Posts Climate, Environment, Forestry

Research Scientist Risto Korpinen and colleagues are developing biopreservatives from birch bark which will protect solid wood and cardboard from moisture.

The purpose of tree bark is to protect the growing tree. For example, in forest fires pine bark protects the tree against fire, and extractives in the bark protect the tree against disease.

Suberin forms a hydrophobic coat on the fabric skin. Photo: Risto Korpinen.

Risto Korpinen and fellow researchers at Luke are currently investigating how tree bark can be used in protecting other products. Korpinen is investigating whether suberin fatty acids found in birch and aspen can be used to protect solid wood products and paper products.

Korpinen has the idea that in the future suberin treatment will replace the current method where solid wood is treated using copper-based preservatives under pressure. Thus timber protected with natural products could be used in building terracing, jetties, and sand-pits, for example.

“Suberin fatty acid is nature’s own biopolyester. So after use, suberin-treated timber can be burned, for example. If a house-owner wants to remove his terracing, the timber can be used to produce energy by burning and doesn’t need to be removed to special re-cycling centres as required at present,” Korpinen says.

Plastic substitute

When plastic has become a problem in nature due to littering, consumer attitudes to using plastic have become more critical.

Korpinen stresses that plastic as such is not a curse. Nevertheless, he is attracted by the idea that plastics will gradually be replaced by bio-based products in the future. As an example he mentions drinking straws made of cardboard, which can replace plastic ones.

”When consumers start demanding such products and the market is influenced by legislation, change is guaranteed, even though costs might rise.”

Similarly, Korpinen envisions suberin being used to protect paper, cardboard, and even textiles against moisture, replacing the use of plastics based on fossil raw-materials.

”There is a huge market potential for fibre-based packaging because of the increased growth of internet trading. By protecting the surface of the packaging both the package and its contents would be protected against moisture.”

Another potential use of suberin-based products would be food contact packaging, according to Korpinen. For example the coating of liquid packaging such as juice and dairy cartons could prevent moisture from affecting the contents or the natural moisture in the contents being absorbed by the carton.

More use of birch bark

Currently, birch bark is used in energy production. However, a remarkable amount of suberin could be extracted from the sidestreams of hardwood industry and used to replace plastic in coatings. Photo: Risto Korpinen.

Currently birch bark is burnt for energy production in pulp and plywood mills.

With the development of suberin-based products more efficient use of wood could be made according to the principles of cascading use of materials. Cascade use means that raw materials are used as many times as possible, reused, recycled and finally burnt for energy.

”The forest industry used about 14 million cubic metres of hardwood in 2016, mainly birch. 150 000 tons of this were bark. And since birch bark contains about one third suberin, a lot of it could be used”, Korpinen calculates.

Korpinen reminds us that replacing plastic with other materials is not cost free. Plastic products from fossils such as oil have a head start of decades compared with alternatives from renewable sources. The advantages of plastic products are high production volumes, efficiency and low price.

”Plastics have long been accepted in food contact materials and have an overwhelming dominance in many applications”, Korpinen says.

He estimates that impregnation of solid wood with suberin could be a commercial possibility within about 5 years. Approval for such products under EU chemical legislation would take longer.

”With many innovations we soon run up against the current regulations and completing R&D&I processes will be slow, expensive, and laborious. For example cardboard treated with suberin for food contact applications has to be tested and proved, which takes a lot of resources.”

Text: Heikki Hamunen
Photo on top of the page: Antti Haapio/TAMK