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Cannabis — and hemp especially — is one of the best bio-absorbents in the world. It can sequester up to 30 tons of CO2 per hectare and through its roots, it can recover ground contaminated with heavy metals and radioactive materials. Also, its fibers are one of the toughest materials on Earth. Hemp is fast-growing; typically, it is ready to harvest in three to four months. This plant likes a wide range of soil and climate conditions, and requires little to no pesticides. Even after it is processed, hemp fibers can continue absorbing CO2.
These characteristics make cannabis the perfect candidate for construction material. The most popular hemp-based construction material is hempcrete. Hempcrete is made of the inner, woody core of the hemp plant mixed with a lime-based binder. The hemp core, also called “shiv,” has a high silica content that allows it to bind well with lime, a property that’s unique to hemp among all natural fibers.
Hempcrete has received a negative-carbon-material classification, meaning that during its fabrication process, it absorbs more CO2 than the quantity liberated to the atmosphere. This is very important to the environment because carbon dioxide is the main pollutant of the atmosphere, promoting climate change and planet warming. Among all of the carbon-negative materials, hemp is the top performer.
It is lightweight; in fact, it can be as light as a seventh or eighth of the weight of regular concrete and has insulating capacities comparable to fiberglass insulation but none of the harmful synthetic ingredients that commercial insulations contain. Hempcrete acts like a sponge. It absorbs moisture from the air when humid and releases it again when it’s dry. Hempcrete can be used in a wide variety of buildings, from houses and apartment blocks to service and public sector buildings, and even traditional buildings listed as historic.
With more and more countries legalizing cannabis, the specific mechanical solutions have arrived on the market, making processes much more efficient. A concrete mixing station combined with a concrete mixing truck and a conveyor belt is also an excellent solution frequently used by professionals to cast insulating roofs and screeds. Nowadays, prefabricated walls can also be produced for a faster build, without losing any of the benefits of a material that provides excellent thermal and moisture control performances.
Hempcrete buildings that are 10 stories high have been built in Europe but demand is lower throughout the world. Now, Canada-based Global Hemp Group Inc. has started the biggest cannabis-based construction project ever, in Hayden, Colorado. The company purchased 874 acres for a project called the Colorado Hemp Agro-Industrial Zone, which looks to prove the viability of hemp-based construction materials for building homes that are both sustainable and affordable. First, the land will be used to grow cannabis and there will be a 44-acre showcase home area.
This showcase area will display hemp-based building technologies and promote it as a viable industry, according to Global Hemp Group’s website. The company says it will make use of the substantial existing water resources to irrigate and cultivate industrial hemp, process and utilize hemp in the on-site manufacturing of green renewable construction products and finally build affordable carbon neutral/carbon negative housing.
For its part, ANICANN is participating in a competition organized by X-Prize and Elon Musk, looking for a sustainable solution that can absorb 10 giga-tons of CO2 from the atmosphere. Hempcrete is proof of the feasibility of hemp for this task.
In Mexico, hempcrete can be used for temperature isolation in the northern states where the winter can be cold, or in the south, where moisture can cause damage to housing, but without laws that establish a level playing field for all participants, this industry will never grow.