Here is an alternative to fossil resources that can respond to several environmental challenges, including the greenhouse effect, in the field of insulating panels in buildings: a bio-glued product made from shrimp carcasses. Researchers in Clermont are behind the formulation of this glue based on chitosan, a natural polymer, which proves to be as effective as industrial structural glues.
Ahe building sector is at the heart of sustainable development issues. Constructing or renovating buildings in an eco-responsible manner requires considering the work as a whole, from the production of the materials that make it up to its deconstruction. The bio-based materials sector has been identified by the Ministry of Ecology as one of the green sectors with high economic development potential for the future. This is particularly because of its role in reducing our consumption of fossil-based raw materials, limiting greenhouse gas emissions and creating new economic sectors. The use of bio-sourced materials is therefore part of a sustainable development approach.
The Institut Pascal Axe GEPEB in Clermont-Ferrand is a public research laboratory working on the valorisation of polymers such as polysaccharides and proteins. The Institute won the "Valorisation/transfer" trophy for its 100 % natural glue made from shrimp carcasses. Developed for the construction market, it is now intended for all industrial sectors.
Used to assemble two parts and form a compound resistant to high mechanical stresses, so-called structural adhesives are made of synthetic materials (polyurethane, epoxy...) that contain substances potentially toxic to health and the environment, such as volatile organic compounds (VOCs). Given the wide range of applications for these structural adhesives, one of the current challenges is to find alternative materials that have equivalent performance and are not harmful.
This is the challenge taken up by researchers from the Irstea centre and the Pascal Institute in Clermont-Ferrand , specialists in the mechanics of adhesive materials and the development of biomaterials. By combining their respective expertise in the field of materials mechanics (notably the modelling of adhesive behaviour) and the design of biomaterials, they have developed a natural 100 % adhesive based on chitosan, a biopolymer industrially manufactured from the chitin in the shells of crustaceans or fungi. "Formulated from chitosan, an organic acid and a polyol, the glue we have developed is as effective as industrial structural adhesives. It has a mechanical resistance to shear at the glue joint (the reference measurement) of more than 7 mega Pascal and can reach up to 40 MPa". says Jean-Denis Mathias, a researcher at the Irstea centre in Clermont-Ferrand and co-inventor of the biocolle. This is a remarkable result since, until now, no bio-based glue had reached this threshold.
A promising future
This innovation, which is the subject of a patent that has been widely extended internationally  and is co-owned by Irstea and the University of Clermont Auvergne (UCA), was rewarded in 2017 by the Eco-Innovation trophy of the Maison Innovergne (public structure supporting innovation in Auvergne). Thanks to its simplicity of manufacture and, indeed, its low cost, which are another major advantage, this new-generation glue seems destined for a promising future.. "We see great potential in this innovation. And the interest shown by manufacturers of adhesives or the raw materials used in their composition is proof of this. We are currently working on setting up partnerships that will enable us to undertake a pre-industrial development phase, comments Véronique Vissac-Charles, head of Irstea's Valorization and Transfer division.
And already a first attempt has been transformed. Biogluing has been exploited in the collaborative project Demether , which aims to use agricultural by-products, crushed sunflower stalks bonded together with glue, to design insulation panels for buildings. The resulting composite material proved capable of competing with the mechanical and thermal properties of commercially available materials.
Following the Grenelle de l'environnement agreements in 2007, the "Building" label was introduced in 2012 by the public authorities in order to promote the use of bio-sourced construction materials and products. More recently, the law on energy transition for green growth encourages the use of bio-based materials in the construction or renovation of buildings . Potentially transferable in many sectors such as construction, packaging or interior design, the bio-glue from the Irstea and UCA laboratories has probably not finished making headlines...
1] GEPEB and MMS axes of the Pascal Institute, LISC laboratory of Irstea.
2] Bio-sourced adhesive with high mechanical properties - Patent FR2962738 (Cemagref; Blaise Pascal University; University of Auvergne), 2011. Extension in 2017 to 14 countries including Russia and the United States.