Low Ammonia Research Articles

Effects of dietary rumen undegradable protein:rumen degradable protein ratio on nitrogen metabolism in Hanwoo steers.

We investigated the effects of dietary rumen undegradable protein (RUP): rumen degradable protein (RDP) ratio on growth performance, nitrogen (N) metabolism, and rumen and blood parameters in Hanwoo (Korean cattle) steers. Eight Hanwoo steers (average body weight, 393 kg) were allocated to two groups and fed with a high RUP:RDP ratio (46.9:53.1 based on crude protein) or a low RUP:RDP ratio (30.6:69.4) concentrate with iso-crude protein content in a 2×2 Latin square design in two successive periods. The high RUP:RDP group had higher (p<0.01) average daily gain, and lower (p<0.05) ruminal ammonia and plasma urea N concentrations than the low RUP:RDP group. The high RUP:RDP group had lower (p<0.05) urinary N excretion and urinary N per N intake and higher (p<0.1) tendency of retained N than the low RUP:RDP group. The high RUP:RDP group had higher (p<0.1) tendency of N utilization efficiency (retained N per N intake: 28.7% vs. 25.5%) than the low RUP:RDP group. The high RUP:RDP group had a lower (p<0.1) tendency of urinary N per total N excretion, but a higher tendency of fecal N per total N excretion. A high ratio of dietary RUP:RDP may improve N utilization efficiency by reducing urinary N excretion, which may be beneficial for the environment through reducing atmospheric ammonia emissions.

Achieving overall low greenhouse gas and ammonia emissions from digested pig slurry during storage and after field application by maintaining a micro-oxygen level at the storage stage

Achieving overall low greenhouse gas and ammonia emissions from digested pig slurry during storage and after field application by maintaining a micro-oxygen level at the storage stage

Optimizing fermentation quality via lignocellulose degradation: synergistic effects of fibrolytic additives and Lactiplantibacillus plantarum on Elymus dahuricus silage

BackgroundThe harsh environmental conditions on the Qinghai-Tibetan Plateau challenge forage preservation, necessitating resilient strategies for silage making. This study evaluated the effects of fibrolytic additives, alone or combined with Lactiplantibacillus plantarum, on fermentation quality, lignocellulose degradation, and microbial community of Elymus dahuricus silage. The Elymus dahuricus was ensiled with (1) distilled water (C), (2) formic acid (FA), (3) fibrolytic enzymes (FE), (4) fibrolytic microbial consortium (MC), and (5–8) combinations with L. plantarum (Lp) inoculants (CLp/FALp/FELp/MCLp) for 50 days.ResultsThe results demonstrated that fibrolytic additives improved fermentation quality, evidenced by significantly (p < 0.05) higher lactic acid, dry matter and water soluble carbohydrate contents, and lower pH value and ammonia nitrogen contents. Fibrolytic additives significantly (p < 0.05) increased lignocellulose degradation, with SEM and FTIR analyses confirming structural disruption and chemical bond cleavage. The combination with Lp-inoculants further improved fermentation quality and lignocellulose degradation, with FELp demonstrating the highest lignocellulose degradation efficiency and optimal fermentation quality. Formic acid and fibrolytic enzymes established the dominance of L. plantarum by suppressing undesirable microbes and providing fermentable substrates, respectively. Fibrolytic microbial consortium increased the relative abundance of heterofermentative LAB (Lentilactobacillus buchneri and Levilactobacillus brevis) and cellulolytic bacteria (Bacillus subtilis and Enterococcus faecium).ConclusionCombining fibrolytic enzymes with L. plantarum (FELp) presented the greatest lignocellulose degradation and optimal fermentation quality. Fibrolytic microbial consortium (MC/MCLp) promoted heterofermentative pathways, increasing acetic acid. These results highlight the potential of enzyme-bacterial synergy for improving fermentation quality of Elymus dahuricus.Graphical

High‐Performance CuCo Aerogel Electrocatalyst for Relay Electroreduction of Nitrate to Ammonia

AbstractRenewable energy‐driven electroreduction of nitrate to ammonia presents a low‐carbon and promising route for sustainable ammonia synthesis. For Cu‐based electrocatalysts, due to their sluggish kinetics of the hydrogenation steps, nitrite often accumulates on the electrocatalysts surface, resulting in low ammonia yield rate and selectivity, as well as serious deactivation of electrocatalysts. Herein, a continuous relay site construction strategy that integrates the Cu─Co relay sites into an interconnected porous network is proposed. Owing to the adequately exposed interconnected Cu─Co relay sites, regulated adsorption energy of the nitrate and intermediates, promoted hydrogenation ability, and excellent self‐supportability of 3D skeleton, the Cu50Co50 aerogel realizes the high‐efficiency relay catalysis with an ultrahigh NH3 yield rate of 3.3 ± 0.27 mmol·h−1·cm−2 (2110 ± 173 mmol·h−1·gcat−1) and a large NH3 Faraday efficiency of ≈100% at −0.2 V vs. RHE. The potential need for the Cu50Co50 aerogel in the electrocatalysis at an industrial‐level current density remains stable even after 100‐h chronopotentiometry measurement, demonstrating excellent long‐term stability. Besides, the large‐scale preparation (&gt;1 g) of the Cu50Co50 aerogel can be easily achieved, and its exceptional performance is maintained consistently. Such a continuous relay site construction strategy opens a new way for developing advanced electrocatalysts for high‐efficiency relay catalysis.

Pharmaceutical micropollutants removal and N2O production by nitrification process in SBR and SBBR: a review.

Pharmaceutical micropollutants (PMPs) can cause significant environmental risks, with trace levels of exposure harming humans and wildlife. Biotransformation is a high-potential and low-cost way to remove PMPs, where ammonia-oxidizing microorganisms (AOM) are essential for eliminating pharmaceutical micropollutants. On the other hand, AOM are associated with nitrous oxide (N2O) emission generation in nitrifying. In this sense, micropollutants can inhibit the activity of AOB, reducing the ammonia oxidation rate and increasing N2O emissions. To mitigate these challenges, systems that allow satisfactory performance of the metabolism of AOB and NOB, such as the Sequencing Batch Reactor (SBR) and Sequencing Batch Biofilm Reactor (SBBR), are essential. However, no systematic review of the advances or gaps in this field has been published, mainly focused on SBR or SBBR. Thus, this work reviews recent advances regarding PMP biotransformation and N2O production by AOM, emphasizing SBR and SBBR systems. Besides, we compare the removal performances of various micropollutants in biological processes. The biotransformation of emerging pollutants was also presented to explore the metabolic pathways of N2O production and the critical factors that influence N2O emissions in biological processes. Controlling DO levels, intermittent aeration, and maintaining low ammonium concentrations can help mitigate N2O emissions. The simultaneous removal of PMPs and N2O emissions was also analyzed; however, there is still limited research regarding the effect of PMPs on N2O emission production in the nitrification process using SBR or SBBR. However, SBBRs may provide a more stable platform for both PMP removal and minimized emissions, mainly when biofilm characteristics and intermittent aeration are well managed. Thus, this review gives a complete vision of the advances of SBR and SBBR to remove PMPs and minimize the N2O, as well as the future directions that research needs to address to improve the PMPs biotransformation and N2O minimization.

Comparison of the start-up of rotating biofilm contactor reactor with HN-AD bacteria inoculation under high and low influent ammonia conditions.

Comparison of the start-up of rotating biofilm contactor reactor with HN-AD bacteria inoculation under high and low influent ammonia conditions.

Review of direct ammonia solid oxide fuel cells: Low temperature cell structure and ammonia decomposition strategies

Review of direct ammonia solid oxide fuel cells: Low temperature cell structure and ammonia decomposition strategies

Leveraging the gut microbiome to understand the risk factor of cognitive impairment in patients with liver cirrhosis.

The role of the gut-liver axis in liver cirrhosis is becoming increasingly recognized. We investigated the fecal microbiome in patients with liver cirrhosis and its potential function as a predictive biomarker of hepatic encephalopathy. Patients were divided into either a high plasma ammonia (HPA) group or a low plasma ammonia (LPA) group according to the upper limit of normal of plasma ammonia concentration. 16S rRNA sequencing of fecal samples was performed to study how the microbiota affects the clinical symptoms of liver cirrhosis. The Stroop test was used to assess the ability of the brain to inhibit habitual behaviors. Totally, 21 subjects were enrolled. Among the 18 patients with liver cirrhosis, 14 were male, the age range was 42-56 years, and the plasma ammonia level range was 20-125.9 μmol/l. The Stroop test showed more severe cognitive impairment in HPA than in LPA individuals. At the same time, there were significant differences in fecal microbiome characteristics between the two groups, characterized by a further increase in the abundance of the Proteobacteria phylum in the gut (especially aerobic Enterobacteriaceae ). Function predictions of Phylogenetic Investigation of Communities by Reconstruction of Unobserved States in the microbiome further explained the increase in the Enterobacteriaceae -dominated polyamine synthesis pathway in the gut microbiome of HPA groups. Cirrhotic patients with hyperammonemia have a specific fecal bacterial composition (characterized via expansion of Enterobacteriaceae ). The ability to bio-synthesize polyamines that Enterobacteriaceae possesses is likely to be a key factor in the elevation of plasma ammonia.

Prospects for the treatment of different phenotypes of nonalcoholic fatty liver disease complicated by hyperammonemia and sarcopenia: clinical study results

Background: This study examined the effect of lowering ammonia levels on sarcopenia severity in patients receiving pharmacotherapy for different nonalcoholic fatty liver disease (NAFLD) phenotypes. Materials and methods: Moreover, it identified the optimal treatment strategy for managing these comorbid conditions. This single-center, prospective, observational clinical study included 30 adult patients diagnosed with different forms of NAFLD (i.e., steatosis, steatohepatitis, fibrosis, and cirrhosis) who had elevated blood ammonia levels and exhibited signs of sarcopenia. The participants were divided into two groups, which included 15 patients each. Group 1 received standard treatment plus L-ornithine-L-aspartate (9 g/day orally), whereas group 2 received standard treatment alone. The treatment course lasted 4 weeks. Results: The addition of L-ornithine-L-aspartate to standard therapy significantly reduced ammonia levels and improved sarcopenia markers in patients with NAFLD. The study confirmed previous evidence on the role of L-ornithine-L-aspartate in reducing hyperammonemia and hepatic encephalopathy in patients with NAFLD. Moreover, the findings showed sarcopenia regression in patients with NAFLD, including those without cirrhosis, following L-ornithine-L-aspartate intake for 4 weeks at a dose of 9 g/day. Conclusions: Thus, ammonia-lowering agents, such as L-ornithine-L-aspartate, show promise. However, large-scale clinical trials are required to confirm their effectiveness in improving muscle strength loss and hyperammonemia. Further analysis of the relationship between NAFLD, sarcopenia, and hyperammonemia may lead to the development of personalized therapeutic strategies integrating pharmacologic treatments with lifestyle modifications. Addressing these issues through early diagnosis, targeted therapy, and interdisciplinary approaches is crucial for improving patient outcomes.

Optimizing Finishing Pig Performance and Sustainability: The Role of Protein Levels and Eco-Friendly Additive.

This study contributes to promoting green farming and achieving sustainable pork production. Especially under the conditions of resource scarcity and rising environmental demands, efficient and eco-friendly feeding strategies have become key to industry development. We evaluated the effects of supplementing an eco-friendly additive (EFA) in diets with normal and low protein (-2% CP) levels on growth performance, nutrient digestibility, gas emission, fecal score, meat quality, and blood profile in finishing pigs. In this 10-week (70-day and 7-day adaptation period) feeding experiment, 200 crossbred pigs [Duroc × (Landrace × Yorkshire)] with an initial average body weight (BW) of 55.05 ± 3.35 kg were used. The pigs were randomly assigned to four treatment groups in a 2 × 2 factorial arrangement, with five pigs per replicate group, including two gilts and three barrows per pen, and each treatment group was repeated 10 times. The experimental treatments included the following: two protein levels (normal CP and -2% CP) and two EFA levels (0% and 0.5% EFA). The results showed that pigs fed high-protein + EFA diets had a significantly higher ADG from weeks 0-5 compared to the high-protein control group (p < 0.05). From weeks 5-10 and overall, both high-protein + EFA and low-protein + EFA groups had a higher ADG than the low-protein - EFA group (p < 0.05). At week 10, the low-protein + EFA group showed significantly higher nitrogen digestibility and significantly lower ammonia emissions compared to the high-protein - EFA group (p < 0.05). Both EFA supplementation and protein level had significant effects on ammonia emissions. The fecal score was not significantly affected (p > 0.05). In blood profiles, NPY was higher in the high-protein + EFA group than in the low-protein - EFA group (p < 0.05). In terms of meat quality, both EFA-supplemented groups had a higher WHC compared to the low-protein - EFA group, while the high-protein + EFA group had a greater LMA (p < 0.05) and lower drip loss on day 7 after slaughter (p < 0.05). In conclusion, supplementing low-protein diets with EFA can effectively enhance the growth performance of finishing pigs, mitigate environmental pollution, and offer feeding advantages while lowering feed costs.

Enhancement of Partial Nitrification-Anaerobic Ammonia Oxidation in SBR Reactors via Surface-Modified Polyurethane Sponge Biofilm Carrier.

The partial nitrification-anammox process offers a cost-effective, energy-efficient, and environmentally sustainable approach for nitrogen removal in wastewater treatment. However, its application under low ammonia nitrogen conditions faces operational challenges including prolonged start-up periods and excessive nitrite oxidation. This study employed a strategy combining polyurethane surface positive charge enhancement and zeolite loading to develop a carrier capable of microbial enrichment and inhibition of nitrate generation, aiming to initiate the partial nitrification-anammox process in a sequencing batch reactor. Operational results demonstrate that the modified carrier enabled the reactor to achieve a total nitrogen removal efficiency of 78%, with the effluent nitrate nitrogen reduced to 6.03 mg-N/L, successfully initiating the partial nitrification-anammox process. The modified carrier also exhibited accelerated biofilm proliferation (both suspended and attached biomass increased). Additionally, 16S rRNA revealed a higher relative abundance of typical anammox bacteria Candidatus Brocadia in the biofilm of the modified carrier compared to the original carrier, alongside a decline in nitrifying genera, such as Nitrolancea. These microbial shifts effectively suppressed excessive nitrite oxidation, limited nitrate accumulation, and sustained efficient nitrogen removal throughout the reactor's operation.

Differential Cell Death Pathways Induced by Oxidative Stress in Multi-Organs of Amur Grayling (Thymallus grubii) Under Gradient Ammonia Stress.

Ammonia nitrogen is a common contaminant in aquatic environments, and its potential toxicity to organisms has attracted extensive attention. However, few studies have comprehensively evaluated the negative impacts of ammonia stress on cold-water fish. In this study, liver, gill, and intestine specimens of Amur grayling (Thymallus grubii) from three treatment groups (control (0 mg/L), low ammonia (43.683 mg/L), and high ammonia (436.8 mg/L)), were collected for histological observation, biochemical examination, and transcriptomic, metabolomic, and intestinal microbiome analysis. Our results showed that excessive ammonia nitrogen blocked the normal immune function and compromised the integrity of liver and gill tissues through oxidative stress-mediated differential cell death pathways. Meanwhile, the multi-omics analysis revealed that ammonia exposure predominantly altered the carbohydrate, lipid, and amino acid metabolism modes. In addition, it was also demonstrated that ammonia nitrogen stress affected the composition of intestinal microbiota taxa. This study provides insights into the potential risks and hazards of ammonia stress on cold fish in natural waters and provides a reference for the environment control of the water quality in aquaculture.

Influence of High Temperature and Ammonia and Nitrite Accumulation on the Physiological, Structural, and Genetic Aspects of the Biology of Largemouth Bass (Micropterus salmoides).

Hyperthermia and nitrogenous pollutants like ammonia and nitrite are common risk factors that adversely affect fish health and pose significant threats to the aquaculture industry. However, the impacts of high temperatures on the accumulation of nitrogenous pollutants in the water of the aquaculture systems and their toxicity to farmed fish are not well understood. In this study, juvenile largemouth bass (Micropterus salmoides, LMB) were kept at 28 °C and 34 °C in a closed aquatic system to investigate the effects of higher temperatures on ammonia and nitrite accumulation. The fish were fed 2% of their body weight daily for a 14-day experiment. Ammonia levels gradually increased, peaking on day 7 at 34 °C and on day 9 at 28 °C, then decreased to near zero. Nitrite levels remained low initially and increased rapidly along with the reduction in ammonia levels at both temperatures. The 34 °C high temperature accelerated the accumulation of ammonia and its transformation into nitrite compared to 28 °C. Fish were sampled on day 1 (low ammonia and low nitrite, LALN), day 8 (high ammonia and low nitrite, HALN), and day 14 (low ammonia and high nitrite, LAHN) to explore toxic effects. Successive exposure to high levels of ammonia and nitrite caused oxidative stress in the liver and significant pathogenic changes in the liver and spleen, with more pronounced impacts observed at 34 °C. Significant changes in gene expression were detected in the liver and spleen of fish sampled at HALN and LAHN, compared to those at LALN, with upregulated genes primarily associated with extracellular matrix (ECM) and cytoskeleton organization. A second experiment was conducted at the same temperatures but without ammonia/nitrite accumulation. The results of this experiment confirmed the combined effects of hyperthermia and ammonia/nitrite toxicity on the expression of genes involved in ECM-receptor interaction and TGF-beta signaling. These findings are valuable for optimizing cultivation environments and promoting the health of farmed LMB.

Modulation of the microbial community and the fermentation characteristics of wrapped natural grass silage inoculated with composite bacteria

This study evaluated the effects of composite bacterial inoculants on the fermentation quality, microbial community composition, and nutrient preservation of natural grass silage produced in Hulunbuir, Inner Mongolia. Four treatment groups were set, each using distinct combinations of lactic acid bacteria: a control group (C) with no inoculant and three inoculated groups (Group B: Lentilactobacillus buchneri and Pediococcus pentosaceus; Group P: Lactiplantibacillus plantarum A1 and Lactiplantibacillus plantarum LP-21; and Group M: Lactiplantibacillus plantarum, Enterococcus faecium, and Pediococcus pentosaceus). After 240 days of ensiling, the inoculated groups exhibited significantly higher contents of crude protein and dry matter (DM) and lower ammonia nitrogen, neutral detergent fiber, and acid detergent fiber levels than the control group. The M group demonstrated superior fermentation performance, exhibiting the lowest pH (C 5.15; B 4.77; P 4.64; and M 4.57), the highest lactic acid concentration (C 3.40% DM; B 6.80% DM; P 7.73% DM; and M 8.00% DM), and an optimal microbial composition dominated by Lactiplantibacillus and Lentilactobacillus. These improvements were attributed to Lactiplantibacillus plantarum, a bacterium that can produce a substantial amount of lactic acid through homofermentation, thereby lowering the pH, inhibiting the activity of undesirable microorganisms, and enhancing nutrient preservation. High-throughput sequencing revealed shifts in the dominant bacterial phyla from Proteobacteria in raw grass to Firmicutes in silage, with inoculants significantly influencing microbial diversity and functional profiles. Functional prediction indicated enhanced carbohydrate metabolism and nutrient preservation in the inoculated groups. These findings underscore the potential of tailored bacterial inoculants and advanced wrapping technology to improve the quality of silage and thus support sustainable livestock production.Graphical

Structure and Extinction Characteristics of Methane/Ammonia/Pulverized Coal Premixed Flames

Co-firing ammonia with pulverized coal offers a promising approach to reducing carbon emissions from coal-fired power plants. However, ammonia, as a fuel, presents challenges for combustion stability when burning compared to traditional fuels like methane. This study focuses on the extinction limits of ammonia-pulverized coal co-firing flames, a critical factor for efficient and safe combustion. A counterflow flame configuration was developed to investigate ammonia/pulverized coal premixed flames. The apparatus, with two opposed nozzles generating a planar flame, enabled the examination of gas-solid reactions. Pulverized coal was fed into the system, with methane representing the volatile matter to create a high-temperature environment for ignition. Stable methane/ammonia/pulverized coal/air premixed flames were successfully established, whose structure was observed under different conditions. The results show that in counterflow premixed flames, assisted by the methane flame, the ammonia/pulverized coal co-firing process begins with the ignition of gaseous components, forming a gaseous flame front, followed by the ignition of pulverized coal downstream in the high-temperature flue gas. The flame structure features in the coal combustion zone, the gaseous flame zone, the preheat zone, and the unburned zone. Increasing the flame stretch rate results in flame extinction, and the extinction limit of gaseous fuel plays a decisive role in the extinction of the overall gas-solid two-phase flame. For high ammonia blending ratios (50%, 75%, by energy) in the ammonia/pulverized coal mixture, the addition of pulverized coal decreases the overall extinction gaseous flame equivalence ratio at relatively high stretch rates (≥ 40 s-1) but increases the extinction gaseous flame equivalence ratio at relatively low stretch rates (&lt; 40 s-1). For low ammonia blending ratios (0%, 25%), the addition of pulverized coal consistently lowers the extinction gaseous flame equivalence ratio across the range of stretch rates covered in the experiments. Additionally, the study examined synergistic effects, finding limited interaction near extinction, implying that extinction of ammonia/pulverized coal combustion closely follows the behavior of gaseous flame extinction in the mixture in weakly-stretched premixed flames. These findings provide insights for enhancing the stability of ammonia/pulverized coal co-firing.

Rumen by-pass soybean meal reduced ruminal ammonia but did not improve growth performance and nitrogen utilization in growing Hanwoo heifers.

The effects of heat-treated soybean meal (SBM) and citric acid (HCSBM) on the growth performance, rumen fermentation, blood metabolites, nutrient digestibility, and nitrogen (N) utilization were evaluated in growing Hanwoo heifers. Eight growing Hanwoo heifers (initial body weight: 228.5±11.3 kg; age: 9.3±0.3 months) were allocated to a crossover design with two dietary treatments: a control diet containing untreated SBM (Control) and a diet containing HCSBM. There were two 28-day phases in the trial, each containing 14-day measurements and an adaptation period. Growth performance, rumen fermentation parameters, blood metabolites, hematological parameters, apparent digestibility, energy, and N utilization were measured. No significant differences were observed in the growth performance or energy utilization between the diets. The digestibility of dry matter and crude protein (CP) did not differ between the two diets. HCSBM supplementation increased neutral detergent fiber digestibility (p = 0.0874) and acetate molar proportions (p = 0.0748). The HCSBM diet resulted in lower ruminal ammonia nitrogen concentrations and iso-valerate proportions (p<0.05), indicating reduced ruminal protein degradation. Blood metabolites related to protein metabolism showed no significant differences between treatments. The control group exhibited higher red blood cell counts and hemoglobin and hematocrit levels (p<0.05). N excretion or retention did not significantly differ between the dietary groups. Despite enhanced protection against ruminal protein degradation, HCSBM supplementation did not improve N utilization efficiency or growth performance in growing Hanwoo heifers, possibly because of a sufficient N supply from the high CP content in both diets.

A novel microfluidic self-perfusion chip (MSPC) for pumpless 3D cell, microtissue and organoid culture.

Microfluidic systems have revolutionized biological research by enabling precise control over cellular environments at microscale volumes. However, traditional pump-driven systems face challenges such as complexity, cost, cell-damaging shear stress, and limited portability. This study introduces a novel adjustable microfluidic self-perfusion chip (MSPC) that uses evaporation as a driving force, eliminating the need for external pumps. Our design offers improved metabolic waste management and simplified control over fluid dynamics. The chip features adjustable evaporation pore sizes, demonstrating a robust linear relationship (R2 = 0.95) between the pore size and fluid evaporation rate. This ensures consistent fluid flow and effective waste removal, shown by lower ammonia and lactate levels compared to conventional cultures. Its unidirectional flow system and integrated one-way valve maintain cell viability, even under complete evaporation conditions. This innovative platform facilitates the cultivation of complex tissue-like structures, providing a valuable tool for tissue and organ model development, as well as drug screening and toxicity testing. By addressing key limitations of traditional systems, our adjustable MSPC represents a significant advancement in microfluidic cell culture technology, offering improved accessibility and applicability in biological research.

Effect of Precursors on Trimetallic Ruthenium-Based Catalysts Supported on γ-Al2O3 Pellets for Low-Temperature Ammonia Decomposition.

Ammonia is a promising candidate as a liquid hydrogen energy storage medium, but it requires catalytic decomposition (ammonia cracking) to regenerate hydrogen. Recently developed trimetallic ruthenium-potassium-promoter (RuKM) ammonia decomposition catalysts have exceptionally low ammonia decomposition temperatures, able to perform the decomposition as low as 250 °C, which is significantly lower than other known catalysts that require temperatures above 500 °C. However, the effects of the RuKM precursor on the catalytic activity have not been investigated. We report the observed differences of 3% ruthenium/12% potassium/1% yttrium (RuKY) catalysts on γ-alumina synthesized from chloride-, nitrate-, and acetate-based precursors. Catalysts synthesized from chloride-based precursors demonstrated the lowest ammonia decomposition catalytic activity at lower reaction temperatures. In contrast, those synthesized from nitrate-based precursors demonstrated the highest yield, despite similar metal loading. This difference in reactivity is most apparent between 250 and 400 °C, as the conversion rates of the catalysts synthesized with chloride-free precursors are up to 50% greater than those synthesized with chloride precursors. The observed differences in catalytic activity were much less apparent above 450 °C. The observed activation energies of the catalysts were independent of the precursor utilized, despite the difference in catalytic activity, suggesting that the active site composition was the same for all catalysts. These results suggest a pathway to improved ammonia cracking catalysts by tailoring the precursor used in the synthesis.

Lettuce production in a DWC aquaponic system with and without bioflocs compared to a hydroponic system in southern Brazil

Three recirculation systems – aquaponics (Aqua), aquaponics with bioflocs (AquaFloc), and hydroponics (Hydro) – were established to evaluate lettuce production (floating) over 45 days. Juveniles of hybrid tambacus kept in aquaponic tanks were fed commercial feed. Water quality was monitored and vegetable growth was assessed. Metrics of lettuce, such as head diameter, height, fresh matter, dry matter, number of leaves, and chlorophyll concentration, were significantly higher (p < 0.05) in the Hydro system than in the AquaFloc system even after 60 days. The AquaFloc system exhibited 62% fish survival, significantly lower (p < 0.05) ammonia and nitrite concentrations than Hydro, and an absence of nitrate. Electrical conductivity and total dissolved solids concentration were significantly lower (p < 0.05) in AquaFloc than in Hydro, while pH levels were significantly higher (p < 0.05) in both Aqua and AquaFloc, resulting in reduced nutrient availability for plant growth. The Aqua system showed no lettuce growth and experienced complete fish mortality. The fish-to-vegetable ratio used did not meet the nutritional demands of lettuce. Further studies are needed to determine an appropriate fish-to-vegetable ratio that provides sufficient nutrients to plants in aquaponics, along with the maintenance of optimal pH control.

Comparison of the performances and mechanisms of anammox bacteria in-situ self-enrichment under heterotrophic and autotrophic conditions by inoculating ordinary activated sludge.

Comparison of the performances and mechanisms of anammox bacteria in-situ self-enrichment under heterotrophic and autotrophic conditions by inoculating ordinary activated sludge.