Building tomorrow: 9 biobased materials

 Click on the image to download the infographic in PDF.

Industrial solutions are being developed that focus heavily on silver nanoparticles, which possess biocidal properties that can be used to protect various substances (e.g., surfacing, cellophane, paint) from microbial contamination. One major concern is that, over time, these nanoparticles tend to make their way into the environment, where they can negatively impact biodiversity. INRAE has been working with various public- and private-sector partners from the SERENADE Laboratory of Excellence to develop a process for reducing the levels of silver nanoparticles as much as possible in paints. Researchers are currently exploring the efficacy of cellulose nanocrystals produced by the paper industry, although other forms of plant biomass could potentially be utilised. Cellulose nanocrystals are completely natural and biodegradable. The silver nanoparticles attach themselves to the cellulose nanocrystals via a process that controls particle number, distribution, and size. The end result is twofold: not only does the product release minimal amounts of silver, but its biocidal properties are also greater than those of conventional paints thanks to the more even distribution of nanoparticles. INRAE patented this novel technique in 2020, and it could eventually be used to generate more environmentally friendly commercial products.

For over 10 years, the INRAE Research Unit Biopolymers, Interactions, and Assemblies (BIA) has been exploring cellulose’s ability to stabilise emulsions. Normally, to mix two immiscible liquids, such as oil and water, it is necessary to use surfactants that might be harmful to the environment. BIA researchers have managed to replace the surfactants with cellulose nanofibres, which are a renewable and 100% biodegradable resource. One of this technology’s many possible applications is the creation of superinsulation. “For a given material, insulation properties can be enhanced by reducing density and pore size”, explains BIA Research Director Isabelle Capron, “Our methodology allows these characteristics to be fine-tuned.” The emulsion is stabilised exclusively by the cellulose nanofibres. After drying, it forms a rigid panel with impressive insulation properties; it outperforms both mineral wool and polystyrene. “We are still working to further improve resistance and better comply with current industry standards”, elaborates Isabelle Capron. The sole ingredients are water, oil, and cellulose.

Imagine a future in which our windows are covered with an anti-UV film, or our walls and floors physically repel microbes? Lignins are chemical compounds that naturally occur in woody plants such as hemp and trees. These organic molecules are unique because they simultaneously display anti-UV, antioxidant, and antimicrobial properties. Scientists with the Joint Research Unit for the Fractionation of Agroresources and the Environment (UMR FARE) are looking to exploit these properties. They are conducting experiments in which they mix different types of lignins with a water/alcohol solvent and then apply the mixtures to various surfaces. They have been able to obtain surface films with the above desirable traits, which could lead to the development of biobased, antimicrobial paints or coatings. This patented technology has drawn the interest of the building construction industry.

France is among the top producers of sunflowers in Europe: more than 700,000 hectares were sown in 2022. Once the plant’s precious seeds have been harvested, its stalks are most often left behind or sometimes burned. However, sunflowers are highly fibrous and thus display great physical resistance. They are also porous, which means they provide first-rate thermal insulation. These properties indicate that sunflower stalks could be incorporated into the insulation panels used by the building construction industry. Between 2011 and 2015, INRAE and its collaborators explored uses for this undervalued agricultural by-product as part of the Démether project. Sunflower stalks were ground down and then mixed with a chitosan binder. Chitosan is a compound found in the shells of crustaceans. Natural and biodegradable, this binder also possesses antibacterial properties. The Démether project gave rise to a prototype for insulation panels. Inexpensive to produce, they make use of previously unexploited agricultural residues. Several industry partners are seeking to parlay the project’s findings into commercial products. It is worth highlighting that public- and private-sector research alike is exploring the insulation capacity of other plant fibres. 
For example, INRAE has begun looking at flax via the SINFONI Investments for the Future Programme. While flax-based panels display good thermal and soundproofing properties, their sensitivity to moisture means exterior applications remain impossible. Thus, the research continues. At present, 92% of industrially produced insulation is made from mineral wools, which present human health risks, or from cellular plastics, which are environmentally unfriendly. Consequently, plant-based insulation holds a great deal of commercial promise.

Some materials remain difficult to recycle. In France, around 40 million tonnes of non-recyclable waste is buried or incinerated each year. Launched via INRAE's 3BCAR Carnot Institute, the start-up Néolithe has identified an alternative solution: transforming the waste into stone. More specifically, rock fragments can be used as construction aggregates (e.g., as a road base or to make concrete). The waste is first crushed to form a fine powder, which is then mixed with water and a binder. The result is small stones that are 80% waste. Founded in 2019, Néolithe first focused on construction site waste (e.g., insulation, plaster, wood) before expanding to household and industrial waste. In 2022, the start-up announced it was opening an 11-hectare industrial site near Angers. By 2023, the company hopes to have 24 of its “fossilisation” units in place, which could treat up to 20 tonnes of waste per day. These ambitious objectives should respond to the arduous challenges we are facing.