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Bioprocess Biosyst Eng (2012) 35:341349 DOI 10.1007/s00449-011-0572-5
ORIGINAL PAPER
Anaerobic co-digestion of dairy manure with mulched switchgrass for improvement of the methane yield
Jean-Claude Frigon Caroline Roy
Serge R. Guiot
Received: 11 February 2011 / Accepted: 3 July 2011 / Published online: 22 July 2011 Crown Copyright as represented by the National Research Council Canada 2011
Abstract The owners of farm-scale anaerobic digesters are relying on off-farm wastes or energy crops as a co-digestion feedstock with animal manure in order to increase their production of methane and thus revenues. Switchgrass represents an interesting feedstock for Canadian digesters owners as it is a high-yielding low-maintenance perennial crop, well adapted to northern climate. Methane potential assays in batch tests showed methane production of 19.4 3.6, 28.3 1.7, 37.3 7.1 and45.7 0.8 L kg-1, for raw manure, blended manure, manure and mulched switchgrass, manure and pretreated switchgrass, respectively. Two 6-L lab-scale anaerobic digesters were operated for 130 days in order to assess the benet of co-digesting switchgrass with bovine manure (digester #2), at a 20% wet mass fraction, compared with a manure-only operation (digester #1) The digesters were operated at an hydraulic retention time of 37 6 days and at loads of 2.4 0.6 and 2.6 0.6 kg total volatile solids (TVS) L-1 day-1 for digesters #1 (D1) and #2 (D2), respectively. The TVS degradation reached 25 and 39%, which resulted in a methane production of 1.18 0.18 and2.19 0.31 L day-1 for D1 and D2, respectively. The addition of 20% on a wet mass ratio of switchgrass to a manure digester increased its methane production by 86%. The co-digestion of switchgrass in a 500 m3 manure digester could yield up to 10.2 GJ day-1 of puried methane or 1.1 MWh day-1 of electricity.
Keywords Anaerobic digestion Switchgrass
Panicum vergatum Digester Methane
Introduction
The use of anaerobic digestion for methane production from animal manure in farm-scale digesters is well established in Asia and Europe while North America has still small industries that are just developing for the past 10 years. In the USA, there are around 150 operating biogas systems compared with a dozen in Canada, which makes both countries similar in term of installations per capita. The rst operating anaerobic digesters for manure digestion are less than...