Yaks are well-adapted to the harsh environment of the Tibetan plateau, and they emit less enteric methane (CH4) and digest poor-quality forage better than cattle. To examine the potential of yak rumen inoculum to mitigate CH4 production and improve digestibility in cattle, we incubated substrate with rumen inoculum from yak (YRI) and cattle (CRI) in vitro in five ratios (YRI: CRI): 0:100 (control), (2) 25:75, (3) 50:50, (4) 75:25 and (5) 100:0 for 72 h. The YRI: CRI ratios of 50:50, 75:25 and 100:0 produced less total gas and CH4 and accumulated less hydrogen (H2) than 0: 100 (control) at most time points. From 12 h onwards, there was a linear decrease (P < 0.05) in carbon dioxide (CO2) production with increasing YRI: CRI ratio. At 72 h, the ratios of 50:50 and 75:25 had higher dry matter (+7.71% and +4.11%, respectively), as well as higher acid detergent fiber digestibility (+15.5% and +7.61%, respectively), when compared to the 0:100 ratio (P < 0.05). Increasing the proportion of YRI generally increased total VFA concentrations, and, concomitantly, decreased the proportion of metabolic hydrogen ([2H]) incorporated into CH4, and decreased the recovery of [2H]. The lower [2H] recovery indicates unknown [2H] sinks in the culture. Estimated Gibbs free energy changes (∆G) for reductive acetogenesis were negative, indicating the thermodynamic feasibility of this process. It would be beneficial to identify: 1) the alternative [2H] sinks, which could help mitigate CH4 emission, and 2) core microbes involved in fiber digestion. This experiment supported lower CH4 emission and greater nutrient digestibility of yaks compared to cattle. Multi-omics combined with microbial culture technologies developed in recent years could help to better understand fermentation differences among species.

Finding an appropriate solution to find stable and continuous green energy is one of the significant problems of scientists in the field of renewable energy. In this study, a mixed type of system implementing two geothermal gas turbine energy combined using an innovative method, the suggested system continuously merits productivity of different production. Also, it implements renewable energies to provide the required power to generate conducts which is considered important in the green transient of governments. In addition, thermodynamic rules were used to analyze the suggested system. The results obtained from analysis and equations in the EES software show that power production and thermal load and cooling equal 1432.3kw, 937.9kw and 128.8kw, respectively. the total energy and exergy efficiency is calculated at 58.31 % and 42.17 %. The system's return on investment is calculated in twenty years, with the electricity price of 0.15$/GJ, 6.02 years and with the fuel price of Cfuel = 21$/GJ, 7.15 years, and the system reaches profitability. to improve system function, the multiple optimized genetic algorithm is used. The objective function in optimizing the system is exergy efficiency and total cost, which is considered optimization MATLAB software, which means a decrease of total cost and an increase of exergy efficiency.

Livestock on the Qinghai-Tibetan Plateau is of great importance for the livelihood of the local inhabitants and the ecosystem of the plateau. The natural, harsh environment has shaped the adaptations of local livestock while providing them with requisite eco-services. Over time, unique genes and metabolic mechanisms (nitrogen and energy) have evolved which enabled the yaks to adapt morphologically and physiologically to the Qinghai-Tibetan Plateau. The rumen microbiota has also co-evolved with the host and contributed to the host's adaptation to the environment. Understanding the complex linkages between the rumen microbiota, the host, and the environment is essential to optimizing the rumen function to meet the growing demands for animal products while minimizing the environmental impact of ruminant production. However, little is known about the mechanisms of host-rumen microbiome-environment linkages and how they ultimately benefit the animal in adapting to the environment. In this review, we pieced together the yak's adaptation to the Qinghai-Tibetan Plateau ecosystem by summarizing the natural selection and nutritional features of yaks and integrating the key aspects of its rumen microbiome with the host metabolic efficiency and homeostasis. We found that this homeostasis results in higher feed digestibility, higher rumen microbial protein production, higher short-chain fatty acid (SCFA) concentrations, and lower methane emissions in yaks when compared with other low-altitude ruminants. The rumen microbiome forms a multi-synergistic relationship among the rumen microbiota services, their communities, genes, and enzymes. The rumen microbial proteins and SCFAs act as precursors that directly impact the milk composition or adipose accumulation, improving the milk or meat quality, resulting in a higher protein and fat content in yak milk and a higher percentage of protein and abundant fatty acids in yak meat when compared to dairy cow or cattle. The hierarchical interactions between the climate, forage, rumen microorganisms, and host genes have reshaped the animal's survival and performance. In this review, an integrating and interactive understanding of the host-rumen microbiome environment was established. The understanding of these concepts is valuable for agriculture and our environment. It also contributes to a better understanding of microbial ecology and evolution in anaerobic ecosystems and the host-environment linkages to improve animal production.

This study investigates different aspects of an innovative multi-heat recovery-based solar-geothermal polygeneration system, acclaiming the exergetic, exergoeconomic, and energetic concepts. Principally, using two renewable energy sources, the whole framework of the system encompasses Concentrated PhotoVoltaic Thermal (CPVT) solar collectors, Flat Plate Solar Collectors (FPSCs), geothermal wells, an Ejector Refrigeration Cycle (ERC) Organic Rankine Cycle (ORC) integrated with a Solid Oxide Electrolyzer Cell (SOEC), heating production units, an air dryer, and an Organic Rankine Cycle (ORC) unit. Afterward, the sensitivity analysis utilized for the parametric study makes a multi-aspects optimization in diverse scenarios in which NSGA-II, as well as, fuzzy TOPSIS and fuzzy VIKOR decision makings, are handled to designate the optimal solution. The suggested system has professionally been devised thanks to the characteristic of maximum use of energy of the streams circulated. Hence, crucial variables evaluated are more influenced by the variation in the geothermal heater pinch point temperature gradient. Also, in the optimization scenario based on unit cost of products / exergy efficiency, the TOPSIS selects the optimal objectives of 4.29%/1.13 $/GJ, while the VIKOR selects 4.06%/1.07 $/GJ, respectively.

For aerobic static composting, fresh cow, pig, and chicken manures were used as feedstock and mixed with 10 % corn straws, which was considered as the bulking agent. In the composting process of different livestock and poultry manures, the changing trends of temperature, pH, conductivity, density, and other parameters were intensively studied. The results were as follows: (1) after the tail biogases of composting systems - using cattle manure, pig manure, and chicken manure - were introduced into the biofilter, the concentration of O-2 decreased slightly, but the concentration of CO2 increased. The odour in these tail biogases declined significantly, and thus the biodegradation of tail biogas was obvious. (2) The oxygen consumption in the different periods of the composting process of these three manures was almost the same, and the average oxygen consumption for the three manures was 0.928, 0.937, and 0.945 m(3)/kg, respectively. Under standard conditions, the density of oxygen is 1.429 g/L, and the average oxygen consumption in the composting processes of these three manures was 1.326, 1.338, and 1.350 kg/kg, respectively.

The thermal-hydraulic characteristics of a novel fin punched with curve trapezoidal vortex generators (CTVG) are investigated numerically. The effects of multi-parameters including the geometry of CTVG, the location of CTVG, and working condition on thermal performance are considered. On one hand, CTVG can availably lessen the size of tube wake zone, decrease the mechanical energy consumption and heighten the fin heat transfer ability in this area. On the other hand, the secondary flow strength is strengthened because the longitudinal vortices generated by CTVG, which efficiently enhances the heat transfer on the fin downstream CTVG. Close relationship exists between the volume-averaged secondary flow strength and the mean Nusselt number. For studied cases, the optimal circumferential location angle of ? = 90? is found, while the optimal radial location Dg is about 1.8 times the tube outside diameter. The smaller is the height or base length of CTVG, the better the thermal performance of the enhanced fin punched with CTVG. Better thermal performance is achieved as the fin spacing is about 0.24 times the tube outside diameter.

Numerical analysis is an effective method for evaluating the thermal performance and predicting the state of a shell and tube bundle latent heat thermal energy storage (LHTES) unit. However, numerical analysis is time-consuming owing to the unsteady nature of the heat storage process. A small computational domain is required to reduce the computing time. Generally, a shell and single-tube unit is a favorable computational domain. It is necessary to determine the difference between the results of a shell and single-tube unit and a shell and tube bundle unit before this computational domain can be used. Herein, two types of computational domains are selected to identify such differences, namely a shell and single-tube unit and a shell and tube bundle unit. A three-dimensional, unsteady, and fully coupled numerical model is developed. The results obtained using the shell and single-tube unit with uniform wall heat flux and uniform wall temperature are compared with those obtained in the shell and tube bundle unit. The results show that the heat transfer in the shell and tube bundle unit is not adequately reflected by that in the shell and single-tube unit under adiabatic thermal boundary condition. However, by changing the heat flux added to the boundary or uniform wall temperature of the shell and single-tube unit, the principal performance of the shell and tube bundle unit can be accurately modeled using the shell and single-tube unit, particularly after the stored energy reaches its half capacity; the time-averaged relative error of the heat storage performance is below 14.0 %. The shell and tube bundle unit contains 27 tubes in the case studied. If the shell and single-tube unit is used as the numerical domain, the simulation speed can be increased by 96 times.

The semi-continuous digestion experiment of food waste was carried out based on a solar-assisted heat anaerobic digestion reactor. The effects of organic load regulation (OLR of 2.0, 4.0, 6.0 and 7.0 kg m−3 d−1 VS (volatile solid)) on methane production, physical and chemical parameters, and microbial community structure were studied. The results showed that 6.0 kg m−3 d−1 VS could achieve the optimal methane production as the anaerobic digestion limit OLR of kitchen waste. At this stage, the accumulation of organic acids in the reactor led to a great fluctuation of pH. Artificial alkali regulation could restore the stable operation of the reactor, but the reactor could not withstand the OLR shock of 7.0 kg m−3 d−1 VS. In addition, Qualcomm sequencing results showed that microorganisms showed high functional concentration and poor community richness under low OLR, and increasing OLR could promote microbial richness. At the same time, the Methanosaeta of acetic acid methanogens was relatively abundant in the low OLR stage, while the hydrogen trophic methanogenic bacteria Methanoregula and Methanospirillum showed high activity in the high OLR stage, but the excessive reproduction of acidogenic bacteria in the digestive system would affect the stability of the archaea community when the OLR was too high.

To improve the biogas potential in anaerobic digestion of cattle manure in cold regions, we investigated, in this study, the potential of the anaerobic digestion of cattle manure through sequencing batch anaerobic digestion experiments at sub-mesophilic temperatures (15°C, 20°C, 25°C, and 37°C) for 50 days. Specifically, the changes in the biogas yield, pH, sCOD concentration, enzyme activity, and microbial community structure were examined. The maximum daily yield of biogas was 19.18 mL·gVS−1, which was recorded on day 6 at 37°C, and the final biogas accumulation yield at this temperature was 403.64 mL·gTS−1. The concentration of sCOD gradually increased as enzyme activity increased. The maximum activities of cellulase, hemicellulase, protease, and amylase were recorded in the 37°C experimental group. The decrease in temperature severely limited the activity of different types of enzymes, resulting in a decrease in the activity of microorganisms, which greatly influenced the methanogenic reaction. The dominant bacteria at the phylum level were Bacteroidetes and Proteobacteria, and the dominant methanogen at the genus level was Methanosaeta.

Tibetan sheep are well adapted to harsh environmental conditions and poor-quality forage and are known to produce less methane (CH4) gas than lowland sheep. In this study, rumen inocula from Tibetan sheep (TBI) and from Small-tailed Han sheep (HSI) were incubated in in vitro batch cultures in five ratios (TBI: HSI): 0:100, 25:75, 50:50, 75:25 or 100:0 for 72 h. With an increasing proportion of TBI, there was a linear decrease (P < 0.001) in gas and CH4 production on a degraded dry matter (DM) basis at 12, 24, 48 and 72 h. In addition, increasing the proportion of TBI increased the digestibility of DM (P < 0.05), neutral detergent fiber and acid detergent fiber and total and individual volatile fatty acids (VFA) concentrations at almost all time points. An increase in the TBI: HSI ratio resulted in less metabolic hydrogen ([2H]) incorporated into CH4 and more into propionate. The recovery of [2H] consistently decreased with an increase in the TBI: HSI ratio, indicating the existence of unaccounted [2H] in TBI. It would be important to study the rumen microbiome in Tibetan sheep with the use of classical microbiology and modern -omics techniques to identify [2H] sinks alternative to CH4, which could perhaps be stimulated in other domestic ruminants.

Today, consumers are very health conscious and are more aware of the nutritional value of food, especially of meat, than they were in the past. The aim of this study was to evaluate the carcass parameters and meat quality of Tibetan sheep and Small-tailed Han sheep when consuming a diet of low-protein (~7%) and different energy yields (digestible energy, 8.21, 9.33, 10.45 and 11.57 MJ/kg) in the cold season. Twelve sheep of each breed were divided randomly into four treatments of different diets with three replicates per treatment per breed. Crude protein of the meat decreased linearly (p < .05), whereas energy increased linearly (p < .05) with an increase in energy level. Tibetan sheep tended to have a higher (p < .1) dressing percentage and rib eye area, while live body weight and hot carcass weight did not differ between breeds but increased linearly (p < .01) with an increase in energy level. Water holding capacity, as indicated by pressing loss and drip loss, did not differ between breeds and was not affected by dietary energy. The concentration of n-3 polyunsaturated fatty acids (PUFAs) was greater in Tibetan sheep meat but saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and n-6 PUFA did not differ between breeds. With an increase in energy content of the diet, SFA decreased (p < .05), whereas MUFA increased (p < .05). The n-6:n-3 PUFA ratio was lower (p < .001) in Tibetan sheep meat, while the atherogenic index did not differ between breeds, but tended to decrease (p < .1) with an increase in dietary energy content. The essential amino acid (EAA) content and ratio of EAA:NEAA (non-essential amino acid) were close to the world standards for healthy meat. In summary, (a) Tibetan sheep meat was preferable to Small-tailed Han sheep meat, although differences between breeds were small; and (b) some carcass parameters and meat quality were improved with an increase in dietary energy level when a low-protein diet was offered.

Background The development and maturation of rumen microbiota across the lifetime of grazing yaks remain unexplored due to the varied lifestyles and feed types of yaks as well as the challenges of obtaining samples. In addition, the interactions among four different rumen microbial groups (bacteria, archaea, fungi and protozoa) in the rumen of yak are not well defined. In this study, the rumen microbiota of full-grazing yaks aged 7 days to 12 years old was assessed to determine the maturation patterns of these four microbial groups and the dynamic interactions among them during different growth stages. Results The rumen microbial groups (bacteria, archaea, protozoa and fungi) varied through the growth of yaks from neonatal (7 days) to adult (12 years), and the bacterial and archaeal groups were more sensitive to changes in growth stages compared to the two eukaryotic microbial groups. The age-discriminatory taxa within each microbial group were identified with the random forest model. Among them, Olsenella (bacteria), Group 10 sp., belonging to the family Methanomassiliicoccaceae (archaea), Orpinomyces (fungi), and Dasytricha (protozoa) contributed the most to discriminating the age of the rumen microbiota. Moreover, we found that the rumen archaea reached full maturation at 5 approximately years of age, and the other microbial groups matured between 5 and 8 years of age. The intra-interactions patterns and keystone species within each microbial group were identified by network analysis, and the inter-interactions among the four microbial groups changed with growth stage. Regarding the inter-interactions among the four microbial groups, taxa from bacteria and protozoa, including Christensenellaceae R-7 group , Prevotella 1 , Trichostomatia , Ruminococcaceae UCG-014 and Lachnospiraceae , were the keystone species in the network based on betweenness centrality scores. Conclusions This study depicted a comprehensive view of rumen microbiota changes in different growth stages of grazing yaks. The results revealed the unique microbiota maturation trajectory and the intra- and inter-interactions among bacteria, archaea, fungi and protozoa in the rumen of grazing yaks across the lifetime of yaks. The information obtained in this study is vital for the future development of strategies to manipulate rumen microbiota in grazing yaks for better growth and performance in the harsh Qinghai-Tibetan Plateau ecosystem.

The anaerobic rumen fungal community play a critical role in fibrous material degradation. However, there is a lack of data describing the composition of anaerobic rumen fungal community of full grazing ruminants in the Qinghai-Tibetan Plateau. For this reason, we employed the next-generation sequencing technique to elucidate the rumen fungal structure composition and evaluate the effects of host species on fungal communities. Community comparisons (Bray–Curtis index) between yak and Tibetan sheep revealed that the rumen fungal community was affected by host species (p < 0.05). The alpha diversity indices in the yak were significantly higher than in the Tibetan sheep and Small Tail Han sheep. Neocallimastigomycota was predominant regardless of host species. Within this phylum, unidentified genus of Neocallimastigaceae was the most dominant in all samples, followed by Piromyces and Orpinomyces. Moreover, the shared and unique OTUs in the rumen were identified and most of them belonged to the Orpinomyces. Co-occurrence network analysis identified that each animal species had their own keystone species and most of them were non-dominant flora. Our data indicate that host breeds override living environment as the key factor that determines fungal community in the rumen of grazing ruminants in the Qinghai-Tibetan Plateau.

We examined the effect of supplemental dietary slow-release urea on the growth performance and physiological status of 16 dairy Holstein heifers (10 months of age, 322 ± 10 kg). The heifers were offered a formulated isocaloric and isonitrogenous 70:30 roughage : concentrate ration and were assigned randomly to one of four levels of slow-release urea supplementation (0% [U0 ], 1% [U1 ], 1.5% [U1.5 ] and 2% [U2 ] dry matter [DM]). The total study lasted 95 days, which included a 20 days adaptation period. Dry matter intake (DMI) of U2 was lower than the intakes of U0 and U1 (p < .05), while average daily gains (ADG) of U1 and U1.5 were higher than U0 and U2 (p < .05). Rumen volatile fatty acids concentration did not differ among the four treatments, while ammonia nitrogen concentration increased with an increase in urea level (p < .05). Serum blood urea nitrogen concentration was lower in U1.5 than in U0 and U2 while serum free fatty acids concentration in U2 was higher than in the other three treatments (p < .05). We concluded that the addition of urea at a level of 1.5 to 2.0% DM resulted in a reduction in DMI but the addition of 1.0%-1.5% urea resulted in the highest ADG, with no negative effects on rumen fermentation and health status of the calves.

Studies of genetic adaptation, a central focus of evolutionary biology, most often focus on the host’s genome and only rarely on its co-evolved microbiome. The Qinghai-Tibetan Plateau (QTP) offers one of the most extreme environments for the survival of human and other mammalian species. Yaks (Bos grunniens) and Tibetan sheep (T-sheep) (Ovis aries) have adaptations for living in this harsh high-altitude environment, where nomadic Tibetan people keep them primarily for food and livelihood [1]. Adaptive evolution affects energy-metabolism-related genes in a way that helps these ruminants live at high altitude [2, 3]. Herein, we report convergent evolution of rumen microbiomes for energy harvesting persistence in two typical high-altitude ruminants, yaks and T-sheep. Both ruminants yield significantly lower levels of methane and higher yields of volatile fatty acids (VFAs) than their low-altitude relatives, cattle (Bos taurus) and ordinary sheep (Ovis aries). Ultra-deep metagenomic sequencing reveals significant enrichment in VFA-yielding pathways of rumen microbial genes in high-altitude ruminants, whereas methanogenesis pathways show enrichment in the cattle metagenome. Analyses of RNA transcriptomes reveal significant upregulation in 36 genes associated with VFA transport and absorption in the ruminal epithelium of high-altitude ruminants. Our study provides novel insights into the contributions of microbiomes to adaptive evolution in mammals and sheds light on the biological control of greenhouse gas emissions from livestock enteric fermentation.

The performance of a phase change thermal energy storage (PCTES) unit using circular finned tube is affected by many parameters. Thorough studies of the parameter effect on the performance of PCTES unit are strongly required in its optimum design process. Based on a reported energy efficiency ratio and a newly defined parameter named the heat storage rate, the parameter effect on the performance of PCTES unit using circular finned tube is numerically investigated. When the fin pitch is greater than 4 times of the inner radius of the tube, the fin height and the fin thickness have little effect on the energy efficiency ratio and the heat storage rate. When the fin pitch is small, the performance of PCTES unit becomes better using large fin height and width. The energy efficiency ratio and the heat storage rate are more sensitive to the outer tube diameter. The performance of PCTES unit using circular finned tube is best when water is used as the heat transfer fluid (HTF). When the fluid flow of HTF is in a laminar state, the energy efficiency ratio and the heat storage rate are larger than that in a turbulent state. (C) 2015 Elsevier Ltd. All rights reserved.

In this paper, a mathematical model of shell-and-tube latent heat thermal energy storage (LUTES) unit of two-dimension of three phase change materials (PCMs) named PCM1, PCM2 and PCM3 with different high melting temperatures (983 K, 823 K and 670 K, respectively) and heat transfer fluid (HTF: air) with flowing resistance and viscous dissipation based on the enthalpy method has been developed. Instantaneous solid-liquid interface positions and liquid fractions of PCMs as well as the effects of inlet temperatures of the air and lengths of the shell-and-tube LHTES unit on melting times of PCMs were numerically analyzed. The results show that melting rates of PCM3 are the fastest and that of PCM1 are the slowest both x, r directions. It is also found that the melting times of PCM1, PCM2 and PCM3 decrease with increase in inlet temperatures of the air. Moreover, with increase in inlet temperatures of the air, decreasing degree of their melting times are different, decreasing degree of the melting time of PCM1 is the biggest and that of PCM3 is the smallest. Considering actual application of solar thermal power, we suggest that the optimum lengths are L-1 = 250 mm, L-2 = 400 mm, L-3 = 550 mm (L = 1200 mm) which corresponds to the same melting times of PCM1, PCM2 and PCM3 are about 3230 s and inlet temperature of the air is about 1200 K. The present analysis provides theoretical guidance for designing optimization of the shell-and-tube LHTES unit with three PCMs for solar thermal power. (C) 2013 Elsevier Ltd. All rights reserved.

The effects of temperature difference between the inlet of heat transfer fluid (HTF) and melting point of phase change material (PCM), the HTF inlet mass flow rate on heat charging and heat discharging performance are numerically studied. The results show that charging and discharging processes have three stages for the change of temperature regarding to time in PCM and heat charging or discharging rate regarding to time: rapidly changing period, slowly changing period and more slowly changing period. With the same configuration and under the same HTF inlet temperature, to complete discharging process needs less time than to complete charging process does. The effects of inlet HTF temperature, the mass flow rate on the characteristics of charging and discharging processes are profound.

A mathematical model for the overall exergetic efficiency of two phase change materials named PCM1 and PCM2 storage system with a concentrating collector for solar thermal power based on finite-time thermodynamics is developed. The model takes into consideration the effects of melting temperatures and number of heat transfer unit of PCM1 and PCM2 on the overall exergetic efficiency. The analysis is based on a lumped model for the PCMs which assumes that a PCM is a thermal reservoir with a constant temperature of its melting point and a distributed model for the air which assumes that the temperature of the air varies in its flow path. The results show that the overall exergetic efficiency can be improved by 19.0–53.8% using two PCMs compared with a single PCM. It is found that melting temperatures of PCM1 and PCM2 have different influences on the overall exergetic efficiency, and the overall exergetic efficiency decreases with increasing the melting temperature of PCM1, increases with increasing the melting temperature of PCM2. It is also found that for PCM1, increasing its number of heat transfer unit can increase the overall exergetic efficiency, however, for PCM2, only when the melting temperature of PCM1 is less than 1150K and the melting temperature of PCM2 is more than 750K, increasing the number of heat transfer unit of PCM2 can increase the overall exergetic efficiency. Considering actual application of solar thermal power, we suggest that the optimum melting temperature range of PCM1 is 1000–1150K and that of PCM2 is 750–900K. The present analysis provides theoretical guidance for applications of two PCMs storage system for solar thermal power.

A mathematical model for the overall thermal efficiency of the solar-powered high temperature differential dish-Stirling engine with finite-rate heat transfer, regenerative heat losses, conductive thermal bridging losses and finite regeneration processes time is developed. The model takes into consideration the effect of the absorber temperature and the concentrating ratio on the thermal efficiency; radiation and convection heat transfer between the absorber and the working fluid as well as convection heat transfer between the heat sink and the working fluid. The results show that the optimized absorber temperature and concentrating ratio are at about 1100K and 1300, respectively. The thermal efficiency at optimized condition is about 34%, which is not far away from the corresponding Carnot efficiency at about 50%. Hence, the present analysis provides a new theoretical guidance for designing dish collectors and operating the Stirling heat engine system.