Microbial activity is a daily reality in pulp and paper processes. If not managed properly, bacteria can cause production issues, quality problems, and efficiency losses. But certain bacteria species do more than disturb operations – they are severe safety risks.
Just recently, a Nordic packaging board mill experienced this reality firsthand. During shutdown preparations, a mass tower exploded, damaging hundreds of square meters of roofing and scattering debris across the site. Fortunately, no one was injured.
When Kemira’s experts investigated the scene, they discovered what had gone unnoticed at the mill: the pulp tower contained staggeringly high concentrations of anaerobic bacteria that can produce hydrogen, which is an explosive gas.
“The lesson is clear. You need to know which bacteria are living in your process and understand their potential impact, especially during unusual situations when conditions can shift rapidly. The challenge is that traditional monitoring methods can’t provide the needed visibility to the microbial community structure, or how it is changing,” says Anu Jaakkola, Senior Research Scientist at Kemira.
Microbial community analysis uncovers the threat
The key to discovering what caused the dangerous accident was Kemira’s unique DNA Tools service. DNA Tools is an innovative method to identify and quantify different bacterial genera (types of bacteria) and troublemaker groups present in mill processes. It provides a complete picture of the microbial community in any pulp and paper process: not just the total count, but which bacteria are present and their relative proportions. Combined with Kemira’s deep expertise in microbial troubleshooting, this reveals potential risks to operations and safety.
In the exploded tower investigation, the advanced microbial community analysis revealed that hydrogen-producing bacteria – more precisely Thermoanaerobacterium, Thermoanaerobacter, and Caldicellulosiruptor – represented the vast majority of the bacterial population within the system. These bacteria had likely originated from the mill’s white water system. The shutdown conditions had created an ideal environment for their growth: reduced aeration and increased water retention accelerated their reproduction. As hydrogen accumulated in the pulp tower and mixed with residual ammonia produced in the process, the gas reached explosive concentrations. A spark from static electricity was enough to ignite the explosion.
Kemira’s bacterial profiling helped safety authorities solve the case and identify the root cause of the explosion. The findings also led to new industry recommendations for closer microbial risk assessments at pulp and paper mills, especially during unusual situations such as shutdowns. The case highlights a blind spot in pulp and paper operations: standard monitoring couldn’t have identified the bacteria, detected their growth, or predicted their hazardous potential.
“A high overall bacterial count in the process can be harmless, or it might indicate an alarming shift in the microbial community and the presence of problem-causing bacteria. Without identifying the specific types of bacteria and visibility into your process’s microbial health, there’s no way of knowing,” explains Anu.
Understanding which bacteria are present in your process is key to protecting both runnability and quality.
The daily cost of hidden troublemakers
Explosions are just one extreme. The real cost of microbial activity shows up as operational headaches in pulp and paper mills every single day. Bacteria can create a variety of process issues that impact efficiency, runnability, and end-product quality.
Bacterial growth causes deposits and slime formation, leading to breaks, holes, and spots in the final product. Unplanned downtime and cleaning cycles disrupt production schedules and harm your efficiency and productivity. Certain bacteria cause odor problems, while others cause corrosion that damages equipment and shortens its lifespan.
“For example, recycled board operations face particularly complex microbial challenges,” notes Anu. Bacteria might be the hidden culprit even behind the common strength challenges in recycled grades. “Certain bacteria can degrade cellulose, impacting the strength properties of the board. Understanding which bacteria are present in your process is key to protecting both runnability and quality.”
The difference between managing these problems reactively and preventing them lies in visibility. Most mills monitor the effectiveness of their microbial control programs through quick process measurements and cultivation methods. These approaches may reveal that something is wrong, but not which bacteria are responsible or how to address them effectively.
DNA Tools provides the missing layer by identifying which types of bacteria are present, enabling more precise – and more predictive – microbial control. “We can analyze any sample type,” explains Anu, “from pulps to process waters and raw waters, deposits, and paper product defects. We can even trace the microbial history of the production process by analyzing finished products.” The service is available globally.
“The increased visibility into process microbiology allows for proactive action when changes in the community begin, not only after problems have already emerged and impacted operations.” This precision also means smarter chemical use. Applying the right treatment at the right dose, in the right place, and at the right time reduces both the costs and inefficiencies of undertreatment or excessive dosing.
This targeted approach is grounded in Kemira’s microbial expertise: understanding which bacteria cause problems, and which don’t, and then keeping a close eye on the real troublemakers.
