Abating industrial nitrous oxide emissions in the United States: legal, economic and scientific dimensions

A state-of-the-art review on nitrous oxide control from waste treatment and industrial sources

It is well known that N2O has a very significant impact on the greenhouse effect. Although N2O is not the major contributor to the global warming, while it could stay in atmosphere for about 150 years, and its global warming potential (GWP) is about 2.5 and 310 times as that of CH4 and CO2, respectively. The main source of N2O emission from chemical industries is originated from the process of adipic/nitric acid production. The emission of N2O due to adipic acid production in China is about 0.48∼0.72 million tons per year based on the mass ratio between N2O emission and adipic acid production, which is equivalent to 150∼250 million tons CO2 emission. However, there are few reports on economically reusing N2O from flue gas by direct oxidation method. Therefore, a series of catalysts applied on catalytic N2O conversion to NO for potential production of nitric acid from flue gas have been prepared by co-precipitation method. The basic property of catalysts was characterized by BET, laser particle size analyzer, FT-IR, TG/DTA, and CO2-TPD, etc. The catalyst’s performance was evaluated in a fixed-bed reactor with mixture of 40%(v)N2O+40%(v)N2+20%(v)O2 under 3000 h −1 space velocity and 0.1MPa system pressure. Results showed that catalysts of Pt/Cu-Zn-O and Pt/Zr-Zn-O have good selectivity on NO production, which was about 10% and 15%, respectively, in the temperature range from 550°C to 650°C. The basic experimental results show that it is a promising method to be applied for N2O reuse in adipic acid production and nitric acid industries and also provide the basis for further relative theoretical and experimental studies.

Recently, the control of non-CO2 greenhouse gases has attracted interest as a way to prevent global warming. Several research studies on the development and assessment of technologies to control CH4 and N2O emissions by human activities are under way. In the wastewater treatment field, the development of anoxic/oxic processes and the introduction of bacteria that effectively prevent N2O emission have been studied. Moreover, it has been clarified that eco engineering technologies such as artificial wetlands and soil trench systems are very effective, especially in developing countries. As for landfill disposal, CH4 oxidation by cover soil and the use of CH4 gas as a source of energy have very effectively reduced the emission of CH4. In the combustion field, it was clarified that N2O emissions vary according to the structure of each combustor and its operational conditions. And research and development concerning combustors and their optimum operational conditions are under way. Concerning automobile sources, characteristics of N2O emission from gasoline fueled vehicles installed with a catalyst were examined. Three way catalysts and so on are now being developed. Chemical industries, especially adipic acid production are another non-negligible N2O source, and cracking process related countermeasures have been applied. CH4 and N2O emissions from agricultural land are strongly dependent on the oxidation-reduction environment of soil and on fertilization, so they must be suitably managed. The development and management of ruminants feeding and suitable treatment of animal waste are very important ways to control CH4 and N2O from livestock. Research projects to improve the CH4 and N2O emission-absorption inventory, and to estimate the suitable technologies to control CH4 and N2O emission are now in progress. Combining these projects appropriately will develop technologies and systems and will make great contributions to the control of the emission of GHGs and to global warming.

<div class="htmlview paragraph">This is an optimization study on the use of filtered exhaust gas recirculation (EGR) to reduce the NO emissions of diesel engines. Control of the particulate emissions and provisions for filtered EGR were achieved by an Aerodynamically Regenerated Trap (ART) with collection efficiencies in the order of 99%. The amount of EGR was regulated to provide for substantial NO reduction, without unacceptably decreasing the thermal efficiency of the engine or increasing the CO emissions. EGR regulation was accomplished by monitoring the injection pump setting which was correlated to the fuel flow rate, the speed of the engine, the amount of EGR flow, and the ambient air temperature. Through these parameters, the mixture strength expressed as the equivalence ratio, ϕ, was calculated and related to the power output of the engine. Thus, a map of engine performance parameters was generated and related to measured NO and CO emissions. A series of road tests showed that EGR most effectively reduces NO emissions at high ϕ's (by a factor of two at 20% EGR) which, however, is accompanied by an increase in CO emissions by a factor of two, and a penalty in fuel economy by 8%. Benefits and losses can be optimized by automatically varying the level of EGR, using feedback from the aforementioned engine parameters. An algorithm was developed to govern the electrically controlled EGR valve and tests showed that the NO levels decreased by 30%, while the CO increased by 30%, showing no penalty in fuel economy. The resulting specific NO and CO emissions were well within the current US EPA standards.</div>

The composite fuel of coal gangue and biomass is expected to increase the utilization rate of solid waste and compensate for the disadvantages of separate fuels. However, the NO and SO2 emissions from this composite fuel during the combustion process are a concern, but there are few studies on it. In this paper, corn cobs and wheat straws, typical agricultural biomass discarded in North China, and coal gangue from the mine in Xilingol, China, were selected for co-combustion in a fluidized bed. The emission characteristics of NO and SO2 were studied by changing the ratio of biomass to coal gangue and the combustion temperature. Studies had shown that: to a certain extent, mixing biomass, and coal gangue can reduce the NO and SO2 emissions, and mixing 20% of biomasses had the best effect on NO and SO2 emissions reduction. The SO2 emission reduction effect of wheat straws was better than that of corn cobs, and the NO emission reduction effect of corn cobs was better than that of wheat straws. The NO emissions of wheat straws and corn cobs added to the coal gangue were 6.45% and 7.93% less than those of coal gangue alone. The SO2 emissions of wheat straws and corn cobs added to the coal gangue were 27.45% and 25.94% less than those of coal gangue alone. Both NO and SO2 emissions decreased with the growth of the biomass rate; NO and SO2 emissions increased with the growth of the combustion temperature.

The paper shows an energy-saving effect based on on the organic Rankine cycle (ORC) when using thermal secondary energy resources (SER) for the production of non-concentrated nitric acid (NNA).The production of non-concentrated nitric acid in the Russian Federation is carried out on two types of aggregates: UKL-7 and AK-72. Each unit currently has upgraded versions: UKL-7M and AK-72M, in which the design production capacity has been increased. Nitric acid production at the UKL-7 unit is carried out at a uniform pressure of 0.716MPa at the stages of ammonia conversion and absorption of nitrous gases by water. Acid production on the AK-72 unit is carried out at different pressures at the stages of ammonia conversion and absorption. Ammonia conversion on the AK-72 unit proceeds at a pressure of 0.42 MPa, whereas the absorption process is carried out at a pressure of 1.1 MPa. In this paper, by way of example, the UKL-7 unit is considered. A useful use of SER based on the ORC is to use the heat of compressed air after the axial compressor, which is released into the environment. In this case, the heat of compressed air is used for heating and evaporation of freon in the evaporator of the cycle, heating feed water in front of the deaerator in order to reduce steam consumption. It is also proposed to use the heat of condensation of freon after the turboexpander to evaporate ammonia, which also leads to a reduction in steam consumption. It is proposed to use freon R600a in the ORC.The calculation results show that when using the heat of compressed air and the heat released in the EGU condenser, it is possible to generate about 2,613,600 kWh/ year of electricity, as well as save 39,630 tons of steam per year.

Advances in accounting methodology of nitrous oxide emissions from the adipic acid industry

Global warming is of increasing scientific, community, commercial and political interest, in particular, the assessment, management and mitigation of contributing sources and sinks to global climate change. Global mean surface temperatures have increased by approximately 0.76 ± 0.19°C since pre-industrial times, primarily a result of increased atmospheric concentrations of greenhouse gases, CO2, N2O, CH4, O3 and halocarbons, which have increased as a result of human activities (Forster and Ramaswamy, 2007); Since global warming potentials are higher for N2O (298) and CH4 (25) as compared to CO2 (1) (Forster et al., 2007), their high radiative efficiency and long atmospheric residency results in considerable global warming impact. Anthropogenic activities contribute a large proportion of N2O and CH4 emissions, in particular, the use of N fertilizer for crop production, and the utilisation of wet and flooded soils, which produce large quantities of N2O and CH4 , respectively (Mosier et al., 2004). The aim of the PhD thesis was to gain understanding on the quantities of N2O and CH4 emissions and factors affecting their emissions in two systems, mangrove forest sediments and sugarcane soils in subtropical coastal Australia, to enhance predictive power for emissions estimates and to improve mitigation options. While sugarcane cropping is included in the National Greenhouse Gas Inventory (NGGI) (AGO, 2005a) , we argue that mangroves should also be included in the NGGI if they are impacted by human activities, and constitute a significant source of greenhouse gases. Thus, mangrove sediments within an Australian subtropical catchment, characterized by high urban density and varied nutrient inputs, were studied to provide first evidence of their variation and potential contribution to greenhouse gas emissions. Additionally, farm management options, including water and N fertilizer applications, were monitored in sugarcane soils to assess N2O emissions response and mitigation potential. To achieve these aims, three tools were used to estimate the spatial and temporal variability in N2O and CH4 fluxes, including closed-chambers, microsens ors, and modelling. Emissions measured in situ were correlated to numerous site variables to determine the extent of associations and indicate causalities. Mangrove sediments acted mostly as N2O and CH4 emissions sources, although the magnitude of emissions varied significantly between seasons, and between estuary and coastal sites, depending on substrate. Highest CH4 emissions were detected at estuary sites during summer months, when sediment temperature, and total C and N in sediments was high, while the magnitude of N2O emissions became important during winter months when overall CH4 emissions were low. Sites with high N2O and CH4 emissions were comparable to other worldwide estuarine and coastal mangrove sediments receiving elevated nutrient inputs from natural (guano) and anthropogenic sources (sewage). Under high nutrient conditions in estuary mangrove sediments, microsensor profiles demonstrated that although denitrification produced more N2O, nitrification was the more important process for sediment N2O emission, highlighting the importance of considering N2O processes, production rates, and their location in sediments with regard to diffusive transport to the sediment surface. Sugarcane soils acted as major N2O sources, with seasonal variation in emissions corresponding to availability of soil mineral N, high soil moisture and temperatures. Farm management practices showed variable effects on N2O emissions; while N2O emissions increased with fertiliser N rates, split fertilizer application showed little reduction of N2O emissions. Short-term flooding significantly increased N2O emissions, with magnitude and duration of emissions peaks proportional to moisture availability and mineral N concentrations in soils. Upscaling of N2O emissions to daily values showed reasonable comparison to preliminary model simulations, suggesting modelling could be further explored to improve decision making at farm-management level. Extensions to this model e.g. Wetland-DNDC, could also be applied to mangrove sites. In this instance, the development of an assessment platform to characterize sites, including quantification of site disturbances to nutrient input and hydrology, would assist decision-support and monitoring of changes associated with anthropogenic activities. Accurate representation of N2O and CH4 fluxes within subtropical mangrove sediments and sugarcane soils at farm and catchment levels would thus require (i) assessment of the relative contributions of individual trace gases to net CO2-equivalent emissions, (ii) a careful sampling design of in situ measurements at site-level which captures considerable temporal and spatial variation of N2O and CH4 emissions, and (iii) the integration of model requirements at site-level planning, wherever possible, to improve the confidence of simulated data at larger scales, and to strengthen decision-support systems.

The present study aimed at the investigation of N2O reduction technologies and of the possibility of carrying out technological development as future project, based on the present emission sources and inventory. The total emission in Japan of N2O was estimated to be 82.5 Gg-N2O/year, which consists of 8.28 from fossil fuel combustion, 6.95 from waste incineration, 22.5 from transportation, 28.3 from the chemical industry, 2.1 from sewage treatment, 6.3 from agriculture, and 7.1 Gg-N2O/year from livestock excrement. If the abatement technologies discussed in this study were developed and applied, 69% reduction of N2O emissions would be expected, which would be equivalent to about 25 Gg-N2O/year. The future reduction including of the reduction in adipic acid production would give 46 GgN2O/year, which is 3.88 Tg-CO2/year and about 1.3% of CO2 emission in Japan at 1990. As a common reduction technology to be developed, we recognize that the catalysts in flue gas treatment for combustion and incineration processes and for automobiles should be important.

In order to explore the characteristics of N2O emissions from winter wheat fields in the Loess Plateau under different farming methods and nitrogen levels, the dynamic changes in N2O emissions from rain-fed winter wheat fields were quantified using static box-gas chromatography. Winter wheat 'Xiaoyan22' was used as the material, and a two-factor split area design was adopted. The conventional tillage (CT), straw incorporated into soil (SM), and flat film mulching (FM) were assigned as the main plot, and three nitrogen fertilizer rates (no nitrogen fertilization, 20% nitrogen reduction (144 kg·hm-2), and conventional nitrogen application (180 kg·hm-2)) were assigned as a split plot. Taking CT as a control, the effects of FM and SM on soil N2O emissions under different nitrogen rates were assessed. Furthermore, the correlation between relevant environmental factors and N2O emission flux were analyzed, and N2 emissions were estimated using empirical formulas. The results showed the following:the N2O emissions from the soil of each nitrogen treatment occurred within 20 days, and N2O emission flux peaked within two weeks post-fertilization. The average N2O flux, the total N2O emissions, and the global warming potential of N2O were 1.92-22.75 μg·(m2·h)-1, 0.10-0.46 kg·hm-2, and 26.72-122.15 kg·hm-2, respectively. The N2O emission coefficient of fertilizer nitrogen was 0.05%-0.28%. The total N2 emissions ranged from 0.70-1.82 kg·hm-2. The N fertilization and film mulching significantly increased the N2O emission flux (P<0.05) and the cumulative N2O emissions (P<0.05); however, SM marginally reduced the total N2O emissions. The N2O emission coefficient and global warming potential of fertilizer nitrogen under FM were significantly higher than those under CT and SM (P<0.05). The N2O emissions without nitrogen treatment were only significantly positively correlated with soil water-filled pore spaces (WFPS) (P<0.05); the N2O emissions in the N fertilization condition were significantly positively correlated with WFPS, ω(NO3--N), ω(NH4+-N), and 0-5 cm soil layer temperature (P<0.05). Overall, under the condition of no fertilization, water was the main factor to control the nitrogen transformation and soil N2O emission; nevertheless, under the N fertilization condition, both nitrification and denitrification contributed to the N2O emissions in the rain-fed winter wheat fields. Film mulching practice and nitrogen application markedly increased the N2O emissions, fertilizer nitrogen emission coefficient, and global warming potential in the rain-fed winter wheat fields. Nonetheless, straw incorporated into the soil resulted in a marginal reduction in N2O emissions.

Combination of water-saving irrigation and controlled-release fertilizer application reduced gaseous nitrogen loss in single-crop paddy soil.

Experiments were carried out in a drop tube furnace to investigate the effects of biomass/coal co-firing and air staging on NO emission and combustion efficiency. NO and CO emissions along the height of the furnace were monitored by a gas analyzer, and the content of unburned carbon (UBC) in fly ash was also tested. Results showed that NO emission from straw or wood combustion only account for 1/3 or 1/2 that from coal combustion, respectively. Under the conditions of biomass co-firing, the increase in blending ratio had a positive effect on the reduction of NO emission and combustion efficiency. Moreover, results of air-staging combustion showed that for coal combustion, air staging notably reduced NO emission and combustion efficiency. For biomass combustion, the effect was slight. Synergetic analysis indicated that there was an optimum biomass co-firing ratio around 0.4, when the positive synergetic effects on reducing NO emission and UBC were the most significant. When the co-firing ratio exceeded this optimum value, further increasing the co-firing ratio had little influence on NO emission and combustion efficiency. After air staging was adopted, the degree of synergetic effect on NO emissions was reduced while that of UBC was increased.

How does deep-band fertilizer placement reduce N2O emissions and increase maize yields?

The purpose of this project was to explore the emissions, combustion, and performance effects of running a gasoline/ethanol fuel mixture of 20 percent by volume (E20) in a fuel-injected, two-stroke engine. The engine was operated at five engine speeds that corresponded with the EPA 5-mode emissions test for snowmobile engines. Single parameter sweeps were conducted along with a preliminary recalibration of the test engine at two E0 target values (lambda and mid-pipe temperature) using E20 fuel. Baseline testing showed that running E20 fuel produced a leaner air/fuel mixture compared to E0, resulting in higher lambda values for all modes and higher mid-pipe temperatures in modes 1 and 2. The increase in lambda resulted in lower CO and THC emissions at all modes and an increase in formaldehyde and acetaldehyde emissions. An increase in CO2 and NO emissions followed the trend of increasing mid-pipe temperature at modes 1 and 2. Single parameter sweeps were performed by changing one engine parameter at a time and sweeping over a range of predetermined values. Engine parameters included injection time (duration), injection end angle, and ignition timing. Increasing the amount of fuel injected into the combustion chamber decreased lambda values, decreased mid-pipe temperatures, increased CO and THC emissions, and decreased CO2, NO, formaldehyde, and acetaldehyde emissions. Advancing the ignition timing decreased mid-pipe temperatures which decreased CO2, NO, formaldehyde, and acetaldehyde emissions. CO and THC emissions were increased with the advancement of ignition timing. Opposite trends could be seen with retarding ignition timing, except with NO emissions where retarding ignition timing also resulted in a reduction in NO emissions. Adjusting the injection end angle showed little effect on performance, but increases in CO2, NO, formaldehyde and acetaldehyde emissions were seen at large advances of degrees. Recalibration of injection parameters for E20 fuel to meet E0 baseline lambda values was performed by increasing the injection timing values in the ECU. This created a richer mixture at all modes when compared to the E20 baseline test, while some modes were still leaner than stoichiometric. Matching lambda values resulted in mid-pipe temperatures that were still higher than the E0 baseline test in modes 1 and 2. CO emissions were still lower in all modes except in mode 3 as well as THC emissions except for an increase of two percent in mode 1. CO2 and NO emissions saw a decrease in mode 1 although both values were still higher

Influence of pruning waste biochar and oyster shell on N2O and CO2 emissions from Japanese pear orchard soil