Derek Thomas – Analyst
The ‘green’ trend that has taken hold over the past two decades continues to grow into more industries and subcultures. What began with organic foods and more gas-efficient cars is now pervasive in energy, domestic and commercial cleaning, health care, consumer goods and packaging, and many other industrial and commercial industries. One area seems to be behind the curve in this trend: construction.
To be fair, some incredible advances have been made that make our homes and businesses more efficient once they are occupied (think solar, water efficiency, insulation, and architecture). However, the building materials used have gone relatively unchanged for over a century.
What if there was a material that grew naturally from the earth and didn’t require harsh chemicals to grow or process it? It’d have to be strong. It’d have to have multiple yearly growing cycles and produce a lot of usable bio-mass. It’d have to be economically competitive.
Where can we find such a super plant? Hemp.
Heck, before cannabis prohibition, humans had been using hemp to build for over a thousand years.
But what is hempcrete and is it commercially viable?
Hempcrete is a bio-composite that is made of the inner woody core of the hemp plant (which is the majority mass of the stalk) and mixed with a lime-based binder. Lime based binder are also a natural way to bind the fibers, similar to emulsification. The hemp core or “Shiv” has a high silica content which allows it to bind well with lime. This property is unique to hemp among all natural fibers. The result is a lightweight cementitious insulating material weighing about a seventh or an eighth of the weight of concrete.
Recently, hempcrete was discovered in a bridge structure in France that was built in the 6th century. The bridge is still standing to this day, making it almost 800 years old. Given this, it can be expected that hempcrete has a very long shelf life when properly casted.
The typical compressive strength is around 1 MPa, which is roughly 1/20 that of residential grade concrete. It is a low-density material and is resistant to cracking during movement thus making it highly desirable for use in earthquake-prone areas.
There are additional naturally occurring benefits of hempcrete. It is naturally anti-fungal and greatly reduces the chance for mold. The material is very moisture-resistant and helps prevent wood rot throughout structures where it is incorporated. Finally, it is naturally fire-retardant, making it the only commercial-grade building material that is fire retardant without the need for harsh chemicals.
The material makes for incredibly efficient on-site logistics. Hempcrete is so lightweight that it can be moved easily about the site in tubs and passed up multiple stories of buildings in bucket-brigade fashion to workers filling in cavities. Even more fascinating is how easy it is to clean up hempcrete at construction sites: simply till it into the soil as it will bio-degrade naturally.
Hemp is grown legally in Europe, the UK and Canada through a system of licensed growers producing seed certified low in THC.
credit:420intel.com
