Methane yields from digestion

Steady-state performance of conventional high-rate mesophilic digestion of the biomass-waste blend at the baseline loading and detention time is presented in Table I. The methane yields from replicate baseline runs ranged... 

Amon T, Amon B, Kryvoruchko V, Bodiroza V, Potsch E, Zollitsch W (2006) Optimising methane yield from anaerobic digestion of manure effects of dairy systems and of glycerin supplementation. Int Congr Ser 1293 217-220... 

Representative data from Run 1. which did not achieve steady state, as previously mentioned, are shown in Table V. This represents the baseline run without added nutrients. It was found that to maintain pH in the 6.8-7.2 range, 72 meq NaOH// of feed slurry was required this raised the sodium ion concentration in the digester to about 1670 mg//. Overall, the results of Run I were poor. The methane yield, volatile solids reduction, and energy recovery efficiency as methane in the product gas were low, and the volatile acids concentration in the digester effluent was high. 

The mixed hyacinth-grass-MSW-sludge feed was pretreated with caustic soda solution at mild temperatures and pressures in an attempt to improve feed biodegradability and methane yield. Treatment temperatures (5". 25", 55°, 100", 121"C) and pressures (atmospheric and 30 psig) and dilute caustic concentrations were selected for the pretreatment studies for reasons of lower reaction vessel costs, reduced energy and chemical inputs, and to keep the salt concentration in the digester low. Alkaline treatment under these conditions is expected to be a cost-effective method for increasing methane production from cellulosic feeds (14,17). 

Digester gases were recycled at various recycle ratios from 2 to 125. The best methane yield of 3.95 SCF/lb VS added, which was about 15% higher than the baseline yield, was observed at a gas recycle ratio of 39 (Table III). The gas-phase dilution rate at this recycle ratio was about 0.2 hr. The existence of an optimum gas recycle ratio is rationalized as follows As the gas recycle... 

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