Reduced Gas Production Research Articles

A numerical well model considering capillary end effect for the low-permeability gas reservoir

In the recovery of low permeability reservoir, the capillary pressure has an important effect, which may reduce gas production. Due to the capillary end effect, there are two flow patterns in the vicinity of the production well: both water and gas phases can flow into the production well and only gas phase can enter the production well. Based on the analytical equations of one-dimensional radial flow considering the capillary end effect, an alternative numerical well model for low permeability gas reservoir is constructed. Numerical examples show that the proposed model can reflect the dramatic change for saturation and gas-phase pressure in the vicinity of the production well both for two flow patterns, and therefore can predict the gas and water productions accurately at different grid scales. In contrast, the original Peaceman well model for multi-phase flow, which is directly extended from that for single-phase flow, only can provide good prediction under the condition of that the grid size is enough small. Especially, for the original Peaceman well model, this problem is out of control since it is difficult to estimate a suitable grid size.

The second offshore production of methane hydrate in the Nankai Trough and gas production behavior from a heterogeneous methane hydrate reservoir.

Following the first attempt at producing gas from a naturally occurring methane hydrate (MH) deposit in the Daini–Atsumi Knoll in the eastern Nankai Trough area off Honshu Island, Japan in 2013, a second attempt was made in April to June of 2017 at a nearby location using two producer wells sequentially and applying the depressurization method. The operation in the first borehole (AT1-P3) continued for 12 days with a stable drawdown of around 7.5 MPa and 41 000 m3 of methane gas being produced despite intermittent sand-production events. The operation of the other borehole (AT1-P2) followed, with a total of 24 days of flow and 222 500 m3 of methane gas being produced without sand problems. However, the degree of drawdown was limited to 5 MPa because of a higher water production rate than expected in the second hole. The pressure and temperature sensors deployed in the two producers, along with the two monitoring holes drilled nearby, gathered reservoir response data and information about the long-term MH dissociation processes in the vicinity of the production holes in the temporal and spatial domains. Although the ratio of energy return to the input was considerably larger than that for the depressurization operation, some observations (e.g., the high contrast in the production rates between the two holes and the almost constant or slightly reduced gas production rates) were not predicted by the numerical models. This failure in prediction raises questions about the veracity of the reservoir characteristics modeled in the numerical simulations. This paper presents the operation summaries and data obtained with thought-experiment based-anticipated production behaviors and preliminary analysis of the obtained data as the comparison with expected behaviors. Detailed observations of gas and water production, as well as the pressure and temperature data recorded during the gas flow tests, indicate that the heterogeneous MH distribution within the reservoir was mainly responsible for the discrepancies observed between the anticipated and actual behaviors. Furthermore, the motion of the water that does not originate from MH dissociation introduces complexity, such as the occurrence of concentrated water-producing intervals and unexpected gas production responses to decreases in pressure, into the production behavior. The influence of heterogeneity should be clearly understood for the accurate prediction of gas production behavior based on MH reservoirs.

<b><i>In vitro</i> evaluation of palm fronds as feedstuff on ruminal digestibility and gas production

This study was carried out to evaluate using palm fronds only or supplemented with fibrolytic enzymes as alternative roughage on the ruminal nutrients digestibility and gas production. Treatments were: clover hay ( Trifolium alexandrinum ), palm fronds only and palm fronds plus fibrolytic enzymes (enzymes were mixed with palm fronds in rate of 4 g kg -1 of dry matter (DM). The results showed a reduction (p < 0.05) in gas production, ammoniac nitrogen (NH 3 -N, DM and organic matter (OM) digestibility in palm fronds compared with clover hay. While supplementing palm fronds with fibrolytic enzymes improved DM and OM digestibility compared with palm fronds only without (p < 0.05) differences with clover hay . Also, supplementing palm fronds with fibrolytic enzymes reduced (p < 0.05) gas production compared with other treatments. It could be concluded that adding fibrolytic enzymes improved the utilization of palm fronds as alternative roughage without negative effect on nutrients digestibility and reduced gas production which improve the environmental aspects of feeding ruminant animals.

Production performance analysis for deviated wells in composite carbonate gas reservoirs

The strong heterogeneity of carbonate gas reservoir makes the formation exhibit composite properties. The inner region adjacent to deviated well is full of matrix, natural fractures and vugs, while the outer region contains matrix only. It is very challenging to incorporate geological features of carbonate reservoirs and evaluate the production performance of deviated wells. This paper presented a semi-analytical model to study the pressure behavior and production performance of deviated wells in composite, anisotropic and stress-sensitive carbonate gas reservoirs. In inner region, the interaction between matrix, vugs and fractures can be described by triple-porosity/single-permeability model, in which primary flow occurs only through the fractures, and the outer region can be represented by single porosity media. The stress-sensitive power exponent is proposed and estimated through laboratory experiments and curve fitting, and pseudo-pressure and pseudo-time are introduced to consider this effect. Laplace transformation, Fourier transform and inverse, Stehfest inversion algorithm and point source function are used to calculate the well bottom-hole pressure and production rate. When the inclination angle is equal to 0° approximately, the rate-transient curves of this model match very well with the conventional vertical well model. In addition, the accuracy of the model is validated by comparing the pressure response with monitoring data collected from a deviated well in Gaoshiti-Moxi carbonate gas reservoir. A synthetic case is utilized to analyze the effects of stress-sensitive power exponent, inner region radius, fracture horizontal permeability, horizontal-vertical permeability ratio and inclination angle on gas well production performance. Through the sensitivity analysis of relevant factors, we come to some conclusions that a large stress-sensitive power exponent has negative impact on well performance; a large inner radius, a high fracture horizontal permeability and a large inclination angle can heighten gas production rate in a short period, while it also leads to the drastic declination of production rate; a large horizontal-vertical permeability ratio which means the formation has strong anisotropy can significantly reduce gas production rate. With its high efficiency and simplicity, this semi-analytical approach will serve as a useful tool to evaluate the well productivity and pressure behavior for composite carbonate gas reservoirs.

Assessment of low-carbon iron and steel production with CO2 recycling and utilization technologies: A case study in China

Substance flow analysis (SFA) and energy and economic assessment were used in this study to analyze the utilization of CO2 in the steelmaking system based on four scenarios: the conventional blast furnace-basic oxygen furnace (BF-BOF) process (Baseline case), the BF-BOF process with waste heat and energy recovery (Case-1), the BF-BOF process with CO2 hydrogenation (Case-2), and the CO2-CH4 dry reforming process coupled with an electric arc furnace (EAF) (Case-3). The results suggest that Case-2 is competitive not only in carbon emission but also in energy consumption and economy as it reduces carbon emission and energy consumption by 136 kg and 53.7 kgce respectively. It also increases profits by 9.38 US$ per ton of steel compared to the Baseline case, thus promising to mitigate predicaments in China’s present iron and steel industry. With higher levels of hydrogen in the composition of natural gas, Case-3 reduces carbon emission by 40% more than the Baseline case, but its energy consumption is close to that of the Baseline case. Besides, the production cost is 34% higher in Case-3 than in the Baseline case, owing to the high natural gas price in China. Only when the natural gas price falls to the American value, which is 70% lower than that of China, will Case-3 be economically feasible. In short, high production energy consumption and production costs lead to a lack of technical and economic impetus for Case-3 in the current market, even if it is associated with relatively low carbon emission. The key to solving this problem lies in identifying methods to realize reduced gas production with high efficiency and low cost.

Nanoparticles in mitigating gaseous emissions from liquid dairy manure stored under anaerobic condition.

A number of mitigation techniques exist to reduce the emissions of pollutant gases and greenhouse gases (GHGs) from anaerobic storage of livestock manure. Nanoparticle (NP) application is a promising mitigating treatment option for pollutant gases, but limited research is available on the mode of NP application and their effectiveness in gaseous emission reduction. In this study, zinc silica nanogel (ZnSNL), copper silica nanogel (CuSNL), and N-acetyl cysteine (NACL) coated zinc oxide quantum dot (Qdot) NPs were compared to a control lacking NPs. All three NPs tested significantly reduced gas production and concentrations compared to non-treated manure. Overall, cumulative gas volumes were reduced by 92.73%-95.83%, and concentrations reduced by 48.98%-99.75% for H2S, and 20.24%-99.82% for GHGs. Thus, application of NPs is a potential treatment option for mitigating pollutant and GHG emissions from anaerobically stored manure.

Application of DOE and metaheuristic bat algorithm for well placement and individual well controls optimization

The design of an optimal gas field development and production management is a complicating task because of influencing various factors on decision-making process. Typical factors include number and type of wells, well locations, and production constraints, economic factors of capital expenditure, operating costs, gas sale price, and different engineering and geological parameters. The situation is further complicated due to uncertainty associated with the nonlinear problem of field development optimization.In this study, first, design of experiment (DOE) techniques including uniform design (UD) and Box-Behnken design (BBD) are used for performance prediction of water drive gas reservoirs. Next, a new metaheuristic bat inspired algorithm (BA) will be applied in optimization process of objective function. Undiscounted net present value (UNPV) is used as an objective function for the determination of optimal number of wells (N), individual well locations (I and J), production rate (Qg), perforation thickness (Hp) and the limit of tubing head pressure (THP) for different average reservoir permeability (KG) and permeability anisotropy (Kv/Kh). In this regard, part of gas reservoir with an active bottom aquifer based on actual data is simulated in order to predict gas recovery factor and cumulative water production data that are necessary for performing production optimization.The results show that reducing gas production rate increases the UNPV. Reducing production rate increases ultimate recovery factor and decreases cumulative water production. However, considering time value of money, it is favorable to produce with high rates and consequently deplete the reservoir over short time scales in order to compensate the reduction of profit.

Effect of cellobiose supplementation on in vitro fermentation activity and bacterial numbers of porcine inocula.

In this in vitro study, the modified Hohenheim gas test (HGT) was applied to determine fermentation activity and bacterial composition of pig's faecal microbial inoculum using different concentrations of cellobiose. Incubation procedures included normal buffered and osmotic stress conditions (elevated medium salinity). After 24hr of fermentation, production of gas, ammonia and short-chain fatty acid (SCFA) was measured, and the gene copy numbers of total bacteria, Lactobacillus spp., Bifidobacterium spp., Roseburia spp., Clostridium Cluster IV spp. and Enterobacteriaceae were analysed using real-time polymerase chain reaction. There was a significant reduction in gas production after 24hr when comparing osmotic stress conditions with normal buffered conditions. Under osmotic stress, increasing cellobiose concentrations linearly increased gas production (p<.001), while ammonia, acetic acid and isobutyric acid concentrations decreased (p<.001, p=.012, p=.035 respectively). Under normal buffered conditions, Roseburia spp. gene copies linearly increased with increasing cellobiose concentrations (p=.048). Lactobacillus spp. and Bifidobacterium spp. numbers were higher under osmotic stress (p<.001) compared to normal conditions. Results might point towards a positive impact of cellobiose supplementation on gut health especially under osmotic stress conditions.

Study of production enhancement through wettability alteration in a super-giant gas-condensate reservoir

Near wellbore condensate blockage phenomena commonly reduce gas production significantly. One efficient method for overcoming such problem is wettability alteration. Such issues as wettability state, treatment radius and time to reach the maximum level of production need be optimized prior to field application. In this paper, impact of these parameters are studied on gas and condensate production enhancement through wettability alteration. To do this, behavior of a well located in supergiant offshore Iranian gas condensate field is simulated and analyzed using a compositional model, single well and radial grid. The real fluid and reservoir properties of the studied well are utilized to construct the model. Different wettability states were defined using various relative permeability curves at various distances from the wellbore along with different treatment times are tested to find the best condition. Results indicate that near-wellbore wettability alteration leads to lower critical condensate saturation which has a significant impact on improving production parameters and reservoir recovery factors. Also, the highest recovery factor is achieved at optimal conditions where wettability is altered from strong liquid-wet to intermediate-wet at the small radius around the production well in early times. Furthermore, the inflow performance relationship curve (IPR) moves upward considerably which represents the magnificent production improvement.

Effectiveness of xylanase and Saccharomyces cerevisiae as feed additives on gas emissions from agricultural calf farms

The aim of the present study was to evaluate the potential of supplementing calves’ diets with exogenous enzymes (xylanase; XYL) and yeast (Saccharomyces cerevisiae [SC]) on the sustainable control of methane (CH4) and carbon dioxide (CO2) productions in agricultural calves farming. Three different levels of supplemented diets of XYL (0, 3 and 6 mg/g of dry matter (DM)), SC (0, 2 and 4 mg/g of DM) and mixture of XYL and SC (0, 2 μL XYL + 2 mg SC, 6 μL XYL + 4 mg SC/g of DM) were tested. Asymptotic gas production (GP) consistently decreased by each of the additives with the lowest value at the high dose of XYL + SC mixture (P < 0.05) compared with the control and the low dose of XYL + SC mixture. Methane production was reduced by additives inclusion (P < 0.05) when compared with the control treatment with no additive. Xylanase + SC at all doses increased CO2 production (P < 0.05) whereas the high dose had the most statistically significant (P < 0.05) reduction in GP and CH4 production compared with control, XYL and SC additives at different doses. Interaction between additive and rumen liquor was observed for rate of GP (P = 0.027) and initial delay before GP (P < 0.001). Inclusion of XYL, SC, and XYL + SC mixture had less asymptotic GP while XYL + SC mixture had the lowest initial delay (39%) before GP began. The XYL + SC had the lowest rate of CH4 production (9%) and highest asymptotic CO2 production (81%). The findings of this study indicate that inclusion of XYL or SC additives can improve rumen fermentation and reduce greenhouse gases production. The study also established that the mixture of XYL and SC is more efficient in reducing gas and CH4 emissions for cleaner environmental production conditions in calf farming.

English

The objectives of this trial were to evaluate interactions between microbial degradation of three substrates: date palm leaves as tannin-rich substrate, Astragalus gombiformis (as nitrogen source) and Aristida pungens (as carbon source). The model included the principal effects of single substrate and mixtures of multiple interactions. The forages were fermented alone or mixed with date palm leaves in various combinations (0, 10, 20, 30, 40 and 50%), in buffered rumen fluid using in vitro gas techniques. Gas production (mmol/g of dry matter) at 3, 6, 9, 24, 48 and 72 h of incubation was measured from all feed combinations. Treatments were carried out in triplicate and data were submitted to analysis of variance using a mixed procedure with repetition considered as the random effect. The interactions between feeds were evaluated on the basis of differences between single and mixed substrates on the different variables measured. The results showed that the included palm leaves reduced gas production when associated with A. pungens (p<0.0001), whereas this effect was less significant with A. gombiformis. This effect was more pronounced at earlier times of incubations. The in vitro organic matter digestibility decreased linearly with the increasing inclusion of date palm leaves in the mixtures. It is concluded that date palm leaves may be a suitable feed supplement for small ruminants browsing A. pungens and A. gombiformis in arid regions. The present results also showed that the inclusion level should be lower than 20% and for a short period in order to minimise tannins effect. The description of the fermentation profile of in vitro gas production showed that Sandoval model was poor and not appropriate for the characteristic varieties of arid and semi-arid areas in Algeria and the multiple regression models revealed a good linear regression for both mixtures. Key words: Date palm leaves, forage, semi-arid zone, associative effects, rumen, in vitro fermentation.

PERSPECTIVE USE OF POLY-FUEL GAS GENERATOR IN PRACTICE OF BLAST-FURNACE SHOPS

The analysis of the use of pulverized coal injection (PCI) in the practice of blast furnaces of the Russian Federation was made. It is shown that the current level of injecting of PCI is much lower than in the world’s best practices. The factors hindering the development of this direction in Russia are presented. The authors have analyzed the activities suggested in order to reduce carbon dioxide emissions from the production of iron (ULCOS program). It is proposed to enter the poly-fuel gas generators of bubble type into the blast-furnace shops for the production of hot reducing gases (HRG) for subsequent injection into blast furnaces. The calculation was made for the performance of blast furnace with volume of 1033 m3 and HRG injection of up to 400 Nm3/t of cast iron. When such HRG injection the coke savings are 100–120 kg/t of cast iron. Expected savings of coke while HRG injection of 700 Nm3/t are up to 200 kg/t of cast iron. It is proposed to create a consortium of leading metallurgical enterprises for testing the proposed technology in pilot industrial conditions.

Prediction of Critical Gas Velocity of Liquid Unloading for Entire Well Deviation

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 17846, “Prediction of Critical Gas Velocity of Liquid Unloading for Entire Well Deviation,” by J. Li, Trican Well Service, and F. Almudairis and H. Zhang, The University of Tulsa, prepared for the 2014 International Petroleum Technology Conference, Kuala Lumpur, 10–12 December. The paper has not been peer reviewed. Liquid loading is a common production problem in mature gas wells. Correct prediction of the critical gas velocity at which the well starts to load is very important to the operators because it may allow them to take appropriate measures to prevent liquid loading and extend well production life. In this paper, a database related to the critical gas velocity is compiled with data from published literature. A new model is developed and evaluated with the experimental data. Introduction Gas wells often produce water and other condensate. In the early production stage, the gas-flow rate is high enough to carry the produced liquids to the surface. As the reservoir pressure is depleted, the produced-gas-flow rate decreases until the gas reaches a critical condition, at which time liquid loading is initiated. At the inception of liquid loading, the gas-flow rate is not sufficient to carry the liquid completely to the surface and the liquids start to accumulate at the bottom of the well. A backpressure then builds up, and the increased reservoir pressure will eventually be sufficient to lift the liquid to the surface. Once the liquid slug is pushed out by the gas, the liquid starts to reload the well again and the cycles are repeated until the well is eventually loaded completely and gas production stops. The most common liquid-loading symptoms observed in the field are pressure (or pressure-gradient) fluctuations and reduction of gas production. In general, there are two different liquid-loading principles proposed in the literature: liquid-droplet fallback and liquid-film reversal. The complete paper contains a literature review that follows the development of these principles. Data Compilation Liquid-loading-initiation mechanisms have been investigated in 3-in.-innerdiameter pipes with deviations of 0, 15, 30, and 45° from vertical. Others have used the same flow loop to study the liquid loading at deviations of 60, 70, 80, 85, and 88° from vertical. The superficial gas velocity ranged between 2 and 40 m/s, and the superficial liquid velocity varied from 0.01 to 0.1 m/s. Approximately 450 tests were performed. Pressure gradient, liquid holdup, and liquid-film thickness at the bottom of the tubing were also measured. Highspeed video cameras were used to observe flow pattern and film reversal. Complete film-reversal transition was applied to determine the critical gas velocity for the liquid-loading initiation. In the vertical case, the liquid film around the pipe periphery is almost uniform, and in the deviated case, it is nonuniform. In the latter, there is more liquid accumulated at the bottom of the pipe than at the top. This difference in liquid-film distribution around the pipe yields a difference in flow-pattern transitions and film reversal.

The Effect of Water Vaporization on the Well Productivity in High Temperature Gas Reservoirs

Flow of gas through porous media at high velocity is affected by inertial forces resulted from convective acceleration of fluid particles in the medium, as well as viscous force, as explained by Darcy's equation. The inertial force further develops the additional skin effect, reducing gas production rate. At early stages of production, the pressure drop in the near-well region builds up the molar content of water in gas. This, in turn, results in water vaporization and hence a drop in the connate water saturation. Considering the fact that inertial force is a function of the non-Darcy coefficient, β, which itself is dependent on connate water saturation, this can ultimately reduce the non-Darcy component of pressure drop and therefore inertial forces. The present study focuses on the enhancement of gas well productivity through water vaporization.

Nutritive value of cattle manure vermicast and its effect on in vitro ruminal gas production

Introduction The use of non-conventional feedstuffs is gaining recognition especially in developing countries. Ensiled cattle manure with other feedstuffs has been used in ruminant feeding. Vermicomposting, a tool for manure management can be employed as a means for manure treatment with the aim of enhancing nutritive value of forage. The objectives of the study were to determine the nutritive value of cattle manure vermicast (CMV) and to observe gas production in vitro due to CMV inclusion on rice straw at different proportions. Results Vermicomposting of cattle manure at 2, 4 and 6 weeks linearly increased (P 0.05) significantly crude protein and ash, while it linearly decreased (P 0.05) significantly organic matter, neutral detergent fibre (NDF) and acid detergent fibre. The result showed that, gas production decline with an increased in CMV content (P 0.05). CMV addition to rice straw had no significant (P [ 0.05) effect on rumen pH and microbial crude protein production in vitro. CMV inclusion reduced dry matter degradability and increased partitioning factor at 48 h. 5 % inclusion level of CMV gave the highest results while 30 % CMV had the least results. Conclusion Vermicomposting of cattle manure increased its nutritive value, with increase in crude protein content and decrease in NDF and ADF. Results of in vitro gas production and rumen fermentation profiles from this study indicated that inclusion of CMV reduced gas production and DMD; however, it increased PF48 ,w ith no significant changes in MCP. Vermicomposting has the potential of being used as another tool for forage treatment and addition of CMV could be expected to reduce ruminant gas production, increase ME and microbial protein synthesis.

NiO/Dolomite Catalyzed Steam/O2 Gasification of Different Plastics and Their Mixtures

The catalytic gasification of different individual plastics and their mixtures with a dolomite supported Ni catalyst was evaluated in a drop-tube fixed-bed reactor. The influence of the Ni loading level and the interactions of mixed plastics during steam gasification were both examined. A 5 wt % NiO/dolomite catalyst gave the highest degree of carbon conversion for all evaluated plastics and mixtures. A mixture of the four types of plastic that matched the estimated weight ratio of real plastic waste revealed a lower gas yield than predicted, suggesting their interaction during gasification. The mixtures which contain high-density polyethylene or low-density polyethylene at 0.75 wt/wt led to a reduced gas production, while polystyrene increased it, especially in the polystyrene–polypropylene binary mixture with a markedly higher H2, CO, and CO2 production level than that expected. Thus, it would be beneficial to screen plastic types prior to the generation of suitable gas products.

Efficacy and tolerability of α-galactosidase in treating gas-related symptoms in children: a randomized, double-blind, placebo controlled trial

BackgroundGas-related symptoms represent very common complaints in children. The reduction of gas production can be considered as a valuable target in controlling symptoms. α-galactosidase has been shown to reduce gas production and related symptoms in adults. To evaluate the efficacy and tolerability of α-galactosidase in the treatment of gas-related symptoms in pediatric patients.MethodsSingle center, randomized, double-blind, placebo-controlled, parallel group study performed in tertiary care setting. Fifty-two pediatric patients (32 female, age range 4–17) with chronic or recurrent gas-related symptoms were randomized to receive placebo (n = 25) or α-galactosidase (n = 27). Both treatments were given as drops or tablets, according to body weight for 2 weeks. The primary endpoint was the reduction in global distress measured by the Faces Pain Scale-Revised (FPS-R) at the end of treatment compared to baseline. Secondary endpoints were the reduction in severity and frequency of gas-related symptoms as recorded by parents and/or children.Resultsα-galactosidase significantly reduced global distress (p = 0.02) compared to placebo. The digestive enzyme decreased the number of days with moderate to severe bloating (p = 0.03) and the proportion of patients with flatulence (p = 0.02). No significant differences were found for abdominal spasms and abdominal distension. No adverse events were reported during treatment.ConclusionsAlthough larger and longer trials are needed to confirm this result, α-galactosidase seems to be a safe, well tolerated and effective treatment for gas-related symptoms in the pediatric population.Trial registrationClinicalTrials.gov, NCT01595932

Trace metals requirements for continuous thermophilic methane fermentation of high-solid food waste

The amount of iron, cobalt and nickel required to perform thermophilic methane fermentation using high-solid food waste was examined in this study. To determine this, we devised and applied a theoretical consideration method. Three runs were performed using a completely stirred tank reactor. During the first run, start-up was carried out by decreasing the HRT from 100 to 50 and finally to 30days, which corresponds to a COD loading rate of 1.9, 3.8 and 6.3kgm−3day−1, respectively. Four typical operational parameters—the gas production rate, methane content, pH and total volatile fatty acid (VFA) concentration—were stable except a temporary rise in VFA was observed when the HRT was decreased from 50 to 30days, indicating that the system performed well with COD loading rate of 6.3kgm−3day−1. After day 57 (HRT: 30days, COD loading rate: 6.3kgm−3day−1), the reactor efficiency deteriorated due to the trace metals limitation. A combination of iron, cobalt and nickel (at 10, 1 and 1mgL−1, respectively) was added to the reactor approximately every 45days during the second run. The reduced gas production, methane content and pH were all restored to stable levels after regularly adding the trace metals. During the third run, trace metals were added to the substrate, and no limitation was noted at all. Based on the theoretical consideration and the experimental results, the most suitable values for Fe/COD, Co/COD, Ni/COD are 276, 4.96 and 4.43mgkg−1COD-removed, respectively, for high-solid thermophilic methane fermentation of food waste.

Inclusion of selected levels of Australian native plant Eremophila glabra in fermentation substrate can influence events leading to rumen lactic acidosis in in vitro and in vivo carbohydrate-challenged systems

The aim was to investigate if selected doses of Australian native plant Eremophila glabra influence events leading to rumen lactic acidosis in sheep. The plant was first examined in an in vitro batch culture experiment, where a range of plant inclusion levels (10–1000mg of ground plant) was incubated with 1g of glucose in 10mL of rumen fluid. In this system, cumulative gas pressure, pH, d-Lactate and volatile fatty acids (VFA) concentrations were measured after 24h. There was no change in pH in any E. glabra treatments, doses of 600mg plant/g glucose and above reduced d-Lactate values, with 800mg/g and above also reducing gas production. Based on these in vitro findings, E. glabra was investigated further in vivo. Fistulated sheep (n=8/treatment) were administered with cracked wheat grain only (acidosis control), cracked wheat grain combined with virginiamycin (antibiotic control), or cracked wheat grain combined with dried and ground E. glabra at 200, 400 or 800g/kg wheat. Rumen fluid samples were collected at intervals over 1 d and analysed for pH, d-Lactate and VFA concentrations. Inclusion of plant material at 400g/kg wheat resulted in pH, lactate and VFA concentrations which were comparable to the antibiotic control at 12 and 16h post-administering of wheat. Other inclusion levels of the plant had no effect and 800g/kg wheat also inhibited normal rumen fermentation. Australian native plant E. glabra may have the potential to assist in control of lactic acidosis in sheep, but only when included at 400g/kg wheat or higher.

Comparison of the impact of dextran and reuteran on the quality of wheat sourdough bread

This study investigates the influence of in situ exopolysaccharides (EPS) and organic acids on dough rheology and wheat bread quality. Dextran forming Weissella cibaria MG1 was compared to reuteran forming Lactobacillus reuteri VIP. For in situ production of EPS, sourdoughs were supplemented with 15% sucrose. Control sourdoughs were prepared with the same strain but without sucrose. W. cibaria MG1 and L. reuteri VIP formed 5.1 and 5.8 g kg−1 dextran and reuteran, respectively. Formation of EPS from sucrose led to production of high amounts of acetate by L. reuteri VIP, but only small amounts were detected in W. cibaria MG1 sourdough. EPS containing sourdough or control sourdough was incorporated at 10% and 20% in wheat dough. EPS significantly influenced the rheological properties of the dough, with dextran exhibiting the strongest impact. The addition of dextran enriched W. cibaria MG1 sourdough significantly increased CO2 production, whereas increased acidity in reuteran containing dough reduced gas production. The quality of wheat bread was enhanced when 10% of L. reuteri-sucrose sourdough was added. The positive effect of reuteran was masked by increased acidification after 20% sourdough addition. Incorporation of dextran enriched sourdough (10% and 20%) provided mildly acidic wheat bread with improved bread quality.