Abstract
The aim of this study consisted of manufacturing renewable binderless fiberboards from coriander straw and a deoiled coriander press cake, thus at the same time ensuring the valorization of crop residues and process by-products. The press cake acted as a natural binder inside the boards owing to the thermoplastic behavior of its protein fraction during thermopressing. The influence of different fiber-refining methods was evaluated and it was shown that a twin-screw extrusion treatment effectively improved fiber morphology and resulted in fiberboards with enhanced performance as compared to a conventional grinding process. The best fiberboard was produced with extrusion-refined straw using a 0.4 liquid/solid (L/S) ratio and with 40% press cake addition. The water sensitivity of the boards was effectively reduced by 63% through the addition of an extrusion raw material premixing operation and thermal treatment of the panels at 200 °C, resulting in materials with good performance showing a flexural strength of 29 MPa and a thickness swelling of 24%. Produced without the use of any chemical adhesives, these fiberboards could thus present viable, sustainable alternatives for current commercial wood-based materials such as oriented strand board, particleboard and medium-density fiberboard, with high cost-effectiveness.
Highlights
Recent years have been marked by prominent environmental concerns and regulations, resulting from the continuously growing population and the steady depletion of both fossil and world forest resources
Coriander straw was used as the main raw material, which is the lignocellulosic material consisting of the vegetative stalk parts of the coriander plant and represents the crop residue after the coriander fruits have been harvested
The thermomechanical oil pressing process resulted in a press cake with a residual oil content of 13%, while further deoiling of this cake through solvent extraction led to a deoiled cake material with a residual oil content of 0.9%
Summary
Recent years have been marked by prominent environmental concerns and regulations, resulting from the continuously growing population and the steady depletion of both fossil and world forest resources. The implementation of sustainable resources and processing has become of increasing importance in the materials industry, while current research is focusing on alternative sources of lignocellulosic fibers that could show a competitive nature with current commercial materials. Crop residues and lignocellulosic by-products from the processing of agricultural resources could provide a critical solution, as they exhibit low cost and high availability and do not lead to competition with the food industry for land use. Awareness has been raised and regulations have been set regarding indoor air quality, as the interior use of panels glued with formaldehyde resins may result in the formation of toxic formaldehyde emissions [1]. Synthetic adhesives are relatively expensive and often represent over 30% of the total production cost for particleboard or fiberboard [2]
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