High-performance biocomposites derived from wheat straw and recycled paper? EU-funded researchers have developed new materials and components based on substances isolated from these renewable residues. They have also found a way to extract silica from the straw, offering a greener alternative to current production methods for this compound.
The Innobite project targeted a number of problems along the value chain of bio-based construction materials, says Álvaro Tejado of Spanish research centre Tecnalia, who coordinated this three-year endeavour.
The project found new or better ways to obtain useful substances such as lignin and cellulose from wheat straw and recycled paper, transformed these constituents into improved resins and fibres, and developed the resulting materials into innovative composites. Two new products created by the project silica nanoparticles and an advanced biocomposite should soon be available to customers, Tejado reports.
Transforming straw into gold
One of the projects main achievements, Tejado notes, is a biorefinery process for the extraction of silica (silicon dioxide) from wheat straw. Silica is in huge demand around the world as an additive for paints, drugs, cosmetics and many other applications. Most of it, he explains, is produced by means of energy-intensive processes, which involve heating up sand or silicon tetrachloride, respectively to 2 000 °C and 1 500 °C.
Wheat straw contains large amounts of silica, Tejado explains, and Europe, which produces wheat in vast quantities, generates a lot of it. Innobite had set itself the challenge of finding a way to isolate the substance from this residue, and its efforts to develop an environmentally friendly method proved successful.
We added a new step to an existing biorefinery process used by one of the project partners, Tejado explains. Our method requires temperatures of no more than 80 °C, and its entirely based on sustainable chemistry. This means that it doesnt involve strong acids or similar substances. Instead, we use solvents that we can recover very easily.
This approach to the production of silica is entirely new, the first worldwide to extract this compound from plant residues, Tejado adds at least at industrial level. This breakthrough is currently being patented, and the project partner running the underlying biorefinery process is planning to exploit it soon, he notes. The silica extracted in this way can be provided in a number of forms, including nanoparticles that open up possibilities for a variety of innovative applications.
Fully bio-based, fully bio-degradable
Research further along the value chain was dedicated to the composites i.e. reinforced plastics themselves, and to the resins and reinforcing materials that are combined to make them. Most commercially available biocomposites, even if they are partly derived from renewable resources, are primarily petrol-based and have a large carbon footprint, Tejado says.
Innobite was determined to produce new biocomposites with a much lower environmental impact while simultaneously addressing some of the performance limitations of existing ones. The project focused on resins based on lignin and strengthened by cellulose fibres in various forms.
The partners produced a number of advances, which notably included a significant upgrade of an existing material commercialised by an SME that was a partner in the project. Compared to the original material, the new biocomposite, which is 100 % bio-based and 100 % bio-degradable, is suitable for a wider range of applications, Tejado reports. Innobite, for example, developed it into decking and fencing profiles to test the possibilities. The SME that contributed the original material now intends to use the upgraded composite to extend its product range, Tejado adds.
Innobite thus helped to gain new ground for green construction, and it also found new valuable uses for renewable residues that are currently underexploited. At the moment, we are taking very little from straw and recycled paper, Tejado concludes, but we are obliged to make the most of every resource we have in nature.