Retooling the Pulp & Paper Industry: Enhanced Biosolids Disintegration for Improved Bioenergy Production
Abstract:This research addresses the needs of one of the major industries (pulp/paper sector) in the Province of British Columbia (BC) for efficient biowaste to bioenergy production. The community of Quesnel (BC) was used as a test case for technology development. Under an extensive Bio-Energy/Bio-Products Strategy, the Quesnel River Pulp (QRP) mill is investigating the technical and economic feasibility of producing methane from QRP mill biosolids in an advanced anaerobic digester. Therefore, in this study, thermal (microwave irradiation at 2450 MHz, 1250 W) and ultrasonic (20 kHz, 400 W) pretreatments were applied to QRP waste sludge in order to enhance methane production and reduce sludge retention time (SRT) requirements in the subsequent anaerobic digesters. At the laboratory scale, the effects of four different variables (microwave temperature (in a range of 50-175°C at 25°C increments) and sonication time (15-90 min at 15 min intervals), waste sludge type [waste activated sludge (WAS) and mixed (WAS/primary) sludge] and anaerobic digester temperature [mesophilic (35 ± 2°C) and thermophilic (55 ± 2°C)] were investigated on waste disintegration as well as methane yields from the QRP waste sludges. This experimental design resulted in a total of 96 batch digesters including controls (no pretreatment) and duplicates. Microwave pretreatment proved to be the most effective, increasing methane yield more than 100% compared to control digesters.However, sonication pretreatment for 15 min was the only economical pretreatment alternative with a positive energy balance (output to input energy ratio of 2.7). At similar food to microorganism (F/M) ratios, thermophilic control digesters had higher methane production rates than the mesophilic control digesters.
Document Type: Research Article
Publication date: January 1, 2011
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