Anaerobic co-digestion of excess brewery yeast in a granular biomass reactor to enhance the production of biomethane.

The anaerobic co-digestion of brewery yeast using granular biomass was studied on the lab, pilot and full-scale. The study shows no adverse effects in the co-digestion of yeast and wastewater in concentrations up to 1.1 (v/v)%. In concentrations up to 2.3% the process is manageable; however, not advisable. In concentrations over 2.8% the process exhibits failure due to the overload with suspended solids. An average specific biogas production of 0.560 m(3)kg(-1) of volatile solids was achieved. Full-scale operation with 0.7% yeast concentration showed a 38.5% increase in the biogas production and a 26.2% increase in the organic loading rate, which resulted in an increase of the biomethane/natural-gas substitute ratio from 10% to 16%. The influence of the yeast addition on the structure of the microbial biomass showed up to 7% dissimilarity in the archaeal and a 32% dissimilarity in the bacterial biomass community, which did not present any difficulties.

General Microbial Community Flexibility in Biochemical Methane Potential Assay is Highly Correlated to Initial Biogas Production Rates.

Degradation of brewery spent grain as a novel test substrate was explored in routine biochemical methane potential assays (BMP) using three different inocula. Significant differences in the initial biogas production rates from spent grain, methane yield coefficients and final spent grain degradation were observed between inocula. Initial and developed communities degrading novel substrate showed significant differences in archaeal community fingerprints. Differences were observed irrespective of substrate identity (no substrate, glucose, spent grain) providing evidence of a significant general influence of BMP incubation on the microbial phylotypes. A linear relationship between microbial community flexibility in BMP assay and corresponding initial biogas production rates was identified as a novel parameter to diagnose anaerobic processes, particularly under dynamic conditions like start-up.