Methane and nitrous oxide emission from bovine manure management practices in India

Environmental Pollution 146 (2007) 219e224 www.elsevier.com/locate/envpol

Methane and nitrous oxide emission from bovine manure management practices in India Prabhat K. Gupta*, Arvind K. Jha, S. Koul, P. Sharma, V. Pradhan, Vandana Gupta, C. Sharma, Nahar Singh Analytical Chemistry Section, National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi 110012, India Received 11 May 2005; received in revised form 13 April 2006; accepted 13 April 2006

Emission of CH4 and N2O from bovine manure management in India is discussed. Abstract We report seasonal variation in CH4 and N2O emission rate from solid storage of bovine manure in Delhi as well as emission factors and emission inventory from manure management systems in India. Emission flux observed in the year 2002e2003 was 4.29  1, 4.84  2.44 and 12.92  4.25 mg CH4 kg1 dung day1, as well as 31.29  4.93, 72.11  16.22 and 6.39  1.76 mg N2O kg1 dung day1 in winter, summer and rainy seasons, respectively. CH4 emission factors varied from 0.8 to 3.3 kg hd1 year1 for bovines and were lower than IPCC-1996 default values. N2O emission factors varied from 3 to 11.7 mg hd1 year1 from solid storage of manure. Inventory estimates were found to about 698  27 Gg CH4 from all manure management systems and 2.3  0.46 tons of N2O from solid storage of manure for the year 2000. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Methane; Nitrous oxide; Manure management; Greenhouse gas emission; Livestock waste

1. Introduction United Nations Framework Convention on Climate Change (UNFCCC) has encouraged nations to communicate emission inventories of greenhouse gases (GHG) such as methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) from various sectors like energy and industry, agriculture, land use-land use change and forestry and municipal waste. GHG emissions from agriculture sector include livestock, rice cultivation, crop residue burning and agricultural soil, where livestock-derived GHG emissions in India has maximum share (NATCOM, 2004; Singhal et al., 2005). Production and emission of CH4 and N2O from manure depends on digestibility and composition of feed, species of animals and their physiology, manure management practices and meteorological

* Corresponding author. Tel.: þ91 11 2573 4649; fax: þ91 11 2572 6938. E-mail address: [email protected] (P.K. Gupta). 0269-7491/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2006.04.039

conditions like sunlight, temperature, precipitation, wind, etc. (Brown et al., 2002; Gaur et al., 1984; Yamulki et al., 1999). Manure management includes storage and treatment of manure, before using it as farm manure or burning as fuel. Indian bovine (cattle and buffalo) manure is managed in form of solid storage and slurry/lagoon for manure, dung cake making and biogas generation for domestic fuel, daily spread, pasture and rangeland deposition during grazing and others. Under anaerobic conditions, bacteria decompose the organic material contained in livestock manure to form CH4, CO2 and stabilized organic material. Production of N2O occurs by both nitrification and de-nitrification during storage of manure. As the information about CH4 and N2O emissions from bovine manure management systems in India/Asia is lacking, their previous emission inventories were prepared using IPCC (Intergovernmental Panel on Climate Change) default emission factors (IPCC, 1996) (Garg et al., 2001; Mitra, 1992, 1996; Yamaji et al., 2003, 2004). IPCC guidelines

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suggest nations to develop country specific emission factors (EFs) as its default values may result in large uncertainties in the absence of region-specific information. In the present study, we measured CH4 and N2O emission flux from solid storage of bovine manure. CH4 and N2O emission factors were derived using country specific data to estimate GHG inventory for the year 2000. 2. Materials and methods

Methane EF for manure management practices except solid storage were estimated, using IPCC-1996 tier-II methodology, applying country-specific value of 17% ash content (Gaur et al., 1984), instead of IPCC suggested value of 8% (IPCC, 1996). For calculation of EF, animal population distributed in different climatic zones viz., cool (below 15  C), temperate (15e25  C) and warm (above 25  C) was considered (IPCC Good Practice Guidance, 1996). Methane EF for solid storage of manure for individual bovine was calculated from annual CH4 emission per kg dung managed. Finally, experimentally derived and theoretically calculated EFs were used to obtain CH4 EF for an individual bovine. Total CH4 emission was estimated by multiplying EFs and bovine population in the year 2000. N2O emission was estimated from solid storage using the field experimental data.

2.1. Methane and nitrous oxide emission measurement The flux measurements for CH4 and N2O were carried out from solid storage of manure in different dairies viz. Jharoda, Bhalaswa, Nangali, Kakrola and Gazipur of Delhi during winter (November 2002), summer (June 2003) and rainy (July 2003) seasons. Chamber technique was used for gas sampling (Gupta et al., 1994; IAEA, 1992; Mitra et al., 2002). Gaseous samples from the headspace of chamber were collected at the interval of 10 min, at each site using 50 ml syringes, for half an hour. Ambient air samples at the experimental sites were collected as background. Ambient and manure temperatures at study sites were also recorded. Representative manure samples were taken to determine moisture and density. Weight of manure in column below chamber area of heap/pit was calculated for all sites. Gas samples were analyzed for CH4 by Gas Chromatograph (GC) (make SRI USA, Model 8610 C)-flame ionization detector with methanizer and N2O concentrations by GC-electron capture detector. CH4 (14.2 ppmv) and N2O (0.31 ppmv) calibration gas standards were used. CH4 and N2O flux were calculated for the amount of manure below the chamber area. Methane emission from solid storage of manure (mg CH4 kg1 dung day1) was calculated for each season, followed by seasonal weighted average emission as annual emission per kg dung from solid storage of manure.

2.2. Dry matter excretion, emission factors and inventory Indian bovines were categorized based on their age, type and productivity to calculate dry matter intake (DMI), dry matter excretion (DME) or manure and CH4 and N2O EFs for preparing inventory. Bodyweight of indigenous or non-descript bred of bovine used in estimating gross energy (GE) was derived from reported data in concerned region (Singhal et al., 2005). GE and DMI were estimated as per IPCC Good Practice Guidance-1996 using energy density of feed as 18.45 MJ per kg DM from IPCC, 1996 guidelines. The average digestibility of Indian feed and fodder, which ranged from 50 to 60% was applied to obtain DME per animal. The maximum variations in digestibility were assumed to be 5% and in body weights 10% for calculating GE. Compounded annual growth rate in bovine population between 1997 and 2003 (16th Indian Livestock Census, 2003; 17th Indian Livestock Census, 2005) was applied to the population recorded in 16th livestock census to obtain population for the year 2000 and animals below 3-months age group were excluded, due to their negligible DME. Animal population in each category was multiplied by DME to obtain total dung production. The total dung production was seasonally apportioned in different use patterns of manure and it was assumed that the percentage distribution of dung use pattern was also valid to individual bovine to calculate EF.

3. Results Average CH4 and N2O emission flux, observed from solid storage of manure in different seasons, is summarized in Table 1. The mean CH4 flux observed during field measurements was 6.6  2.19 mg kg1 dung day1 and mean N2O flux was 35.42  7.01 mg kg1 dung day1 (Table 1). Fig. 1 shows the correlation of dung heap temperature with respect to ambient temperature and methane emission. The CH4 emission variability was broadly in agreement with the results reported from dung pat of grazing bovine (Holter, 1997). Bovine population was about 271.31  106 in the year 2000 and their DM requirement was about 538.2 Tg (Table 2). DME in different categories of bovine ranged from 0.7 to 2.8 kg day1 (Table 2). Indian bovine produced about 209.8 Tg of dung (dry weight), after consuming about 470.9 Tg of DM available in the country, as India is deficient in feed resources by 10e15% (NIANP, 2001). Total dung production and different manure use patterns are presented in Table 3. Calculated EFs for CH4 (0.8 to 3.3 kg hd1 year1) and N2O (3 to 11.7 mg hd1 year1- for solid storage of manure) from different bovine categories resulted in annual emission estimate of about 698 Gg CH4 and 2344 kg N2O for India (Table 4). Indigenous cattle were responsible for higher emission (w422.3 Gg) due to their larger population followed by buffalo (w234 Gg) and crossbred cattle (41.3 Gg). 4. Discussions 4.1. CH4 and N2O flux CH4 and N2O flux variation in different seasons (Table 1) might be due to change in environmental conditions, type of animal feed and storage condition of manure. Temperature of solid manure heap during field experiments ranged from

Table 1 Methane and nitrous oxide emission flux from livestock manure during field measurements in different seasons Seasons

CH4 flux (mg kg1 day1) Lower range  SE

Higher range  SE

Mean  SE

Lower range  SE

Higher range  SE

Mean  SE

Winter Summer Rainy Annual

1.57  0.32 1.07  0.44 5.29  1.25 2.38  0.58

13.46  2.1 8.61  4.42 26.65  9.22 15.55  4.49

4.29  1 4.84  2.44 12.92  4.25 6.6  2.19

17.89  2.56 39.55  9.66 3.54  0.6 19.79  3.88

98.97  22.12 104.68  23.66 13.53  4.5 78.89  18.07

31.29  4.93 72.11  16.22 6.39  1.76 35.42  7.01

SE ¼ Standard Error.

N2O flux (mg kg1 day1)

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a

Ambient temperature vs pit temperature

Pit temperature (°C)

heap temp winter 65 60 55 50 45 40 35 30 25 20 15 10

heap temp monsoon

heap temp summer R2 = 0.1921

R2 = 0.1179 R2 = 0.1274

22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52

Ambient temperature (°C)

Methane flux ln(mg kg-1 manure day-1)

b

Heap temp Vs methane emission ln CH4 flux (winter)

In CH4 flux (summer)

In CH4 flux (rainy)

2

1

0

-1

-2 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58

Heap temperature (°C) Fig. 1. Relationship between manure heap temperature and (a) ambient temperature and (b) methane flux.

21 to 59  C, irrespective of ambient air temperature. The other influencing factors might be manure age, moisture content, compaction and dung heap height. Insignificant correlation observed between ambient air temperature and manure heap/pit temperature (Fig. 1a) may be due to high porosity and organic bedding materials inside the dung heap. The low dependency of field CH4 emission on heap temperature might be due to compaction, height, age, moisture and type of feed taken by animals. In earlier study, CH4 flux correlation with heap temperature was reported, which was possibly due to differences

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in animal husbandry practices and environmental conditions (Husted, 1994). Values for CH4 flux, in the present study was in agreement with other reported values from manure composting and solid storage of dung (Husted, 1994; Sommer, 2001; Sommer and Dahl, 1999), however N2O flux were low (Table 3). The higher CH4 flux and lower N2O flux in rainy season might be due to wet environmental or anoxic conditions, as similar feed quality was given to animals. 4.2. Bovine manure use patterns The negative growth rate was recorded in indigenous cattle population in recent years (16th Indian Livestock Census, 2003; 17th Indian Livestock Census, 2005) due to mechanization in agriculture and economic considerations. Dominating share of 1e3 year old cattle in younger population and adult population in total of indigenous bred indicates that the decline in population would continue in future. Dung cake is utilized in most of the states of India, except Himachal Pradesh, Jammu and Kashmir and North-Eastern states and is less utilized in Kerala and Delhi. The estimates of present study for the year 2000 suggested that about 80.5 Tg of dung was utilized for dung cake making based on per capita energy consumption, household energy requirement, manure availability and animal herd size. Earlier estimates for the year 1992e93 were 86.7 Tg (Natrajan, 1998) and 121 Tg (Reddy and Venkatraman, 2002) for the year 1996e97. The differences in estimate might be due to decrease in cattle population, increased use of LPG in urban and rural areas including our calculations on dry weight basis with 10% moisture content in dung cake. The use of dung cake for fuel (3.51% urban and 19.6% rural households) (CSE, 1999) declined from 15.39% to 9.8% (2.0% urban and 12.8% rural) in a decade (Census, 2001). About 7.4% of total dung produced was estimated to be required for biogas plant (Both family and community biogas plants) in country. Out of total DM, about 14% was accounted from rangeland or pasture grazing of livestock (NIANP, 2001) which was about 40% of forage availability in country (Shankar and

Table 2 Gross energy (GE), dry matter (DM), Bovine population and total DM requirement in year 2000 Category

Dairy indigenous Dairy crossbred ND cattle (Indigenous)

ND cattle (Cross bred)

Dairy buffaloes ND buffaloes

Age

Adult Adult Below 1 yr 1 to 3 yr Adults Below 1 yr 1 to 2.5 yr Adults Adult Below 1 yr 1 to 3 yr Adults

Total ND ¼ non-dairy, yr ¼ year, hd ¼ head.

GE required (MJ hd1 day1) 90.54 123.78 37.1 87.88 109.98 38.52 82.95 112.87 124.06 59.14 112.41 149.23

DM (kg hd1 day1) Required

Excreted

4.9 6.7 2 4.8 6 2.1 4.5 6.1 6.7 3.2 6.1 8.1

1.93  0.06 2.35  0.07 0.79  0.02 1.88  0.05 2.61  0.07 0.73  0.02 1.57  0.04 2.14  0.06 2.65  0.08 1.26  0.04 2.4  0.07 2.83  0.08

Population (1000) 47 877 8865 17 249 30 758 68 345 3290 3819 3943 44 295 14 090 16 362 12 422 271 314

% Population Warm

Temperate

Cool

28.1 53.2 26.9 23.5 31.9 52.1 47.2 43.2 31.4 29.3 27.3 26.2

70.6 42.6 71.8 75.4 67 42.9 47.3 46.8 67.7 69.9 71.9 72.9

1.4 4.2 1.3 1.1 1.1 5.0 5.5 10 0.9 0.7 0.9 0.9

Total DM required (Tg) 85.8 21.7 12.7 53.5 148.7 2.5 6.3 8.8 108.7 16.5 36.4 36.7 538.1

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Table 3 Use pattern of bovine dung produced in India for year 2000 Type of use

Winter % of total

Quantity (Tg)

% of total

Quantity (Tg)

% of total

Quantity (Tg)

% of total

Quantity (Tg)

Dung cake Biogas Rangeland Slurry & lagoon Others Manure

51.3 7.4 14 1 1.3 24.9

53.1 7.7 14.5 1 1.4 25.8

51.3 7.4 14 1 1.3 24.9

27.4 4 7.5 0.5 0.7 13.3

NP 7.4 14 1 NP 77.6

NP 3.9 7.4 0.5 NP 41

38.4 7.4 14 1 1 38.2

80.5 15.6 29.4 2.1 2.1 80.2

Total

Summer

103.5

Rainy

Annual

53.5

53

209.8

NP ¼ not practiced.

Saha, 1995). 15e30% animals depend on grasses and grazing (Ranjhan, 1993). Grazing pressure estimations for India as 2.91 adult cattle unit (ACU)/ha, land availability of 0.34 ha/ACU (Tyagi and Shankar, 1995), DM availability, and carrying capacity of natural grasslands in 18 states were reported (Misri and Singh, 1995). About 14% of total feed per ruminant livestock unit per year comes from grazing (NIANP, 2001). About 14% of livestock in India depend on rangeland grazing and their dung is not utilized for any purpose. However, CH4 emission from such rangeland dung pats may occur under anaerobic conditions. About 1% of total dung is also used for other purposes like making of mud houses. One percent of total dung excretion by cattle excepting buffalo is managed in slurry form (Tyagi, 1989) and lagoon system of manure management is negligible in India. After apportionment of above dung use patterns, it was believed that rest of the dung was stored for manure purpose (Table 3). Bovine manure waste is stored in countryside, without any differentiation between age and type of bovine. It is stored in bulk in a ditch or on earth surface near bovine herd for a long period of time, prior to disposal at the time of sowing of crops. 4.3. CH4 and N2O emission factor (EF) and estimates Similar CH4 EF observed for dairy crossbred cattle and dairy buffalo (Table 4), may be due to feeding of buffalo with low

digestible feed (higher roughage content), leading to larger amount of DME, with low volatile solids. The higher N2O EF for mature buffalo may be due to higher nitrogen excretion in dung. Most of the CH4 EFs calculated in this study are lower than EFs calculated during GHG inventory preparation for India’s national communication (NATCOM) to the UNFCCC (Gupta et al., 2004) (Table 4). This might be due to higher coefficients viz. percentage of volatile solids in DME and higher CH4 conversion rate used, in NATCOM calculations, including non-availability of field measurement data. IPCC default values for CH4 EF for manure management was 5 kg hd1 year1 for cattle and buffalo, irrespective of their age and productivity. The higher value of EFs in IPCC as compared to NATCOM and present study may be due to non-availability of detailed bovine performance data. According to IPCC-1996, average milk production (kg hd1 day1) is 2.5 in cattle and 2.7 in buffalo, however as per data available it is 1.7, 5.73 and 3.6 in dairy indigenous and crossbred cattle and buffalo, respectively, wherein the percentage population of crossbred cattle is very low. The mature males work for an average of 1.7 h day1 (IPCC average 2.74 h day1). IPCC default value for volatile solids excretion is 3.1 kg hd1 day1 whereas even total DME is less than 3 kg (Table 1). Methane emissions estimated were lower by about 15% with the GHG inventory prepared for the NATCOM (Gupta et al., 2004), with reduced uncertainties (Table 4).

Table 4 CH4 & N2O emission factors and emission estimates from bovine manure management in India for year 2000 and comparison with NATCOM Category

Dairy cattle ND cattle (Crossbred)

ND cattle (Indigenous)

Dairy buffalo ND buffalo

Total

Crossbred Indigenous 0e1 year 1e2.5 year Adult 0e1 year 1e3 year Adult 0e1 year 1e3 year Adult

CH4 EF (kg hd1 year1)

CH4 emission (Gg)

Present

NATCOM

Present

NATCOM

3.3  0.16 2.7  0.13 0.8  0.04 1.7  0.08 2.3  0.11 0.8  0.04 2  0.1 2.8  0.14 3.3  0.06 1.2  0.02 2.3  0.04 2.7  0.05

3.5  0.8 3.8  0.8 1.2 2.8 2.9  1.4 1.1 2.3 2.5  0.9 4.4  0.6 1.8 3.4 4

23.5  1.2 157  7.7 2.5  0.1 6.3  0.3 8.9  0.4 14.7  0.7 61.6  3 189  9.4 145.9  2.5 17  0.3 37.5  0.6 33.6  0.6

33.7  7.1 167.6  9.6 3.6 8.8 9.9  3.5 20 79.7 172.9  64.1 194.9  26.6 25.4 55.6 49.7

697.8  27

821.6  110.9

N2O EF (mg hd1 year1) 8  1.6 9.7  1.9 3.3  0.6 7.8  1.5 10.8  2.1 3  0.6 6.5  1.3 8.9  1.7 11.0  2.2 5.2  1 9.9  2 11.7  2.3

ND ¼ non-dairy, EF ¼ emission factor, NATCOM ¼ India’s initial national communication of greenhouse gases to UNFCCC.

N2O emission (kg) 70.9  14 465.2  91.8 10.8  2.1 29.6  5.8 42.6  8.4 52.2  10.3 200.3  39.5 605.5  119.5 485.3  95.7 73.6  14.5 162.4  32 145.5  28.7 2343.8  462.4

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4.4. Sources and reduction of uncertainty Standard error of mean was reported as measure of uncertainty, rather than standard deviation of mean (Tables 1 and 4), because of broad range of fluxes observed from field sites. Similar approach was followed for uncertainty calculations in EFs. To minimize the uncertainty in EFs and emission inventory calculations, steps were taken viz., animal population data were apportioned into cool, temperate and warm regions (IMD, 1999) and 30% of <1 year bovine population under <3 months of age were excluded from calculation (Singhal et al., 2005). However, uncertainties exist in fraction of population for feeding situations, digestibility, body weights, genetic and ecology factors. 5. Conclusion Field measurements for the daily mean flux of CH4 and N2O averaged over the year from solid storage of dung were 6.6  2.19 mg CH4 kg1 dung day1 and 35.42  7.01 mg N2O kg1 dung day1 respectively. Indian bovine generates about 210 Tg of dung on dry weight basis after consuming about 471 Tg of dry matter. Methane emission factors varied from 0.8 to 3.3 kg CH4 hd1 year1 for bovine categories and were lower than IPCC default values. N2O EFs from solid storage of manure ranged from 3 to 11.7 mg N2O hd1 year1 for different bovine. Inventory estimates from Indian bovine manure management systems were found to be about 698  27 Gg CH4 and 2.3  0.46 tons of N2O for the year 2000. It may be inferred that country specific climate and animal husbandry practices are important factors for GHG emission from manure management. Acknowledgements The authors are grateful to the Ministry of Environment & Forests, Govt. of India and M/s Winrock International India Delhi for their financial assistance under NATCOM activities. Authors acknowledge the keen interest and encouragement of Dr. Vikram Kumar, Director NPL, Dr. A.P. Mitra, Sri S.C. Garg, scientist NPL and Dr. S.K. Gupta, Head, Material Characterization Division NPL. References 16th Indian Livestock Census, 2003. Summary report All India, Volume 1A, Livestock and Poultry-1997. Department of Animal Husbandry and Dairying, Ministry of Agriculture, Government of India, Krishi Bhawan, New Delhi. 17th Indian Livestock Census, 2005. Provisional data of 2003 livestock census, (Online). Available from: (accessed 12.02.2005). Brown, H.A., Wagner-Riddle, C., Thurtell, G.W., 2002. Nitrous oxide flux from a solid manure pile measured using a micrometeorological mass balance method. Nutrient Cycling in Agroecosystem 62, 53e60. Census, 2001. Distribution of households by availability of separate kitchen and type of fuel used for cooking. Census of India 2001. (Online).

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