What is hemp concrete? – Wikileaf


Photo credit: Shutterstock

Hemp is well known for its incredible versatility and is often used in a variety of industries for virtually countless applications including health and beauty, textiles, plastics, petroleum, batteries and fuel. One particular use of hemp is often overlooked, but if used more frequently, it could have immense environmental benefits.

What is this mystical substance? Hempcrete! A mixture of lime and hemp chips – a woody hemp fiber from the heart of the plant that would normally be wasted – hempcrete is used for construction applications such as walls, floors and insulation. It may not seem revolutionary at first glance, but using hemp as a building material could actually have a huge impact on how we build the many structures that make our lives possible. Hempcrete could even turn out to be revolutionary. Keep reading to learn more.

Hempcrete Vs. Concrete

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

A field of green hemp.

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

Concrete is by far the most widely used man-made material on the planet, popping up everywhere from dams to parking structures. Concrete, however, has a huge environmental costand contributes about eight percent of global carbon dioxide emissions.

How does hempcrete stand up to conventional concrete? Buildings made with hemp concrete are carbon neutral and breathable, and over the life of the house, reduce heating and cooling costs due to its ability to retain and dissipate heat. Hempcrete also makes buildings stronger, yet lighter, while remaining weatherproof and fireproof. 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 people with 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 resist mold.

Man using machinery to smooth gray hemp concrete

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

Currently, there are no international standards to build with hemp, or codes to formalize how it should be used structurally and safely. In fact, special permits must be obtained to build with hemp, and rules and regulations vary from state to state. Additionally, as with anything cannabis-affiliated, banks are reluctant mortgage a house built with hemp.

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

science time reports that the students hope to develop a one-step process to separate lignin from biomass at low temperatures, to enable much cleaner and faster pulping of hemp fibers without the production of black liquor.

hands holding beige hemp stalks

Research is currently underway to find effective ways to work with hempcrete. Photo credit: Shutterstock

Assistant Professor and Principal Investigator Charles Cai said science time that the goal of their project “is to produce hempcrete as a lighter, stronger and more environmentally friendly alternative to conventional fossil-based concrete.” Cai also thinks a more efficient process would encourage builders to use hempcrete, as well as for other industrial applications like textiles.

The history of using hemp for construction

Building with hemp – despite its current nascent nature in the United States. – is not a new construction material. Structures made from hempcrete-like materials built by the Gauls, who are now modern France, date back approximately 2,000 years. Unlike the United States, countries like Japan and France did not have hemp bans and used it for construction for thousands of years.

A gray rumbling French town left behind by a World War II bombing raid.

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

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

France, to date, continues its ancient tradition grow and use hemp. Although China is the world’s largest hemp producer, France is second, with around a quarter of the world’s hemp supply.


In the United States, the first hemp home was built in North Carolina in 2010. Today, there are approximately 50 hemp homes scattered across the country. Now that the United States has finally legalized hemp with the passing of the Farm Bill 2018, perhaps infrastructure such as processing plants and agricultural equipment designed for hemp, in addition to more user-friendly regulations, will be put in place to support a growing industry.


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