Paper and cardboard are preferred packaging options for many types of food including cereals, dry foods like instant soups and beverages like milk and pasteurized juices. To obtain the desired properties, paper and cardboard packaging has to be coated with film that provides a barrier to mechanical impacts, moisture, grease and oxygen. Typically, the coatings are made of polyethylene (PE), which is synthesized from crude oil.
While the solution works in the short term, it has created several long-term challenges: About 7 million tons of coated paper, paperboard and cardboard are currently manufactured worldwide each year. The PE coating negatively impacts the recyclability so that the environmental impact of these packaging solutions is not as good as it should be. As experts and consumers are also questioning the extensive reliance on petroleum-based plastic film, it becomes increasingly clear that alternative solutions are needed.
An international consortium of experts from research institutes as well as the packaging and food industries has taken on the challenge with support from the European Community’s Seventh Framework Programme. Rather than solving one problem by creating a host of others, the Bioboard consortium that includes the Fraunhofer Institut für Verfahrenstechnik und Verpackung, the international knowledge transfer company Iris and the food industry association of Austria looks at how a new coating for paper and cardboard could help reduce waste as well.
“We wanted to catch two birds with one stone”, says project coordinator Dr. Elodie Bugnicourt. The agroindustry generates more that 20 million tons of whey, 65 000 tons of dried juice protein and 140 000 tons of dried potato pulp annually; by-products that are usually discarded. “Rather than looking at this as a problem, we saw it as a solution”, says Bugnicourt. In 2007, the massive amounts of whey protein that are discarded every year gave rise to the Wheylayer project, the precursor of the Bioboard project that explored the viability of plastic packaging made from whey protein.
As the packaging industry inquired about whether the material was suitable for paper and cardboard coating, the Bioboard research started. The properties of whey protein and potato pulp seemed promising. Whey protein, a by-product from cheese production, is sometimes used as a protein supplement for athletes but most of it is treated as waste. “We were very careful to find raw materials that are not used as food or animal feed”, says Bugnicourt. Several bio-based materials such as corn and soy have resulted in price pressure and changes in land use because they competed with food. By using waste materials, this trap can be avoided.
Still, developing cardboard coating has its challenges. “A lot more research is necessary before the product is market-ready”, says Bugnicourt. The characteristics necessary for beverage cartons and flexible food pouches are not easily incorporated. In addition to being impermeable to humidity, oxygen and grease, the material also has to have the right characteristics to serve as a laminate, it has to be flexible enough so that the coated carton can be folded easily and the laminate has to be thermo-resistant. Another challenge lies in the manufacturing processes of the coated paper. While coating with petroleum-based PE has been tried and tested over the years, in contrast, the processes for the bio-based coating are new and don’t function without glitches yet.
For the researchers, the challenges are learning steps rather than deterrents. “We may have to adjust our processes or create other packaging products”, explain Bugnicourt. One option could be bio-based bubble-wrap. Still, the overall goal remains: To create bio-based recyclable packaging that makes good use of waste and thus has a positive impact throughout its lifecycle.