Greenhouse gas emissions and mitigation potential from fertilizer manufacture and application in India Reyes Tirado1 *, S. R. Gopikrishna2, Rajesh Krishnan2 and Pete Smith3 1

Greenpeace Research Laboratories, School of Biosciences, Innovation Centre Phase 2, Rennes Drive, University of Exeter, Exeter EX4 4RN, UK 2 Greenpeace India, 60 Wellington Street, Richmond Town, Bangalore 560025, India 3 Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, UK

Synthetic nitrogen (N) fertilizers, by both very energy-intensive manufacture and inefficient N use in farm soils, contribute rationally to emissions of greenhouse gases (GHGs) and, thus, climate change. India consumes !14Mt of synthetic N per year, of which about 80 per cent is produced, and is the second-largest producer and consumer in the world, after China. We estimate that GHG emissions from synthetic N fertilizer in India reached !100Mt of carbon dioxide equivalent (CO2-e) in 2006/2007; about half of these emissions resulted from the 11Mt of synthetic N produced in the country that year (48Mt of CO2-e) and the other half resulted from the 14Mt of N applied to Indian farm soils in the same year (51Mt of CO2-e, ranging between 28 and 163Mt of CO2-e). Emissions from synthetic N fertilizers represent 6 per cent of India’s total anthropogenic emissions, comparable to cement industry and to the whole road transport system. There is significant potential to mitigate these emissions: savings from increased N use efficiency and from shifting away from synthetic fertilizer could reduce total fertilizers emissions to 37Mt of CO2-e, and the contribution of fertilizers to India’s emissions would drop from 6 to 2 per cent. Keywords: climate change mitigation potential; ecological farming; greenhouse gas emissions; nitrous oxide; synthetic nitrogen fertilizer

Introduction Nitrogen (N) fertilizer manufacture and application contribute significantly to emissions of greenhouse gases (GHGs) and, thus, climate change. The manufacture of N fertilizers is very fossil-fuel intensive and thus its contribution to emissions through CO2 is very high. The application of N fertilizer to farm soils also emits the potent GHG nitrous oxide (N2O). Globally, about 6 per cent of total human-induced GHG emission originates from both N fertilizer manufacture and application to farm soils (Bernstein et al., 2007; Smith et al., 2007). Currently, close to 100Mt of synthetic N fertilizer is consumed globally every year, a 10-fold increase since the 1960s. But fertilizer use in many countries is largely inefficient,

because much of this N is lost to air, water and land. N losses are involved in a cascade of environmental and human health problems, from climate change and dead zones in the oceans to cancer and reproductive risks (Galloway et al., 2008). The urgent need to understand anthropogenic N fixation and reduce N losses is especially important in countries that are experiencing rapid industrial change and massive increases in N fertilizer production and use (Vitousek et al., 2009). India is the second-largest producer and consumer of N fertilizer in the world, after China, with close to a 15 per cent share of the global total (International Fertilizer Industry Association (IFA), 2008). In some Indian regions (e.g. Punjab and Haryana), the overuse and imbalanced use of fertilizers have

*Corresponding author. Email: [email protected] INTERNATIONAL JOURNAL OF AGRICULTURAL SUSTAINABILITY 8(3) 2010 PAGES 176–185, doi:10.3763/ijas.2009.0422 # 2010 Earthscan. ISSN: 1473-5903 (print), 1747-762X (online). www.earthscan.co.uk/journals/ijas

Greenhouse gas emissions and mitigation potential

caused problems of soil degradation and environmental pollution (Prasad and Badarinath, 2006). Synthetic N fertilizer represents 75 per cent of the total reactive N input in the country (Velmurugan et al., 2008). N fertilizers attract government subsidies on plant nutrients, which have resulted in a large increase in national N fertilizer production and consumption and the creation of many industrial fertilizer plants in recent decades (Fertiliser Association of India (FAI), 2007). N consumption increased by more than 32 per cent from 2002 to 2006, and in 2006 India had to import about 20 per cent of its N fertilizer, unable to keep pace with consumption (FAI, 2007). Production has grown at an average rate of 6 per cent annually since 1981, slowing down in the last years, in part limited by fossil fuel availability and the cost of energy. Natural gas is the main fuel and feedstock used for fertilizer production in India, where it accounts for 62 per cent of the energy used in fertilizer manufacture. Less efficient and more polluting fuels, such as naphtha and fuel oil, also represent a large share, 15 and 9 per cent, respectively, of the energy used in fertilizer manufacture (values as of 2006/2007, FAI, 2007). In addition to emissions from manufacture, N fertilizers applied to farm soils result in emissions of N2O, the largest share of N2O emissions worldwide (IPCC, 2007). The concern over N2O emissions arises from its long atmospheric life (166 + 16 years) and its higher global warming potential (296 times that of CO2) (IPCC, 2007). The goal of this paper is to assess the specific GHG emissions from synthetic N fertilizer manufacture and application in India and to estimate the mitigation potential of these emissions with practices that work towards a sustainable farming system.

Methods We compiled data from the Fertiliser Association of India from 1960/1961 to 2006/2007 on most current figures of production and consumption of the various forms of synthetic N fertilizers in India (Figure 1, FAI, 2007) and used the best-available specific emission factors to estimate GHG emissions according to Intergovernmental Panel on Climate Change (IPCC) methodology (IPCC, 2006). In 2006, India consumed nearly 14Mt N, producing about 80 per cent of this amount (Figure 1). Of the various forms in which synthetic N fertilizers

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are available, urea accounts for 81 per cent of the total N fertilizer produced and consumed in 2006/ 2007. Estimation of emissions from the manufacture of synthetic N fertilizers To calculate emissions from the manufacture of N fertilizers in India, we used emission factors for each type of N fertilizer produced, selected from those available in the literature based on its methodology and agreement with IPCC’s recommendations (Table 1, Wood and Cowie, 2004; IPCC, 2006). Specific emission factors for the particular production technology in India are not available. We used the most up-to-date and accurate emission factors that include the whole life cycle of the production of each fertilizer. CO2 emissions from fossil fuels consumed as energy source and feedstock dominate GHG emissions from ammonia synthesis, with emissions from other sources (e.g. transport) making minor contributions. The synthesis of urea is based on the combination of ammonia and CO2, and its emissions are dominated by CO2 emitted during ammonia synthesis. The production of urea is usually linked to an ammonia plant, where by-product CO2 from ammonia synthesis is used as a primary input in urea production. There is a relatively large discrepancy between different emission factors for urea, attributed to how this utilization of by-product CO2 is interpreted within the fertilizer life cycle. Because some researchers (e.g. Kongshaug, 1998) did not conduct full life cycle analysis studies, they considered that this consumption of CO2 constitutes a net reduction in by-product CO2 emissions, hence the comparatively low emission factors. However, Kongshaug himself acknowledged that in a life cycle analysis for fertilizers, it is not correct to exclude these emissions, as CO2 will be released during usage of the fertilizer (Kongshaug, 1998). Davis and Haglund’s (1999) emission factors, including emissions of this by-product, have been adopted here (Table 1). Estimation of emissions from the application of synthetic N fertilizers The amount of N2O emitted from N fertilizers in soils depends mostly on the amount of fertilizer applied and, to a lesser extent, on the specific characteristics of the site, such as temperature, soil or crop type (Dobbie et al., 1999; Dobbie and Smith, 2003). In spite of these variations, the IPCC recommends the

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Figure 1 | Consumption of N fertilizers in India from 1960/1961 to 2006/2007 (top) and consumption of total nitrogen in China, India and USA (bottom) Data sources: Fertiliser Association of India (FAI, 2007) and International Fertilizer Industry Association (IFA, 2008)

use of a default emission factor for direct emissions from N inputs in managed agriculture soils of 1.25kg of N2O emitted per 100kg of N applied to soils (EF1 in IPCC tier 1 methodology; IPCC, 2006). However, emissions factors for direct N2O emission from soils after application of synthetic fertilizer are quite variable and uncertain. Some authors recommend the use of an Indian-specific emission factor that is lower by almost 44 per cent than the

IPCC default emission factor (Garg et al., 2006). This revised emission factor of 0.70kg of N2O emitted per 100kg of N applied to soils (Bhatia et al., 2004; Garg et al., 2006) is based on rice– wheat systems, with emissions of 0.76kg for rice and 0.66kg of N2O per hectare for wheat for urea application (Pathak et al., 2004, as cited in Garg et al., 2006). Table 2 illustrates the wide variation of values for emissions of N2O from agricultural soils

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Table 1 | Emission factors for the different synthetic N fertilizer products used in this study N fertilizer product

Emission factor g CO2-e kg

21

Region of estimate

N

Per cent emitted as CO2

N2O

CH4

Reference

Urea

4018.9

Europe

97.6

0.1

2.3

Davis and Haglund (1999)

Nitrogen in NP and NPK

4812.0

Europe

97.9

0.2

1.9

Davis and Haglund (1999)

Ammonium sulphate

5644.6

Germany

46.9

52.9

0.2

Wood and Cowie (2004)

Ammonium phosphate N

6392.9

Europe

97.9

0.3

1.8

Davis and Haglund (1999)

Ammonium nitrate

7030.8

Europe

39.6

59.5

0.9

Davis and Haglund (1999)

Calcium ammonium nitrate

7481.9

Europe

38.9

60.4

0.7

Davis and Haglund (1999)

Table 2 | Nitrous oxide emission factors for Indian, Asian and global scenarios Emission factor

kg N2O per 100kg N

Crop

Fertilizer

Reference

Global, IPCC default tier 1

1.25

Any

Any

IPCC defaulta (2006)

Global, top-bottom model

4.00

Any

Any

Crutzen et al. (2008)

Asian-wide, model

8.00

Rice

Urea

Li et al. (2004)

New Delhi, IARI

0.14

Rice

Urea

Ghosh et al. (2003)

New Delhi, IARI

0.60

R–W

Urea

Malla et al. (2005)

New Delhi, IARI

0.60

R–W

Urea

Pathak et al. (2005)

New Delhi, IARI

0.70

R–W

Urea

Pathak et al. (2002)

12.80

R–W

Urea

Babu et al. (2006)

Specific data for India

Ludhiana, Punjab

Notes: The emission factors used in this study are in bold. IARI: Indian Agricultural Research Institute, R– W: rice –wheat rotation. a IPCC (2006), IPCC emission factors also available at www.ipcc-nggip.iges.or.jp/EFDB/main.php.

for global, Asian and Indian scenarios, which range from 0.14 to 12.8kg of N2O per 100kg N within India. The discrepancy for Indian values seems to be related to limited locations for data collection, as most values are derived from very controlled experimental conditions in the Indian Agricultural Research Institute in New Delhi (Table 2). In contrast, the only study in a field site in the centre of the rice–wheat region, in Ludhiana (Punjab), which recorded emissions every week during the growing seasons of both rice and wheat, showed a significantly higher value of emissions, 12.8kg N2O per 100kg N (Babu et al., 2006). Another recent study in rain-fed rice paddy in a subhumid region in eastern India recorded N2O emissions of about 2.4kg per 100kg N, which were reduced to 1.8kg per 100kg N when rice

paddy was integrated with fish stocking (Datta et al., 2009). We calculated emissions for India with the current reference IPCC global emission factor of 1.25kg N2O per 100kg N (IPCC, 2006), and with the lower factor recommended for India (0.70kg N2O per 100kg N; Garg et al., 2006, based on Pathak et al., 2004, 2002) and the higher one modelled by Crutzen (4.00kg N2O per 100kg N; Crutzen et al., 2008), which is, however, still lower than that modelled by Li et al. (2004) for Asia (see Table 2). We also included calculations with the emission factor from the site in Ludhiana, which corresponds to the region of most intensive agriculture and highest N application rate in India (FAI, 2007).

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Results Total emissions from synthetic N fertilizer in India reached !100Mt of carbon dioxide equivalent (CO2-e) in 2006/2007; about half of these emissions resulted from the 11Mt of synthetic N produced in the country that year (48Mt of CO2-e) and the other half resulted from the 14Mt N applied in Indian farm soils the same year (51Mt of CO2-e, ranging between 28 and 163 [up to 522]Mt of CO2-e, depending on the emission factor used, Table 2, Figure 2). These 100Mt CO2-e total emissions from N fertilizers represent 6 per cent of the total country emissions in 2005, comparable to sectors such as cement or iron and steel industries. Emissions from fertilizers are similar in quantity to emissions from residential, commercial and service sectors combined and to emissions from the whole road transport system (Figure 3). India-specific climate change mitigation potential from the fertilizer sector can be roughly estimated, assuming changes in N use efficiency and the type of fertilizer used: Ecological fertilization. We define ecological fertilization as that not using synthetic N but relying on the variety of methods that exist to incorporate N into soils (growing legume cover crops, adding compost or manure, etc.) (Tirado, 2009). We use ecological instead of organic fertilization to avoid restriction to ‘certified organic’ farming practices. Recent meta-analysis has estimated that N-fixing legumes used as green manure can provide an alternative to all the synthetic fertilizers currently in use worldwide, without compromising food production (Badgley et al., 2007). Fertilizing with recycled organic residues, such as manure or compost, can provide additional sources to substitute synthetic N. Potentially shifting from synthetic N fertilizer to various means of ecological fertilization that maintain N input and high yields will save fossil-fuel burning in the production of synthetic fertilizers (48Mt of CO2-e in 2006/2007). A complete shift to ecological fertilization would mean a reduction in total emissions from N fertilizers in India from !100Mt of CO2-e in 2006/07 to !50Mt of CO2-e (Figure 4). This estimate assumes that substituting synthetic with organic sources of N would not result in additional GHG emissions, given that (1) manure is applied in dry form in India, and thus use of this manure for

fertilization will not result in significant additional emissions since emissions for dry manure management are negligible (IPCC, 2006), and (2) composting of organic waste (crop residues, food and some manure) and its addition to soil will substitute the general waste management practice of open burning or incineration, which have higher associated emissions than composting (IPCC, 2006).

These savings also assume that emissions from ecologically fertilized soils are similar to emissions from synthetically fertilized soils. However, this might differ among farming practices. There is evidence that emissions from some soils fertilized without synthetic N might emit less N2O per N applied under nonirrigated semi-arid climates (Meijide et al., 2009). We acknowledge that a more detailed analysis, with practice-specific emission factors and experimental data (when made available), will be needed to validate our estimates: N use efficiency. Average N losses in Indian agro-ecosystems have been estimated to be about 60 per cent of N applied to soils, but losses can be as high as 80 per cent of N applied under weather conditions unfavourable for plant growth (Cassman et al., 2002; Bijay and Singh, 2008). The N applied in excess to crop needs is particularly susceptible to N2O emissions from soils (McSwiney and Robertson, 2005). To calculate potential savings from minimizing N excess, we assume that the average N losses of 60 per cent of synthetic N applied in India could be reduced by half, to an average of 30 per cent as in much of Europe and North America (Ju et al., 2009). This increase in N use efficiency would translate into savings in the input needed of N fertilizers (synthetic or ecological) plus savings from emissions from soils after application. This would mean reductions of about 30 per cent in emissions, from !100Mt of CO2-e in 2006/07 to !70Mt of CO2-e. Combining these two mitigation options, total emissions could potentially be reduced to 37 per cent of current emissions, with savings of 63Mt of CO2-e per year, and the contribution from N fertilizers to the country’s emissions will drop from 6 to 2 per cent (Figure 4).

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Figure 2 | GHG emissions from the manufacture of nationally produced synthetic N fertilizers (top) and from synthetic N application to soils (bottom) in India from 1960/1961 to 2006/2007. The total values given are for the year 2006/2007. Bottom: emissions calculated with three emission factors (EFs): IPCC (1.25kg N2O/100kg N), Indian-specific (0.70kg N2O/100kg N) and global top-down model (4.00kg N2O/100kg N) emission factors (details in Table 2). Emissions estimated with the only emission factor measured in rice – wheat field sites in intensive farming regions (Ludhiana, Punjab (Babu et al., 2006), Table 2) will reach up to 522 million tonnes of CO2-e in 2006/2007

Discussion Our results show that N fertilizer manufacture and application in India contribute significantly to emissions of GHGs, but we also show that there could be significant mitigation potential if an efficient ecological farming system is implemented.

Emissions from fertilizers in India have been increasing at an annual rate of 3 per cent during the last decade, and in the last two years emissions from the increased consumption of fertilizers increased by 8 per cent per year. Emission rates will probably become even higher in the years to come if chemically intensive agriculture continues to advance in the

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Figure 3 | Emissions from different sectors in India in the year 2005 (grey bars, data from Garg et al., 2006) and from calculations in this study (black and white bars). Percentages show the contribution of each sector to the country’s global GHG emissions in 2005, which totalled 1751 million tonnes of CO2-e (Garg et al., 2006)

Figure 4 | Mitigation potential (Mt CO2-e year21) for emissions from N fertilizer production and application in India, relative to current emissions in 2006/2007, from a shift to ecological fertilization and an increase in N use efficiency from 30 to 60 per cent

country and if India is able to produce all the synthetic N fertilizer it consumes. As the second global producer of N, the contribution of N fertilizer manufacture to total emissions in India is double the contribution of fertilizer production globally (3 vs. 1.5 per cent) (Bernstein

et al., 2007). Besides, our estimates for emissions from production reflect the minimum possible emissions in India, since we are using emission factors for more efficient and less heavy-fuelintensive European fertilizer plants. There seem to be large discrepancies between reported emissions from ammonia production in the only National Inventory data from 1994 (Government of India, 2004) and emissions calculated here from best available emission factors. The first national communication on emissions from ammonia production in 1994 has the value of 14.4Mt CO2-e, which represents only 33 per cent of the value in our estimates for the same year in Figure 2. The official number reported coincides with the potential emissions from the burning of natural gas used by the fertilizer industry in 1994 (Government of India, 2004). The Energy Information Administration reported 40.07Mt CO2 emitted from the burning of natural gas in India in 1994, 40 per cent of which was used for fertilizer production (FAI, 2007); hence, emissions from natural gas burning in fertilizer plants would total about 16Mt CO2 in 1994. This accounting system underestimates emissions for a number of reasons: (1) it excludes emissions from the burning of dirtier naphtha and fuel oil in fertilizer plants, (2) it excludes emissions of GHGs other than CO2 emitted in the manufacturing process (N2O, CH4), and (3) it excludes emissions of CO2 embedded in

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urea that is released as soon as it is applied to farm soils (Kongshaug, 1998; Wood and Cowie, 2004). All these additional emissions should be included in order to obtain an accurate estimation of emissions from the manufacture of synthetic N fertilizers.1 Our estimates of direct emissions of N2O from the application of synthetic fertilizers in soils following IPCC emission factors are in agreement with estimates from the Indian experts in charge of the National Inventory, who recently calculated emissions from the application of synthetic fertilizers to soils in India in 2005 to be 45Mt of CO2-e (Garg et al., 2006); however, it is unclear which emission factor is used for this most recent estimate. In 2007, emissions of N2O from synthetic fertilizers in soils ranged from 28Mt of CO2-e to 522Mt of CO2-e, depending on which emission factor was used (0.70kg N2O per 100kg N as in the New Delhi Indian Agricultural Research Institute, or 12.80kg N2O per 100kg N as in the Ludhiana field experimental site, see Table 2). The official emissions reported 33Mt CO2-e from synthetic N fertilizers in 1994 (the only official data available on India’s First National Communication to the UNFCCC2; Government of India, 2004). This value is also in agreement with our estimates (35Mt CO2-e). However, the estimate using a country-specific emission factor (0.70kg N2O per 100kg N), as calculated by Bhatia et al. (2004) and recommended by Garg et al. (2006), for future National Inventories, is significantly lower, 18Mt CO2-e for 1994.3 These discrepancies highlight the danger of underestimating N2O emissions by using emission factors extrapolated from very specific conditions to the whole country. There is a lack of field measurements of emissions across India that take into account different climatic, soil and cropping characteristics. Until a more specific emission factor is available for the whole country, we suggest that the use of IPCC default factors provides a better way of estimating emissions over a country with diverse farm landscapes. Potential savings in emissions within the Indian fertilizer sector can be as high as 63Mt CO2-e year21. Mitigation options include practices both to increase N use efficiency and to shift away from synthetic fertilizers. These savings can be achieved by reducing the overuse of synthetic N fertilizer and without reducing the total N input into crops, thus without compromising food production. According to Badgley et al.’s (2007) global meta-analysis, fertilizing with legumes could provide a significant share of this N without

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changes in yield. In addition, it has been estimated that organic residues in India, including a variety of sources from manure to urban compost to compost of the invasive water hyacinth, could provide a total of 14.22Mt N per year (Bisoyi, 2003). This amount of N that could be potentially recovered is similar to the amount of N consumed currently in India every year. Obviously, the recovery of this N and its availability for farmers will require major structural developments. The benefits of recycling these residues would also include the reduction of heavy nutrient pollution and eutrophication found in Indian watercourses and coastal areas (Bijay and Singh, 2008). Smith et al. (2008) showed that the mean estimated N2O mitigation potential from nutrient management for South Asia (roughly India, Pakistan, Sri Lanka and Bangladesh) was 20Mt CO2-e year21 (range 3– 94Mt CO2-e year21). However, N2O mitigation potential according to Smith et al. (2008) is based on United States Environmental Protection Agency models that consider reductions in fertilizer use to 80 per cent of current levels and assume there is no excess use; hence this reduction implied a reduction in yields (and soil carbon returns) and thus lower net mitigation rates. Our rough estimate of N use efficiency savings of 30Mt CO2-e year21 is within the above range, although it assumes a higher reduction in N use (to 70 per cent of current levels), and only on excess N input. However, we acknowledge that this value needs further validation from country data on optimal N inputs and yields. Increasing N use efficiency and implementation of ecological fertilization not only reduce the dependence on synthetic N fertilizers but also promote longterm soil fertility and contribute to sequestering carbon in agriculture soils, and thus further help mitigate GHG emissions (Pretty et al., 2002). However, the potential alternative use of the organic resource, and the total amount available, needs to be considered. Biophysical mitigation potential by 2030 from increased carbon sinks in farm soils can reach up to 330Mt CO2-e year21 in South Asia (Smith et al., 2008), and lower estimates show 160Mt CO2-e year21 for India (Lal, 2004). N input through ecological fertilization could potentially work concurrently to reduce emissions from synthetic N fertilizers and promote soil carbon sinks. Some studies have shown an increase in organic soil carbon with organic N fertilization (Drinkwater et al., 1998; Kramer et al., 2006; Fließbach et al., 2007). Manure has approximately one-fifth the impact on climate change

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compared to synthetic N fertilizers (Moreno-Caselles et al., 2002; Bellarby et al., 2008) but a full life cycle analysis to estimate GHG costs from livestock production systems needs to be conducted to assess the real potential of manures for GHG emission reduction. One example of an easy-to-use and inexpensive tool to achieve higher N use efficiency and avoid overapplication of fertilizers is the leaf colour chart developed for rice–wheat systems in the Indo-Gangetic Plains (Singh et al., 2002). The leaf colour chart is a series of panels with colours based on the wavelength characteristics of rice leaves, which enables the precise application of N fertilizer based on the plant need at specific times and locations in the field. The use of this tool in Indian rice systems showed savings of about 25 per cent of N application without losses in yield (Singh et al., 2002). This example highlights the potential for reduction in synthetic N fertilizer use, which that could bring about large economic benefits for farmers and environmental benefits for both regional water quality and global climate.

Acknowledgements

References

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We thank Sarah Pilgrim and three anonymous reviewers for comments that great improved our manuscript.

Notes 1. On 11 May 2010, when this manuscript was in press, the Government of India released its most recent inventory of national GHG emissions. In this new inventory, emissions from ammonia manufacturing are 30 per cent lower than in 1994, 10.1Mt CO2-e. In spite of potential improvements in N manufacturing efficiency, we believe this value clearly continues to underestimate emissions from manufacturing of N fertilizer, especially since N production increased 31 per cent from 1994 to 2007. 2. United Nations Framework Convention on Climate Change. 3. In the updated May 2010 GHG emissions inventory from the Government of India, the emission factor used for N2O from soils is 0.70kg N2O per 100kg N, which as explained above is in danger of underestimating emissions from Indian farm soils.

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Greenhouse gas emissions and mitigation potential

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