Hempcrete: Building with green plants

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  Quantumrun Foresight
• November 17, 2023

Insight summary

Hempcrete, a blend of hemp and lime, is emerging as a sustainable alternative in the building and construction sector, offering eco-friendly, insulating, and mold-resistant properties. Notably utilized by Dutch firm Overtreders, hempcrete is gaining traction for its low environmental impact and biodegradability. While its porous nature poses some limitations, it offers fire resistance and a healthy indoor environment. As hempcrete gains more attention, it's being considered for retrofitting buildings and even for carbon capture infrastructure. With its thermal properties, job-creation potential, and applicability in developing countries, hempcrete is poised to be a cornerstone in the global move toward zero-carbon construction.

Hempcrete context

Hemp is currently utilized in various industries, including the production of clothing and biofuel. Its potential as an environmentally friendly building material is also gaining recognition due to its capacity to sequester carbon. In particular, the combination of hemp and lime, called hempcrete, is being increasingly used in zero-carbon building projects because it is highly insulating and mold-resistant.

Hempcrete involves blending the hemp shives (small wood pieces from the plant's stalk) with either mud or lime cement. Although hempcrete is non-structural and lightweight, it can be combined with conventional building systems. This material can be cast-in-place or prefabricated into building components like blocks or sheets, much like regular concrete.

An example of construction firms using hempcrete is Overtreders, based in the Netherlands. The company created a community pavilion and garden using 100 percent biobased materials. The walls were made of pink-dyed hempcrete sourced from locally grown fiber hemp. The pavilion is set to be relocated to the cities of Almere and Amsterdam, where it will be utilized for 15 years. Once the modular building elements reach the end of their lifespan, all components are biodegradable.

While hempcrete has numerous advantages as a building material, it also has drawbacks. For example, its porous structure reduces its mechanical strength and increases its water retention capacity. Although these concerns do not render hempcrete unusable, they impose significant limitations on its applications.

Disruptive impact

Hempcrete is sustainable throughout its life cycle because it uses natural waste materials. Even during the plant's cultivation, it requires less water, fertilizer, and pesticides than other crops. Additionally, hemp grows quickly and easily in nearly any part of the world and yields two harvests annually. 

While growing, it sequesters carbons, prevents soil erosion, suppresses weed growth, and detoxifies the soil. After harvesting, the remaining plant material decomposes, adding nutrients to the soil, which makes it an attractive option for crop rotation among farmers. As the benefits of hempcrete become more highlighted, more construction firms will likely experiment with the material to fulfill their zero-carbon initiatives.

Other features make hempcrete versatile. The lime coating on hempcrete is fire-resistant enough to allow occupants to evacuate safely. It also minimizes fire propagation and reduces the risk of smoke inhalation because it burns locally without producing smoke. 

In addition, unlike other building materials, hempcrete does not cause respiratory or skin problems and is vapor-permeable, ensuring a healthy indoor environment. Its lightweight composition and the air pockets among its particles make it both earthquake-resistant and an effective thermal insulator. These characteristics may incentivize governments to work with green companies to produce hempcrete prototype structures, such as India-based GoHemp.

Applications of hempcrete

Some applications of hempcrete may include: 

• Hempcrete being used to retrofit existing buildings, reducing the carbon footprint of the construction industry and improving energy efficiency.
• Carbon capture firms using hempcrete as a carbon sequestration infrastructure.
• The production, processing, and installation of hempcrete creating jobs in the agriculture, manufacturing, and construction industries.
• Hemp cultivation providing a new revenue stream for farmers. 
• Hempcrete's thermal insulation properties reducing energy consumption in buildings, leading to lower heating and cooling costs.
• Hempcrete being utilized to provide affordable, environmentally friendly options for housing in developing countries.
• The development of new processing techniques and machinery leading to advancements in other industries, such as textiles.

Questions to consider

• How can governments and policymakers promote sustainable building materials like hempcrete?
• Are there any other sustainable building materials that you think should be explored further?