Reduced Gas Production Research Articles

Fecal flora in irritable bowel syndrome: Characterization using molecular methods

Fecal flora in irritable bowel syndrome: Characterization using molecular methods

Effect of mimosa tannin and pectin on microbial protein synthesis and gas production during in vitro fermentation of 15N-labelled maize shoots

Gas production, ammonia concentration, efficiency of microbial protein synthesis (EMPS), and incorporation of 15N into microbial protein (i.e., net microbial synthesis) were investigated using an in vitro gas production technique. EMPS was expressed as ammonia disappearance from the incubation medium per ml of gas produced after 24 h of incubation of 15N-labelled maize shoots (M), or M treated with mimosa tannin (MT), pectin (P), polyethylene glycol (PEG), MT + P or MT + PEG. Cumulative gas production at 24 h (ml/g DM) varied between 132 and 211. The lowest gas production at 24 h was with M supplemented with MT and MT + P. Inclusion of PEG allowed gas production in the M + MT + PEG treatment to equal that of M. The ammonia concentration measured in maize shoot treatments at 24 h was in the range of 52−97 mg NH 3/l. Lowest levels were observed for M + P and M + MT + P, and highest for M. EMPS was higher for M + MT + P, M + P and M + MT versus M and M + MT + PEG. EMPS was negatively correlated with 24 h cumulative gas production ( R 2 = 0.82; P < 0.001). Incorporation of 15N into the microbial pellet was lower with inclusion of MT and MT + P, consistent with reduced gas production in these treatments compared with M. There was a positive relationship ( R 2 = 0.90; P < 0.001) between incorporation of 15N and gas production. Inclusion of MT and/or P altered partitioning of nutrients towards higher EMPS, rather than gas production. However, net microbial protein synthesis was reduced in M + MT and M + MT + P, possibly due to restriction of microbial growth by MT.

The influence of tannin, pectin and polyethylene glycol on attachment of 15N-labelled rumen microorganisms to cellulose

The microbial attachment to and gas production from α-cellulose (Sigma; C-8002) without and with mimosa tannin (MT), pectin (P), polyethylene glycol (PEG), MT + P or MT + PEG, were investigated using the in vitro gas production system. Microbial attachment based on 15N-labelled rumen microorganisms in the residual pellet after 24 h incubation was estimated, which varied from 113.7 to 161.3 μg 15N per g residual pellet. C + MT had the lowest microbial attachment ( P < 0.05) of all treatments and C + P the highest ( P < 0.05). Both pectin and PEG improved microbial attachment when added to C + MT ( P < 0.001). Gas production was measured at 2, 4, 6, and 24 h. Mimosa tannin drastically reduced gas production only at 24 h ( P < 0.001). Pectin increased gas production throughout the incubation period ( P < 0.001). Both pectin and PEG increased gas production at 24 h, when added to C + MT ( P < 0.05), however, for C + MT + P, the gas production was only half ( P < 0.05) of the gas produced in the control (when only C incubated). A rapid degradation of pectin early in the incubation could have reduced the interaction of pectin with the MT. Microbial attachment agreed well with gas production at 24 h ( R 2 = 0.84, P < 0.001). However, the inclusion of MT and pectin may have resulted in differences in microbial profiles, thereby altering the capability of the adhered microbes to degrade cellulose. This assertion is supported by the lower gas production (ml per μg of 15N) in the residual pellet measured for C + MT (0.054) and C + MT + P (0.159), compared with the other treatments (0.32 for C; 0.34 for C + P; 0.33 for C + PEG; and 0.33 for C + MT + PEG). A MT concentration of 194 g/kg diet reduced microbial attachment and activity of rumen microorganisms in vitro. Polyethylene glycol counteracted the effect of MT on microbial attachment and activity. Pectin exerted a beneficial effect on attachment and fermentation in the initial hours of incubation. A ratio of pectin to MT of 1:1 improved microbial activity of C + MT but inhibition of microbial activity by MT remained at 24 h as indicated by the lower gas production of C + MT + P compared with the control. The results support the hypothesis that there is considerable interaction between tannins, microbes and non-starch-polysaccharides (NSP) in animal feeds and that these interactions may influence the functional ability of microbes in the gastrointestinal tract of animals.

Influence of Brine Concentration, Brine Temperature, and Presalting on Early Gas Defects in Raw Milk Pasta Filata Cheese

Thirty-one 3.8-kg blocks of Ragusano cheese were made on each of 6 d starting with a different batch of raw milk on each day. On d 1, 3, and 5, cheeses were not presalted and on d 2, 4, and 6, all cheeses were presalted. Before brine salting, one of the 31 blocks of cheese was selected at random for analysis (i.e., at d 0). The remaining 30 blocks were randomly divided into 2 batches of 15 blocks each, one group was placed in 18% brine, and the other group was placed in saturated brine. For the 15 blocks within each of the 2 brine concentrations, 5 blocks each were placed in brine tanks at 12, 15, and 18°C. Cheese blocks were sampled immediately before brine salting (d 0) and after 1, 4, 8, 16, and 24 d of brine salting. Presalting the curd with 2% added salt before stretching reduced the coliform count in the cheese by 1.41 log and resulted in a major reduction in early gas formation. Across all treatments in the present study, the average reduction in gas formation due to presalting was 75%. Reducing brine temperature had the second largest impact on reducing gas production, but did not reduce the coliform count in the cheese. Reducing brine temperature from 18 to 12°C made a larger reduction in early gas formation in cheeses that were not presalted (from 6.8 to 1.8% gas holes, respectively) than in cheeses that were presalted (from 1.9 to 0.5% gas holes, respectively). To achieve the same absolute level of gas production in the nonpre-salted cheese as was achieved in presalted cheese in combination with 18°C brine, the brine temperature for the nonpresalted cheese had to be lowered from 18 to 12°C. Reducing brine concentration, although effective at increasing the rate of salt penetration into the block, did not have any impact on coliform count and had minimal impact on reducing gas production. The condition where reducing brine concentration was able to make a reduction in gas production was for cheeses that were not presalted and brined at 18°C. Presalting is a very simple and practical approach to reducing the problem of early gas formation in combination with strategies to improve milk quality and cheese making conditions. Further work is needed to understand the impact of different levels of presalting on death of coliforms and gas production in the cheese.

In vitro effects of Monensin and Tween 80 on ruminal fermentation of barley grain:barley silage-based diets for beef cattle

Two in vitro incubations utilizing batch rumen culture procedures were conducted to study the effects of Monensin and Tween 80, alone and in combination, on ruminal fermentation. Dried, ground backgrounding and finishing diets for feedlot cattle were used as substrates in experiments 1 and 2, respectively. The diets, formulated as total mixed rations, contained (DM basis) barley grain and barley silage in ratios of 58:42 (backgrounding diet, BKGD) or 93:7 (finishing diet, FNSH). Inoculum comprised ruminal fluid collected from cattle fed BKGD or FNSH diluted with two volumes of mineral buffer, and amended with Monensin (0, 2.5 or 15 μg/ml) and Tween 80 (0, 0.1 or 0.5 μl/ml) in a 3 × 3 factorial arrangement of treatments. Incubations were conducted anaerobically for 4, 12 or 24 h at 39 °C ( n = 3). 15N-labelled ammonium sulphate was included to enable measurement of microbial N production (MN). Interactive effects ( P < 0.001) of Monensin and Tween 80 on acetate:propionate (A:P) ratios at 4 and 12 h of incubation, on MN at 4 and 24 h, and on accumulation of reducing sugars (RS) at 4, 12 and 24 h were observed with BKGD, but not with FNSH. Tween 80 applied at 0.5 μl/ml increased ( P < 0.05) in vitro true dry matter disappearance (TDMD) and RS accumulation at 4 h and MN at 24 h, but reduced ( P < 0.05) A:P ratio at 12 h of incubation with BKGD. Similar effects of Tween 80 on RS and A:P ratio were observed with FNSH. In contrast, throughout 24 h of incubation with either substrate, Monensin reduced gas production (GP), TDMD, MN and the A:P ratio, and increased RS accumulation (BKGD, P < 0.01; FNSH, P < 0.001). These effects on A:P and RS were enhanced ( P < 0.001) if Monensin and Tween 80 were supplemented together. Amylase, carboxymethylcellulase and β-glucanase activities in the incubation liquid were increased ( P < 0.01) by Monensin and Tween 80 supplemented in combination with both diets; xylanase activity was increased ( P < 0.001) with BKGD only. Effects on enzyme activity when Monensin and Tween 80 were supplemented individually were diet-associated, but interactive effects of Monensin × Tween 80 on each of the four activities were observed both with BKGD ( P < 0.05–0.001) and with FNSH ( P < 0.01). Supplementing Tween 80 with Monensin synergistically enhanced the Monensin-mediated increase in RS concentration and reduction of A:P ratio in the incubation mixtures. This effect may have potential to improve energy efficiency in feedlot cattle.

Surface tension of HCl-based stimulation fluids at high temperatures

Surface tension of hydrochloric acid (HCl) solutions plays a key role in matrix stimulation of gas wells. A low surface tension is required to reduce the capillary forces that trap the aqueous phase in the formation. Accumulation of the aqueous phase near the well-bore area, known as water blockage, leads to a significant reduction in gas production. This work provides, for the first time, surface tension of acid-stimulating fluids at temperatures up to 120 °C, HCl concentrations up to 28 wt.%, and pressures up to 220 bar. A pendant drop apparatus specially designed for corrosive fluids was used to measure the surface tension between acid solutions and nitrogen. The effects of commonly used acid additives on the surface tension of HCl solutions were also studied in detail. These additives included corrosion inhibitors, acetic acid, formic acid, methanol, mutual solvent, a nonionic fluorocarbon surfactant, iron control chemicals, and hydrogen sulfide scavengers. In addition to surface tension values of HCl up to 28 wt.% HCl at temperatures up to 120 °C, experimental results indicated that several acid additives are capable of significantly lowering the surface tension of HCl solutions. The trends discussed in this study can be used to better design acid formulae used to stimulate deep gas wells.

An in vitro study on the ability of polyethylene glycol to inhibit the effect of quebracho tannins and tannic acid on rumen fermentation in sheep, goats, cows, and deer

Abstract. Batch cultures of rumen microorganisms, using rumen fluids from 4 ruminant species, sheep, goats, cows, and deer, were used to study the ability of polyethylene-glycol (PEG 6000) to inhibit the effect of 2 types of tannins, quebracho (QUE, a condensed tannin) and tannic acid (TA, a hydrolysable tannin) on several in vitro rumen fermentation characteristics. Both QUE and TA were able to impair ruminal fermentation (they reduced gas production, extent of degradation, ammonia-N, and volatile fatty acid concentrations, etc.; P &lt; 0.05), with differences depending on the inoculum donor. The clearest effect of tannins was the reduction of the rates of fermentation, which was observed in all species (P &lt; 0.05). The detrimental effects of tannins were removed by the presence of PEG in most cases, but there were important variations and noticeable exceptions. Thus, for instance, PEG failed to revert the negative effect of TA on the rate of fermentation and the extent of degradation (P &lt; 0.05). The extent of the limited ability of PEG to completely inhibit the negative effects of tannins on in vitro ruminal fermentation seems to depend both on the type of tannin and the species of the rumen inoculum donor.

Modelling and simulation of syngas unit in large scale direct reduction plant

The production of reducing gas is usually a bottleneck to capacity increase in direct reduction plants. Modelling and simulation of reducing gas production result in better design and operation of these plants. In the present work, a mathematical model is discussed that relates to a Midrex reformer, which is different from conventional steam reformers in some respects. Both process side and furnace side have been included in an integrated model. Simulation results have been tested against available data from an actual plant. The model predictions have been found to be reasonably accurate. The effects of three process variables, feed gas temperature, feed gas pressure and excess air, on reformer performance have been investigated. Simulation results confirm that an increment in feed gas temperature is the most effective method of increasing performance.

Condensed tannin content of several shrub species from a mountain area in northern Spain, and its relationship to various indicators of nutritive value

The condensed tannin (CT) content of eight shrub species ( Cytisus purgans, C. scoparius, Genista florida, G. occidentalis, Calluna vulgaris, Erica arborea, E. australis and Juniperus communis) from a grazing mountain area of northern Spain was analysed and related to various indicators of nutritive value. Chemical composition, in vitro gas production, OM degradation and true DM digestibility were evaluated in samples collected in January and June. With the exception of two samples comprised of considerable amounts of flowers, the shrub legumes examined had low contents of CT (less than 6.51 g quebracho tannin equivalents/kg DM) which would generally be considered unlikely to affect digestion of nutrients in the gastrointestinal tract of animals. However, Ericaceae species and J. communis, which are evergreen species, showed a high CT content (higher than 176 g quebracho tannin equivalents/kg DM) throughout the year. CT were negatively correlated ( P<0.05) with OM degradation and cumulative gas production, and positively correlated with lag time, which is consistent with the extensively reported suppressive effect of condensed tannins on rumen degradation and on the interference of these compounds with microbial attachment to feeds. The positive correlation between these plant secondary compounds and the partitioning factor (OM degradation/total gas production) indicates that the effect of CT is more strongly reflected in the reduction of gas production than in the reduction of OM degradation.

The Effect of a Mixture of Live Lactic Acid Bacteria on Intestinal Gas Production in Pigs

Probiotics are believed to be bene? cial for the host through the improvement of the microbial environment in the intestine. Reduction of flatulence is considered to be one of the effects of probiotics. We examined the effect of a commercial mixture of live lactic acid bacteria (LAB) on gas production by pig intestinal digesta aiming at the estimation of its effect on flatulence. Eight castrated male pigs (average B.W. 12 kg) were randomly divided into two groups, which consumed a diet with or without LAB. After 15 days of oral administration of the mixture (Biofermin S, 0.1 g/kg B.W.), the whole digesta from the jejuno-ileum, cecum, gyri centripetales and gyri centrifugales was removed. Moisture, pH and organic acid concentration of the digesta were not affected in most cases by LAB, although a decrease in acetate:propionate was observed (p<0.05) in the cecum and gyri centripetales. In vitro incubation of these digesta showed a signi? cant reduction in gas production (p<0.05) by LAB. The reduction was mainly caused by a decrease in carbon dioxide. In contrast to that, hydrogen sulfide was significantly increased (p<0.05, except for in the jejuno-ileum), by LAB. A negative correlation was seen between hydrogen sulfide and methane production. Keywords: flatulence, gas production, lactic acid bacteria, pig, probiotics, small and large intestine.

The Effect of a Mixture of Live Lactic Acid Bacteria on Intestinal Gas Production in Pigs

Probiotics are believed to be beneficial for the host through the improvement of the microbial environment in the intestine. Reduction of flatulence is considered to be one of the effects of probiotics. We examined the effect of a commercial mixture of live lactic acid bacteria (LAB) on gas production by pig intestinal digesta aiming at the estimation of its effect on flatulence. Eight castrated male pigs (average B.W. 12 kg) were randomly divided into two groups, which consumed a diet with or without LAB. After 15 days of oral administration of the mixture (Biofermin S, 0.1 g/kg B.W.), the whole digesta from the jejuno-ileum, cecum, gyri centripetales and gyri centrifugales was removed. Moisture, pH and organic acid concentration of the digesta were not affected in most cases by LAB, although a decrease in acetate/propionate was observed (p &lt; 0.05) in the cecum and gyri centripetales. In vitro incubation of these digesta showed a significant reduction in gas production (p &lt; 0.05) by LAB. The reduction was mainly caused by a decrease in carbon dioxide. In contrast to that, hydrogen sulfide was significantly increased (p &lt; 0.05, except for in the jejuno-ileum), by LAB. A negative correlation was seen between hydrogen sulfide and methane production.

Biological sulfate reduction using molasses as a carbon source.

The feasibility of using a laboratory-scale upflow anaerobic sludge blanket process for sulfate reduction with molasses as a carbon source was demonstrated. Competition between methane-producing bacteria (MPB) and sulfate-reducing bacteria (SRB) was influenced by the chemical oxygen demand-to-sulfur (COD:S) ratio in the feed. Sulfate removal greater than 80% could be achieved at COD:S greater than 10 when MPB predominated. Activity of MPB and SRB was inhibited at a dissolved sulfide concentration of approximately 200 mg/L. Competition between MPB and SRB was intense as the COD:S was reduced from 5 to 2. Further reduction in the COD:S to 0.7 led to the formation of sulfidogenic granules. The COD removal decreased to approximately 30% at a COD:S less than 2 because of accumulation of sulfurous precipitates and the nonbiodegradable portion of molasses in the sludge. Reduced gas production rates further imposed limitations on diffusion of the organic substrate into granules. Sulfidogenic process operation yielded sulfate removal as great as 70% at a COD:S of approximately 3.5.

Effect of antimicrobial agents on livestock waste emissions.

Various antimicrobial agents were evaluated with the purpose of reducing the microbial fermentation in stored cattle waste and the resulting odor emissions. Duplicate sealed 2-L flasks with 500 ml waste slurry, with and without antimicrobial inhibitors, were used to measure the production of short-chain volatile fatty acids, lactate, and total fermentation gas over 27-30 days. A combination of chlorhexidine diacetate (2 mM), iodoacetate (2 mM), and alpha-pinene (3.8 mM) reduced gas production 80% (1000 ml to 200 ml) and total volatile fatty acid production 50% (145 mM to 72 mM). Pinene had little antimicrobial effect; rather, it served as an effective masking agent, giving the waste a less offensive odor. A combination of chlorhexidine diacetate and the deaminase inhibitor, diphenyliodonium chloride (1.3 mM) had a similar effect in reducing short-chain volatile fatty acid production (145 mM to 80 mM). It is concluded that a combination of antimicrobial agents may be useful in controlling odor emissions and conserving organic matter in livestock wastes, therefore providing a potentially more useful byproduct waste when used as plant fertilizer.

Horizontal Well Gas/Water Shutoff-Field Results

Abstract Many horizontal wells have been drilled to control gas or water coning. However, after breakthrough, attempts to control inflow location along these wells have been expensive and frequently unsuccessful in reducing GOR and WOR. Cemented casing, casing with ECPs, open hole packers, selective stimulation and formation plugging agents have all been tried. Husky's experience with slightly inclined wells, over the past several years, suggested a "new" technique, which has recently been proven successful. Simply lowering tubing in a well, slightly inclined from horizontal, resulted in doubling of oil production rate and reducing gas production by 50%. Details of well configuration, field production results and a simple analytical model, explaining why it works, are presented in this paper. Special reservoir conditions which must exist for this technique are also discussed. Introduction One of the most successful applications of horizontal wells has been the reduction of gas or water coning(1–6), while at the same time improving areal drainage(7. 8). However, because of reservoir heterogeneity and pressure gradients across a reservoir, caused by production and injection operations, breakthrough of gas or water often occurs in one small part of a horizontal well. The resulting production of large amounts of gas or water with the oil increases processing cost and depletes reservoir energy. Therefore many attempts have been made to control inflow from along horizontal wells. Cemented casing, casing with ECPS(9), open hole packers(7), selective stimulation(5) and formation plugging agents(4) have all been tried, often without success. While experimenting with slightly inclined wells, a possible "new" way to control excess gas and water production was discovered. Husky has drilled slightly inclined wells in the Black, Rainbow, and Rainbow South Fields to eliminate uncertainty of oil/water contact location(9), and to drain oil from a moving oil bank in waterflooded pools with a gas cap, but no gas injection. There are several other possible reasons to drill a slightly inclined well, including to drain multiple porosity stringers and to allow the end of the well to be plugged off when excess gas or water production occurs. Production logs have shown that horizontal wells can act as good horizontal separators(3. 11). Also, drawdowns in many horizontal wells have been shown to be very low, in the range detectable only by quartz or sensitive strain gauges(7). These factors suggest that it might be possible to control the type of fluid being produced from some wells by simply changing the tubing inflow points. Although many authors have explored the effects of pressure drops in horizontal wells(12. 13), the specific use of variable tubing inflow points to control producing GOR or WOR has not been clearly stated. Analytical Model A simplified spreadsheet model was built to evaluate wellbore pressure changes and fluid inflow along a slightly inclined wellbore. The model incorporates the effects of productivity, gravity, momentum and single phase friction pressure drop. The tubing inflow location to achieve maximum flow of oil without gas or water production was evaluated.

Influence of protein fermentation on gas production profiles

With modern equipment, accurate gas-production profiles can be obtained reflecting the organic-matter fermentation in rumen fluid. Although the gas production caused by fermentation of carbohydrates is well understood and described, ignoring the influence of protein fermentation may lead to misinterpretation of the gas-production data. Gas-production profiles, from grass samples differing in growing days, and hence in protein content, showed an unexpected low gas production for the young samples compared to the old ones. The influence of protein fermentation on gas-production profiles was studied by incubation of mixtures of casein with glucose, Zulkovsky starch and/or potato starch. After prolonged incubation, the fermentation of casein produced only 32% gas compared with carbohydrates and it was calculated that each percentage of protein caused a reduction in gas production of 2.48 ml g −1 organic matter. Relative to potato starch, casein was fermented in an earlier stage of incubation. After correction for the influence of protein fermentation, gas production of the youngest grass sample was the highest and of the oldest sample the lowest. It showed that protein fermentation influenced gas production mainly in the initial hours of incubation, because the major part of protein is part of the soluble fraction. It is concluded that a comparison of gas-production profiles of feed samples differing largely in protein content may lead to a misinterpretation, which necessitates correction for protein fermentation.

Yeast cell metabolism investigated by CO2 production and soft X-ray irradiation

Results obtained using a new technique for studying cell metabolism are presented. The technique, consisting in CO2 production monitoring, has been applied to Saccharomyces cerevisiae yeast cells. Also the cells were irradiated using the soft X-ray laser-plasma source at Rutherford Appleton Laboratory with the aim of producing a damage of metabolic processes at the wall level, responsible for fermentation, without great interference with respiration, taking place in mitochondria, and DNA activity. The source was calibrated with PIN diodes and X-ray spectrometers and used Teflon stripes as target, emitting X-rays at about 0.9 keV, with a very low penetration in biological material. X-ray doses delivered to the different cell compartments were calculated following a Lambert-Bouguet-Beer law. Immediately after irradiation, the damage to metabolic activity was measured again by monitoring CO2 production. Results showed a general reduction in gas production by irradiated samples, together with non-linear and non-monotone response to dose. There was also evidence of oscillations in cell metabolic activity and of X-ray induced changes in oscillation frequency.

Development of the gas production technique to assay for anti-nutritive compounds in temperate tree fodders with polyphenol adsorbents using inoculum based on fresh cattle faeces

The polyphenol concentration in various tree fodders has been assayed by the gas production technique using rumen fluid inoculum either by fermentation of whole samples +/- a polyphenol adsorbent (Khazaal et al., 1994) or simply by the reduction of gas production caused by acetone extracts of the fodders (Wood and Plumb, 1995). Successful replacement of rumen fluid as a source of anaerobic bacteria by faeces from ruminant animals has been reported both for two-stage Tilley and Terry dry-matter digestibility (DMD) (El Shaer et al., 1987) and for the gas production technique (Davies, 1991). The use of faeces based inoculum +/- polyphenol adsorbents was therefore tested and optimized for fallen paulownia and poplar leaves using the gas production technique (the trees were commercial hybrids of Paulownia and Populus species respectively). A series of trials was carried out to: develop the use of preliminary incubation of the faeces inoculum; optimize the adsorbent type, molecular weight (MW) and quantity; optimize the faeces concentration in the inoculum and the use of glucose as a pre-incubation stimulant; and evaluate the use of differences in Tl /2 for gas production and end DMD +/- adsorbent to assess the effect of anti-nutritive compounds (ANCs) on the relative rate and extent of fermentation.All trials were carried out using 100 ml plastic vaccine flexibottles as containers maintained at 39°C in water baths. Gas was manually extracted with disposable syringes, generally at 3, 6, 9,12,15,18, 21, 24, 30, 36, 42, 48, 60, 72 h and bottles were well shaken at these times.

Effects of nitrobenzene and zinc on acetate utilizing methanogens

Determination of anaerobic degradation rates and toxic effects of nitrobenzene (NB) on acetate utilizing methanogens was the first objective of this research. Serum bottles were used for anaerobic toxicity assays with an acetate enrichment culture of methanogens. Ten mg/l of nitrobenzene did not inhibit total gas production in the acetate enrichment methanogenic culture. Twenty and thirty mg/l of nitrobenzene caused reversible inhibition of methanogenesis. Batch kinetic experiments showed that 20 mg/l of nitrobenzene was degraded with a first-order rate constant, k, of 0.37 d −1. Acetate was not degraded during the first 7 days when the measured nitrobenzene concentration was higher than about 1 mg/l. The second objective was to determine the effect of zinc on nitrobenzene degradation in methanogenic systems. Ten mg/l of spiked zinc caused a reduction of gas production in the systems with 10 mg/l of nitrobenzene; 20 mg/l of zinc led to failures of systems with 10 and 20 mg/l of nitrobenzene. With 10 and 20 mg/l of added zinc, the k value for nitrobenzene degradation decreased to 0.18 d −1 and 0.14 d −1, respectively. With 20 mg/l of Zn, acetate was not degraded at all even after nitrobenzene concentration reached 0.1 mg/l, indicating toxicity of Zn to methanogenesis. Abiotic control tests with autoclaved culture showed that adsorption alone could remove 60–70% of spiked nitrobenzene in 36 days. However, the samples extracted from solids in the methanogenic test systems showed that nitrobenzene was below the detection limit of 0.1 mg/l, indicating biodegradation of nitrobenzene in these systems. Traces of benzene were seen as an intermediate in the liquid samples. Headspace analysis showed that nitrobenzene and benzene were below detection limits.

Porosity in cooked beef from controlled atmosphere packaging is caused by rapid CO 2 gas evolution

Meat packaged and stored in CO 2 atmospheres (O 2 < 200 ppm) develops pores during cooking. Packaging beef in CO 2 or 0.25 M NaHCO 3 (pH 5.6) duplicated pore formation. Beef stored in vacuum-packaging following storage in CO 2 exhibited pores after cooking. Dialysis with distilled water eliminated pore formation and reduced gas production during cooking of beef stored in 0.25 M NaHCO 3 or CO 2. Differential scanning calorimetry showed that the thermal denaturation temperature of purified collagen was not affected by CO 2 storage. These data suggest that pore formation is linked to release of CO 2 in meat during cooking. Cooking denatures proteins; thus, CO 2 released during cooking may gather at the weakest point of the muscle, the perimysium, producing pores.

CO2 Foam: Results From Four Developmental Field Trials

SummaryFour pattern-scale CO2-foam field trials were conducted to determine the effectiveness of foam in reducing CO2 channeling, to evaluate the economic potential of the process, and to develop application criteria and procedures. The trials were conducted under various process and geologic conditions so that the resulting technology would be applicable in a number of different CO2 floods. Two different surfactants, Rhodapex (formerly Alipal) CD-128 and Chaser CD-1045, and two injection methods, alternating vs. coinjection of CO2 and surfactant, were tested in San Andres (west Texas) and platform carbonate (southeast Utah) reservoirs. In all, 161,000 Ibm of active surfactant was injected in the four field trials, with one well undergoing foam treatment for as long as 18 months. The treatments resulted in a significant reduction in gas production and indications of increased oil production. The total cost of the four treatments (excluding labor and overhead) was $700,000.