Eco friendly spruce bark can replace toxic chemicals

Maria Hedberg, staff scientist at the Department of Odontology at Umeå University, has seen how spruce bark can keep microbes in check.
Photo Credit: Fotonord

Scientific Frontline: "At a Glance" Summary

• Main Discovery: A water-based spruce bark extract functions as a potent, eco-friendly biocide that effectively replaces toxic synthetic chemicals used to control harmful bacterial growth in industrial paper milling and wastewater systems.
• Methodology: Researchers developed a "decoction" by boiling spruce bark in water and pressing it to release complex bioactive compounds, such as tannins, which was then introduced directly into industrial process fluids to inhibit microbial activity.
• Key Data: In a pilot trial at a paper mill, the extract reduced bacterial levels by 99% within 16 hours, exhibiting a slower onset but a more sustained duration of action compared to traditional synthetic biocides.
• Significance: This approach valorizes abundant forestry waste that is typically burned, reducing industrial reliance on hazardous chemicals while preventing operational issues like slime accumulation and the production of explosive or foul-smelling gases.
• Future Application: The extract is being scaled for widespread use in paper pulp production and municipal wastewater treatment plants to mitigate pipe clogging and corrosion caused by microbial biofilms.
• Branch of Science: Industrial Biotechnology, Environmental Microbiology, and Agricultural Sciences 
• Additional Detail: The chemical complexity of the natural extract makes it significantly more difficult for bacteria—specifically spore-forming species like Clostridium—to develop resistance compared to single-molecule synthetic agents.

Maria Hedberg identified above all a predominance of spore-forming bacteria, here Clostridium sp
 Image Credit: Maria Hedberg

A decoction made from spruce bark can replace toxic chemicals used to inhibit bacteria that otherwise produce dangerous gases and slime in paper mills and wastewater systems. This is shown in a collaborative project between SLU and Umeå University. 

“It was surprising that so many species were highly sensitive to the spruce bark extract. But considering that the same compounds in the bark protect the spruce tree from various microbes, it is not that strange,” says Maria Hedberg, staff scientist at the Department of Odontology at Umeå University. 

In the “factory soup” of fibers destined to become paper and cardboard, microorganisms also thrive in the lukewarm water. Particularly when recycled paper is used, large quantities of bacteria enter the process. If these microbes are allowed to grow, they produce explosive, toxic, foul‑smelling gases and a thick slime that clogs pipes and reduces paper quality. Today, a cocktail of biocidal chemicals is added to keep microbial growth in check. 

Now, a research team in Umeå has developed a more environmentally friendly method to control the bacteria. By boiling spruce bark in water and then pressing it, they obtain an extract that can be added to the process water. 

99 percent disappeared 

In a pilot project at the paper mill in Obbola, south of Umeå, 99 percent of bacteria disappeared after 16 hours when spruce bark extract was added. In fact, the results suggest that spruce bark extract may be more effective than synthetic chemicals. 

Initially, the chemical biocide was indeed stronger (more toxic), but over a slightly longer period the spruce bark extract delayed gas formation significantly better. This long‑lasting effect is important to avoid problems during production stoppages. 

Maria Hedberg’s experience of working with human bacteria and studying how they react to different substances was crucial in the project. She was responsible for the part of the research that examined the antimicrobial properties of the spruce bark extract. In the study, she analyzed samples from two types of environments: the paper industry and municipal wastewater systems. From these environments, representative, dominant bacterial species were isolated, and their sensitivity to the extract was tested. 

“We mainly see a predominance of spore‑forming bacteria such as Bacillus and Clostridium species, as well as filament‑forming bacteria like Thiothrix. At the same time, the bacterial flora in recycled paper pulp is extremely complex, with many species present,” says Maria Hedberg. 

Harder to develop resistance 

The bacteria also seem to have more difficulty developing resistance to the spruce bark extract, which has a far more complex chemical structure than the pure chemicals normally used. 

“Most likely, it is simply more demanding for bacteria to ‘outsmart’ the spruce bark extract compared to a traditional biocide. The extract consists of many components with complex structures, which makes it harder for microbes to develop resistance. The tannins likely play an important role in the extract’s antimicrobial effect,” Maria Hedberg says. 

A by‑product with potential 

The method has been developed within CEforestry, a European collaboration project led by the Swedish University of Agricultural Sciences, SLU. The aim is to make better use of forestry by‑products. Spruce bark is abundant, as all timber is debarked at the processing plants. The bark is low in value today and is burned. But as a raw material for an antibacterial extract, the bark would gain higher value. 

In addition to paper mills, spruce bark extract could likely also be beneficial in municipal wastewater systems, where bacteria that produce corrosive and foul‑smelling gases – and slime that clogs pipes – cause problems. 

To use the extract on a larger scale, more development is needed. Large‑scale trials in paper mills are required to confirm its effectiveness. A machine is also needed to produce the extract – preferably on‑site at the factory. 

“Spruce bark extract has all the prerequisites to become a strong and sustainable alternative to synthetic products in paper mills and wastewater treatment plants,” says Mehrdad Arshadi, project leader at the Swedish University of Agricultural Sciences, SLU. 

Published in journal: CEforestry

Title: Methodology of spruce extracts as biocides replacement in a wastewater system (PDF)

Authors: Mehrdad Arshadi, Torgny Mossing, Ulla-Britt Östman, Carina Jonsson, Michael Finell, Maria Hedberg, Anders Johansson, Olof Öhgren, and Risto Korpinen

Source/Credit: Umeå University | Ingrid Söderbergh

Reference Number: btech021726_01

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