The aim of the study was to evaluate the effect of grazing Lolium perenne (Lp) and Bromus valdivianus (Bv) on the average daily weight gain (ADG) and nitrogen use efficiency (NUE) of Holstein ...Friesian heifers. Thirty heifers strip-grazed two pasture treatments (Lp and Bv) under a randomized complete block design (n = 3). Nutrient concentration and pasture intake were determined. Urine samples were taken, and the total volume of urine and microbial growth were estimated. Retained nitrogen (N), N intake, N excreted in feces and urine and the nitrogen use efficiency (NUE) were calculated. Lolium perenne showed greater WSC and ME but lower NDF than Bv, whereas crude and soluble protein were unaffected. There were no effects of species on ADG or feed conversion, and DMI was not affected by grass species, or the synthesis of microbial protein and purine derivatives. Ammonia in the rumen, urinary N and total N excreted were greater for heifers grazing Bv. In conclusion, the consumption of forage species did not alter the ADG or NUE of grazing heifers, but N partitioning was modified for heifers grazing Bv, due to the lower WSC/CP ratio compared with Lp.
Ammonia-lyases and aminomutases are mechanistically and structurally diverse enzymes which catalyze the deamination and/or isomerization of amino acids in nature by cleaving or shifting a C–N bond. ...Of the many protein families in which these enzyme activities are found, only a subset have been employed in the synthesis of optically pure fine chemicals or in medical applications. This review covers the natural diversity of these enzymes, highlighting particular enzyme classes that are used within industrial and medical biotechnology. These highlights detail the discovery and mechanistic investigations of these commercially relevant enzymes, along with comparisons of their various applications as stand-alone catalysts, components of artificial biosynthetic pathways and biocatalytic or chemoenzymatic cascades, and therapeutic tools for the potential treatment of various pathologies.
•Ammonia is considered a key energy carrier.•Potential applications include low carbon energy storage, transportation and power generation.•Technologies discussed with an emphasis on current ...limitations and recent advances.
Ammonia is considered a key energy carrier with potential applications for low carbon energy storage, transportation and power generation. This carbon-free molecule offers several advantages, including high energy density and a well-established production and distribution infrastructure that have been optimized for over a century. In this perspective, we analyze the potential roles of ammonia as an energy carrier, and summarize research areas requiring further development for the implementation of ammonia as a building block in the global low-carbon energy landscape. Ammonia technologies are reviewed with an emphasis on current limitations and recent advances. Focus is placed on available technologies for ammonia synthesis, decomposition into COx-free hydrogen and direct use of ammonia for power generation and transportation.
Alternative carbon-neutral synthetic fuels are needed to decarbonize the transportation sector, bridging the gap between batteries and biofuels. Herein, we analyze the economics of hydrogen-, ...nitrogen-, and carbon-based fuels made by carbon-neutral pathways in a post-fossil world where only water, air, and renewable electricity are available for fuel synthesis. We find that ammonia has the lowest source-to-tank energy cost by a significant margin. With this technoeconomic analysis as motivation, we demonstrate a direct ammonia fuel cell (DAFC) prototype with a peak power density of 135 mW cm−2. The DAFC employs an ammonia-tolerant precious-metal-free cathode catalyst and a high-temperature-stable hydroxide exchange membrane.
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•The economics of hydrogen, methanol, and ammonia are analyzed for vehicle fuel cells•Ammonia is found to have the lowest source-to-tank energy cost•Acta 4020 is identified as an ammonia-immune oxygen reduction reaction catalyst•A high-performance direct ammonia fuel cell prototype is demonstrated at 80°C
Hydrogen has attracted the most research and development interest due to the efficiency and performance of hydrogen-fueled proton exchange membrane fuel cells (PEMFCs). However, transmission, distribution, dispensation, and storage are expensive for hydrogen as a highly compressed gas. Switching to a liquid or liquefied fuel offers substantial savings but requires a high-performance power source.
When considering carbon-neutral pathways starting from sun, wind, air, and water, we show that ammonia has the lowest source-to-tank cost. We then focus on the direct ammonia fuel cell as the key technological barrier to realizing the economic benefits of ammonia. We show how a high peak power density of 135 mW cm−2 can be achieved using ammonia-tolerant catalysts, high-stability hydroxide exchange membranes, and optimized operating conditions.
Zhao et al. find that ammonia has the lowest source-to-tank energy cost for vehicle fuel cells when considering carbon-neutral pathways starting from sun, wind, air, and water. A direct ammonia fuel cell with high power output is achieved, reducing the key technological barrier to realizing the economic and environmental benefits of ammonia as a transportation fuel.
Reactions of the zinc(I) complex Zn2(Mesnacnac)2 (Mesnacnac=(2,4,6-Me3C6H2)NC(Me)2CH) with solid K3Bi2 dissolved in liquid ammonia yield crystals of the compound K4ZnBi2(NH3)12 (1), which contains ...the molecular, linear heteroatomic BiZnBi4- polyanion (1a). This anion represents the first example of a three-atomic molecular ion of metal atoms being iso(valence)-electronic to CO2 and being synthesized in solution. The analogy of the discrete BiZnBi4- anion and the polymeric ${{{\hfill 1\atop \hfill \infty }}}$(ZnBi4/2)4- unit to monomeric CO2 and polymeric SiS2 is rationalized.
•Green ammonia production processes are investigated and compared with state-of-the-art methane-to-ammonia process.•Power-to-ammonia process can achieve the highest system efficiency of over 74%.•The ...steam cycles with three pressure levels are able to maximize the heat utilization at the system level.•Power-to-ammonia will be competitive (payback times below 5 years) with solid-oxide fuel cells.
To reduce the fossil-fuel consumption and the impacts of conventional ammonia production on climate change, green ammonia production processes using green hydrogen need to be investigated. For commercial production scale, potential alternatives can be based on biomass gasification and water electrolysis via renewable energy, namely biomass- and power-to-ammonia. The former generally uses entrained flow gasifier due to low CO2 and almost no tar, and air separation units are shared by the gasifier and ammonia synthesis. The latter may use solid-oxide electrolyzer due to high electrical efficiency and the possibility of heat integration with the ammonia synthesis process. In this paper, techno-economic feasibility of these two green ammonia production processes are investigated and compared with the state-of-the-art methane-to-ammonia process, considering system-level heat integration and optimal placement of steam cycles for heat recovery. With a reference ammonia production of 50 kton/year, the results show that there are trade-offs between the overall energy efficiency (LHV) and ammonia production cost for all three cases. The biomass-to-ammonia is the most exothermic but is largely limited by the large heat requirement of acid gas removal. The steam cycles with three pressure levels are able to maximize the heat utilization at the system level. The power-to-ammonia achieves the highest system efficiency of over 74%, much higher than that of biomass-to-ammonia (44%) and methane-to-ammonia (61%). The biomass-to-ammonia reaches above 450 $/ton ammonia production cost with a payback time of over 6 years, higher than those of methane-to-ammonia (400 $/ton, 5 years). The power-to-ammonia is currently not economically feasible due to high stack costs and electricity prices; however, it can be competitive with a payback time of below 5 years with mass production of solid-oxide industry and increased renewable power penetration.
1,3,2-diazaphospholenes catalyze metal-free transfer hydrogenation of a NN double bond using ammonia-borane under mild reaction conditions, thus allowing access to various hydrazine derivatives. ...Kinetic and computational studies revealed that the rate-determining step involves simultaneous breakage of the BH and NH bonds of ammonia-borane. The reaction is therefore viewed as a concerted type of hydrogenolysis. PUBLICATION ABSTRACT
•The ammonia emission from an ammonia WFGD system is clearly defined.•The ammonia emission includes the filterable ammonia, the condensable ammonia, and the gaseous ammonia.•A piecewise sampling ...system is built to sample them, respectively.•The gaseous ammonia emission contributes very little to the total ammonia emission.•Parameter optimization is promising in ammonia emission control.
Ammonia and its contribution to secondary organic and inorganic aerosols are harmful to the environment and human health. The ammonia-based wet flue gas desulfurization (ammonia-WFGD) is effective in removing SO2 from industrial flue gas but also is a potential source of ammonia emission. In this paper, experiments were done in a pilot-scale ammonia-WFGD system. The definition of the ammonia emission was first stated to include the gaseous ammonia, and the solid or liquid aerosols containing ammonia. The emitted ammonia was then distinguished into the filterable ammonia, the condensable ammonia, and the gaseous ammonia based on their behaviors during emission processes. A piecewise sampling system was built accordingly to sample them, respectively. The parameters, such as the flue gas temperature, the desulfurizing solution temperature, the solution concentration, and the pH, were adjusted to investigate their influences on the ammonia emission characteristics. Results showed that large amounts of ammonia were emitted from the ammonia-WFGD system, in which the gaseous ammonia accounted for around 19%, with the filterable ammonia and the condensable ammonia sharing the rest 81%. The flue gas temperature, the solution concentration, and the solution pH were equally important to the total ammonia emission control. Theoretically, optimizing any one of the above three parameters could lower the ammonia emission by 38%. All the parameters had impacts on the individual ammonia emissions, although to different extents. It is worthwhile to conduct further researches on parameter optimizations to achieve better ammonia emission control.
Ammonia induces a phase transformation of perovskite (CH sub(3)NH sub(3))PbI sub(3), leading to a rapid (<1 s) change in its color from brown to colorless (400-800 nm). This color change is reversed ...within seconds upon removing the NH sub(3) source.
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