3.3 Biological treatment for pulp and paper sludge
- Pakinee Thianheng
- PhD student,
- KTH
- Co-author(s): Johan Larsbrink, Lauren McKee
- Supervisor (PhD-students/postdocs): Lauren McKee
- Swedish waste management (Avfall Sverige) prioritizes waste prevention, recycling, and energy recovery over landfilling. Since 2001, Sweden has prohibited landfilling of organic waste. Despite strong sustainability policies, thousands of tonnes of sludge from the pulp and paper industry are still disposed of in landfills. One problematic waste stream is precipitation sludge (PS), generated from cardboard manufacturing at ~8,000 tonnes per year. PS contains ~75% organic matter (dry weight), mainly low-quality fibers mixed homogeneously with metals and other elements from the production process. Consequently, PS is non-recyclable and resistant to natural degradation in landfills. Moreover, a high-water content in PS limits combustion for energy recovery. Unavoidably, PS is currently landfilled, raising concerns about land use, reforestation, and metal leakage into surrounding ecosystems. In discussion with a Swedish pulp mill, even a 5% reduction in sludge volume could make a significant impact for waste management for the industry. This study aims to develop biorefinery techniques to reduce sludge volume and facilitating future metal recovery. We have used DNA and RNA sequencing to identify microorganisms present in PS and the biocatalysts they produce. By enhancing these microorganisms in mini-bioreactors in the lab, we achieved a 5% reduction in sludge mass and a 25% reduction from visual observation in sludge volume through microbial degradation of cellulose, xylan, and starch. Future work will characterise the enzymes responsible for this degradation to develop optimised biorefinery tools.
- Time of presentation: 9.40