complications. Around the world, more than 4 billion tons of concrete are produced each year, accounting for nearly 8 percent of global CO2 emissions. Concrete production stresses global water supplies as well: a 2018 study in Nature Sustainability found that the concrete industry accounts for nearly one-tenth of all industry water withdrawals, and 1.7 percent of all global water withdrawals. Concrete production poses significant human health risks primarily from respirable crystalline silica (RCS) dust—tiny particles of the mineral crystalline silica—created during heavy industrial processes such as cutting, grinding, sawing or crushing concrete. According to the Occupational Safety and Health Administration (OSHA), the 2.3 million Americans exposed to RCS dust at work are vulnerable to silicosis, lung cancer, chronic obstructive pulmonary disease (COPD), and kidney disease.
Due to these environmental and human health risks, some experts are promoting hempcrete, or hemplime, as the future of the construction industry. Hempcrete is a bio-composite walling and insulation material that is used to construct and retrofit buildings. As its name suggests, hempcrete is made from the hemp plant. Hempcrete processors combine hemp hurd (the woody core of the hemp plant stem) with a lime-based binder and water to create hempcrete. The use of hempcrete for homes and commercial buildings began in France in the 1980s and soon spread to other European nations such as Belgium, the Netherlands, and the United Kingdom.
Unlike concrete, hempcrete offers numerous environmental and human health benefits. HempStone LLC, a U.S. hempcrete company, notes that hempcrete is healthy, resilient, and sequesters carbon. It is non-toxic, biodegradable, anti-fungal, anti-pest, fire-resistant, and excellent at thermoregulation. Hemp is also a rapidly renewable resource—on 1.5 acres of land, it takes only 12 weeks for farmers to grow enough industrial hemp to build a 1,500-square-foot home. Since hemp plants enhance soil health by holding soil together and reducing erosion, farmers can grow hemp on the same parcel of land many times over. Hempcrete is also a flexible building material that allows for creative designs that can mold to a variety of aesthetic preferences. Last but not least, hempcrete is a “better-than-zero-carbon-material” (as described by Hempcrete UK) because it traps more atmospheric carbon in the lifetime of the building than was emitted during production, transportation, and construction.
While European countries have used hempcrete for decades, the United States has been slow to adopt this sustainable concrete alternative. According to Steve Allin, director of the International Hemp Building Association, since American farmers grow hemp in relatively small amounts, compared to other commodity crops, supply is the main barrier to increased hempcrete construction projects in the United States. Industrial hemp cultivation only became legal at the federal level under the Agriculture Improvement Act of 2018 (H.R.2), which still includes restrictions on hemp growth. Asheville-based architect Anthony Brenner explains, “there’s a stigma that marijuana and industrial hemp are the same thing, but the THC content of industrial hemp is actually only 0.035 percent.”
Another challenge is that large-scale American hemp processing facilities are few and far between. “We have not learned of any large-scale commercial hemp decortication facility operational in the U.S.,” wrote Charles Wortmann and Ismail Dweikat of the University of Nebraska-Lincoln’s Institute of Agriculture and Natural Resources. Further, the U.S. Hemp Building Association is still in the process of working with the International Code Council (ICC) and the American Society for Testing and Materials (ASTM) to “solve the permitting and performance issues that have prevented hempcrete from gaining a larger presence in the U.S.” The combination of these factors means that many builders who use hempcrete in the United States import the hemp hurd from Europe, which leads to high hempcrete costs and high CO2 emissions.
Despite these obstacles, some contractors have managed to construct hempcrete buildings in the United States. The “Push House,” the first hempcrete house in America, was built in 2010 for the family of the former mayor of Asheville, N.C., Ross Martin. Now, there are hemp houses in Texas, Hawaii, and Virginia and companies such as American Hemp, Left Hand Hemp, HempStone LLC, and Hempitecture specialize in hempcrete architecture and construction. Still, as of 2018, only 50 homes in the United States have been built with hempcrete. One of Hempitecture’s suppliers, Sunstrand, filed for bankruptcy in January of this year.
As our world becomes increasingly urbanized, the temptation will be to continue building with concrete. However, if the United States can overcome the initial policy and infrastructure hurdles, hempcrete will help open the door to a more sustainable construction industry and a greener future.
Author: Maeve Arthur
Top-Rated Climate Nonprofit – 4-Star Charity