Comment on acp-2022-657

Simultaneous reduction of NOx emission and SOx emission aided by improved efficiency of a Once-Through Benson Type Coal Boiler

We describe the recent developments of Environment Canada's atmospheric mercury model (GRAHM) and its application to the intercontinental source-receptor relationships of mercury. The model includes 2188 Mg yr-1 global anthropogenic emissions, 1600 Mg yr-1 terrestrial emissions and 2600 Mg yr-1 oceanic emissions). Transport, chemical transformation and deposition of Hg0, Hg(II) and Hg(p) are simulated in GRAHM within a meteorological assimilation and forecasting system. Current version of the GRAHM includes GEM oxidation by ozone in the troposphere and halogen oxidation in the Polar and the marine boundary layers. It also includes dynamic exchange of mercury fluxes at air-snow/ice interface. The model simulates springtime atmospheric mercury depletion events (AMDEs) and the net accumulation of mercury in snow in the Polar Regions. We performed one reference simulation with emissions as above and four perturbation simulations with 20% reduced anthropogenic emissions over East Asia, South Asia, Europe and North Africa and North America. 20% reduction in anthropogenic emissions of mercury over East Asia, South Asia, Europe and North Africa and North America represent 7.7%, 1.6%, 2.5% and 1.3% reduction in global anthropogenic emissions respectively. The deposition over East Asia, South Asia, Europe and North America are reduced by 13.5%, 7.9%, 8.3% and 4.3% due to the emission reductions within the same regions. Deposition in North America is found to be most affected by the emission reductions in other regions and the deposition in East Asia is least affected by outside reductions. The deposition in the Arctic is nearly equally sensitive to the unit emission reductions in Europe and East Asia and is most sensitive in springtime due to the high deposition related to AMDEs.

In this study, real voyage data and ship specifications of a general cargo ship are employed, and it is assumed that diesel generators are replaced with hydrogen proton exchange membrane fuel cells. The effect of the replacement on CO2, NOX, SOX, and PM emissions and the CII value is calculated. Emission calculations show that there is a significant reduction in emissions when hydrogen fuel cells are used instead of diesel generators on the case ship. By using hydrogen fuel cells, there is a 37.4% reduction in CO2 emissions, 32.5% in NOX emissions, 37.3% in SOX emissions, and 37.4% in PM emissions. If hydrogen fuel cells are not used instead of diesel generators, the ship will receive an A rating between 2023 and 2026, a B rating in 2027, a C rating in 2028–2029, and an E rating in 2030. On the other hand, if hydrogen fuel cells are used, the ship will always remain at an A rating between 2023 and 2030. The capital expenditure (CAPEX) and operational expenditure (OPEX) of the fuel cell system are USD 1,305,720 and USD 2,470,320, respectively, for a 15-year lifetime, and the hydrogen fuel expenses are competitive at USD 260,981, while marine diesel oil (MDO) fuel expenses are USD 206,435.

Influences of future anthropogenic emission changes in China on atmospheric nitrogen deposition in the northwestern Pacific.

Aerosol emissions from human activities are extensive and changing rapidly over Asia. Model simulations and satellite observations indicate a dipole pattern in aerosol emissions and loading between South Asia and East Asia, two of the most heavily polluted regions of the world. We examine the previously unexplored diverging trends in the existing dipole pattern of aerosols between East and South Asia using the high quality, two-decade long ground-based time series of observations of aerosol properties from the Aerosol Robotic Network (AERONET), from satellites (Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI)), and from model simulations (Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). The data cover the period since 2001 for Kanpur (South Asia) and Beijing (East Asia), two locations taken as being broadly representative of the respective regions. Since 2010 a dipole in aerosol optical depth (AOD) is maintained, but the trend is reversed—the decrease in AOD over Beijing (East Asia) is rapid since 2010, being 17% less in current decade compared to first decade of twenty-first century, while the AOD over South Asia increased by 12% during the same period. Furthermore, we find that the aerosol composition is also changing over time. The single scattering albedo (SSA), a measure of aerosol’s absorption capacity and related to aerosol composition, is slightly higher over Beijing than Kanpur, and has increased from 0.91 in 2002 to 0.93 in 2017 over Beijing and from 0.89 to 0.92 during the same period over Kanpur, confirming that aerosols in this region have on an average become more scattering in nature. These changes have led to a notable decrease in aerosol-induced atmospheric heating rate (HR) over both regions between the two decades, decreasing considerably more over East Asia (− 31%) than over South Asia (− 9%). The annual mean HR is lower now, it is still large (≥ 0.6 K per day), which has significant climate implications. The seasonal trends in AOD, SSA and HR are more pronounced than their respective annual trends over both regions. The seasonal trends are caused mainly by the increase/decrease in anthropogenic aerosol emissions (sulfate, black carbon and organic carbon) while the natural aerosols (dust and sea salt) did not change significantly over South and East Asia during the last two decades. The MERRA-2 model is able to simulate the observed trends in AODs well but not the magnitude, while it also did not simulate the SSA values or trends well. These robust findings based on observations of key aerosol parameters and previously unrecognized diverging trends over South and East Asia need to be accounted for in current state-of-the-art climate models to ensure accurate quantification of the complex and evolving impact of aerosols on the regional climate over Asia.

Recent Chinese air pollution actions have significantly lowered the levels of fine particulate matter (PM2.5) in North China via controlling emissions of sulfur dioxide (SO2) and nitrogen oxides (NO x ) together with primary aerosols, while the emissions of another precursor, ammonia (NH3), have not yet been regulated. This raises a question that how effective the NH3 emission controls can be on the mitigation of PM2.5 pollution along with the reduction of SO2 and NO x emissions. Here we use a regional air quality model to investigate this issue focusing on the PM2.5 pollution in North China for January and July 2015. We find that the efficiency of the PM2.5 reduction is highly sensitive to the NH3 emission and its reduction intensity. Reductions in the population-weighted PM2.5 concentration (PWC) in the Beijing–Tianjin–Hebei region are only 1.4–3.8 μg m−3 (1.1%–2.9% of PM2.5) with 20%–40% NH3 emission reductions, but could reach 8.1–26.7 μg m−3 (6.2%–21%) with 60%–100% NH3 emission reductions in January 2015. Besides, the 2015–2017 emission changes (mainly reduction in SO2 emissions) could lower the PM2.5 control efficiency driven by the NH3 reduction by up to 30% for high NH3 emission conditions, while lead to no change or increase in the efficiency when NH3 emissions become low. NO x emission reductions may enhance the wintertime PM2.5 pollution due to the weakened titration effect and can be offset by simultaneously controlling NH3 emissions. Our results emphasize the need to jointly consider NH3 with SO2 and NO x emission controls when designing PM2.5 pollution mitigation strategies.

Analysis of combustion and emissions characteristics of a DI diesel engine fuelled with diesel/biodiesel/glycerol tert-butyl ethers mixture by altering compression ratio and injection timing

Reduction of nitrate (NO3) and ammonia (NH3) emission to the environment has, since the 1980s, been targeted by Danish environmentally friendly regulations. Nitrate pollution of aquifers and surface waters caused by farming was observed at the start of the 1980s, and in the mid-1980s, NH3 emission was known to contribute reactive nitrogen (N) to the environment. Manure is a significant source of plant nutrient loss, because there might be a lack of economic incentives and knowledge for the farmers to obtain a high nutrient utilization of the manure. This article gives a presentation of the initiatives and regulations intended to reduce the emission, the actual reduction in emission achieved, and the effect of the regulation on farmers' economy, which is considered important in the discussion about how we can reduce pollution of the environment and at the same time have an economically sustainable agriculture. In the 1980s, the Ministry of Environment and the farmers' union agreed on launching a “good agricultural practice” program, aimed at reducing N loss by increasing N use efficiency and reducing fertilizer N import. This had no or limited effect on emission, and in the late 1980s, regulations were introduced with mandatory stipulations on manure storage capacity, application of manure during the growing season, and limitation on the number of animals per hectare agricultural land (Harmony Rules). Early introduction of the Harmony Rule in 1985 has since prevented very high local surpluses of N and phosphorus. In 1993/94, legislation was introduced for a system of farm-specific N quotas and minimum requirements for utilization of N in animal manure, controlled by the Ministry of Agriculture and Environment based on fertilizer accounts for each farm. The legislation requirements for utilization of N in manure were based on research at the universities and a large number of trials on commercial farms conducted by the Danish extension service (SEGES). These convinced most farmers of the potential manure N fertilizer efficiency. From 1993/94, the N quotas were based on optimal N levels to the crops, but from 1998/99 to 2016/17, they were reduced to 10–20% below the economically optimal rate. From 2016/17, the reduced N quotas were replaced by an expansion of the catch crop requirement in the legislation. The effect is that NO3- leaching has been reduced by 45% by restricting manure application to the period with crop demand for plant nutrients, by undersupplying with N as related to the economically optimum application rate, and by compulsory cultivation of crops that take up N during most of the year. Regulation has resulted in a 51% reduction in NH3 emission from livestock buildings, manure stores, and manure application. In 2020/21, the required N fertilizer efficiency of manure N (equivalence to N in mineral fertilizers) is 75% of N in cattle slurry and 80% for pig slurry, higher than in any other countries known to us. The N quotas are based on the optimal level, and the requirement for compulsory catch crops is 40–50% for the main part of the country. The farmers can use alternatives to catch crops like a reduced N quota or early establishment of winter cereals. The revision of the “regulation system” was intended to improve the economy of the crop production, but the effect was that complexity and volume of legislation have increased significantly, without much effect on farmers' economy. It is recommended that the regulation is kept simple and that it reflects the processes leading to plant uptake and emissions.

As an exercise in model sensitivity, the Environmental Protection Agency's regional oxidant model (ROM) was run for several simulations to study the impact of across‐the‐board reductions in anthropogenic volatile organic compound (VOC) and NOx emissions on the photochemical environment of the eastern United States. The ROM, which simulates most of the physical and chemical processes responsible for the formation of O3 on regional scales, was used to simulate a widespread high O3 episode in the eastern United States. Separate simulations were performed over the period July 2–10, 1988, for each of the sensitivity runs. An operational evaluation and several model diagnostics were performed on the base case simulation. The sensitivity runs reduced anthropogenic NOx and VOC emissions separately and in combination in increments of 25% of full scale emissions. Biogenic emissions were held constant across all sensitivity tests. Seventeen of the potential 25 nodes of the NOx, VOC emissions reduction matrix were simulated. In the analysis the modeled domain (the eastern half of the United States) is subdivided into several chemically coherent regions. Several chemical species, including afternoon average concentrations of O3, PAN, HNO3, OH, and HO2 + RO2, are examined to gain an understanding of how the reduction in emissions affected the overall chemical system for each sensitivity test. Results are presented as a series of statistical and graphical displays illustrating the response of the system within the selected subdomains to the emission reductions.

Ammonia emissions and mitigation from a concrete yard used by cattle

Kaohsiung Harbor is adjacent of Kaohsiung City, a metropolis that has long suffered from air pollution. The annual releases of air pollutants such ad SOx, NOx, COx, PM, and HC from stationary and land-based mobile sources in Kaohsiung City have recently been thoroughly studied. However, emissions from vessels (another mobile source) have not been extensively investigated and understood. Evaluation ship emission in Kaohsiung’s harbor waters may be crucial to controlling air pollution in Kaohsiung city. This work, therefore, estimates the emission of air pollutants from in 1997 and evaluates their contributions to total emission in the city of Kaohsiung. Various approaches of estimation based on different databases and assumptions yielded different results. The emission of NOx, PM, HC, and CO were 13786, 341, 713, 1684, ton/yr, respectively, from vessels in Kaohsiung’s harbor waters, as estimated by Ship Operation method/Cargo method. Emissions of SOx and NOx were 4055 and 9125 ton/yr, respectively according to Lloyd’s emission factor/fuel consumption approach and emission of SOx and NOx were 4837 and 5114 ton/yr, respectively, according to ship exhaust measurement/calculation. The contribution of SOx and NOx from shipping in the Kaohsiung city area were significant. Around 10~20% of NOx and 10~12% of total SOx emissions in Kaohsiung city were attributed to ships in the harbor waters of Kaohsiung.

Trends of sulfur and nitrogen deposition from 2003 to 2017 in Japanese remote areas

BackgroundIn Europe, ammonia (NH3) emissions strongly contribute to fine particulate matter (PM2.5) pollution and associated premature human mortality. The National Emission Ceilings Directive 2016/2284/EU has set an obligation for all European Union countries to reduce the NH3 emissions by 6%, relative to 2005, by 2020. This study aims to assess the costs and benefits of four NH3 emission abatement options for the compliance of the agricultural sector with the commitments of the European air quality regulatory framework. A regional atmospheric model (WRF/Chem) was used to assess the effects of regulating NH3 emissions reductions on PM2.5 concentrations over Europe. Non-market valuation techniques (value of statistical life) were used to monetize the associated health outcomes.ResultsWe calculated that 16 out of the 28 EU member states exceeded their 2020 NH3 emission ceilings in 2016. The highest exceedances from the 2020 emission commitment level occurred in Latvia (15%), Germany (12%) and the UK (12%). Simulation of the required NH3 emission reduction by WRF/Chem showed that relatively large reductions in PM2.5 concentrations occur over central-western Europe and the UK. The largest health benefits (> 5% reduction in premature mortality) were found for Scandinavia. The economic benefit from avoided premature deaths over Europe amounts to 14,837 M€/year. The costs of four NH3 emission abatement options, where each would fully achieve the required emission reduction, range from 80 M€/year for low nitrogen feed to 3738 M€/year for low-emission animal housing, with covered manure storage (236 M€/year) and urea fertilizer application (253 M€/year), in between.ConclusionOur analysis indicates that the costs of compliance by the agricultural sector with the commitments of the European air quality regulations are much lower than the economic benefit. Thus, much more ambitious reduction commitments for NH3 emissions could be applied by the EU-28. The monetization of the health benefits of NH3 emission abatement policies and the assessment of the implementation costs can help policy-makers devise effective air pollution control programmes.

Volumetric combustion has been developed to realize a high substitution ratio of biomass in co-firing boilers, which features an intensive flue gas internal recirculation inside furnace. However, the characteristics of NOx and SOx emissions in large-scale boilers with volumetric combustion were not fully clear. In this paper, an Aspen Plus model of volumetric combustion system was built up based on a co-firing boiler. In order to characterize the reductions of NOx and SOx, three biomass substitution ratios were involved, namely, 100% biomass, 45% biomass with 55% coal, and 100% coal. The effects of flue gas recirculation ratio, air preheating temperature, oxygen concentration, and fuel types on pollutants emission in the volumetric combustion system were investigated. According to the results, it was concluded the higher substitution ratio of biomass in a co-firing boiler, the lower emissions of NOx and SOx. Moreover, flue gas internal recirculation is an effective pathway for NOx reduction and an increased recirculation ratio resulted in a significant decreasing of NOx emission; however, the SOx increased slightly. The influences of air preheating temperature and O2 concentration on NOx emission were getting weak with increasing of recirculation ratio. When 10% or even higher of flue gas was recycled, it was observed that almost no NOx formed thermodynamically under all studied conditions. Finally, to reach a low emission level of NOx, less energy would be consumed during biomass combustion than coal combustion process for internal recirculation of flue gas.

Irrigation and lava meal use reduce ammonia emission and improve N utilization when solid cattle manure is applied to grassland