Bioenergy Generation from Municipal Solid Waste and Glycerin Waste: Population Dynamics

This paper studies the microbial community, effluent characteristics, and bioenergy generation (hydrogen and methane production) in a two-phase dry-thermophilic (55 degrees C) anaerobic codigestion process treating actual municipal solid waste (20% solid content) and biodiesel waste (glycerin waste, 1% v/v). Four different hydraulic retention times (from 11.5 to 4.5 d) and four organic loading rates (from 8.2 to 21.1 g VS/L/d) were studied to identify optimal conditions (maximum values of biogas and microbial activity). Optimal conditions (2.6 +/- 0.3 L H-2/L/d, 3.4 +/- 0.3 L CH4/L/d, and 109 9 X 10(-13) L CH4/ cell/d) were obtained at 5.9 d HRT. Fermentation end products yield propionic acid as the major product in the secondary effluent. The average values of the ratios of Eubacteria/Archaea and acetogens/hydrolytic-acidogenic bacteria were respectively 83:17 and 30:53 in the first phase (1.5 d HRT) and 76:24 and 39:37 in the second phase (4.4 d HRT).