Almost any part of the hemp plant has an industrial use: from hemp seeds, which are quite similar to those of other cereals, to hemp fibre—strong and resistant—and the woody inner part of hemp stalk, known as “hurd” or “shives.” Hemp hurd is a wonderful material with many uses. It can be employed to produce paper pulp, fibreboard sheets, hempcrete, and substrate for plants. Additionally, raw hemp shives can be used in biofilters and as cattle bedding. Hemp hurd takes up 50% more water than sawdust and woodchips, and pulp is easy to compost. Shives can also be employed to produce chemical products, such as cellophane and rayon, and many other industrial materials.
In the past, hemp hurd or shives served another purpose. Pascal Madoz Ibáñez described a building in the vicinity of Callosa de Segura where carbonised shives were employed to produce gunpowder.
These broken fragments from the woody inner part of hemp are referred to as hurd, and few people know its by-products and uses. However, in countries that uphold sustainable manufacturing, hurd is a sub-product that may represent the main benefit from this plant. If hay processing plants were unavailable, the Hanfland Austrian method would be required, i.e. threshing lines of dry hay with an axial-flow combine. According to adjustments and yield rates, 3000 kg could be produced at a bulk price that is slightly similar to the price of hay.
France is a pioneer in the very short history of modern building with hemp, which originated by chance 20 years ago thanks to an inventor called Charles Rasetti, who tried it out when he was renovating his house “Maison de Turquie”. Initially, mineralised hemp shives were used, but it was eventually found that mineralisation was not necessary to produce mortar or to use shives as loose filling. We must not fail to note that most of hemp stalk consists of hurd, which is also the cheapest part of the plant—usually burnt in fields before different uses were discovered. Building stood as an ideal solution for the great amount of this waste material.
Among hemp’s most featured properties, we can highlight its thermal, acoustic, and bioclimatic qualities, which add up to substantial energy saving. Hemp also offers an interesting protection for materials against electromagnetic radiation and brings environmental benefits resulting from both cultivation and its use in building. Given hemp’s short growing period and yield per hectare—4 times higher than wood yield from forests—a greater amount of CO2 is captured.
In Germany, this material enjoys a high reputation when restoring timber frame houses that have endured for centuries, answering to current temperature demands without neglecting their structure or aesthetic appearance. Loose hemp granulate is also quite commonly used as an insulation filler on any floor or roof. Once certain technical difficulties are overcome, insulating hemp mortar could be produced in the future, which would be ideal for industrial developments.
Hemp Hurd: A Top-Grade Biocomposite
The market for hurds used in bio-composites for interior auto parts has proven its stability and growth opportunities. Some leading companies in the market, such as Audi, BMW, Mercedes-Benz, and some French carmakers use biocomposites in the interiors of mid-range and high-end vehicles. Some contain as much as 25 kilos of hemp fibre. These are price-competitive with traditional plastics and produce no environmental damage.