by Erin Hiatt – July 26, 2022

Hemp is well known for its incredible versatility and is often used in a variety of industries for practically innumerable applications including health and beauty, textiles, plastic, oil, batteries, and fuel. One particular use of hemp is often overlooked, but if used with more frequency, could have immense environmental benefits. What is this mystical substance? Hempcrete! A mix of lime and hemp shivs – a hemp, woody fiber from the core of the plant that would be normally wasted – hempcrete is used for construction applications like walls, floor, and insulation. That might not sound groundbreaking at first glance, but using hemp as a building material could actually have a massive impact on how we build the many structures that make our lives possible. Hempcrete might even turn out to be revolutionary. Read on to learn more.

Hemp is a sustainable crop that can grow from seed to harvest in about four months and grows well in many different types of soil and climates. It needs little water and is naturally resistant to pests, reducing the need for toxic herbicides. 

Hemp is very resistant to pests and therefore uses very little pesticides. Photo credit: Shutterstock

Concrete is by far the most used man-made material on the planet, showing up everywhere from dams to parking structures. Concrete, however, has an enormous environmental cost , and contributes about eight percent of the world’s carbon dioxide emissions. 

How does hempcrete stand up to classic concrete? Buildings made with hempcrete are carbon neutral and breathable, and over the life of the home, reduce heating and cooling costs because of its ability to retain and dispel heat. Hempcrete also makes buildings stronger, yet lighter, while still remaining weatherproof and fire retardant. Buildings constructed with hempcrete are also less prone to mold, which can irritate the nose, throat, lungs, skin, and eyes, but could be especially problematic for those who have allergies or asthma.

Hempcrete is ideal for low-rise construction, but cannot be used as a foundation or structure. Instead, it was intended to be used more like drywall. Hemp used at ground level could lose its ability to withstand mold. 

A man using hempcrete as floor insulation. Photo credit: Shutterstock

Currently, there are no international standards for building with hemp, nor codes to formalize how it should be used structurally and safely. In fact, special permits have to be obtained to build with hemp, and rules and regulations vary from state to state. Furthermore, like with anything cannabis-affiliated, banks are reluctant to mortgage a home built with hemp. 

For a piece of good news, researchers at the University of California, Riverside, were recently awarded a $12,000 grant to study new ways to process hemp to make hempcrete, among other applications. Currently, making hempcrete entails the pulping process, which creates runoff called “black liquor,” a chemical stew containing lignin residues and organic sulfides. 

The Science Times reports that students are hoping to develop a one-step process to separate lignin from biomass at low temperatures, to allow for much cleaner and faster pulping of hemp fibers without the production of black liquor. 

Research is currently in the works to find efficient ways to work with hempcrete. Photo credit: Shutterstock

Adjunct professor and lead researcher, Charles Cai, told The Science Times that their project goal “is to produce hempcrete as a lighter, stronger, and more environmentally friendly alternative to conventional fossil-based concrete.” Cai also believes that a more efficient process would help encourage builders to use hempcrete, as well as for other industrial applications like textiles. 

Building with hemp – despite its current fledgling nature in the United States. – is not a new building material. Structures made from hempcrete-like materials constructed by the Gauls, which is now modern-day France, date back approximately 2,000 years ago. Unlike the United States, countries like Japan and France did not have a hemp prohibition and utilized hemp for building for thousands of years. 

The French were quick to use hempcrete to rebuild after the bombings of WWII. Photo credit: Shutterstock

Hempcrete, in its more modern form, was developed in France in the mid-1980’s. During World War II, many buildings were extensively damaged, and 40 years after the War, builders were seeking innovative ways to renovate earlier repairs in buildings that were hundreds of years old. They discovered that adding hemp cellulose to lime mortars is an excellent insulating material, as well as being able to absorb and release moisture, critical for historic buildings. The success of these restorations inspired builders to apply it to other projects. 

France, to this day, continues its ancient tradition of growing and using hemp. Though China is the world’s number one grower of hemp, France is second, growing about one-quarter of the global hemp supply. 

In the United States, the first hemp home was constructed in North Carolina in 2010. Today, there are about 50 hemp homes scattered across the country. Now that the U.S. has finally legalized hemp with the passage of the 2018 Farm Bill, perhaps infrastructures like processing plants and hemp-designed farm equipment, in addition to friendlier regulations, will be implemented to support a sure-to-be-growing industry.

Education, Hemp, Science & Technology

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