Canadian fields are brimming with plant fibres that can replace synthetic fibres produced by the synthesis of chemical compounds. Hemp and flax are particularly sought after in the textile sector, as their fibres are strong, soft and hypoallergenic. However, extracting high-quality natural fibres in an environmentally friendly way is no easy task. McGill University Bioresource Engineering professor and researcher Vijaya Raghavan has been tackling this problem with the help of his research team. Their work has led to the development of new processes that maximize the extraction of plant fibres and the production of value-added components for the hemp and flax industries.
In addition to being more efficient, these processes result in higher quality fibre.
The challenge lies in the fact that plant fibres are tightly bound to the stems by pectin, which acts as a sort of plant "mortar". To break this sturdy bond, hemp and flax stems are traditionally soaked in large amounts of water for several weeks. In order to improve the efficiency of this step known as "retting", Professor Raghavan and his colleagues turned to microwave energy, whose thermal effect greatly reduces the need for water. The researchers also addressed the drying stage, which requires a tremendous amount of time and energy to reduce the moisture content of the retted stems from 65% to the industry standard of 10%. They propose a pre-drying system based on electro-osmosis. During this step, an electric field is applied to two electrodes, which attract water molecules from the fibres as they pass through a roller press. This is followed by a final short period of microwave-assisted hot air drying.
In addition to being more efficient, these processes result in higher quality fibre. As an added bonus, they can also be used to isolate certain active compounds found in hemp straw, such as antioxidants and bio-oils used in the food and biofuel industries.