Hemp

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.