Reduce Ammonia Emissions Research Articles

Use of Bio-Preparations to Reduce Ammonia Emissions from Cattle Farming: Effects of Manure Storage Time and Ventilation Intensity

Ammonia emissions are both an environmental and health issue. Biological preparations (also known as biopreparations) have attracted interests as a tool to reduce ammonia emissions from livestock. However, little is known about their effectiveness in modulating evaporating NH3 from manure. The aim of this study was to evaluate the effectiveness of one biopreparation product (MycroZyme© Micron Bio-Systems Ltd., Bridgwater, UK) by studying the dynamics of NH3 gas evolution, taking into account factors such as manure storage time (fresh or stored) and the application method (sprayed or mixed). Experimental studies were performed with control manure (manure without biopreparation) and manure treated with the biopreparation. Data showed that the use of biopreparation slowed down the ammonia emission from manure, so the ammonia concentration in the wind tunnel decreased on average from 21.69 ± 0.9 to 14.43 ± 1.5 ppm. The effect of the biopreparation on ammonia evaporation was higher in the presence of more intensive ammonia emission conditions; i.e., when the manure was fresh, there was no crust on the surface, and the airflow over the manure was intense, and there was a large gradient of ammonia concentration on the manure surface. Based on the obtained results, recommendations were made to reduce ammonia emissions in litter-less cowsheds, where liquid manure is stored.

Delaying tillering nitrogen topdressing until the midtillering phase improves nitrogen use efficiency and reduces ammonia emission via rice canopy recapture

Tillering nitrogen (N) topdressing is commonly employed to enhance primary-tiller number and achieve a high grain yield for wetland rice. Unfortunately, farmers typically apply N fertiliser shortly at tillering initiation following basal fertilisation, and substantial soil ammonia (NH3) volatilisation occurs due to the low N demand of small plants. Herein, we hypothesised that delaying topdressing N until the midtillering phase could increase canopy recapture of soil NH3 emission and better synchronise N supply with crop N demand, leading to reduced NH3 losses and increased fertiliser N use efficiency. A field experiment was conducted to investigate the effect of conventional tillering N topdressing (CT) at the early tillering stage (2 weeks after basal N application) and delayed tillering N topdressing (DT) until the midtillering phase (∼4 weeks after basal N application) on NH3 emission from soil and the soil-plant system, as well as N uptake, N use efficiency and yield. The 2-year field results showed that DT did not hinder effective tiller production or above-ground dry biomass compared with CT, but improved plant N uptake and total N accumulation after midtillering, leading to 18–27 % higher agronomic efficiency. Correspondingly, 8.9–15 % increases in grain yield were observed for DT compared with CT, mainly attributable to increased panicle number per area and filled grain number per panicle. Following tillering N application, NH3 loss from the soil-plant system under CT accounted for 22 % of top-dressed N, showing only a slight decline compared with that of soil emission. For DT, NH3 loss from the soil-plant system was reduced to 6 %, even though 15 % soil NH3 emission was observed, indicating a more than two-fold increase for in-canopy NH3 recapture. Correspondingly, cumulative net NH3 losses for the entire rice season were decreased by 31% under DT relative to CT. These results provide evidence that delaying tillering N topdressing until the midtillering phase when rice canopy formation is enhanced, can better synchronise fertiliser N supply with crop demand and increase in-canopy NH3 recapture. A large discrepancy remains between NH3 emission from soil and the soil-plant system at midtillering and panicle initiation stages, highlighting the overestimation by the soil dynamic chamber method when quantifying NH3 losses due to overlooking the contribution of canopy recapture of soil-emitted NH3.

The Environmental Impact of Lowering Dietary Crude Protein in Finishing Pig Diets—The Effect on Ammonia, Odour and Slurry Production

Excess nitrogen excretion, ammonia and odour are environmental pollutants associated with pig production. Reducing dietary crude protein (CP) will lower the amount of nitrogen excreted, reducing the potential for ammonia emissions, if diets are adequately formulated to supply amino acids and production performance is maintained. Crude protein content in diets for finishing pigs has been lowered recently, but the quantitative effect of this reduction on ammonia, odour, and slurry output is not well-established. The relationship between ammonia and odour is equivocal, and the effect on slurry production is unclear. The objective of this study was to investigate the effect of lowering dietary CP on ammonia emission, odour emission and slurry output of finishing pigs. Thirty entire boar pigs were individually housed in groups of six, from 10 weeks of age (30 ± 3.0 kg) and offered standard diets. At 75 kg (±1.5 kg) pigs were assigned to one of three treatment diets; (1) 180 g/kg CP, 11.0 g/kg total lysine (High CP), (2) 150 g/kg CP, 11.1 g/kg total lysine (Medium CP), and (3) 130 g/kg CP, 9.0 g/kg total lysine (Low CP). After three weeks on the experimental diets pigs were moved, six each week, to individual calorimetry chambers to measure ammonia and odour emissions. Pigs were offered treatment diets ad libitum. At the end of the recording period, the pigs were removed from the chamber, weighed and feed disappearance recorded to calculate intake. The slurry in each chamber was collected and analysed. The reduction in CP in the diet from 180 g/kg to 150 g/kg resulted in a 22% reduction in ammonia emissions, and from 180 g/kg to 130 g/kg resulted in a 47% reduction (p < 0.001). Slurry output from pigs offered the 130 g/kg CP diet was reduced by 39% (p < 0.001) and dry matter increased by 35% compared to slurry from pigs offered the 180 g/kg CP diet (p < 0.05). Water usage (p = 0.017), slurry output and nitrogen and phosphate in the slurry (p < 0.05, respectively) were found to decrease linearly with decreasing dietary CP content. There was no significant effect of reducing CP on performance or odour emission but hydrogen sulphide emissions decreased linearly (p < 0.010) with decreasing dietary CP. There was a weak positive relationship between odour emission and ammonia (linear: R2 = 0.25, p = 0.005) with odour emission reduced as ammonia emission reduced. Reducing dietary CP in finishing pig diets could reduce ammonia emissions, water usage and slurry and nutrient output from pig production.

Phylogenetic placement of thermophilic ammonium-tolerant bacteria and their distribution in various composts.

Previous studies isolated the thermophilic ammonium-tolerant (TAT) bacterium Bacillus sp. TAT105 that grew in composting swine manure with the assimilation of ammonium nitrogen and reduced ammonia emissions during composting. Those studies also investigated the potential for applications of TAT105 to composting. It was observed that the concentration of TAT bacteria, phylogenetically close to TAT105, increased during composting. The objectives of this study were to identify the phylogenetic placement of these TAT bacteria and investigate their distribution in various composts. The phylogenetic placement of TAT105 was examined based on the sequence of 16S ribosomal RNA gene. The genomic DNA homology between TAT105 and the type strains of bacterial species that were phylogenetically close to TAT105 were examined by DNA-DNA hybridization. Moreover, the tolerances of these strains to NH4Cl and NaCl were analyzed using a cultivation method. Concentrations of TAT bacteria in various composts were evaluated using an agar medium specific to TAT bacteria and polymerase chain reaction followed by restriction fragment length polymorphism analysis. TAT105 was most closely related to Bacillus thermolactis and Bacillus kokeshiiformis. Many variants of these species have been detected in various environments, including composts. The type strains of these species displayed TAT characteristics that were similar to those of TAT105. Among the composts examined in this study, TAT bacteria were detected at high concentrations (105 to 109 colony forming units per gram of dry matter) in most of the composts made from cattle manure, swine manure, bark, and excess sludge. TAT bacteria comprised B. thermolactis, B. kokeshiiformis, and their phylogenetically close relatives. They were considered to be adaptable to composting of some certain materials, and a favorable target for searching for strains with some useful function that could be applied to composting of these materials.

Simultaneous reductions in antibiotic, antibiotic resistance genes and nitrogen loss during bioaugmentation tylosin fermentation dregs co-composting

Considering the main problems presented in the typical solid wastes antibiotic fermentation dregs (AFDs) composting that the residual antibiotics could result in the propagation of antibiotic resistance genes (ARGs), and the reduced value of agronomic production caused by the ammonia gas (NH3) emissions. This study established a bio-augmented tylosin fermentation dregs (TFDs) aerobic co-composting system to investigate the effects of a novel isolated high-efficiency strain Klebsiella sp. TN-1 inoculation on tylosin degradation, reduction in ammonia emissions, and ARG abundances during this process.Results showed that the application of strain Klebsiella sp. TN-1 extended the thermophilic stage and promoted compost maturity. Moreover, bio-enhanced co-composting with strain Klebsiella sp. TN-1 led to a totally degradation of tylosin, and removed most of ARGs, metal resistance genes (MRGs) and mobile genetic elements (MGEs), and also effectively reduce ammonia emission by 49.76 %.via increasing ammoxidation rates. Principal co-ordinates analysis further suggested that the strain Klebsiella sp. TN-1 had little influence on the bacterial community composition, while the changes of other physical and chemical properties during this process were the main reasons for the evolution of bacterial community and propagation of ARGs in the TFDs co-composting.This study suggests the potential of the bio-enhanced strain Klebsiella sp. TN-1 for antibiotic biodegradation and its application for nitrogen conservation in the AFDs co-composting process, which could decrease the risk of ARGs spreading and make compost products more secure.

Investigating the time-dependent dose–response relationship of ammonia emissions reduction through the application of a urease inhibitor in pig fattening houses

In agricultural production, over 95% of ammonia emissions are released into the air. This released ammonia then reacts with other air pollutants to form particulate matter, endangering human health and ecosystems. One approach to counter this effect, which is directly related to the presence of the enzyme urease, is the use of a urease inhibitor. This study is the first to systematically investigate the time-dependent dose–response relationship between a urease inhibitor (dose levels: 10 mg m −2 , 25 mg m −2 and 50 mg m −2 ) and ammonia emissions in mechanically ventilated pig fattening houses over four experimental periods in one year. The inhibitor was applied simultaneously in five identical compartments on a daily basis. A new approach was used to determine the reduction effect by combining the case–control in time and direct case–control approaches. A maximum reduction of 21% in ammonia emissions was achieved in these experiments. The inhibitor had an effect on the first day, which lasted up to four days after the application phase. The higher the dose level of the inhibitor, the longer the reduction effect. Compared to cattle, higher dose levels of urease inhibitor are required for pigs. Further investigations on emission location within the compartment, on appropriate inhibitor doses levels depending on compartment design, animal behaviour or housing system as well as on automatic application systems are essential for the target-oriented use of a urease inhibitor in pig houses. • Dose–response relationship between a urease inhibitor and ammonia emissions. • A maximum reduction of 21% in ammonia emissions was achieved in these experiments. • The higher the dose level of the inhibitor, the longer the reduction effect. • Reduction calculation combines case–control in time and direct case–control.

Recent innovations in various methods of harmful gases conversion and its mechanism in poultry farms

Poultry breeding takes place in intensive, high-production systems characterized by high animal density, which is a source of harmful emission of odorous volatile organic compounds (VOCs), ammonia (NH3), hydrogen sulfide (H2S) and greenhouse gases, which in turn sustain animal welfare. This study identified and examined the characteristics of chemical compounds emitted in intensive poultry farming (laying hens, broilers) and their toxicity, which led to recommending methods of deodorization. Emphasis was placed on the law relative to air purification in poultry farms. Various methods of air treatment in poultry farms have been described: the modification of animal diet to improve nutrient retention and decrease the amount of their excrement; chemical oxidation technologies (ozonation, photocatalysis, Fenton reaction); various types/brands of biofilters, bioscrubbers and membrane reactors. Numerous studies show that biofilters can reduce ammonia emissions by 51%, hydrogen sulfide by 80%, odors by 67%, while scrubbers brings down ammonia emissions by 77% and odors by 42%, and the application of UV light lowers ammonia emissions by 28%, hydrogen sulfide by 55%, odors by 69% and VOCs by 52%. The paper presents both the solutions currently used in poultry farming and those which are currently in the research and development phase and, as innovative solutions, could be implemented in the near future.

A urease inhibitor reduces ammonia emission in fattening pigs reared on slatted floor in summer conditions

Intensive pig farming is a main contributor to ammonia (NH 3 ) emissions. Urease inhibitors block the conversion of the excreted urea into ammonium and may reduce effectively these emissions at the housing level. This study evaluated the effect of applying a urease inhibitor in a naturally ventilated and fully slatted pig house. Emissions were compared using two approaches: in-time evaluation and case-control approach. Two identical rooms in size and management were used in this experiment. Seventy growing pigs of 70 kg weight were placed in each room. One room was treated with the urease inhibitor EBN (based on phosphorodiamidate) during 12 days (treatment phase) at a rate of 0.17 mL m −2 day −1 . The study also included a pre-treatment phase of 2 days and a post-treatment phase of 15 days. Temperature and concentrations of NH 3 and carbon dioxide (CO 2 ) were recorded every 2 min, and then aggregated on an hourly basis. Natural ventilation rate was calculated using the CO 2 balance method. The case-control approach showed more reliable results since only two days were available for the in-time approach. On average, emissions were reduced by 29% over the treatment phase. After each application, the maximum abatement potential was found between 4 and 14 h after application of the inhibitor. This study was conducted under specific farm and climate conditions. More studies are needed to confirm the abatement potential in a wider range of situations. • A urease inhibitor was tested in a naturally ventilated pig farm in summer conditions. • In-time evaluation and case-control approach were used to assess the mitigation potential. • Urease inhibitor reduced ammonia emission by 29%. • Response time of ammonia abatement after application was quantified.

Twenty‐year phosphorus trends in forage systems receiving aluminum sulfate‐treated poultry litter

AbstractAdding aluminum sulfate or alum to poultry litter is a best management practice (BMP) that reduces ammonia emissions and P runoff and leaching, although its long‐term effects on forage growth and P uptake are largely unknown. The objective was to determine if reducing soluble P in litter with alum would result in forage P deficiencies or reduce yields. A 20‐yr study was conducted to determine effects of four rates of alum‐treated litter, untreated litter, and ammonium nitrate (NH4NO3), as well as an unfertilized control on tall fescue (Festuca arundinacea Schreb.) yield and P uptake. Phosphorus uptake increased as litter rates increased for both sources but was greater (P ≤ .05) for untreated litter, likely owing to high water‐extractable P in soil. Over 20 yr, both litter sources had greater P uptake than NH4NO3. Average annual yields by fertilizer source across rates were 6.92, 6.64, 5.10, and 3.38 Mg ha–1 for alum‐treated litter, untreated litter, NH4NO3, and the control, respectively. Forage yields increased with litter application rate, but there was no difference due to litter source, whereas yields were 34% lower with NH4NO3 due to soil acidification and forage P deficiency (≤0.2% P). Multiple regression indicated tall fescue P uptake was affected by total P application rate and water‐extractable phosphorus (WEP), whereas yields were influenced by N rates, Mehlich III P levels, soil pH, and precipitation. These results indicate that amending soils with alum‐treated litter does not adversely affect tall fescue yields or P utilization, therefore alum is a sustainable BMP in pasture systems.

Better performance of compound fertilizers than bulk-blend fertilizers on reducing ammonia emission and improving wheat productivity

Compound fertilizer and bulk-blend fertilizer are two major types of fertilizers used in wheat production. However, it remains unclear which type of fertilizers has lower ammonia (NH3) emission and greater wheat productivity. We conducted a field experiment in Hefei, China during 2018–2019 and 2019–2020 wheat growing seasons. The objectives were to assess the effects of three compound fertilizers and three bulk-blend fertilizers on NH3 emission and wheat growth, and elucidate the mechanisms involved. The seven treatments included the control test without N application (CK), bulk-blend fertilizer (BF), bulk-blend fertilizer with bentonite (BFb), bulk-blend fertilizer with humic acid (BFh), compound fertilizer (CF), compound fertilizer with bentonite (CFb), and compound fertilizer with humic acid (CFh). Results showed that compared with bulk-blend fertilizers, the corresponding compound fertilizers decreased total area-scaled NH3 emissions by 10.2%−19.2% and yield-scaled NH3 emissions by 12.8%−23.5%, increased average soil nitrification rate by 7.2%−20.9%, and reduced average soil NH4+ content by 7.2%−16.8% and average soil pH by 0.3%−1.0%. Greater soil nitrification rate in compound fertilizer treatments was partly responsible for the decreases in soil NH4+ content, soil pH, and NH3 emission, and then led to the increases in soil inorganic N content, grain yield, and N use efficiency. Compared with bulk-blend fertilizers, the corresponding compound fertilizers increased grain yields by 2.3%−12.2% and N use efficiency by 8.6%−43.9% (except for CF in 2019–2020). Overall, compound fertilizers had better performances than bulk-blend fertilizers in reducing NH3 emission (area-scaled and yield-scaled) and improving wheat productivity; while adding functional materials (e.g., bentonite and humic acid) and using proper application methods (e.g., banded application) are possible strategies for decreasing NH3 emission from bulk-blend fertilizers.

Trends in secondary inorganic aerosol pollution in China and its responses to emission controls of precursors in wintertime

Abstract. The Chinese government recently proposed ammonia (NH3) emission reductions (but without a specific national target) as a strategic option to mitigate fine particulate matter (PM2.5) pollution. We combined a meta-analysis of nationwide measurements and air quality modeling to identify efficiency gains by striking a balance between controlling NH3 and acid gas (SO2 and NOx) emissions. We found that PM2.5 concentrations decreased from 2000 to 2019, but annual mean PM2.5 concentrations still exceeded 35 µg m−3 at 74 % of 1498 monitoring sites during 2015–2019. The concentration of PM2.5 and its components were significantly higher (16 %–195 %) on hazy days than on non-hazy days. Compared with mean values of other components, this difference was more significant for the secondary inorganic ions SO42-, NO3-, and NH4+ (average increase 98 %). While sulfate concentrations significantly decreased over this period, no significant change was observed for nitrate and ammonium concentrations. Model simulations indicate that the effectiveness of a 50 % NH3 emission reduction for controlling secondary inorganic aerosol (SIA) concentrations decreased from 2010 to 2017 in four megacity clusters of eastern China, simulated for the month of January under fixed meteorological conditions (2010). Although the effectiveness further declined in 2020 for simulations including the natural experiment of substantial reductions in acid gas emissions during the COVID-19 pandemic, the resulting reductions in SIA concentrations were on average 20.8 % lower than those in 2017. In addition, the reduction in SIA concentrations in 2017 was greater for 50 % acid gas reductions than for the 50 % NH3 emission reductions. Our findings indicate that persistent secondary inorganic aerosol pollution in China is limited by emissions of acid gases, while an additional control of NH3 emissions would become more important as reductions of SO2 and NOx emissions progress.

Assessing the long-term impact of urease and nitrification inhibitor use on microbial community composition, diversity and function in grassland soil

Reductions in ammonia (NH3) and nitrous oxide (N2O) emissions from agricultural systems are critical for achievement of sustainability targets that underpin international efforts on climate and biodiversity. Urease inhibitors (UI) such as N-(n-butyl) thiophosphoric triamide (NBPT) and nitrification inhibitors (NI) such as dicyandiamide (DCD) slow down microbial and chemical N transformation rates in soil, resulting in decreased environmental N losses. To date there has been minimal assessment of the long-term non-target impacts of UI and NI on soil microbial communities and biological function in grasslands. Utilising a temperate grassland field experiment where fertilisers (with or without inhibitors) were repeatedly applied over a five year period, we assessed the impact of individual or combined inhibitor use on microbial community composition, abundance and function via a combination of functional assays, quantitative polymerase chain reaction (qPCR) assays and amplicon sequence analysis. We also investigated the effect of N inhibitor use on the N functional community, and whether the form of applied N fertiliser (i.e. calcium ammonium nitrate (CAN) or Urea) affected microbial community composition and function. Treatments included a Control (no N); CAN; Urea; Urea + NBPT (UI); Urea + DCD (NI); and Urea + DCD + NBPT (NI & UI). There was no impact of either UI or NI use on non-target microbial community composition or abundance. Function and the abundance of N cycling communities were mainly unaffected by fertilisation or the use of inhibitors. The observed effect of NI was primarily on the nitrification process. There was a significant reduction in nitrification potential associated with the use of NI, and in the case of the Urea + DCD treatment a reduction in COMAMMOX nitrifier abundance, and an increase in potential N mineralisation and N2O emissions. Finally, there was a significant impact of fertilisation and fertiliser type (i.e. CAN or Urea) on the fungal community structure but no impact on bacterial community structure. These results provide a knowledge base that will inform policy regarding the utilisation of N inhibitors as a mitigation measure for reducing gaseous N losses in grasslands.

Exogenous protease supplementation to the diet enhances growth performance, improves nitrogen utilization, and reduces stress in finishing pigs.

We have conducted this experiment to evaluate a new exogenous protease in finishing pigs' growth performance, nutrient digestibility, gas emission, blood profiles, and meat quality. A total of 200 pigs of 52.15 ± 2.31 kg average body weight (BW) were divided into four dietary treatments named as: CON, basal diet; TRT1, basal diet + 0.05% protease; TRT2, basal diet + 0.1% protease; TRT3, basal diet + 1.5% protease. Each treatment consisted of 10 pens, where five pigs were allotted to each pen according to their body weight and sex. The dietary treatments were allotted to the pens in a randomized block design. During this 10-week-long experiment, BW, average daily gain (ADG), average daily feed intake (ADFI), and gain to feed ratio (G:F) were calculated for Week 0-5, Week 6-10, and the overall period. During Week 6-10, ADG was higher in TRT2 and TRT3 than in the CON and TRT1 groups. At the same time, a linear increase was observed in ADG and G:F of the pigs. In addition, the final BW of pigs' was linearly increased by protease supplementation. On Week 10, there was a linear trend of increase (p = 0.0575) in crude protein digestibility and a trend of linear reduction (p = 0.0651) in NH3 gas emission. In blood profile, cortisol presented a linear decrease in both Week 5 (p = 0.251) and Week 10 (p = 0.0585). In addition, increasing doses of protease showed a trend of linear increase (p = 0.0592) in creatinine, whereas linear reduction was observed in the concentration of epinephrine (p = 0.0636) and norepinephrine (p = 0.0167) during Week 10. In conclusion, protease supplementation helped in improving daily gain in finishing pigs through protein digestibility with associated reduction of ammonia emission and blood stress hormones.

Addition of earthworm castings reduces gas emissions and improves compost quality in kitchen waste composting

In this study, we demonstrate that the addition of earthworm castings (EC) in kitchen waste composting reduces ammonia and greenhouse gas (GHG) emissions and improves compost maturity. Kitchen waste (KW) was mixed with sawdust at a ratio of 7:3 as the compost stock. Four treatments with different proportions of EC added (0%, 2.5%, 5.0%, and 7.5% on the basis of the initial kitchen waste mass) were designed and utilized in a composting process lasting 85 days. The results showed that the GHG and ammonia emissions were considerably reduced in the treatments with EC added. In addition, EC amendment prolonged the thermophilic stage and shortened the composting period. The addition of EC reduced ammonia, methane, and nitrous oxide emissions by 61%, 48%, and 94%, respectively, also indicating that nitrogen in the compost was conserved. Nitrogen and major nutrients were best preserved in the EC 7.5% treatment, which produced a compost product with a better nutrient profile. Furthermore, the total global warming potential of the KW composting process was reduced by 74% by using the mixture with EC. An effective reduction in GHG emissions was observed already with the addition of 2.5% EC, but a significant reduction in ammonia emissions was observed for the EC 7.5% treatment. Therefore, the results of this study suggest that EC is an effective additive in KW composting. More specifically, addition of EC at 7.5% of the initial KW mass was most recommendable for mitigating potential global warming effects and improving compost quality.

Combining microbially induced calcite precipitation (MICP) with zeolite: A new technique to reduce ammonia emission and enhance soil treatment ability of MICP technology

The byproduct ammonia limits the wide application of the urea-hydrolysis based microbially induced calcite precipitation (MICP) technique. Here, we proposed a new technique termed the “MICP-zeolite technique” to reduce ammonia emission, which combined ammonia removal by zeolite with the MICP process. To understand the new technique, 1) the ability of the used zeolite to adsorb bacteria and remove ammonia was tested; 2) the MICP and MICP-zeolite techniques were applied to soils via both a mixing way and an injecting way to evaluate their performance in ammonia emission, soil cementation, and permeability reduction; 3) many properties of the zeolite and treated/untreated sands were characterized including surface charge, microstructure, surface area, pore size distribution. The results present that the zeolite can adsorb Sporosarcina pasteurii strongly, due to its larger specific surface area, rougher and outwardly-protruding surface, and less negative charge. Contact time, pH, temperature, and zeolite dosage affected ammonia removal efficiency. The MICP-zeolite technique resulted in less ammonia emission, greater soil strength, and lower permeability, and the injecting way is more effective in soil cementation. In soils treated by the proposed technique, the clogged pores were more, the precipitated crystals were more and smaller, the number of micropores and macropores reduced more, and the zeta-potential of particles increased more. Collectively, the MICP-zeolite technique is superior to the MICP technique in treatment effect and environmental friendliness.

Reduction of Ammonia Emission using Deceleration Cylinder Cutoff in a Gasoline Spark Ignition Engine

<div class="section abstract"><div class="htmlview paragraph">The newly proposed Euro 7 emission standards have added regulations limiting ammonia emissions for gasoline vehicles. This paper proposes a new emissions-control strategy to satisfy the regulated ammonia emission levels, using deceleration cylinder cut-off (DCCO) to reduce or eliminate conventional deceleration fuel cutoff (DFCO) and the associated lean-rich excursions in the three-way catalyst during oxygen saturation and desaturation. The improved air-fuel ratio management closer to stoichiometry lowers the ratio of CO to NO<sub>x</sub> and thus the ammonia (<i>NH</i><sub>3</sub>) formation rate inside catalytic converter. Tests show more than 80% reduction of ammonia emission on the WLTC drive cycle without increasing other regulated emissions.</div></div>

Calcium acetate as calcium source used to biocement for improving performance and reducing ammonia emission

In construction engineering and mining engineering, CaCl2 is the most commonly used calcium source in microbial-induced carbonate precipitation (MICP) technology because it can generate CaCO3, which has a high degree of crystallization and is thermodynamically stable, in tailings or soil. However, this calcium source is not the best choice for biocement. This study aims to compare the stability, strength, NH3 emission, and other effects of CaCl2, Ca(CH3COO)2, and Ca(NO3)2 in bio-cement to determine the best calcium source for bio-cement. The results indicate that after curing for 28 days, the strength of bio-cement with Ca(CH3COO)2 as its calcium source is higher than that with CaCl2 and Ca(NO3)2 as calcium sources. After adding cement to three calcium sources (CaCl2, Ca(CH3COO)2, and Ca(NO3)2), the CH3COO− sample is more stable and has higher biomass and urease activity than the Cl− and NO3− samples. Since CH3COO− is a weak acid, CH3COOH generated by CH3COO− can easily react with NH3 under the alkaline condition provided by cement, reducing NH3 emissions. When Ca(CH3COO)2 was used as a calcium source, the NH3 emission of its sample decreased by 54.2% and 51.4% compared with CaCl2 and Ca(NO3)2. Therefore, CH3COO−, as an anionic calcium source, will have more application prospects than CaCl2 and Ca(NO3) in bio-cement production.

Construction of recombinant Pichia pastoris strains for ammonia reduction by the gdhA and glnA regulatory genes in laying hens

Ammonia emissions have become an important environmental challenge for the livestock industry. Probiotics are often used as additives to reduce ammonia, and the ammonia reduction efficiency of common probiotics is approximately 20–40%. In this study, we constructed a gdhA recombinant Pichia pastoris strain, glnA recombinant Pichia pastoris strain and gdhA-glnA Pichia pastoris recombinant strain using the gdhA and glnA genes, which have the potential function of reducing ammonia emissions. The results of in vitro fermentation showed that compared with the control, wild-type Pichia pastoris and pPICZA strains, the gdhA, glnA and gdhA-glnA recombinant strains significantly reduced ammonia emissions in laying hens (P < 0.05), with emission reduction efficiencies of 63.95%, 65.68% and 74.04%, respectively. The reason may be that the recombinant Pichia pastoris strains can convert ammonium nitrogen into amino acids for self-growth through ammonia assimilation, and reduce the pH, uric acid and urea content in the intestinal tract of livestock and poultry, and urease activity. Therefore, the construction of recombinant strains can provide technical support for reducing ammonia pollution in the livestock industry.

Incentivising ammonia emission abatement through in-house slurry acidification: Evidence from a discrete choice experiment in Germany

This article assesses farmers' willingness to participate in a stylised scheme supporting the adoption of slurry acidification techniques in livestock facilities. Slurry acidification is a novel technique, developed in Denmark, to reduce ammonia emissions. In a discrete choice survey of 129 German livestock farmers, the respondents were asked to choose among different support schemes and the status quo. The attributes presented in the choice sets were the expected emission reduction, the cost share on offer, a factor by which the additional nitrogen in acidified slurry must be accounted for in fertiliser plans, and concessions on current fertiliser regulations. A mixed logit model showed that the majority of respondents valued emission reductions, a higher cost share and concessions on the statutory requirements of the Fertiliser Ordinance. A latent-class model was applied to reveal preference heterogeneity. It identified three preference classes with different perceptions of the scheme's attributes.

Ambient observations indicating an increasing effectiveness of ammonia control in wintertime PM2.5 reduction in Central China

Ammonia emission reduction is increasingly being considered one of the control measures to mitigate wintertime fine particulate matter (PM2.5) pollution. Three wintertime observations from 2012 to 2018 in Wuhan, China, were analyzed to examine the effectiveness of ammonia control in wintertime PM2.5 reduction based on the critical total ammonia concentration (CTAC, i.e., the inflection point of effective ammonia control for PM2.5 mass reduction based on the asymmetric response of PM2.5 to ammonia control). The CTAC gradually approached 0% (immediate effectiveness), with values of −26% in 2012, −23% in 2015, and −9% in 2018. At the observed ambient conditions, there were significant positive correlations of the CTAC with sulfate and total nitrate changes, in contrast to the negative correlation of the CTAC with total ammonia change. An approximately 10% total ammonia reduction could offset the decline in CTAC attributed to a 30–40% sulfate or 20–30% total nitrate reduction in Wuhan. This study indicates that the combined control of SO2 + NOx (NO+NO2) remains the preferred way to reduce inorganic particles in Central China at present, despite a tendency of the ambient chemical state moving towards effective ammonia control. However, as the CTAC approaches 0%, the effectiveness of ammonia and NOx reduction measures targeting wintertime PM2.5 can greatly exceed that observed during the 2012–2018 period in Central China.