Hemp

1-15 usd/kg
Circularity potential
Very high
Strength
High
Production energy
Ultra low
Stiffness
Medium
Embodied CO2
Ultra low
Density
Medium

Hemp (Cannabis sativa) is cultivated for its fibres, seed oil and woody stem. While the seeds are a source of food, the core of the stem leftover from fibre production is converted into shives that are used for particle board and building materials, for example. In the past, the core has not been used intensively, but this is rapidly changing with the development of hempcrete, a biocomposite made up of hemp shives and lime-based binder.

The plants grow fast and tall, up to 4 m, helping to suppress weeds. And there are very few pests and diseases that affect these hardy plants – its very low protein content means it is not consumed by insects. This means pesticides are not needed. Even though restricted in some areas due to its association with marijuana, it is cultivated across Europe and Asia, and parts of Canada and United States.

The bast fibres are similar to those derived from flax, jute and ramie, and made up of 50-70% cellulose, 10-15% hemicellulose, 5-15% lignin and 5-10% pectin. Hemp contains more lignin than flax (linen), and the fibres tend to be less strong and stiff.

The majority of hemp fibre contains a mix of short and long fibres. The majority of it goes into nonwovens, such as for insulation, as opposed to fine textiles. It also goes into paper production. It is pricier than wood, but offers superior mechanical properties, and so tends to be reserved for speciality papers that require the extra strength it offers.



Hemp fibre has been used in textiles for millennia. Relatively recently, it has begun to be utilised as technical textile and as fibre reinforcement in composites. As a fibre in fashion textiles, it is often compared to linen (flax). Flax has slightly superior strength, stiffness and fineness, and is more commonly cultivated as a textile fibre, so more widely available as a high quality fabric. Hemp tends to be a little coarser and more industrial, but if processed like flax into linen, the two can be almost indistinguishable without detailed analysis.

Tensile strength is depend on fibre diameter. Fineness ranges from around 10 microns or so up to 0.8 mm. Thinner fibres have superior strength and stiffness.


Design properties
Cost usd/kg
10-15
Embodied energy MJ/kg
3.4-22
Carbon footprint kgCO2e/kg
0.1-0.64
Density kg/m3
1480
Tensile modulus GPa
17.5-70
Tensile strength MPa
310-900
Hardness Mohs
1
Thermal conductivity W/mK
0.2-1.6
Temperature min-max °C
-40 to 150
Thermal
insulator
Electrical
insulator