Dry Gas Production Research Articles

PSVIII-23 Effects of different growth height on the yield, chemical composition, silage fermentation profile, in vitro and in situ digestibility of Broussonetia papyrifera

Abstract Broussonetia papyrifera (BP) is a woody roughage source with high protein content. The experiment was conducted to explore the effects of different growth height (GH) on the BP yield, chemical composition, silage fermentation profile, as well as ruminants in vitro and in situ digestibility of different parts of BP. The three different harvested GH of BP were 0.8, 1.2, and 1.6 m, respectively. Samples from leaf, stem, and whole plant of BP were collected (each one has three replicates), making silage, and detected the nutritional composition of them. The results were analyzed by one-way analysis of variance with Duncan’s multiple comparisons. Fresh weight increased with the GH increased (P < 0.05). No significant difference was observed in dry matter (DM) and crude protein (CP) yield of leaf, and CP yield of whole plant between 1.2 to 1.6 m GH (P > 0.05). With the increase of GH, neutral detergent fiber (NDF) of BP increased, while CP content decreased (P < 0.05). Stem had the highest NDF and acid detergent fiber (ADF) content, and the lowest CP content and buffer capacity. The BP silage fermentation quality was deteriorated (lactic acid content decreased and pH values increased) with GH increased. For the different parts of BP, leaf silage had the highest pH and stem silage had the highest lactic acid content (P < 0.05). The leaf and its silage had the highest in vitro dry matter digestibility and gas production compared to others. The BP in situ digestibility were corresponded with in vitro results. DM, CP, NDF, and ADF effective digestibility rates of whole plant with 1.2 m GH were 439.6, 455.1, 412.9, and 381.3 g/kg, respectively. In conclusion, the BP nutritional quality decreased with GH increased and it could be used as a potential feedstuff for ruminants.

Chemical and biological treatment of cotton gin trash for fattening Santa Ines lambs

Two experiments were used to evaluate the effects of using cotton gin trash (CGT) treated with urea and exogenous fibrolytic enzymes (EFE) on feed chemical composition, in vitro dry matter digestibility and gas production (Trial 1), and apparent in vivo digestibility, intake and growth performance of feedlot Santa Ines lambs (Trial 2). The Trial 1 used a completely randomized 2×4 factorial design with four replications of treating CGT with urea (0 and 6%) and EFE (0, 2, 4, 6 g/kg; 75% cellulase, 25% hemicellulase). The Trial 2 used a complete randomized design with 8 replications to evaluate the use of CGT treated with 6% urea and one of four EFE concentrations (0, 2, 4, 6 g/kg) in 50% concentrate and 50% CGT diets; the control diet contained untreated CGT. In Trial 1, there was interaction between urea and EFE dose for DM, EE, ADF, TN, and fractions A and C of nitrogen (P < 0.001). Urea reduced all cell wall components (P < 0.05) except for hemicellulose (P > 0.05). Increasing EFE resulted in a linear decrease of NDF, ADF, cellulose, hemicellulose, and lignin. Both urea and EFE increased (P < 0.05) IVDMD. There was an interaction (P < 0.001) between urea and EFE for TN and nitrogen fractions A and C. Independently of EFE dose, urea affected all carbohydrate fractions. Increasing EFE linearly increased (P < 0.001) NFC and decreased (P < 0.008) fractions B2 and C. An EFE vs. urea interaction (P < 0.02) affected L, CGP, BIO and TDOM. The CGT pre-treated with urea and 2 g/kg of EFE generated the greatest total gas production but urea without EFE resulted in the least gas production. In Trial 2, increasing EFE linearly increased DM and OM intakes and quadratically NFC intake; as well as linearly increased (P < 0.002) DM, OM and NFC digestibilities. However, fiber apparent digestibility (ADF and FC) was negatively affected by EFE (P < 0.05). Final BW, BW gain and ADG linearly increased with EFE dose (P < 0.02). Combining urea and EFE was efficient in reducing structural cell wall components and improving the in vitro digestibility and gas production of CGT. The EFE improved OM, fiber and NFC digestibility and DM, OM and NFC intake that supported greater growth performance of feedlot sheep.

Effect of wheat straw types on biological delignification and in vitro rumen degradability of wheat straws during treatment with Irpex lacteus

Irpex lacteus was inoculated in eight different cultivars of wheat straw and incubated under solid-state conditions at 28 °C for 56 days to determine the effects of wheat straw types on the delignification and rumen degradability of wheat straw. The results showed that I. lacteus degraded 625 g/kg of lignin (sa) and increased 320 g/kg of neutral detergent soluble after 56 days of incubation on average. Corresponding to lignin degradation, the average in vitro dry matter digestibility and gas production of the treated wheat straw were improved by 21 % and 32 %, respectively, and the mean ratio of acetate and propionate decreased from 3.68 to 2.99. It is concluded that I. lacteus has broad adaptability to variations in wheat straw and its use is a promising means to improve their nutritional value.

Nature-inspired hybrid techniques of IWO, DA, ES, GA, and ICA, validated through a k-fold validation process predicting monthly natural gas consumption

Current study aimed to combine the multi-layer Perceptron (MLP) neural network technique with five metaheuristic computational algorithms, namely invasive weed optimization (IWO-MLP), dragonfly algorithm (DA-MLP), evolution strategy (ES-MLP), genetic algorithm (GA-MLP), and imperialist competitive algorithm (ICA-MLP) for estimating the monthly natural gas consumption (NGC). For the case of this study, the NGC data was collected from the United States (U.S.) was chosen. To achieve this, a dataset composed of eight independent factors, namely, dry gas production, NGPL production, gross withdrawals, supplemental gaseous fuels, net storage withdrawals, marketed production, net imports, and balancing items, along with a dependent variable of natural gas consumption is provided. Out of 39 samples, a 3-fold ratio is taken to select the datasets of training and testing randomly. During the calculation phase, and through a trial and error procedure, the optimal parameters of the MLP, IWO-MLP, DA-MLP, ES-MLP, GA-MLP, ICA-MLP networks are taken into consideration. To assess the reliability of the proposed technique with the real collected data, three well-known statistical criteria, including mean square error (MSE) and root mean square error (RMSE) as well as coefficient of determination (R²), are introduced. These indices help to measure the level of accuracy of the used models. It is found that the IWO can be a better predictive network comparing to other hybridized techniques reducing the error performance of the MLP method. The predicted results reveal that hybridizing optimization algorithms could improve the prediction accuracy and helps the MLP to perform more efficiently. The recorded in testing MSE for the IWO-MLP, DA-MLP, ES-MLP, GA-MLP, ICA-MLP prediction techniques (i.e., used for U.S. natural gas consumption estimation) were found 0.000013, 0.002358, 0.024744, 0.013244, and 0.048572, respectively. In the sense of U.S. natural gas consumption prediction, the training R2 value to 0.9999, 0.9996, 0.9971, 0.9996, and 1.0000 and testing R2 value of 0.9999, 0.9995, 0.9956, 0.9984, and 0.8115 show that the outputs of the ensemble models are more correlated with the real data.

Identifying thermogenic and microbial methane in deep water Gulf of Mexico Reservoirs

The Gulf of Mexico (GOM) produces 5% of total U.S. dry gas production (USEIA, 2016). Despite this, the proportion of microbial and thermogenic methane in discovered and producing fields from this area is still not well understood. Understanding the relative contributions of these sources in subsurface environments is important to understanding how and where economically substantial amounts of methane form. In addition, this information will help identify sources of environmental emissions of hydrocarbons to the atmosphere. We apply stable isotopes including methane clumped-isotope measurements to solution and associated gases from several producing fields in the U.S. Gulf of Mexico to estimate the proportions, properties and origins of microbial and thermogenic endmembers. Clumped isotopes of methane are unique indicators of whether methane is at thermodynamic isotopic equilibrium or affected by kinetic processes. The clumped methane thermometer can provide insights into formation temperatures and/or into kinetic processes such as microbial methanogenesis, early catagenetic processes, mixing, combinatorial processes, and diffusion. In this data set, we find that some fluids have clumped isotope methane apparent temperatures consistent with the methane component being produced solely by the thermogenic breakdown of larger organic molecules at substantially greater temperatures than those reached in shallow reservoirs. A portion of these reservoirs with hot clumped isotope methane temperatures are consistent with exhibiting a kinetic isotope effect. Other reservoirs have clumped isotope methane apparent temperatures, and other isotopic and molecular proportions, consistent with mixtures of microbial and thermogenic methane. We show that in certain cases the evidence is most consistent with formation of the microbial methane in the current reservoir. However, in other cases the methane is produced at significantly shallower depths and is then transported to greater depths as a result of post generation burial of methane bearing sedimentary sequences to the current reservoir conditions. For the first time, we show that methane of an unambiguously purely microbial origin (i.e. those that do not contain obvious contributions of thermogenic methane) is dominantly generated at temperatures less than 60 °C, despite burial to greater depths. This finding suggests that, while microorganisms are able to generate methane at temperatures up to 105 °C under laboratory conditions (Brock, 1985), in the Gulf of Mexico, microbial methane is dominantly produced in the 20–60 °C window.

Ilmenite as low-cost catalyst for producer gas quality improvement from a biomass pilot-scale gasifier

In this work, in-situ application of natural occurring ilmenite (FeTiO3) for upgrading the producer gas from a pilot-scale bubbling fluidized bed gasifier was performed and its influence on the gas characteristics and gasifier performance was analyzed.Without using ilmenite, the producer gas average composition (volumetric basis, dry gas) was 15.2% CO, 7.6% H2, 3.8% CH4 and 15.6% CO2, with 0.50 H2:CO molar ratio and 5.0 MJ/Nm3 lower heating value. For this condition, 1.6 Nm3 gas/kg biomass (dry basis) specific dry gas production, 44.5% cold gas efficiency and 68.4% carbon conversion efficiency were attained.Using ilmenite as catalyst, the producer gas average composition (volumetric basis, dry gas) was 13.9% CO, 11.7% H2, 4.0% CH4 and 17.9% CO2, with 0.84 H2:CO molar ratio and 5.1 MJ/Nm3 lower heating value. For this condition, 1.7 Nm3 gas/kg biomass (dry basis) specific dry gas production, 49.8% cold gas efficiency and 75.5% carbon conversion efficiency were attained. Thus, in-situ application of ilmenite generally improved the gasifier performance and induced an increase of H2 concentration and H2:CO molar ratio in the producer gas of 35.1% and 40.7%, respectively, improving its suitability for advanced gas applications that require high H2:CO ratios, such as liquid fuels and chemicals synthesis.

Feasibility of Using Small-Scale GTL Plants To Mitigate Flaring in North Dakota Evaluated

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 195209, “Evaluation of Small-Scale Gas-to-Liquid Economic Feasibility To Mitigate North Dakota Flaring Issues,” by Pascoela da Silva Sequeira and Rouzbeh Ghanbarnezhad Moghanloo, SPE, University of Oklahoma, prepared for the 2019 SPE Oklahoma City Oil and Gas Symposium, 9–10 April, Oklahoma City, Oklahoma, USA. The paper has not been peer reviewed. Booming shale gas production in the United States has created excess capacity, which has caused natural gas prices to plummet and significant percentages of production to be flared. On the other hand, the country’s imports of crude oil and its production of diesel, gasoline, and other products is increasing. Mitigating this situation depends on finding practical, economical, and efficient ways of making natural gas marketable. A potential solution is small-scale gas-to-liquids (GTL) plants. The complete paper describes a Monte Carlo simulation approach and field analysis showing that a small-scale GTL plant in North Dakota could be a profitable solution to mitigating the state’s current flaring rate of 35% of the natural gas produced. Introduction The shale gas revolution has negatively affected natural gas prices. According to the US Energy Information Administration, dry natural gas production in the US will increase through 2050 by 59%, from 73.6 Bcf/D in 2017 to 118 Bcf/D in 2050, and the price of natural gas will remain lower than $6.00/MMBtu throughout the same period, causing producers to vent and flare excessive gas. In 2017 alone, the total natural gas flared in the US was approximately 335 Bcf, according to the World Bank-led Global Gas Flaring Reduction Partnership. Most intense natural gas flaring occurs in fields that are far from consumers and transportation infrastructures such as interstate pipelines. Some of the heaviest flaring comes from the Bakken Field in North Dakota. While most of the natural gas consumers in the US are located along the East coast, the Bakken’s distance from the seaboard makes transportation of the produced natural gas difficult. Natural gas production in North Dakota reached a record high of 1.94 Bcf/D in August 2017, and as a result of the lack of infrastructure to collect, gather, and transport it, more than 35% of the gross withdrawals were flared rather than marketed. By October 2018, production had increased to 2.04 Bcf/D, with 20%, or 527 MMcf/D, flared. According to the North Dakota Pipeline Authority, 80% of the flared gas came from the wells that connected to pipelines, but where capacity was insufficient to capture all of the production. The other 20% was from the wells that were not connected to a pipeline. North Dakota’s Industrial Commission has established a target to limit natural gas flaring to 10% by 2020. The fundamental problem is not the technical aspect of natural gas production, but determining a way to market natural gas that is practical, economically feasible, and efficient. One option for marketability would be to convert natural gas into hydrocarbon liquid through a GTL processing plant.

Exploring the Innovative Evolution of Hydraulic Fracturing

Fueled by a culture of innovation, hydraulic fracturing has transformed the energy landscape from inside North America out. But achieving that paradigm shift took years of improving subsurface understanding, technology development, and fine-tuning the completions practice through trial and error. Authors from Liberty Oilfield Services set out to document this evolution in SPE 194345 as they took a deep dive into fracturing history. Their paper traces the advancements in fracturing study and deployment from its earliest days to the present. Fracturing first took place in 1947 and has grown exponentially in uptake over the past 2 decades. The result has been the shale revolution, which has catapulted the US to at or near the top of the world in both crude oil and natural gas production. Between 2000—just after fracturing pioneer Mitchell Energy began commercial shale production—and 2018, yearly US dry gas production went to 83 Bcf/D from 53 Bcf/D while US crude output climbed to just under 11 million B/D from 5.8 million B/D, according to data from the US Energy Information Administration. Once largely dependent on imports, the country has become a net gas exporter and oil exports are reaching new heights. During that same period, increased fracturing intensity and a better knowledge of the subsurface complexities associated with the completions practice resulted in North American pressure pumping horsepower rising tenfold, yearly frac stage count growing twentyfold, and proppant mass pumped jumping fortyfold. Since the turn of the millennium, “the difference has really become that we bring the frac down to the hydrocarbon molecule in the rock,” said Leen Weijers, vice president of engineering at Liberty Oilfield Services, at the recent SPE Hydraulic Fracturing Technology Conference in The Woodlands, Texas. “We do that with multistage horizontal wells and a focus on complexity, creating a plumbing system that is two miles long and maybe half-a-mile-wide and maybe 500 ft in height.” Background: Mineral Rights, Fracture Study Weijers et al. first noted the importance of private mineral ownership in spurring unconventional development in the US. Mineral owners can develop, borrow against, or sell their land, meaning they have a direct stake in the high-risk, high-reward mineral development game. As the industry became more aware of the gas and oil recovery potential from shale, small independents began scooping up acreage, benefitting from their familiarity with the communities in which they operated or planned to operate. A major step forward in understanding the subsurface impact of hydraulic fracturing, Weijers et al. said, came with the realization by Warpinski et al. (1991) that fractures are complex, with dozens of parallel fractures growing simultaneously during a job in a narrow, 20–40 ft-wide zone. This dispelled the previous belief that simple bi-wing fractures extended from the wellbore, stimulating further study of fracture growth.

Effect of the upstream gas on the evolved coal gas in the dry distillation zone of the fixed bed gasifier

For a fixed bed gasifier, coal gas is mainly derived from dry distillation zone and gasification zone. The upstream gas from gasification zone will inevitably affect the composition and production of dry distillation gas. Therefore, the composition of upstream gas and the reaction conditions of dry distillation zone were simulated to perform experiments of Yining coal pyrolysis under a series of atmospheres. Some new discoveries are obtained. H2O and the hydrogen-containing gas have a significant impact on the release of dry distillation gas. H2O inhibits the release of CO, CO2 and CH4, but promotes the release of H2 which is not from char−H2O gasification. When the hydrogen-containing gas passes through dry distillation zone, the path of stabilizing radicals is completely changed, resulting in that coal pyrolysis changes from a process of generating H2 under inert atmosphere to a process of consuming a large amount of H2. In addition, water gas shift reaction is the only homogeneous reaction observed obviously in dry distillation zone, which can promote the production increase of CO2, but can not prevent the production decrease of H2 in coal gas.

Effects of Adding Different Levels of Lactobacillus Inoculant to Alfalfa Silage Ensiled With Orange Pulp on In Vitro Gas Production and DM Digestibility

This study was conducted to study the effects of supplementation alfalfa silage with orange pulp and difference of Lactobacillus buchneri on in vitro dry matter digestibility and gas production. wilted alfalfa with no additive (control), wilted Alfalfa and orange pulp (1750 g wilted Alfalfa mixed with 750 g fresh orange pulp) treated with LAB for final application rates of 0, 2.5, 5 and 7.5 g LAB inoculant/ton of wilted alfalfa and orange pulp (LAB0, LAB1, LAB2, LAB3, respectively). Alfalfa hay harvested at flowering stage and after 24 hours wilted and mixed orange pomace with ratio of 2100 g and 760 g, respectively, and was ensiled for 90 days. The data were analyzed in a completely randomized design with three replications. After 24 h incubation, treatments AO (alfalfa + orange pulp) and CON (without additive) had the highest and lowest in vitro gas production (p

PSI-14 Humic substances alter ammonia production and the microbial populations within a RUSITEC fed a mixed hay – concentrate diet.

The aim of this study was to examine the effects of humic substances on fermentation characteristics and microbial communities using the rumen stimulation technique (RUSITEC). The experiment was conducted as a completely randomized design over a 15-d period with 3 treatments duplicated in 2 runs with 2 replicates per run. Treatments consisted of a control diet (forage:concentrate; 60:40) without humic substances or humic substances added at either 1.5 g/d or 3.0 g/d. Dry matter disappearance, pH, fermentation parameters and gas production were measured from d 8 to 15. Samples for microbial profiling were taken on d 5, 10 and 15 using the digested feed bags for solid-associated microbes (SAM) and fermenter fluid for liquid-associated microbes (LAM). The inclusion of humic substances had no effect (P ≥ 0.19) on DM disappearance, pH or the concentrations of VFA. The production of NH3 was linearly decreased (P = 0.04) with increasing levels of humic substances in the diet. There was no effect (P ≥ 0.43) of humic substances on total gas, CO2 or CH4 production. The number of OTUs was significantly reduced in the 3.0 g/d treatment compared to the control on d 10 and 15; however, the microbial community structure was largely unaffected (P > 0.05). In the SAM samples, the genera Lachnospiraceae XPB1014 group, Succiniclasticum, and Fibrobacter were reduced in the 3.0 g/d treatment and Anaeroplasma, Olsenella, and Pseudobutyrivibrio were increased at d 5, 10, or 15. Within the LAM samples, Christensenellaceae R-7 and Succiniclasticum were the most differentially abundant genera between the control and 3.0 g/d HS treatment samples (P < 0.05). This study highlights the potential use of humic substances as a natural feed additive which may play a role in nitrogen metabolism without negatively affecting the ruminal microbiota.

Alternative to mathematical models of gas production: numerical experiment

Computational experiment for comparison of quasi-one dimensional and two dimensional mathematical statements of the conjugate problem of heat exchange between gas producing well and the rocks has been carried out. The problem consists of solution of differential equations describing non-isothermal gas flow in the well and the heat conduction equation for surrounding rocks. The dependence of the coefficient of heat exchange of the gas with the hydrate layer on the time-varying flow area is taken into account in a quasi-stationary mathematical model of hydrates formation (dissociation) in gas well. The results of computational experiment correspond to two cases of production of wet and dry gas at the Otradninsky gas-condensate field.

Low-cost catalysts for in-situ improvement of producer gas quality during direct gasification of biomass

In this work, the concept of biomass direct (air) gasification was demonstrated in a pilot-scale bubbling fluidized bed and the influence of in-situ application of low-cost catalytic materials on the produced gas characteristics and gasifier performance was analyzed. Three different low-cost catalysts were tested: bottom bed ashes resulting from combustion of residual forest biomass derived from eucalyptus, char particles resulting from wood pellets direct (air) gasification, and synthetic fayalite (Fe2SiO4). Without using catalysts, the produced gas composition was 7.7–16.9%v CO, 3.2–8.3%v H2, 0.5–3.4%v CH4 and 9.5–14.6%v CO2, with 2.4–4.3 MJ/Nm3 lower heating value, specific dry gas production between 1.0 and 1.8 Nm3 dry gas/kg biomass (dry basis), cold gas efficiency between 13.7 and 30.5% and carbon conversion efficiency between 30.7 and 50.9%. With the use of catalysts, the produced gas composition was 14.2–37.6%v CO, 9.5–14.7%v H2, 2.6–3.5%v CH4 and 3.6–14.8%v CO2, with 3.9–6.3 MJ/Nm3 lower heating value, specific dry gas production between 1.4 and 2.0 Nm3 dry gas/kg biomass (dry basis), cold gas efficiency between 38.1 and 66.3% and carbon conversion efficiency between 56.8 and 86.6%. The highest increase in H2 concentration (352% increase) was observed on experiments using wood pellets char as catalyst while the highest increase in CO (305% increase), lower heating value (123% increase), specific dry gas production (62% increase), cold gas efficiency (262% increase) and carbon conversion efficiency (174% increase), was observed on experiments using synthetic Fe2SiO4 as catalyst.

Sediment gravity-flow deposits and three-dimensional stratigraphic architectures of the linked Cutoff, upper Bone Spring, and upper Avalon system, Delaware Basin

The Bone Spring play and associated Avalon subplay represent a succession of calcareous, siliceous, and carbonaceous sediment gravity-flow deposits associated with significant production of oil, condensate, and dry gas in the Delaware Basin, Texas. Correlation of the upper Bone Spring and upper Avalon systems to the outcropping Cutoff Formation slope system and lower San Andres composite sequence (Permian composite sequence 9 [PCS9], 2–4 m.y.) in the Guadalupe Mountains region allows us to investigate how slope and basinal accumulation patterns are linked to deposit types and migration patterns of the active sediment factory (shelf system). The Cutoff–upper Bone Spring–upper Avalon interval in the northern Delaware Basin records the multivariate evolution of a deep-water system associated with a drowned carbonate platform margin (large-scale inflection) characterized by (1) an increase in the rate of sediment supply to the drowned platform, (2) a transition along the relict platform from styles of sediment transport dominated by turbidity currents to styles dominated by mass-transport events, and (3) a landward shift in the locus of deposition downdip of the relict shelf margin. Reservoir-prone strata of PCS9 associated with turbidite systems demonstrate basinward-stepping geometries along shallow slope gradients downdip of the relict shelf margin and aggradational geometries along steep slopes. Nonreservoir strata associated with carbonate-rich mass-transport deposits of PCS9 accumulate near the relict shelf margin on both shallow and steep slopes. Insights developed from this study can help to improve exploration activities in the Delaware Basin and in other basins having analogous deep-water systems.

Humic Substances Alter Ammonia Production and the Microbial Populations Within a RUSITEC Fed a Mixed Hay - Concentrate Diet.

Humic substances are a novel feed additive which may have the potential to mitigate enteric methane (CH4) production from ruminants as well as enhance microbial activity in the rumen. The aim of this study was to examine the effects of humic substances on fermentation characteristics and microbial communities using the rumen stimulation technique (RUSITEC). The experiment was conducted as a completely randomized design with 3 treatments duplicated in 2 runs (a 15-day period each run) with 2 replicates per run. Treatments consisted of a control diet (forage:concentrate; 60:40) without humic substances or humic substances added at either 1.5 g/d or 3.0 g/d. Dry matter disappearance, pH, fermentation parameters and gas production were measured from day 8 to 15. Samples for microbial profiling were taken on day 5, 10, and 15 using the digested feed bags for solid- associated microbes (SAM) and fermenter fluid for liquid- associated microbes (LAM). The inclusion of humic substances had no effect (P ≥ 0.19) on DM disappearance, pH or the concentrations of VFA. The production of NH3 was linearly decreased (P = 0.04) with increasing levels of humic substances in the diet. There was no effect (P ≥ 0.43) of humic substances on total gas, CO2 or CH4 production. The number of OTUs was significantly reduced in the 3.0 g/d treatment compared to the control on d 10 and 15; however, the microbial community structure was largely unaffected (P > 0.05). In the SAM samples, the genera Lachnospiraceae XPB1014 group, Succiniclasticum, and Fibrobacter were reduced in the 3.0 g/d treatment and Anaeroplasma, Olsenella, and Pseudobutyrivibrio were increased on day 5, 10, and 15. Within the LAM samples, Christensenellaceae R-7 and Succiniclasticum were the most differentially abundant genera between the control and 3.0 g/d HS treatment samples (P < 0.05). This study highlights the potential use of humic substances as a natural feed additive which may play a role in nitrogen metabolism without negatively affecting the ruminal microbiota.

The Crucial Role of Skeleton Structure and Carbon Number on Short-Chain Alkane Activation over Zn/HZSM-5 Catalyst: An Experimental and Computational Study

For the initial activation of short-chain alkanes over Zn/HZSM-5 catalyst, the impact of branching degree and carbon numbers of reactants on the competition between dehydrogenation and cracking was systematically studied by experiment and calculation. The experiments were carried out on fixed-bed flow micro-reactor over HZSM-5 and Zn/HZSM-5 catalysts, by using n-butane/i-butane and propane/n-hexane as reactants with different branching degree and carbon numbers. Compared with HZSM-5, Zn/HZSM-5 obviously accelerated the cracking of C–H bond of short-chain alkanes and increased the selectivity of BTX aromatics. The selectivity to hydrogen produced from n-butane and n-hexane was higher than i-butane and propane, respectively. On the contrary, the selectivity to methane was correspondingly lower, i-butane and propane with high percentage of terminal carbons effectively suppressed the dehydrogenation. The key point to decide the reaction process through dehydrogenation or cracking is the initially activated sites of reactant. To verify this conclusion, theoretical calculations were carried out. The results showed that the (Zn–O–Zn)2+ Lewis acid sites of Zn/HZSM-5 accelerated the cracking of C–H and C–C bond simultaneously. Namely, if the initial activation occurred on the terminal carbons of reactant, the subsequent reaction would be kinetically competitive between cracking and dehydrogenation. Cracking would inevitably occur (thermodynamically favorable), and then the by-products of methane and ethane were produced in large amount. If the initial activation occurred on the internal carbons, the dehydrogenation reaction is kinetically favorable, which is beneficial to reducing the dry gas production. Therefore, cracking is more favorable than dehydrogenation for smaller alkanes and branched alkanes with high percentage of terminal carbons. The percentage of terminal carbons of short-chain alkanes determines the probability of dehydrogenation route over Zn/HZSM-5. The activation of the internal carbon via the dehydrogenation route is more favorable for the normal alkane with higher carbon number during the first stage of conversion suppressing the formation of the by-products of methane and ethane.

Effects of a wax organogel and alginate gel complex on holy basil (Ocimum sanctum) in vitro ruminal dry matter disappearance and gas production.

The objectives of this study were to: (a) select an ideal organogel for the oil phase of a novel gel encapsulation technology, (b) optimize the formulation of an organogel and sodium alginate-based gel complex, and (c) examine the rumen protective ability of the gel by measuring 48-h in vitro ruminal dry matter disappearance and gas production from encapsulated dried and ground holy basil leaves. A rice-bran wax and canola oil organogel was selected for the oil phase of the gel complex as this combination had a 48-h dry matter disappearance of 6%, the lowest of all organogels analyzed. The gel complex was formulated by homogenizing the organogel with a sodium alginate solution to create a low-viscosity oil-in-water emulsion. Average dry matter disappearance of gel-encapsulated holy basil was 19%, compared to 42% for the free, unprotected holy basil. However, gel encapsulation of holy basil stimulated gas production. Specifically, gas production of encapsulated holy basil was four times higher than the treatment with holy basil added on top of the gel prior to incubation rather than encapsulated within the gel. Although the gel itself was highly degradable, it is speculated encapsulation thwarted holy basil's antimicrobial activity. © 2018 Society of Chemical Industry.

Use of in vitro dry matter digestibility and gas production to predict apparent total tract digestibility of total dietary fiber for growing pigs.

In vitro DM disappearance (IVDMD) and gas production methods have been developed and used to measure in vivo nutrient digestibility of feed ingredients, but further validation is needed for ingredients containing high concentrations of insoluble fiber such as corn distiller's dried grains with solubles (DDGS). A 3-step in vitro procedure and resulting gas production were used to predict in vivo apparent total tract digestibility (ATTD) of total dietary fiber (TDF) among 3 sources each of wheat straw (WS), soybean hulls (SBH), and DDGS. A total of 34 barrows and 2 gilts (84 ± 7 kg BW) were used in a changeover design to determine the ATTD of 9 dietary treatments. The WS, SBH, or DDGS sources were the only ingredients containing fiber in each diet, and all diets were formulated to contain the same TDF concentration (22.3%). The in vivo experiment was conducted in 2 consecutive 13-d periods, each including a 10-d adaptation and a 3-d collection period to provide 8 replications/dietary treatment, and 0.5% TiO was added to each diet as an indigestible marker. Pigs had ad libitum access to water and were fed an amount of feed equivalent to 2.5% of initial BW in each period. The in vitro experiment was used to determine IVDMD and gas production of the 9 ingredients (5 to 8 replicates/ingredient) fed during the in vivo experiment. Gas production kinetics were fitted using a nonlinear model and analyzed using a mixed model, and predictions were evaluated using correlations and regression models. There were differences ( < 0.01) in ATTD of TDF among WS (26.7%), SBH (78.9%), and DDGS (43.0%) and among sources of DDGS (36.0 to 49.8%). Differences ( < 0.05) in IVDMD from simulated gastric and small intestinal hydrolysis were observed among WS (13.3%), SBH (18.9%), and DDGS (53.7%) and among sources of WS (12.8 to 13.8%), SBH (17.0 to 20.5%), and DDGS (52.0 to 56.9%). Differences ( < 0.05) in IVDMD from simulated large intestine fermentation (IVDMDf) were also observed among WS (23.3%), SBH (84.6%), and DDGS (69.6%) and among sources of WS (18.7 vs. 26.8%). In vitro DM disappearance from simulated total tract digestion of SBH (88.9%) and DDGS (86.1%) were greater ( < 0.01) than that of WS (33.5%). Differences ( < 0.01) in asymptotic gas production (A; mL/g DM substrate) were observed among WS (121), SBH (412), and DDGS (317), and ATTD of TDF was highly correlated with IVDMDf and A. In conclusion, low variability in ATTD of TDF and IVDMD among sources of WS and SBH evaluated in the current study may not justify the use of in vitro measurements, but in vitro fermentation accurately predicts ATTD of TDF among sources of corn DDGS.

Fermentation quality and in vitro methane production of sorghum silage prepared with cellulase and lactic acid bacteria.

ObjectiveThe effects of lactic acid bacteria (LAB) and cellulase enzyme on fermentation quality, microorganism population, chemical composition and in vitro gas production of sorghum silages were studied.MethodsCommercial inoculant Lactobacillus plantarum Chikuso 1 (CH), local selected strain Lactobacillus casei (L. casei) TH 14 and Acremonium cellulase (AC) were used as additives in sorghum silage preparation.ResultsPrior to ensiling Sorghum contained 104 LAB and 106 cfu/g fresh matter coliform bacteria. The chemical compositions of sorghum was 26.6% dry matter (DM), 5.2% crude protein (CP), and 69.7% DM for neutral detergent fiber. At 30 days of fermentation after ensiling, the LAB counts increased to a dominant population; the coliform bacteria and molds decreased to below detectable level. All sorghum silages were good quality with a low pH (<3.5) and high lactic acid content (>66.9 g/kg DM). When silage was inoculated with TH14, the pH value was significantly (p<0.05) lower and the CP content significantly (p<0.05) higher compared to control, CH and AC-treatments. The ratio of in vitro methane production to total gas production and DM in TH 14 and TH 14+AC treatments were significantly (p<0.05) reduced compared with other treatments while in vitro dry matter digestibility and gas production did not differ among treatments.ConclusionThe results confirmed that L. casei TH14 could improve sorghum silage fermentation, inhibit protein degradation and decrease methane production.

Characteristics of the gas produced during biomass direct gasification in an autothermal pilot-scale bubbling fluidized bed reactor

Direct (air) biomass gasification was demonstrated in a pilot-scale bubbling fluidized bed reactor and the influence of process parameters analyzed. For the operating conditions used, namely equivalence ratio between 0.17 and 0.36 and bed temperature between 700 and 850 °C, the process was demonstrated as autothermal and operating under steady-state. The dry gas produced shows the following composition (volumetric basis): 14.0–21.4% CO, 14.2–17.5% CO2, 3.6–5.8% CH4, 1.3–2.4% C2H4, 2.0–12.7% H2 and 48.9–61.1% N2. The lower heating value of the dry gas was between 4.4 and 6.9 MJ/Nm3, with the highest values observed during the experiments with lower equivalence ratio. The specific dry gas production was between 1.2 and 2.2 Nm3/kg biomass (dry basis), the cold gas efficiency between 41.1 and 62.6% and the carbon conversion efficiency between 60 and 87.5%.The integrated analysis of new data from this study and a survey of published data shows that direct (air) biomass gasification produces gas mixtures with a wide range of variation in characteristics, that can be correlated with the biomass fuel properties and operating conditions used. Therefore, for each type of process application it is required specific experimental information to support an adequate scaling to the industrial scale.