For the past seven years, VTT Technical Research Centre of Finland has been developing a cellulose-based recyclable, biodegradable, and compostable ‘transparent paper’ as a replacement for fossil-based film using a more environmentally friendly production process than used for cellophane. Following the first successful pilot run of the film, Dr. Vinay Kumar, senior scientist and project manager at VTT, provides details on the new material and its potential to replace plastic film.
Packaging World:
Can you share some background on VTT Technical Research Centre of Finland?
Dr. Vinay Kumar:
VTT is one of the leading RDI [research, development, and innovation] organizations in Europe. We develop technology using scientific efforts to help society and businesses grow in a sustainable way. We have been around since 1942, and we work on all the topics you can imagine—starting from biomaterials to energy to quantum computing. So VTT is a very widespread organization in the sense that we don’t only work on one or two topics, we work on a lot of things. Working on this many disciplines is actually very helpful because we’re able to connect the dots from different sectors. We can use the ideas from one sector and implement them in another one. That allows us to be at the forefront of these technology developments. Usually organizations don’t have that kind of widespread research effort.
How do you select the projects you work on?
We have three different kinds of projects. One type is what we call internally funded instruments, which are supported by the government of Finland. And it is with these kinds of projects that we develop our competence. So that money is used for improving our own fundamental understanding of different technologies, which we aim to then scale up with partners or customers. That brings me to the second type of project, which are the public-funded instruments supported by the EU or Business Finland, which is the government funding arm of Finland, for example. Those kinds of projects usually allow us to take these technologies to the next level. So for example, with our internal funding instruments, if we’re working at a low TRL [technology readiness level] of one, two, or three, then with these public partnerships, we can work in the range of two to six TRL sometimes.
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Then we have the third type, where we have direct, one-to-one engagements with customers where companies are paying for the research, so the projects are highly confidential. This is where the technology is transferred to the industry. So usually they are at a high TRL because our aim is to then transfer that knowledge to the industry so they can use it in their business. But sometimes they also start from relatively low TRL because it happens quite often that our customers might be looking into the future, let’s say five or six years from now, and that’s when they come to VTT because we’re in a position to guide them there. So these types of developments start from a relatively low TRL, and then we help our customers to get to a high TRL.
Can you explain what cellulose is and how you extract it?
To put it simply, cellulose is the building block of all plants and trees. When you look at wood, for instance, it’s typically made of three components. One is cellulose, which is about 50%, and then we also have lignin and hemicellose. The lignin and hemicellulose are there to support the cellulose to keep the structure together. Cellulose is the structural element that gives strength to the plant. These fibers are strong, and they’re able to keep things in place for the tree. But that’s not the only function of cellulose; it also helps transport nutrients and water. But usually its strength is one of its main contributions.
To extract cellulose, starting from wood, you remove the other two components. There are different chemical and mechanical processes to remove the lignin and hemicellulose. Then you reach a grade of cellulose that can be fully purified, or it can still contain some hemicellulose and lignin. These grades have different names, depending on what process has been used to produce them.
One example of this is writing and printing paper. That’s usually white. That’s where you are using a relatively purified grade of cellulose pulp. But then you might have also seen brown cardboard, which is used for some packaging and transport applications. In that case, you haven’t removed all the lignin. Lignin is brown, which gives wood its color. So there you have lignin-containing cellulose in some cases. These are just some ways to take cellulose out.
Cellulose is interesting as a material because once you extract it as cellulose fiber, there are different ways to process it further into products. You can make paper out of it. You can also make films out of it, using a different processing step. Cellulose can also be converted to fully transparent films. You can call it transparent paper because you’re using a different process to convert it into a film. That’s what we’re doing at VTT with this project; we’re converting cellulosic materials into films and coatings for packaging applications.
Are there other advantages of cellulose-based films and coatings versus fossil-based plastic beyond the fact that they’re renewable materials?
This renewable nature is something that’s inherent to cellulosic materials anyway, so that’s definitely an advantage. One thing people usually don’t talk about though is the carbon footprint for production of these films and coatings. Typically cellulose-based materials have a lower carbon footprint when you produce them compared to fossil-based materials.
Then, the biggest advantage that I personally find important is the biodegradability or compostability of these materials. Plastic is a material that does not biodegrade for several hundred years, and if you think of the usage time of a package, it might actually be just a minute. For instance, if you go to McDonald’s and get something in a plastic package, the use time of that package is very, very short. The same applies to candy wrappers, for example. The moment you open it, the use case has ended, but that plastic stays for 400 or 500 years. That implies that we haven’t selected our materials very carefully, and that’s where the cellulosic materials have the advantage because they actually biodegrade quite quickly.
Cellulosic materials also enable recyclability of many packaging applications because they’re paper-like materials, so they can be recycled in the paper stream. That’s a big issue, especially in the EU where we’re targeting improved recyclability of packaging materials. Cellulosic materials, either as films or coatings, bring the inherent advantage of improved recyclability because when you use these materials, you are going towards mono-material packaging where recyclability is much simpler.
Ali Harlin, research professor at VTT (left), and Dr. Vinay Kumar, senior scientist and project manager at VTT (left) shown on the research center’s CelluloseFilm pilot line in Biorukki, Espoo, Finland.
In some situations, cellulose films also have barrier functions that are competitive with multilayer plastic. Of course, cellulosic materials do not have a good moisture barrier because they’re water loving, but they offer very good oxygen and grease barriers. That’s where they can actually compete very well with plastics. It’s this particular feature of these materials that allows us to shift to simpler packaging solutions because usually you need multilayer structures of different plastics, which makes it very difficult to separate them when the consumer is trying to recycle. For a consumer, it might appear that it’s one material because all plastic films appear transparent. When you use cellulose, you can simplify these multi-material-component systems to a mono-component system, and that improves recyclability quite well, and you’re also getting the function of good barrier.
It’s been shown that the best applications for compostable materials are foodservice packaging that brings food along with the packaging, delivering nitrogen-rich materials to the composters. Are those the best applications for cellulose-based packaging?
I’d say that’s definitely one of the key applications. We’re targeting compostability as the end use for cellulose-based packaging. I would also add that when we’re approaching a scenario where you replace plastic, we’re approaching it from two angles. One is, where is it easiest to replace plastic in terms of meeting the performance requirements? And many of those cases are quite simple. We have been using plastic films in some cases just because there was no alternative, but now cellulose films can become an easy replacement for plastic in those situations, foodservice being one of them.
Then there are situations where you would probably not meet the performance requirement as such, but it would make sense to replace the plastic. These are non-food packaging applications such as packaging for electronics or household items. These are also interesting in the sense that in these cases, we’re not usually looking for barrier properties, especially in household items. For example, when you buy a pair of scissors, you’re not concerned about the barrier properties of the material; it’s mostly the strength and how it holds the item inside. In this case, these paper-based solutions could be perfect.
As another example, you might have heard that now we have shifted to paper-based straws, especially in the EU, where plastic straws have been banned. One interesting observation I made during a visit to the supermarket was that all the paper straw bags were made from plastic. So think about it, we have replaced the plastic straw with the paper straw, and we’re still packing that in a plastic package. That was very surprising to me because if you can replace the plastic straw, which actually goes into the liquid, with a paper-based straw, why can’t you just have a paper- or a cellulose-based film package for that? It just blows my mind. I mean, why wouldn’t we do that? So these are the kinds of examples where I call them an easy replacement. It’s just that the company hasn’t really considered the packaging material as something they can fix.
You also mentioned that this film is recyclable?
Yes, so we have different technologies for these cellulose-based films. We have a so-called nano-cellulose or Microfibrillated cellulose films [MFC], which allow full recyclability in paper-based streams. And then we have these regenerated cellulose films, which can also go to the paper stream. During recycling though, it doesn’t convert back to fibers since it’s a dissolved cellulose grade. When you collect this paper in a stream, it breaks down when you break down the paper, and it can be separated from the pulp during recycling. Those tests are still ongoing. We’re now verifying this particular recyclability concept for regenerated cellulose films.
What stage are you at with R&D for these materials?
We started the lab research on this topic quite a while back, it was probably more than six or seven years ago, but the new pilot line, where we’re scaling up the production and improving the film development, that started in the summer of 2022. We now have the pilot line up and running. In March, we did the first successful run from end to end. So basically, we produced the film on a roll on the pilot line. It took us about one and a half years to get there because it was a new pilot, we built it from scratch. There’s nothing like it anywhere in the world. Of course, we had different parts of the equation working before that, but in March, for the first time, everything worked together, and we were able to run the film.
That’s the stage we’re at now. We’re very excited we got it to work. We currently have a very big R&D program where we’re using our pilot to optimize the film production. It’s called the Films For the Future project—F3, we call it. In short, it’s a program funded by the European Regional Development Fund, ERDF, and there are 34 industrial partners involved that are also partly sponsoring the program. They represent the whole value chain starting all the way from raw materials suppliers to chemical suppliers, and then to the film producers, the converters, and the brand owners. So it’s a combined effort. This program started in September of 2022, and it will end this September.
The program has been very successful so far. As I mentioned, we’ve been able to run the pilot with full roll-to-roll production, and the initial results from the films we’re producing on the pilot are super exciting. We’ve been able to optimize the mechanical performance of the films, and the films are fully transparent. When we have visitors to the pilot, we’ve sometimes seen that they are not able to identify which one is plastic and which one is the cellulose film produced on the pilot line. That’s an exciting thing for us to observe because we know that this one is cellulose film, and this is the plastic one.
Can you tell me more about the pilot line?
We call it the CelluloseFilms line. This line is specifically targeting the development of regenerated cellulose films using technologies that allow us to produce the films sustainably. We’re minimizing the environmental impact by using less harmful chemicals. For example, typically, sulfuric acid is used for the regeneration of these films. Sulfuric acid is very strong; it’s not the safest thing to work with. We have replaced that with much milder acids, almost like kitchen chemicals, you could say. We’re now running with these, and we have optimized our film properties to the same level even though we’re working with less harmful chemicals. We’re not releasing any carbon disulfide or hydrogen sulfide, which are the emissions that result from the viscose process used to produce cellophane.
What will it take for this to become commercial once you’ve done all the R&D?
As a project manager for this program, I would be extremely happy if one of our partners decided to take the technology on and push it forward for industrial development. Of course, VTT will be helping along the way, but the idea would be that either the partners in the program or some other company would come on board and take the technology and develop larger-scale production.
Now it’s getting to the stage where companies are very excited because we’ve been able to demonstrate the process to show that this can be done roll to roll. With the right attitude and the right team, a company should be able to take the technology to the next level quite rapidly. We have gathered all the knowledge needed to raise the bar for industrial implementation. But yes, VTT’s job is kind of done after the research and development effort. Of course then the onus is on the industry to take this, and of course VTT helps along the way.
There are a lot of biopolymers on the market. What does this solution offer that others do not?
I would say one of the key differentiating factors is the environmental impact, which we’re trying to reduce significantly. For example, we’re not using harsh assets in regeneration. Our dissolution process is such that we’re not emitting carbon disulfide or hydrogen sulfide in the process. So our dissolution is much more environmentally friendly. And then the film production itself is done in such a way that we can optimize or play with the different parameters. So the aim is not only to optimize the final film properties, but also to optimize the process in a way that the environmental footprint just keeps coming down. We’re not looking at it just from one angle where we want the best film; we’re trying to do it in such a way that we get the best film, but one that does not come with ifs and buts about sustainability. Sustainability should be inherent to the film, whether it’s through raw material selection or the process selection or the chemical selection or the drying processes.
What makes your film different than traditional cellophane?
The production of cellophane involves a viscose process, which starts with dissolved pulp. So you need to use a purified grade of pulp and carbon disulfide or hydrogen sulfide. Viscose is not a very environmentally friendly process because of these emissions. These initial steps of the film production are where we differentiate quite a bit. And then, since our film production process is technologically different, it allows us to optimize our washing and drying stages. So we’re able to work on those quite differently compared to the viscose production process.
The goal of VTT as an organization is to bring forward processes for film production that allow us to use more environmentally friendly approaches from all angles. As I mentioned, we use typical kraft pulps as starting materials, and we use as little energy as possible for film drying. We also don’t use strong chemicals for regeneration, and we can even recycle the chemicals used for dissolution. So we’re trying to approach it from all angles.
You mentioned that multi-material film can now be mono material by using cellulose film. Can you explain?
I’d say there are some applications where you could actually work with this film as such. One thing I forgot to point out when I was differentiating this film concept from other films is that this can be applied as a coating layer on paper or paperboard. That allows you to achieve a so-called all-cellulose structure, where you have paper, which is cellulose based, and then you have a cellulose-based coating on top. And we can do it in situ, meaning we don’t have to laminate the film with paper, but we can actually apply the coating to the paper. This can be a very good substitute for multilayer structures in foodservice packaging because it has an inherent grease barrier. If you think of a burger wrap or a tray for French fries, for example, you could actually have an inherent grease barrier with the paper because you have the cellulose film on top, and because it’s not plastic, and it’s not a different material, you have suddenly shifted from a multi-component system to a single-component system.
Would this work for liquid packaging applications?
This is not something that’s suitable for liquids; you would need an additional layer. But it can work very well as an oxygen-barrier layer in the case of liquid packaging board, for instance, so you could potentially replace an aluminum or polymer layer used for oxygen barrier.
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One example where it could also work very well is a disposable cup, because the lifespan of a disposable cup is actually relatively short. We’re not talking about several hours; we’re just talking about some minutes or maybe half an hour maximum. So in this case, if you had a fully cellulose-based structure with a coating of cellulose on the paper, you don’t need a thick plastic layer. But if you could somehow support that with some additional coating, which is only on the scale of some microns, it would allow you to have this short time protection. Then you would have a very good solution where it’s mostly cellulose-based, and it enables good recyclability.
How important is collaboration in the development of more sustainable packaging solutions?
Fifteen years ago, collaboration along the value chain in packaging was almost non-existent, meaning it was more like a supplier-vendor relationship. But now, with the challenges we’re facing and the legislation that’s coming in, we need system-level changes. For system-level changes to take place, collaboration along the value chain is critical. It’s about time that the entire value chain comes together to understand each other’s challenges and to discuss, for example, how a recycler’s challenge is not just their challenge anymore, it’s also the challenge of the brand owner and the challenge of the original producer of the package. This is the time it needs to happen, and I think we’re heading in the right direction. PW
