Low-density insulation blocks and hardboards from amaranth (Amaranthus cruentus) stems, a new perspective for building applications

Nowadays, amaranth appears as a promising source of squalene of vegetable origin for the cosmetic industry. Squalene represents up to 6% (w/w) of oil from seeds. It can be isolated from vegetable oil for subsequent use. This triterpene is highly appreciated in cosmetology, especially for the formulation of moisturing creams. Indeed, it has the ability to quickly penetrate the skin without leaving traces or oily sensations on it, and it blends well with other oils and vitamins. The squalene currently marketed is almost exclusively extracted from the liver of sharks, causing at the same time their overfishing. Thus, providing to the cosmetic industry a squalene of renewable origin is a major challenge for the cosmetic industry. As amaranth oil is one of the most concentrated vegetable oils in squalene, this is the reason why the amaranth plant has experienced renewed interest in recent years. In addition to the seeds, a stem is also produced during the amaranth cultivation. Representing up to 80% (w/w) of the plant aerial part, it is composed of a ligneous fraction, the bark, on its periphery, and a pith in its middle. In this study, a mechanical fractionation process was developed to separate continuously bark and pith. The use of both fractions to produce renewable materials for building applications was also investigated. On the one hand, the bark was succesfully used to produce hardboards, with the deoiled seeds acting as natural binder. Such boards are a viable alternative to commercial wood-based panels (e.g., plywood, chipboard, OSB or MDF). On the other hand, the pith was transformed with success into cohesive and machinable low-density insulation blocks revealing a thermal conductivity near from that of polystyrene