Techniques for enhanced anaerobic digestion and bioenergy conversion of pulp and paper sludge

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Canada is the world's largest exporter of forest products. As a result, Canada's forest-related industry, such as pulp and paper (P&P) mills, plays a significant role in the Country's economy. Most P&P mills employ physical treatment and aerobic biological processes to treat their wastewater, generating large amounts of sludge. Canadian mills generate over 2 million dry tons of sludge every year, which is greater than the Country's annual municipal wastewater sludge production. The current sludge management practices in mills are cost and energy-intensive and pose negative environmental impacts, including a significant contribution to greenhouse gas emission from landfills or lagoons. An alternative sludge management option is implementing an anaerobic digestion (AD) process for bioenergy conversion of P&P sludge. AD is a biochemical process converting organics into methane-rich biogas and fertilizer. This technology has been widely used for various organic waste but received little attention for P&P sludge due to its complex physio-chemical compositions limiting the performance of AD. The proposed research program will investigate different techniques, including hydrothermal pre-treatment (HTP), anaerobic co-digestion (AnCoD), and a two-stage AD process to overcome the major challenges confronting anaerobic digestion of P&P sludge. The specific objectives of this research include i) To investigate the effects of hydrothermal pre-treatment individually and in the presence of external conductive materials on P&P sludge characteristics (e.g., organic solubilization) and on the performance of the subsequent AD in terms of bioenergy recovery, organics removal, and digestate characteristics, ii) To investigate process improvement and simultaneous production of biohydrogen and biomethane from P&P sludge via two-stage AD process, iii) To study the long-term performance and evaluate the effects of feedstock characteristics, mixing ratios, and microbial community during AnCoD of P&P sludge, food waste, and manure. The success of this research program will be expected to create major green energy revenues in the longer-term in Canada as it focuses on renewable energy production from organic waste. The highly qualified personnel (HQP) involved in this program will make excellent use of the unique capabilities of The Beaty Water Research Centre, an interdisciplinary research and education facility at Queen's University. They will develop a deep understanding of advanced bioprocess engineering for organic waste treatment and energy recovery. They will also gain hands-on experiments in various bioreactors' design and operation and develop skills in various advanced analytical techniques. This training will enable them to have rewarding careers in industry or academia in the growing areas of green chemical engineering and waste management.