Impact of different particle size distributions on anaerobic digestion of the organic fraction of municipal solid waste

• Published in: Waste management (Elmsford) 2013-02, Vol.33 (2), p.297-307
• Main Authors: Zhang, Y., Banks, C.J.
• Format: Article
• Language: English
• Subjects: Anaerobic digestion; Anaerobiosis; Applied sciences; Biofuels - analysis; Bioreactors; Dry shredding; Exact sciences and technology; Municipal solid waste; Organic fraction; Particle Size; Particle size reduction; Pollution; Refuse Disposal - methods; Solid Waste - analysis; Urban and domestic wastes; Wastes; Wet maceration
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/j.wasman.2012.09.024

► Method and extent of particle size reduction affected digester operation. ► A smaller mean particle size did not necessarily lead to improved performance. ► Use of macerated material in wet digesters caused foaming due to gas entrainment. ► Coarser material was successfully treated in dry digesters. ► Finer shredded and rotary cut material acidified in dry digesters. Particle size may significantly affect the speed and stability of anaerobic digestion, and matching the choice of particle size reduction equipment to digester type can thus determine the success or failure of the process. In the current research the organic fraction of municipal solid waste was processed using a combination of a shear shredder, rotary cutter and wet macerator to produce streams with different particle size distributions. The pre-processed waste was used in trials in semi-continuous ‘wet’ and ‘dry’ digesters at organic loading rate (OLR) up to 6kg volatile solids (VS) m−3day−1. The results indicated that while difference in the particle size distribution did not change the specific biogas yield, the digester performance was affected. In the ‘dry’ digesters the finer particle size led to acidification and ultimately to process failure at the highest OLR. In ‘wet’ digestion a fine particle size led to severe foaming and the process could not be operated above 5kgVSm−3day−1. Although the trial was not designed as a direct comparison between ‘wet’ and ‘dry’ digestion, the specific biogas yield of the ‘dry’ digesters was 90% of that produced by ‘wet’ digesters fed on the same waste at the same OLR.