Low-Density Insulation Blocks and Hardboards from Amaranth (Amaranthus cruentus) Stems, a New Perspective for Building Applications

Abstract

Nowadays, amaranth appears as a promising source of squalene of vegetable origin. Amaranth oil is indeed one of the most concentrated vegetable oils in squalene, i.e., up to 6% (w/w). This triterpene is highly appreciated in cosmetology, especially for the formulation of moisturizing creams. It is almost exclusively extracted from the liver of sharks, causing their overfishing. Thus, providing a squalene of renewable origin is a major challenge for the cosmetic industry. The amaranth plant has thus experienced renewed interest in recent years. In addition to the seeds, a stem is also produced during 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 fractionation process was developed to separate bark and pith. These two fractions were then used to produce renewable materials for building applications. On the one hand, the bark was used to produce hardboards, with the deoiled seeds acting as natural binder. Such boards are a viable alternative to commercial wood-based panels. On the other hand, the pith was transformed into cohesive and machinable low-density insulation blocks revealing a low thermal conductivity value.

Influence of Thermocompression Conditions on the Properties and Chemical Composition of Bio-Based Materials Derived from Lignocellulosic Biomass

“…In addition, mechanisms involving cellulose, hemicellulose and lignin degradation under thermocompression have been described [11], inducing self-polymerization and crosslinking upon further condensation reactions between furfural and lignin, in turn contributing to self-bonding [12,13]. Cohesive binderless boards have been successfully produced through the thermocompression of lignocellulosic fibers from sunflower cake [14], wheat straw [15], Miscanthus sinensis [16], banana bunches [17], kenaf core [18], coriander straw [19], rice straw [20], amaranth stems [21], oil palm trunks [22] and sugarcane bagasse [23]. However, binderless lignocellulosic materials exhibit greater sensitivity to water than materials obtained with binders.…”

Bio-based materials from sunflower co-products, a way to generate economical value with low environmental footprint

“…In addition, synthetic adhesives are relatively expensive, accounting for up to 30% of the total production cost (Van Dam et al, 2004a). The production of binderless panels (Tajuddin et al, 2016) or the use of natural binders such as lignins (Theng et al, 2019), starch (Evon et al, 2021b) or proteins (Evon et al, 2015a) avoid the use of such chemical additives.…”

Twin-Screw Extrusion Process to Produce Renewable Fiberboards

“…For the defibration of lignocellulosic materials to produce fiberboards, the most recent works have used rice straw 25 , 28 , coriander straw 26 , 29 , oleaginous flax shives 27 as well as sunflower 30 , 32 and amaranth 31 barks. The current interest of lignocellulosic biomasses for such an application (i.e., mechanical reinforcement) is explained by the regular depletion of forest resources used for producing woodbased materials.…”

“…Similarly, panels entirely based on amaranth 31 and sunflower 32 , combining extrusion-refined fibers from bark as reinforcement and seed cake as a protein binder, were successfully produced. They showed flexural strengths of 35 MPa and 36 MPa, respectively.…”