High-Rate two-phase process for the anaerobic degradation of cellulose, employing rumen microorganisms for an efficient acidogenesis.
TL;DR: A novel two‐stage anaerobic process for the microbial conversion of cellulose into biogas has been developed using a mixed population of rumen bacteria and ciliates in a UASB‐type methanogenic reactor.
Abstract: A novel two-stage anaerobic process for the microbial conversion of cellulose into biogas has been developed. In the first phase, a mixed population of rumen bacteria and ciliates was used in the hydrolysis and fermentation of cellulose. The volatile fatty acids (VFA) produced in this acidogenic reactor were subsequently converted into biogas in a UASB-type methanogenic reactor. A stepwise increase of the loading rate from 11.9 to 25.8 g volatile solids/L reactor volume/day (g VS/L/day) did not affect the degradation efficiency in the acidogenic reactor, whereas the methanogenic reactor appeared to be overloaded at the highest loading rate. Cellulose digestion was almost complete at all loading rates applied. The two-stage anaerobic process was also tested with a closed fluid circuit. In this instance total methane production was 0.438 L CH/sub 4//g VS added, which is equivalent to 98% of the theoretical value. The application of rumen microorganisms in combination with a high-rate methane reactor is proposed as a means of efficient anaerobic degradation of cellulosic residues to methane. Because this newly developed two-phase system is based on processes and microorganisms from the ruminant, it will be referred to as Rumen Derived Anaerobic Digestion (RUDAD)-process.
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01 Jan 1993
TL;DR: Biological methanogenesis plays a major role in the carbon cycle on Earth and is the terminal step in carbon flow in many anaerobic habitats, including marine and freshwater sediments, marshes and swamps, flooded soils, bogs, geothermal habitats, and animal gastrointestinal tracts as discussed by the authors.
Abstract: Biological methanogenesis plays a major role in the carbon cycle on Earth. Methanogenesis is the terminal step in carbon flow in many anaerobic habitats, including marine and freshwater sediments, marshes and swamps, flooded soils, bogs, geothermal habitats, and animal gastrointestinal tracts. CH4 escaping from anaerobic habitats can serve as a carbon and energy source for aerobic methanotrophic bacteria, and can escape to the atmosphere, where it is a major participant in atmospheric chemical reactions and is an important greenhouse gas.
753 citations
TL;DR: It has been shown that the production of propionic acid is not always related to high hydrogen partial pressure, and when the operating pH was increased to 5.5, the yield of Propionic acid became significant.
Abstract: It has been found, in this study, that a new ethanol-type fermentation can be obtained in a continuous flow, high-rate acidogenic reactor receiving molasses as the feed. The operating pH must be maintained at about 4.5 to avoid onset of propionic fermentation. The acidogenic reactor had a VSS level of 20 g/L and its organic loading was as high as 80 to 90 kg COD/m(3) d. The operating ORP was around -250 mV. The ethanol-type fermentation was characterized by a simultaneous production of acetic acid and ethanol, while the yield of propionic was minimal even at a high organic loading rate of 80 to 90 kg COD/m(3) d, and also, the hydrogen partial pressure was as high as 50 kPa. Thus, this study has shown that the production of propionic acid is not always related to high hydrogen partial pressure. When the operating pH was increased to 5.5, the yield of propionic acid became significant.
359 citations
TL;DR: The application and modification of ADM1 is shown to simulate energy production of the digestion of cattle manure and renewable energy crops and an energy balance model is presented, which enables the dynamic calculation of the net energy production.
218 citations
Cites background from "High-Rate two-phase process for the..."
...Digestion near 100% could be assumed for the study carried out by Gijzen et al. (1988)....
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TL;DR: Challenges with AD of lignocellulosic biomass, factors contributing to its recalcitrance, and natural microbial ecosystems, such as the gastrointestinal tracts of herbivorous animals, capable of performing hydrolysis efficiently are highlighted.
189 citations
TL;DR: A two-stage rumen-derived anaerobic digestion process was tested for the conversion of water hyacinth shoots and a mixture of the shoots with cowdung into biogas, and 100% conversion efficiency of the VFA intoBiogas with a methane content of 80% was achieved.
Abstract: A two-stage rumen-derived anaerobic digestion process was tested for the conversion of water hyacinth shoots and a mixture of the shoots with cowdung (7:3) into biogas. Under conditions similar to those of the rumen and loading rates (LR) in the range of 11.6–19.3g volatile solids (VS) l−1d−1 in the rumen reactor, the degradation efficiencies were 38% for the shoots and 43% for the mixture. The major fermentation products were volatile fatty acids (VFA) with a maximum yield of 7.92mmolg−1 VS digested, and biogas with a yield of 0.2lg−1 VS digested. The effect of varying LR, solid retention time (SRT) and dilution rates on the extent of degradation of the water hyacinth–cowdung mixture was examined. Overall conversion of the substrate was highest at the loading rate of 15.4gVS.l−1d−1. Varying the retention times between 60 and 120h had no effect on the degradation efficiency, but a decrease was observed at retention times below 60h. The overall performance of the reactor was depressed by changing the dilution rate from 0.5 to 0.34h−1. By applying a LR of 15.4VS. l−1d−1, a SRT of 90h and a dilution rate of 0.5h−1 in the rumen reactor, and connecting it to a methanogenic reactor of the upflow anaerobic sludge blanket type, 100% conversion efficiency of the VFA into biogas with a methane content of 80% was achieved. The average methane gas yield was 0.44lg−1 VS digested.
87 citations
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571 citations
TL;DR: The rate of the hydrolysis of cellulose was so low that this was shown to be the rate‐limiting step in overall anaerobic digestion and elucidated the true rate‐ Limiting step of an aerobic digestion.
Abstract: The characteristics of the degradation of cellulose, soluble starch, and glucose in the acidogenic phase and the effects of the substrate loading rate and biological solids retention time on the methanogenic phase of anaerobic digestion were investigated. The results obtained from continuous experiments using laboratory-scale anaerobic chemostat reactors elucidated the true rate-limiting step of anaerobic digestion. The specific rate of substrate utilization decreased in the following order: glucose, soluble starch, acetic acid, and cellulose. The rate of the hydrolysis of cellulose was so low that this was shown to be the rate-limiting step in overall anaerobic digestion. Among methanogenic bacteria Methanosarcina would provide a higher substrate utilization rate than Methanothrix, and the maximum allowable substrate loading rate in the methanogenic phase was 11.2 g acetic acid/L day.
364 citations
TL;DR: Cellodextrin utilization by noncellulolytic rumen bacteria and extracellular hydrolysis of cellodextrins increase the possibility that cross-feeding occurs in the rumen and help to explain the high numbers of noncellULolytic bacteria in ruminants fed fibrous diets.
Abstract: Water-soluble cellodextrins were prepared from microcrystalline cellulose by using fuming hydrochloric acid and acetone precipitation. This cellodextrin preparation contained only trace amounts of glucose and cellobiose and was primarily composed of cellotetraose and cellopentaose. When various species of cellulolytic and noncellulolytic bacteria were cultured with cellodextrins, their growth rates and maximal optical densities were in most cases similar to those observed with cellobiose. Time course samplings and analyses of cellodextrins by high-pressure liquid chromatography indicated that longer-chain cellodextrins were hydrolyzed extracellularly to cellobiose and cellotriose. Cellodextrin utilization by noncellulolytic rumen bacteria and extracellular hydrolysis of cellodextrins increase the possibility that cross-feeding occurs in the rumen and help to explain the high numbers of noncellulolytic bacteria in ruminants fed fibrous diets.
128 citations