Kinetics of biomethanation of solid tannery waste and the concept of interactive metabolic control.

Control of interspecies electron flow during anaerobic digestion: significance of formate transfer versus hydrogen transfer during syntrophic methanogenesis in flocs. [Methanobacterium formicicum; Desulfovibrio vulgaris]

Abstract: Microbial formate production and consumption during syntrophic conversion of ethanol or lactate to methane was examined in purified flocs and digestor contents obtained from a whey-processing digestor. Formate production by digestor contents or purified digestor flocs was dependent on CO/sub 2/ and either ethanol or lactate but not H/sub 2/ gas as an electron donor. Floc preparations accumulated fourfold-higher levels of formate (40 ..mu..M) than digestor contents, and the free flora was the primary site for formate cleavage to CO/sub 2/ and H/sub 2/ (90 ..mu..M formate per h). Inhibition of methanogenesis by CHCl/sub 3/ resulted in formate accumulation and suppression of syntrophic ethanol oxidation. H/sub 2/ gas was an insignificant intermediary metabolite of syntrophic ethanol conversion by flocs, and it exogenous addition neither stimulated methanogenes nor inhibited the initial rate of ethanol oxidation. These results demonstrated that >90% of the syntrophic ethanol conversion to methane by mixed cultures containing primarily Desulfovibrio vulgaris and Methanobacterium formicicum was mediated via interspecies formate transfer and the <10% was mediated via interspecies H/sub 2/ transfer. The results are discussed in relation to biochemical thermodynamics. A model is presented which describes the dynamics of a bicarbonate-formate electron shuttle mechanism for control of carbon andmore » electron flow during syntrophic methanogenesis and provides a novel mechanism for energy conservation by syntrophic acetogens.« less

The study of cow dung as co-substrate with rice husk in biogas production

Abstract: The co-digestion of cow dung with rice husk for biogas production at laboratory scale was the subject of this investigation. The study was carried out at room temperature that is, 26 - 29°C for a period of 52 days with a total solid concentration of 8% in each sample (fermentation slurry). The biogas produced was collected by water displacement method which was subsequently measured. Sample A (50 wt % cow dung, 50 wt % rice husk) showed a cumulative biogas production of 161.5 ml at the end of the 38th day of the experiment after which there was no further production. The production from sample B (25 wt % cow dung, 75 wt % rice husk) was not significant, while there was no production from sample C(0 wt % cow dung, 100 wt % rice husk). Key words: Biogas, cow dung, rice husk, co-digestion.

Anaerobic digestion of tannery waste: semi-continuous and anaerobic sequencing batch reactor processes.

Abstract: Disposal of the vast amounts of tannery waste that are currently generated is a significant problem. Anaerobic treatment of different types of tannery waste (fleshings, skin trimmings and wastewater sludge) was investigated. The biochemical methane potential is the same at 37 degrees C or 55 degrees C and an assay of this was shown to be an appropriate screening tool with which to estimate the susceptibility of a substrate to anaerobic digestion. The start-up procedure of a tannery waste thermophilic anaerobic digestion in 100 days using seed from mesophilic digester processing municipal sludge is presented. The specific methane production potential at 55 degrees C is estimated to be 0.617 m(3)kg(-1) of volatile suspended solids for tannery waste sludge, 0.377 m(3)kg(-1) for tannery waste trimmings and 0.649 m(3)kg(-1) for tannery waste fleshings. Additional concerns such as chromium content, salinity and temperature fluctuations were also addressed. Chromium content and salinity showed no adverse effects; however a reactor temperature reduction of 4.4 degrees C led to a drop in biogas production of 25%, indicating a requirement to keep the temperature constant at 55 degrees C.

Anaerobic digestion of chrome-tanned leather waste for biogas production

Abstract: The introduction of cleaner technologies through the reuse of wastes, producing a clean fuel (biogas) and its utilization for energy recovery, can improve the environmental performance of the tannery industry. The degradability assessment of collagenic substrates (tanned or not) is necessary to evaluate the possibility/need of using prior treatments or mixtures of tannery wastes before its use as a growing substrate for anaerobic degradation processes. In this work, the biodegradation mechanism was studied by comparing collagenous substrates containing different concentrations of chromium (tanning degree) which helps the comprehension of the interrelation effect between microorganisms and substrate. This work presents the results from assays carried out in biorreactors to generate biogas by protein-based substrates at bench scale under controlled conditions. In the bioreactors, four substrates (soybean meal, hydrolyzed collagen, hide powder and wet-blue leather shaving) were inoculated with three different biological sludges collected from wastewater treatment plants (sewage anaerobic sludge, slaughterhouse anaerobic sludge and tannery aerobic sludge). The mole fractions of methane, carbon dioxide, nitrogen and oxygen in the generated gases were evaluated by gas chromatography. The experiments showed a previous adaptation of some of the tested inocula (seeds) and allowed to visualize and discuss the effect of the Chromium III concentration in the substrates over the rate and total biogas production for each of the inocula . The rising of chromium concentration in the substrate significantly reduced the biogas and methane yield. The maximum rate of biogas production for chrome leather shaving occurred in periods between 3 and 36 days, reaching a biogas yield of 162.2 mL g −1 and methane fraction of 73.7%. Better results were obtained using slaughterhouse and tannery sludges due to its preadaptation to collagen based protein substrates. The results indicated a considerable gain in biogas production (74–181%), if the leather substrate is treated or mixed with readily degradable materials prior to its use as substrate for anaerobic digestion (destabilizing the chrome–collagen complexes, increasing of the water dispersion and lowering the stability of chrome–collagen complexes).

Evaluation and kinetics of biogas yield from morning glory (Ipomoea aquatica) co-digested with water hyacinth (Eichhornia crassipes)

Abstract: Morning glory (MG, Ipomoea aquatica ) with water hyacinth (WH, Eichhornia crassipes ) were co-digested for 17 weeks at five different MG:WH ratios of 100:0, 70:30, 50:50, 30:70 and 0:100 (w:w dry basis) Fixed quantity of cow dung slurry was added to each treatment as inoculum to seed the digesters Biodegradation and maximum biogas yield models based on first-order kinetics were fitted to the experimental biogas yields to describe the cumulative and predict maximum biogas yields, respectively from each treatment From the results, it was observed that MG was viable and prolific for biogas production Although co-digestion did not have significant ( p > 005) effect on biogas yield, MG:WH (50:50) recorded the highest yield (029 dm 3 kg −1 vs fed day −1 ) However, co-digestion affected ( p ≤ 005) total bacterial count The biodegradation model described the observed biogas yields satisfactorily as indicated by the high R 2 Similarly, the high R 2 values and percentages of predicted maximum yield/observed maximum yield showed that the maximum biogas yield model predicted the maximum yields satisfactorily Biogas yield from MG:WH (100:0) was the best described and predicted by the biodegradation and maximum yield models, respectively

Photometric ninhydrin method for use in the chromatography of amino acids.

Abstract: For the investigations on the chromatographic separation of amino acids outlined in the preceding communication (1)) it was necessary to have available a suitable quantitative method for the determination of the concentration of amino acids in the effluent from the column. For this purpose, the method should be sufficiently general to include the determination of most of the amino acids and peptides likely to be encountered in protein hydrolysates or other material of biological origin. The method should have as high a sensitivity as possible to permit the determination of low concentrations of amino acids in the effluent from the chromatogram. Also the laboratory procedure should be fairly simple to permit the method to be applied conveniently to large numbers of effluent samples. It appeared probable that a photometric method would best fulfil these requirements. The two calorimetric methods of this type which had received the most study were the procedures based on the use of /3-naphthoquinonesulfonic acid and ninhydrin (triketohydrindene hydrate) as reagents. For reasons which will be described, the ninhydrin reaction was selected for further investigation. The color reaction between CY-NH2 acids and ninhydrin has been studied extensively in the past. It has been established that colored compounds are formed not only with amino acids, but also with peptides, proteins, and other classes of substances possessing free amino groups. The reaction is known to be extremely sensitive for qualitative work. In earlier attempts to render the color reaction quantitative (2-S), however, it has been found that the color yield per microgram of amino acid decreased markedly as the concentration of amino acid was reduced. In addition, the results have not been reproducible. In the present investigations, it has been observed that, when the color development is carried out in tubes exposed to the air, these difficulties appear to result primarily from the influence of dissolved oxygen. Improved results can be obtained when the reaction is performed in tubes evacuated to 20 mm. Under these conditions, the relationship between color yield and amino acid concentration is more nearly linear, although the deviations are still marked. By the addition of a strong reducing agent directly to the reaction medium, however, the oxidative side reaction has been eliminated. In preliminary experiments

The determination of hydroxyproline.

Abstract: There has been a great need for a satisfactory method for the determination of hydroxyproline to facilitate the study of the composition of proteins. Lang (1) and Waldschmidt-Leitz and Akabori (2) developed a calorimetric estimation involving oxidation to pyrrole with sodium hypochlorite and color formation with isatin or p-dimethylaminobenzaldehyde. However, oxidation was said to be incomplete and a correction factor was necessary. Dakin (3) and Bergmann (4) estimated hydroxyproline by isolation procedures. These procedures also required the use of large correction factors, as well as relatively large quantities of protein. McFarlane and Guest (5) devised a calorimetric method for hydroxyproline involving sodium peroxide oxidation and color formation with copper and isatin. This method yielded low values according to Devine (6), and in our hands similar results were obtained. The unique high hydroxyproline content of collagen suggests the desirability of an accurate method for the determination of this amino acid in small quantities as a means of estimating the amount of collagen or gelatin in a mixture of proteins. Because hydroxyproline so far has not been found to be a nutritive requirement for a microorganism, a chemical procedure is required. A short and simple calorimetric method is here described that is applicable to the determination of hydroxyproline in hydrolysates of 40 to 100 y of collagen with a reproducibility of f2 per cent (Table II) and an accuracy of f2 per cent (Table I) as judged by recovery of hydroxyproline from elastin hydrolysates and from an amino acid mixture simulating collagen. Oxidation, in the manner of McFarlane and Guest with sodium peroxide, yields products that form an intense red color with p-dimethylaminobenzaldehyde. The intensity of color produced with 5 to 15 y of hydroxyproline is 4 to 5 times that formed in previous colorimetric procedures. Because of this greater intensity of color and because of a different preliminary treatment of the hydroxyproline solutions, only 1 to 2 per cent as much protein is required as in earlier methods. In acid hydrolysates of proteins, the only amino acid other than hy-

Renewable Energy Resources

Abstract: 1. Principles of Renewable Energy 2. Solar Radiation and the Greenhouse Effect 3. Solar Water Heating 4. Other Solar Thermal Applications 5. Photovoltaic Power Technology - PV 6. Hydropower 7. Wind Resource 8. Wind Power Technology 9. Biomass Resources from Photosynthesis 10. Bioenergy Technologies 11. Wave Power 12. Tidal-current and Tidal-range Power 13. Ocean Gradient Energy: OTEC and Osmotic Power 14. Geothermal Energy 15. Energy Systems: Integration, Distribution and Storage 16. Using Energy Efficiently 17. Institutional and Economic Factors Review 1: Electrical Power Review 2: Fluid Dynamics Review 3: Heat Transfer Review 4: Solid State Physics for Photovoltaics Review 5: Units and Conversions: Algebraic Method Appendix A: Units and Conversions Appendix B: Data Appendix C: Some Heat Transfer Formulas Appendix D: Comparisons of Technologies Short Answers to Selected Problems Index

Conversion processes in anaerobic digestion

Abstract: Six different conversion processes are identified in the degradation of particulate organic material (biopolymers) to methane. Hydrolysis of particulate material is followed by the degradation of the hydrolysis and intermediary products by five independent groups of microorganisms. Process and growth kinetic data for the six processes are reviewed. The kinetic data are applied to the design of an anaerobic digester for raw domestic sludge. Variations in loading rates primarily affect acetate decarboxylation and, thereby, may cause shifts in pH which, in turn, cause the digester to operate in the acidic regime.

Methanobacillus omelianskii, a Symbiotic Association of Two Species of Bacteria*

Abstract: Two bacterial species were isolated from cultures of Methanobacillus omelianskii grown on media, containing ethanol as oxidizable substrate. One of these, the S organism, is a gram negative, motile, anaerobic rod which ferments ethanol with production of H2 and acetate but is inhibited by inclusion of 0.5 atm of H2 in the gas phase of the medium. The other organism is a gram variable, nonmotile, anaerobic rod which utilizes H2 but not ethanol for growth and methane formation. The results indicate that M. omelianskii maintained in ethanol media is actually a symbiotic association of the two species.