N2O emissions

Upscaling Annual NO and N2O Emissions to Regions 100km X 100km)... 

Stored manure, manure on floors of housing facilities using bedded pack, or drylot manure are not significant sources of N2O emissions, but... 

In the same way, N20 emission in pretreatment process was calculated, whereas N2O emission in this combustion step was taken from references for German waste, it is estimated to be 3.41 kg C02 eq./ton RDF (GWPN20 = 298) [15]. 

Because the operating temperature is lower, FBC units release more N2O than do PC units. Nitrous oxide is a greenhouse gas that absorbs 270 times more heat per molecule than carbon dioxide and as such is likely to come under increased scrutiny in the future. The emissions at full load from coal-fired units are around 65 mg/MJ [0.15 Ib/MBtu], but these increase as load is reduced and furnace temperature falls. Measurements from biomass-fired FBCs have not been made. Combustion processes do not contribute greatly to current U.S. N2O emissions agriculture and motor vehicles account for 86 percent of the total. 

Figure 8.8 shows the results for the fallow periods. These lasted 5 to 11 weeks and were weedy. The soil was generally aerobic, and moderate amounts of NOs accumulated (7-20 kg N ha ). Moderately high, continuous N2O emissions occurred, apparently during nitrification of mineralized organic N in the topsoil and possibly also during denitrification in the wet subsoil. The flux of N2O was greatest immediately after rainfall and after the field was flooded for rice at the end of the fallow, as a result of denitrification of accumulated NOs". 

Mosier AR, Duxbury JM, Freney JR, Heinemeyer O, Minami K. 1998a. Assessing and mitigating N2O emissions from agricultural soils. Climatic Change 40 7-38. 

N2O contributes to the greenhouse effect with 4% (Schonwiese 1995). N2O emissions from agriculture come from mineral and organic N-fertilisers and from leguminous crops. The emission levels depend on the kind of fertiliser and on the application technique. The N2O emission factors for the most frequently applied forms of mineral N-fertilisers are < 0.5%, for organic manure 1.0 - 1.8% and for N from legumes, about 1% of the fixation rate. 

The following factors may increase N2O emissions, specifically in organic farming systems (Piorr and Werner 1998) ... 

Several authors (Kilian et al. 1997 Kopke and Haas 1997 Piorr and Werner 1998 Unwin et al. 1995) eoneluded on the basis of these arguments that the N2O emission potential per heetare is lower on organic farms than on eonventional farms. 

The literature review on N2O emissions did not lead to a profound basis that would allow final conclusions on farming system effects with respect to N2O emissions. Most information available is based on deduction, while only one study provides quantitative data. Data on N2O net balances, however, is nonexistent. Thus, currently no differences on N2O between the organic and conventional farming systems can be identified. 

Quantitative research results on N2O emissions in different farming systems are scarce. Based on deduction, experts conclude that N2O emissions per hectare tend to be lower on organic farms than on conventional ones, while N2O emissions per kg milk are rather equal or higher respectively. However, due to the fact that almost no quantitative data is available, no definite differences between organic and conventional farming systems can be identified. 

Following existing convention, oxides of nitrogen (NOj,) are considered here to consist of NO and NO2 since N2O generally is treated separately, and in addition, N2O emissions are small compared with those of NO and NO2. The NO, emission index for methane-air flames then is defined here as... 

Nitrous oxide contributes severely to global warming and the depletion of ozone in the stratosphere (Crutzen 1981, Bouwman 1996). Almost 90% of the global atmospheric N2O is formed during the microbial transformation of nitrate (NO ) and ammonia (NH ) in soils and water. In OECD countries the agricultural contribution to N2O emissions is estimated at 58% (IPCC 2001). Soils fertilised with inorganic fertilisers and manure stores are seen as the largest sources (Chadwick et al. 1999, Brown ef al. 2002). 

Flessa, H., Rtiser, R., Dorsch, P., Kamp, T., Jimenez, M., Munch, J.C. and Beese, F. 2002. Integrated evaluation of greenhouse gas emissions from two farming systems in southern Germany. Special consideration of soil N2O-emissions. Agriculture, Ecosystems and Environment 91(1-3 175-189. 

Deep plough-based organic systems may increase energy consumption in agroecosystems (Kouwenhoven ef al. 2002), which is another important indicator of environmental impact. In contrast, mulch-based systems and systems in which manure is left on the soil surface or is shallowly incorporated would enhance N volatilisation losses to the atmosphere. However, compared to ploughing, shallow incorporation (rotovation) of an organic ley did not significantly increase cumulative nitrous oxide (N2O) emissions from soil (van der Weerden ef al. 2000). 

Seitzinger, S.P., Kroeze, C., and Styles, R.V. (2000) Global distribution of N2O emissions from aquatic systems natural emissions and anthropogenic effects. Chemosphere Global Change Science 2, 267-279. 

Several different approaches are being examined to reduce N2O emissions. Primary measures are aimed at preventing N2O from being formed. Secondary and Tertiary abatement measures have focused on two locations for N20 removal 1) directly downstream of the ammonia oxidation catalyst and 2) in the tail gases (see Figure 9.2 or Figure 9.3)222. 

Some issues regarding technological achievements, with or without zeolites, by catalysis for pollution abatment have been reviewed recently (2, 3), as well as an review of the best available technologies for reducing NOx and N2O emissions from industrial activities (4). 

Calculated lifetimes of N2O in combustion products indicate that for temperatures above 1500 K, the lifetime of N2O typically is less than 10 ms, suggesting that except for low temperature combustion, as found in fluidized bed combustors and in some post-combustion NO removal systems, N2O emissions should not be significant, a conclusion that is in agreement with the most recent measurements of N2O emissions from combustion devices. 

Jin, X., and Gruber, N. (2003). Offsetting the radiative benefit of ocean iron fertilization by enhancing N2O emission. Geophys. Res. Lett. 30(24), 2249, doi 10.1029/2003GL018458. 

High precision time series of atmospheric N2O have been successfully used to quantify N2O emissions from temporal upweUing events along the coast off CaU-fomia (Lueker et al., 2003) and from the Southern Ocean (Nevison et al., 2005). This seems to be a promising approach, however, it depends on the existence of high-precision N2O time series, which are at the moment only available at a few coastal sites (Prinn et al., 2000). 

Bengal), Barnes et al. (2006) found no seasonality. However, N2O emissions were negatively correlated with tidal height indicating that N2O from sediment pore-water was released during hydrostatic pressure drop toward low water. A reahstic estimate of the N2O emissions from mangroves is not possible at the moment because of the very small number of available measurements. 

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