The bioeconomy is swapping oil for wood, and the research company Cellutech is an important facilitator, building bridges between academy and industry. The company is exploring how transparent wood and special composite materials can be put to use – but a cellulose-based foam material will be the first application of scale.

”We are looking to replace fossil plastics with cellulose based materials. Plastic can mean any number of things, but the truth is that they often are a perfunctory choice; it really doesn’t make much sense to choose a material that will persist for 450 years in nature and use it to make disposable items. We need to develop a circular model of thinking, and incorporate it right from the design phase. Cellutech is working with the industry to test materials in real-world applications, in Sweden and around the world”, Åsa Ek, CEO of Cellutech, says in an interview with the Swedish podcast Skogspodden.

”Cellutech is a very special company; we act as a middlelayer between research and industry. From our location at the Royal Institute of Technology, we pick up ideas from the Wallenberg Wood Science Center and develop them further towards industry applications. Forest-based materials is the common denominator”, Åsa Ek explains.

Renewable styrofoam-like materials from pulp

Cellutech presented a wooden bicycle helmet in 2015; the padding was made from nanocellulose foam. Photo: WWSC

Cellulose is present in all trees and plants. In the company’s Cellufoam material, cellulose extracted from Swedish pulp is turned into a porous foam, which can be shaped into slabs just like styrofoam or cellular plastic – a polystyrene which is used as padding in containers and as insulation in construction. Replacing it with a renewable alternative would have a major impact: the annual global consumption is more than 7 million tonnes, and the world market is estimated to be worth more than 100 MSEK annually by 2020. The market for foam plastics in general is ten times that amount.

”Cellufoam is the material we have brought closest to the market. It is light, durable, protective and insulating”, Åsa Ek says. ”We can create any number of foams to meet different material requirements, and we can adjust the properties, from rigid foams to soft and flexible ones. We are now on our way to test this in several applications to motivate scaling up the process. We have a strong indication that it can be just as competitive as the existing foams once we reach industrial scale production, and we believe it can be on the market by 2019-2020.”

Product development together with the companies

Wood can be described as a composite material in itself, combining cellulose, lignin and hemicellulose. Cellulose is a natural polymer, organizing itself in fibers of different sizes. In wood, they are held in place by lignin, similar to how concrete fills out the space between the reinforcement rods in a building. Hemicellulose builds a layer between the two. In pulp production, the cellulose is extracted while lignin is removed as a residue. The smallest building block of cellulose, the structure that builds up the fibers, is called nanocellulose.

”Cellufoam was originally a material made entirely from nanocellulose, which we were able to process into a lightweight foam. We presented a bicycle helmet in 2015 as proof-of-concept, where the foam was used as padding on the inside. It attracted a lot of interest and resulted in many new business connections.”

Cellutech went on with the product and process development in close collaboration with manufacturers. To make the material more cost-efficient and competitive, the company eventually turned to microfibrillated cellulose instead of nanocellulose.

”I have been working with wood-based materials for almost ten years, and I have seen the attitude towards them shift a lot in the industry. Customers are beginning to challenge material choices, and the industry is hungry for new solutions; there is a genuine interest in transforming”, says Åsa.

Other materials have been explored in parallel with the foam product. Hollow cellulose spheres, for instance. a potential filler in packaging or in composite materials. Superhydrophobic coatings could be used to protect the cellufoam slabs. Some materials have properties which one hardly expects from wood – like the company’s flexible magnetic nanocellulose composite, or the mind-boggling see-through wood.

Transparent wood can save energy in buildings

The transparent wood is a polymer composite, with the supporting capacity of wood. It can save energy on lighting and heating, and offers brand new opportunities in construction. Integrated solar power in facades, for instance. Photo: Cellutech.

The transparent material is constructed as a composite, where the insterstices in the wooden structure is filled with an optically transparent polymer. The result is a material which is stronger and lighter than glass, and transparent without being completely clear. It can be used in load-bearing constructions, and opens entirely new possibilities as a building material. It could for example be used to make panels which are half window, half facade, that let the sunlight in and heat the building, saving a lot of energy in the process.

”Transparent wood is an incredibly exciting material which is still in its infancy; we can combine the structural stability of wood with transparency. There is a lot of basic research going on at the Wallenberg Wood Science Center, and we are following that closely, looking at potential uses and applications. The technology works with any polymer as long as it has the right optical properties; obviously, renewable polymers is the most interesting option.”

The transparency would also allow solar cells to be integrated in facade panels. Since wood is both renewable and affordable, it might turn out to be a cost-efficient way to cover large surfaces.

”The oil era has stifled initiative and invention in wood-based materials. Now that it is being questioned, a flood of innovation is released”, Åsa Ek says: ”A couple of decades from now, oil-based foam plastics will likely be a thing of the past.  But it doesn’t stop there: we will probably be surrounded by other new, renewable material solutions that we can’t even imagine today.”

The article was published in September 2018.