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Methane Production Rate (methane + production_rate)
Selected AbstractsPilot-scale anaerobic thermophilic digester treating municipal sludgeAICHE JOURNAL, Issue 1 2006M. A. de la Rubia Abstract The work reported concerns anaerobic thermophilic municipal sludge digestion (55°C) in a completely mixed anaerobic digester on a pilot-plant scale (850 L). The experimental protocol was defined to examine the effect of increasing the organic loading rate (OLR) on the efficiency of this digester and to report on its steady-state performance. The reactor had previously been converted from mesophilic to thermophilic conditions following the protocol previously proposed by the authors: this was achieved by a modified method that combined systems investigated in Chicago and in Vancouver. The reactor was subsequently subjected to a program of steady-state operation over a range of sludge retention times (SRTs) of 27, 20, and 15 days. The digester was fed with raw sludge [containing approximately 34.8 g/L volatile solids (VS)] three times per day. Under thermophilic conditions and with a 27-day SRT, the reactor was operated with an OLR of 1.48 kg VS m,3 day,1. The solids removal efficiency of the reactor was 42.9%, whereas the volumetric methane production rate in the digester reached 0.35 m3 m,3 day,1. Over an operating period of 150 days, an OLR of 2.63 kg VS m,3 day,1 was achieved with 41.8% VS removal efficiency in the pilot sludge digester (SRT: 15 days). During this period the volumetric methane production rate in the digester reached 0.20 m3 m,3 day,1 and 0.20 m3/kg VSr (VS reduction). The greatest efficiency in terms of substrate removal was 54.3% for an OLR of 1.71 kg VS m,3 day,1 and SRT of 20 days. Under these conditions, the generation of biogas and methane was at levels of 0.86 and 0.58 m3 m,3 day,1, respectively, with a methane yield of 0.70 m3/kg VSr. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Influence of Hydrodynamic Conditions on Biofilm Behavior in a Methanogenic Inverse Turbulent Bed ReactorBIOTECHNOLOGY PROGRESS, Issue 3 2003S. Michaud This paper presents a study about the influence of gas velocity on a methanogenic biofilm in an inverse turbulent bed reactor. Experimental results indicate a dynamic response of the growing attached biomass to the changes of hydrodynamic conditions, mainly attrition constraints. Short but intensive increases of gas velocity (Ug) are shown to induce more detachment than a high but constant gas flow rate. Hydrodynamic conditions control the composition of the growing biofilm in terms of cells and exocellular polymeric substances (EPS). The cell fraction within the biofilm (Rcell) was found to be inversely proportional to the gas velocity. The specific activity expressed in methane production rate or COD removal rate is higher in biofilms formed under high hydrodynamic constraints. The control of the hydrodynamic conditions in a biofilm reactor should make it possible to obtain a resistant and active biofilm. [source] Seasonal variation in rates of methane production from peat of various botanical origins: effects of temperature and substrate qualityFEMS MICROBIOLOGY ECOLOGY, Issue 3 2000Inger Bergman Abstract The methane produced in peat soils can vary over the growing season due to variations in the supply of available substrate, the activity of the microbial community or changes in temperature. Our aim was to study how these factors regulate the methane production over the season from five different peat types of different botanical origin. Peat samples were collected on seven occasions between June and September. After each sampling, the peat soils were incubated at five different temperatures (7, 10, 15, 20 and 25°C) without added substrate, or at 20°C with added substrate (glucose, or H2/CO2, or starch). Rates of methane production averaged over the season differed significantly (P<0.05, R2=0.76) among the five peat types, the minerotrophic lawn producing the highest rates, and the hummock peat producing the lowest. The seasonal average Q10 values for each plant community varied between 4.6 and 9.2, the highest value being associated with the ombrotrophic lawn and the lowest value with the mud-bottom plant community. For the unamended peat samples, the rates of methane production from each plant community varied significantly (P<0.05) over the season. This implies that the quality of organic matter, in combination with changes in temperature, explains the seasonal variation in methane production. However, addition of saturating amounts of glucose, H2/CO2 or starch at 20°C significantly reduced the seasonal variation (P<0.05) in methane production in peat from the minerotrophic lawn, wet carpet and mud-bottom plant communities. This suggests that substrate supply (e.g. root exudates) for the micro-organisms also varied over the season at these sites. Seasonal variation in methane production rates was apparent in peat from the hummock and ombrotrophic lawn plant communities even after addition of substrates, suggesting that the active biomass of the anaerobic microbial populations at these sites was regulated by other factors than the ones studied. [source] Hydrolysis and microbial community analyses in two-stage anaerobic digestion of energy cropsJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2007D.G. Cirne Abstract Aims:, The roles of the diverse populations of micro-organisms responsible for biodegradation of organic matter to form methane and carbon dioxide are rudimentarily understood. To expand the knowledge on links between microbial communities and the rate limiting, hydrolytic stage of two-stage biogas production from energy crops, this study was performed. Methods and Results:, The process performance and microbial communities (as determined by fluorescence in situ hybridization) in two separate two-stage batch digestions of sugar beets and grass/clover were studied. The microbial populations developed in the hydrolytic stage of anaerobic digestion of beets and grass/clover showed very few similarities, despite that the hydrolysis dynamics were similar. In both substrates, the solubilization of organic material was rapid for the first 10 days and accompanied by a build-up of volatile fatty acids (VFAs) and lactate. Between days 10 and 15, VFA and lactate concentrations decreased, as did the solubilization rates. For both substrates, Archaea started to appear in the hydrolytic stage between days 10 and 15, and the fraction of Bacteria decreased. The major bacterial group detected in the leachate fraction for beets was Alphaproteobacteria, whereas for grass/clover it was Firmicutes. The number of cells that bound to probes specifically targeting bacteria with cellulolytic activity was higher in the digestion of grass than in the digestion of beet. Conclusions:, This study allowed the identification of the general bacterial groups involved, and the identification of a clear shift in the microbial population when hydrolysis rate became limiting for each of the substrates investigated. Significance and Impact of the Study:, The findings from this study could be considered as a first step towards the development of strategies to stimulate hydrolysis further and ultimately increasing the methane production rates and yields from reactor-based digestion of these substrates. [source] | ||||||||||