Huub J. Gijzen

Application of rumen microorganisms for an enhanced anaerobic degradation of solid organic waste materials

Abstract Organic waste materials of various origin and composition were screened for anaerobic digestion by a mixed population of rumen microorganisms. High loading rates could be applied, varying between 17·1 (coffee pulp) and 34·4 g (papermill sludge) of Volatile Solids per litre per day (VS litre−1 day−1) at retention times of only 60 h. Degradation efficiencies obtained for most waste materials were in the range of 60–70%, irrespective of their chemical composition. During the degradation of lignocellulosic wastes an apparent lignin degradation up to 48% was observed. Average production of Volatile Fatty Acids and biogas per gram of VS digested varied between 6·6 and 8·2 mmoles and 0·18 and 0·29 litre (approximately 40% CH4), respectively, for most wastes. Molar proportions of butyrate were higher with substrates rich in cell solubles, as compared to cellulosic and lignocellulosic substrates which yielded more propionate. Rumen ciliates belonging to the Entodinium group were predominant during the fermentation of substrates rich in cell solubles, whereas ciliates of the Diplodinium group were predominant with cellulosic and lignocellulosic substrates.

Application of rumen microorganisms in the anaerobic fermentation of an organic fraction of domestic refuse.

Abstract The application of rumen microorganisms in an ‘artificial rumen’ reactor for the anaerobic fermentation of an organic fraction of domestic refuse was studied. The acidogenic-phase digestion was optimized by testing various combinations of solid retention times and loading rates. VS conversion rates of about 60% were achieved at a loading rate of 40g of volatile solids per litre per day, a solid retention time of 90 h and a hydraulic retention time of 12 h. Specific production rates for volatile fatty acids and biogas were 7·5 mmol and 0·21 litres per g volatile solids digested, respectively. The mean molar ratio of acetic, propionic and butyric acids was 68:16:16. The methane content of the biogas was about 44%.

Application of rumen microorganisms for a high rate anaerobic digestion of papermill sludge

Abstract The anaerobic digestion of papermill sludge containing a high amount of inorganic matter was studied. Despite the presence of about 58% inorganic matter in the substrate, a high rate of hydrolysis and subsequent acid formation could be achieved in an acidogenic reactor which was inoculated with rumen microorganisms. Degradation efficiency of neutral detergent fibre amounted to 62% at high loading rate (34·2 g volatile solids per litre per day) and short solid retention time (51 h). In order to study the effect of accumulation of inorganic matter in the reactor, degradation efficiency was studied at various loading rates and solid retention times. An increase of solid retention time to 74 h resulted in a decreased degradation efficiency, probably due to an increased ash content in the reactor under these conditions. The effect of inorganic matter accumulation was also studied after coupling of the rumen derived acidogenic reactor to an upflow anaerobic sludge blanket-type methanogenic reactor. By using this two-stage digestion process an overall conversion of papermill sludge into biogas could be realized. The operation over about three months of the two-stage process was studied in terms of process stability, nutrient recycling and accumulation of inorganic matter.

Anaerobic digestion of onion waste by means of rumen microorganisms

Abstract Onion waste materials have been screened on anaerobic digestion by a mixed population of rumen microorganisms. Both peels and pulp are degraded with an efficiency of about 50–70% at retention times of only 60 h. The degradation of onion pulp, rich in cell solubles, gave rise to a relatively high production of butyrate and valerate.

Improved anaerobic conversion of lignocellulosic waste using rumen microorganisms

By the discovery and structural elucidation of methanofuran, methanopterin, coenzyme M and factor F~s o the route of reduction of CO2 to methane appears to be roughly established (see for reviews: Daniels et al., 1984; Keltjens, 1984; Vogels et al., 1986), though a number of questions remain to be answered. Least is known about the first step of reduction of COz resulting in formylmethanofuran as the first detectable intermediate (Leigh, 1983). This endothermic reaction appears to be intimately coupled to the exothermic final steps of reduction by a phenomenon known as the RPG-effect. Our experiments ruled out the possibility that this coupling is a matter of consumption and production of energy in the first and terminal step, respectively. The formyl group bound to methanofuran is transferred to tetrahydromethanopterin (H4MPT) in an ATP-independent reaction resulting into the formation of 10-formyl-HgMPT that is subsequently converted to 5,10-methenyl-H4MPT by a cyclohydrolase. The terminal step of methanogenesis, the reductive demethylation of methylcoenzyme M is catalysed by a complex system of enzymes and the coenzymes component B and ATP. The coenzymes are involved in an activation process. Component B, which is an adenosine derivative, that may contain coenzyme M, can replace ATP at the activation, whereas ATP in the presence ofmethylcoenzyme M can replace component B.