The aim of this research was to study the anaerobic conversion efficiency of the organic fraction of municipal solid waste (OFMSW). In order to compare and appraise our techniques and respective conversion efficiencies, primary sewage sludge (PSS) assays were also performed. OFMSW has a high cellulose content (32.9% TS) followed by lignin (12.5% TS), protein (9.61% TS), lipids (5.94% TS) and hemicellulose (5.2% TS). PSS is equally rich in lipids (19.8% TS), protein (18.2% TS) and lignin (19.6% TS), followed by cellulose (13.4% TS) and hemicellulose (5.5% TS).

Assays were run in CSTRbiodigesters operated at 35°C and 20 days hydraulic retention time (HRT). Three organic loading rates - 1.0, 2.7 and 3.8 OFMSW g VS/Lr.d (gram of volatile solids per liter of reactor per day) - were studied. PSS was assayed only at 1.0 g VS/Lr.d.

Concerning the conversion efficiencies, the most important component for the OFMSW anaerobic digestion is cellulose (74.0 - 77.8% conversion), while lipids (70.0 - 80.6% conversion) are the most important for PSS. The biodegradability of the other organic components are also presented and discussed.

Some literature data about OFMSW anaerobic digestion processes are discussed in view of the results presented here.

The similarities between our results and those of the so-called dry fermentation processes are also discussed in order to evaluate efficiencies of biogas and CH4 production versus volatile solids removal.

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