INTEG CROP&LVSTK SY
INTEG CROP&LVSTK SY AGRON 515
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Date Created: 09/26/15
Methane nitrous oxide and carbon dioxide emissions from ruminant livestock production systems D E Johnson H W Phetteplace amp AF Seidl Dept of Animal Science zDept of A gricultural amp Resource Economics Colorado State University Ft Collins CO USA Summary System inputs with greenhouse gas GHG implications were summarized for typical US beef production systems and for representative US and NZ dairy systems The GHG emissions are expressed in carbon dioxide equivalents COZeq and related to livestock system product output The US beef systems are estimated to produce om 13 to 16 kg of COzeq per kg of live weight sold and the dairy systems 13 kg of COzeqkg of milk while the pasture based NZ dairies produced 16 kgkg milk Relative source strengths varied Nitrous oxide was the largest COzeq source of beef system emissions 52 with 36 and 12 from methane CH4 and carbon dioxide C02 The amount of methane per wt sold was quite uniform across location in the US while nitrous oxide was variable ranging from 7 in WI to 9 kg COzeqkg sold in TX Methane was the largest COzeq source 39om CA dairies while nitrous oxide N20 was the largest in NZ dairies High CH4 in CA was due to extensive use of anaerobic lagoon diSposal of manure while excess N content and ux on NZ pastures caused higher relative N20 emissions Utilization of best management practices and manure amendments to sequester carbon in the crop and forage land of ruminant livestock production systems have modest potential to offset their GHG emissions Keywords greenhouse gas cattle production system Introduction The unique gastrointestinal tract of ruminants coupled with large populations andor body size and appetites results in annual global atmospheric emissions of about 77 Tg of methane enterically and 7 Tg 39om manure handling systems Inventories and mitigation proposals of GHG s release from livestock have usually emphasized the enteric source eg RLEP 1998 Additional investigations of overall production systems however show other important sources Ward et al 1993 Johnson et al 1997 With the more complete source estimates of N20 Mosier et al 1998 as recommended for inventory purposes by IPCC 2000 the livestock production system emissions as carbon dioxide equivalents N20C028q of some systems exceeded those for CH4 Johnson et al 2000b Robertson et a1 2000 found N20 to be the single greatest source of COzeq emissions om nearly all agronomic systems in Midwest US observations This paper brie y reviews and updates prior summaries Johnson et al 2000a 2001 including embodied C02 inputs and expands coverage of management and mitigation strategy effects on cattle production system variations and relative source strengths of GHG emissions Details of systems spreadsheet assumptions can be found in a report to EPA Johnson et al 2000a or by query to the authors Estimation procedures Beef and dairy systems were divided into 6 to 16 claSSes based on age physiological or production stage eg replacement animals lactation etc The systems are based on the maintenance of and output from 100 head of mature cows Inputs and outputs for each class Q were described from national National Agricultural Statistics Service National Animal Health Monitoring System state Cooperative Extension Service and industry National Cattlemen39s Beef Assoc CattleFax sources Comparable information from the Livestock Improvement Corporation LIC and the Meat and Wool Economic Service MWB were consulted for New Zealand Stocker cattle weaned calves prior to feedlot 39om each location were fed out in one of two representative feedlots Texas TX or Iowa IA Production characteristics for each system include mature weights mortality culling calving replacement and growth rates and live weight of beef output at the farm gate Table 1 Dietary requirements and enteric CH4 emissions were derived per IPCC 2000 Good Practice Inventory guidelines an adaptation ofNRC 1989 1996 net energy requirements Key assumptions include 6 of diet energy loss as methane generally except for 35 for the feedlot phase quot Nitrous oxide estimates were 125 of crop Nfertilization and up to 25 from manure 6f leached N Carbon dioxide emissions 39om fertilizer synthesis and fossil iel use for cropping transportation insecticide and herbicide synthesis and application are based on Pirnentel et al 1980 in the US and Wells 1998 in NZ Methane and nitrous oxide were convertedtoC Qeqiisingthe factors of 21 and 310 gg IPCC 1996 Local sources were used to de ne typical feedstuff ingredients crop production practices and yields fertilizer insecticide and herbicide applications manure handling JCI use for crops irrigation transport feed grain processing cost of production for feed and animal management and revenue U 3 only from cattle or milk sold see partial list in Table 1 Byproduct feeds are apportioned to crOpping inputs relative to value of the crop products The C02 emission estimates are based on US practices Pimentel 1980 with diesel as the fuel of choice The US dairy cows averaged 613 kg live weight 37 replacement rates and 11 mo lactations producing 7200 to 9000 kg of milk annually containing 35 fat and 33 protein The US systems are dry lot or mixed operations with pasture comprising 0 to 31 of the herd diet Table 1 Alfalfa hay corn silage cereal grains soybean meal and39byp dii39cts cd tif tEd the principal diet ingredients averaging 105 MJ MEkg DM in the US Anaerobic lagoon disposal was used for 50 of the manure in California CA and very little in Wisconsin WI Fertilizer application rates ranged from 27 to 91 kg of N and 13 to 18 kg of P per ha The New Zealand pasture based dairy was characterized as a Holstein herd of cows weighing 511 kg producing 3444 kg of milk with 434 fat and 341 protein during a 270 day lactation annually LIC 1999 with a 15 replacement rate MWBNZ 1999 Mortality rates of 13 for cows Holmes 1999 and 4 to 5 for heifers and calves were assumed The diet contained 101 MJ MEkg DM 80 to 85 from pasture with the balance being haylage and a small fraction of maize silng Pa ieyields were 12 T DMha with fertilizer applications of63 and 78 kg on N an d Pha Wilcock et al 1999 and no irrigation Manure was applied to pESture primarily by grazing animals with 3 disposed through anaerobic lagoons at milk sheds Russell 1999 Results and discussion The 100 cow beef systems cowcalf through feedlot produced 37 t of live weight sales annually which includes 9 t from cull cows and bulls Table 1 Their diet was composed of 55 pasture and 20 hay These totals include the feedlot phase that used no pasture and only 10 to 20 forage Manure 10 t of manure N per herd was disposed on pastures for the cowcalf and stocker phases and by drylot methods from the feedlots Land requirements ha for the herds stockers and feedlot cattle from these five US counties with large numbers of beef cows averaged 315 ha range 122 to 745 Nitrogen fertilizer use averaged 22 therd with moderate variation by location Table 1 Characteristics of simulated US beef cowcalf through feedlot US and NZ dairy production systems US Beef US Dairies New Characteristics Zealand loo cow herds Average CA W CV l Dairy Mature cow weight kg 497 2 635 590 511 Cows calves replacements hd 168 1 167 180 127 Replacement 16 5 33 4O 15 Calving rate 92 3 93 93 96 Calf mortality to wean 10 42 91 108 90 Adult mortality 14 64 50 38 13 Live weight sold t 37 4 213 232 183 Milk sold kgcow 0 8982 7169 3444 Pasture 55 8 0 31 81 Other roughage 20 45 43 30 15 Total haherd 315 85 103 166 41 Nitrogen syn 103 kg 22 35 93 44 26 Fuel herd 1031 10 13 34 3o 4 Manure on pasture 89 4 0 42 94 Manure anaerobic lagoon 0 50 3 3 CV coefficient of variation CA California WI Wisconsin The GHG emissions as COzeq averaged 580 t CV7 from the cowcalf through feedlot beef production units Table 2 These US beef systems averaged 155 kg COgeqkg of live weight produced The emissions are predominantly from the cowcalf phase 77 with lesser amounts from the stocker 11 and feedlot 12 phases Digigigg gas source shows approximately 36 from CH4 52 from N20 and the balance from C02 Manure disposal accounted for a small fraction of the CH4 emissions since none of the beef systems simulated used anaerobic lagoons however manure from grazing or use for fertilizer produced a large part of the N20 emissions Nitrous oxide emission equivalents were the most variable among locations CV 33 Total COzeq emissions from the 100cow US dairy systems were about double those from the beef systems and 80 t390100 higher than loocow NZ dairies Table 2 When expressedas C02eqproduct however the NZ herd emissions of 162 kgkg of milk quotiiere slightly gf 39iiier These dairy system estimates are higher than found by Cedarberg 1998 who reported 10 kg C02 equivalent per kg milk on a whole farm or life cycle basis for conventional dairy farms in Sweden The CA dairy has the lowest C01eqmilk even with a larger amount of methane production from the 50 df manure disposal via anaerobic lagoons Comparison of the dairies according to enteric C114 per unit of milk shows even more advantage to the CA dairy which produces 12 less than those in WI and 40 less than those in NZ This comparison illustrates the strong effect of increasing productivity per cow resulting in reduced feed requirements and thus GHG output per unit of milk Examination of the fractional source of these varying amounts of GHG39s also shows considerable variation by production system M N a The CH4C02eq was the single largest contributor 45quotin39the CA dairy system with Nzocoreq and co contributing similar propertia ri39s39ef the balance of GHG emissions In W1 C02 emissions contributed the most COzeq at 40 of the total emissions while CH4 and N20C02eq were approximately equal The NZ System Was different 39i 39tlf rtth largest single source39rwas N20C02eq at 47 with 40contributed ot 39CII emeq 39The NZ syste i wasalso unique in that only 13 of the GHG39s were from C02 a re ection of dependence on hydroelectric power sources Table 2 Source strengths of beef and dairy GHG emissions annual C 0299 US Beef Cow Feedlot COzeq CA Dairy WI Dairy NZ Dairy Source of GHG Mean CV COzeq COzeq COzeq Enteric CH4 t per herd 206 10 320 292 207 kgkg product 55 03 036 041 060 Manure CH4 tper herd 52 15 185 l8 l6 kgproduct 014 04 021 003 004 N201 t per herd 301 33 330 298 259 kgproduct 81 09 037 042 076 3 C02 2 339 t per herd 67 11 296 407 74 quot kgproduct 18 03 033 057 022 Total GHG t per herd 580 68 1130 1015 556 11 kgproduc39t 155 10 126 138 162 tper ha 18 15 110 62 136 Nitrous oxide emissions are inherently highly variable Mosier et al 1998 and were estimated by IPCC 2000 methods Nitrous oxide COzeq emissions ranged from 301 to 330 t per 100cov39v beef or dairy herds Table 3 From 16 to 54 of the N20 emissions resulted from manure application or deposition dun39ng grazing A second source39ab39olit3930 quot is from indirect emissions of leached gaseous 6i mnoffN Other sources include legumes crop residues and manure management Nitrous oxide emissions are likely to be even more variable than indicated by this analysis because of variations by N application rates to soils season soil type ambient temperature soil moisture etc Table 3 Nitrous oxide emission sources t C02eq100cow herd om US cattle and NZ 1 S a dairy production systems 3 United States New Zealand Beef CA dairy WI dairy Dairy N20 Sources Annual t NzoCOzeq Synthetic fertilizer 12 51 24 15 Manurea 45 67 37 4 Manure management 10 70 28 0 Legume 63 29 43 5 Crop residueb 42 6 34 13 Grazing 90 0 43 139 Volatilized 19 19 17 16 Leaching 76 88 72 66 Total N20 therd 301 330 298 260 aIncludes animal waste and broiler litter bIncludes waste grass x N 5 Total annual N20 emissions expressed per land range from 04 from the UT beef system to 64 t N20C02eqlha from the NZ dairy The higher emissions are considerably above the 24 and 26 t N20 COzeq ha lyr39l noted previously for NZ grasslands Sherlock et al 1992 and Dutch dairy systems Velthof and Oenema 1997 The higher emissions likely re ect the increased emphasis of FCC 2000 default estimates for leached nitrogen 30 of manure and fertilizer applied to soil plus the inclusion of emission estimates om the N in grass residue Management andor mitigation strategy effects The variations in resource inputs and outputs 39om the dairy systems provide interesting insights to causes of variations in COzeqproduct Such variations in production or management techniques may serve as mitigation options The magnitud bf variations in GHGsourees per milk vary 39om 22fold for nitrous oxide to 8fold for manure methaneby production systemquot The wide range in manure methane emissions re ects the heavy dependence on anaerobic lagoon disposal used the CA systems resulting in 16quot396f COzeq from this source ascornparedJQS to 2 from NZ and WT systems respectively Not surprisingly anaerobic lagoon Use for dispOSal isthe most obiiidits tafg tfor G mitigation be a39us of the major increases in mefhane and some increases in nitrous oxide eriiiSsiOns 39 The dairy systems comparison reveals what appears to be a major limitation of V n U pastureonly dairy production systems the reduced rmlk production per cow resulting in a liigheiife d and methane cost associated with the higher proportion of feed going to maintenance This limitation occurs in spite of the approximately equal concentration of available energy Meal of MEkg diet DM in the pastures of NZ as found in the concentrate containing diets in the US Ruminant nutritionists feel that the bulky high moisture nature of grass causesthe limitation to ld g d fdMl E lk production of these cows since the geriatienpotential to produce milk has been shovvntqb aEpr1ma tely equal in US and NZcows If the C A eow39s prodiic d any as39 iiieh fat plus protein in their milk as the NZ cowsyr and lagoon use kept about equal the CA GHG emissions per unit milk would increase about 73 Conversely if NZ cows could eat enough grass and produce as much milk fat and protein annually as the CA cows the GHG emissions per unit milk would fall 37 Such factors can be illustrated with our model comparisons If the body weights are all equalized to the heaviest cows eg 635 kg as in CA the emissionsmilk increase 3 in WI and 15 in NZ other things being equal Thus i if easing annual per cow or better yet milk energy per cow has marked impacts on GEWAdditionally in nulung meiseqaaiizem that in CA numbers of young developing heifers would need to approximately double in NZ increasing the associated GHG emissions by about 12 for the herd with the same milk production If all of the above productivity weight manure ete factors are equalized across systems the total COzeqmilk are about equal but 39om somewhat different sources a 14 lower carbon dioxide cost in NZ is largely offset by a larger nitrous oxide emission Thegpastuvgeiystems at least in theNZ39govgryegraSS39swards contain about 70 more nitrogen than is39i equired which resultsm more nitrousoxide lossesthreugh manurerl guine xation crop residue andquot leagheilSlIs dureesm 39 39 An additional factor not considered is the number of calves availableiqprpduce beef omilgda rdmh i beis will be considerably greater 39with39fewer39cull cows 39om the NZ herd Lower replacement rates leave more calves to produce meat without maternal maintenance requirements and concomitant GHG emissions It is clear that these systems each have advantages and disadvantages Previous exercises Johnson et al 2001 with the cowcalf phase model showed emission responsiveness to modi ed herd characteristics or management criteria Changes of 10 in calvin l nQrtality rates have little effect onlierd emissions but nearly linear e ecmgl gleiHG euljgionpgr gain of the cowcalf phasELquotCha gi Ethe culling or cow repl EEment rate om 17 to 27 39 increased total herd COzeq by about 3 but gave a somewhat unexpected result of decreasing the cowcalf phase COzeqgain by 9 Thus an increased rate of slaughter of mature cows improves the emissions per product culls calves ratio With a 20 heavier mature cow size there was an increase of about 15 in each of the GHG but when these emissiOns were expressed on a per kg gain basis there was a 2 reduction in GHG emissions FrOm an economic standpoint increasing cow weights in this scenario improved pro tability Feed cost will probably determine whether the large cow scenario is pro table Appmmatelyym 9th total GHG emissions 39tesutt39 ngof beef fdduction 391 1 from t e stocker and 13 om the39feEdIOI39pl iaEes Presentedas zeq wt gainTurFmg Ethhase the ac at p 7 I ost ef cient39a d pfodmzes onlyquot 60 as much COzeq as the stocker phase at t39d approximatelyone rdilia i dfil cow calf phase Figure 1 Large emissions by the co WLcalf phasei3 ecfth greaterproportion of fEed used for maintenance Lower feedlot phase emissions per gain re ect the opposite high rates of gain and low proportions of feed forii riaintenance as well as the much low iilr39nethane emissions per unit of feed from cattle fed these 92 concentrate diets Emissions from C0 and N20 become dominate and about equal for the feedlot phase o39fUS beef production A scenario was examined in which all of the weaned beef calves went directly to the feedlot bypassmm stocker p ase Commough feedlot system w Wy I 39Kr VT r39t ciirectl eedl t the cattle 39 the s stem 80 less days and WU39c e39j s39t slightly more gain l e tota m fm med by about DWIWW iel and fertilizer use As would be expected these cattle emitted less CH4 per unit gain while N20 and C02 emissions were similar to the baseline scenario Overall the total COzeq were 8 less than the baseline Of themitigation strategies tested delivering the calves directly to the feedlot from an intensive grazing IG cowcalf mmmsmmmmmme reduced C02eqan71 increased o tabilmtigation strategy of choice Best management practices BMP for pasture or rangeland Follet et al 2001 andor cropland Lal et al 1998 used in or to produce feedstu s for livestock operations present signi cant tentials to offset GHG emissions with increased 39 uestrations pasture in the southeastern US although such increases in soilC are no e y in areas with less than moderate rainfall Other factors that must be considered are yield per ha or fertilizer inputs A simulation of likely yield increases 50 fertilizer inputs 20 forage composition changes and animal responses to intensive rotational grazing in the US for example would increase N20 decrease CH4 and total COzeq emissionsgain slightly o set 13 tol7 of emissions by soilC increases and decrease net GHGgain by 14 to 20 In any case these projections of Csequestration should be viewed as 39ballpark39 because of the highly variable and difficult to measure productivity animal harvest ef ciency and nutritive value of pasturerange Additionally long term 10 and fertilization of pastures can yield C sequestration losses as reported recently by Lambert et al 2000 following an l8yr study in New Zealand Table 4 An estimate of annual land use and C sequestration potential of US beef production systems 1 00cow herd basis Location in US Items AL TX UT VA w1 Mean Land Use haherd Managed pasture 143 102 129 104 94 Rangeland 0 239 587 0 0 Hay crops 131 223 210 152 206 Grain crops 137 427 68 124 73 Total haherd 170 406 745 132 122 Csequestration tlha t carbonherd BMP on pasture 04 57 41 52 42 38 BMP on range 0 0 12 29 0 0 BMP on hay crop 02 26 45 42 30 4 1 BMP on grain crOp 08 11 34 54 99 58 Total Csequestration 71 92 91 55 48 Csequestration COzeq 259 336 332 201 176 C02eq emissionsherd 605 638 555 554 548 Cseq offset potential 43 53 60 36 32 C02 Equivalents per gain kg Cow Calf Stocker D AA In d 39 DI non Feed lot CowFeedlot Figure 1 Relative source strengths of C Ozeq by beef production phase 39 Literature Cited Cedarberg C 1998 Life cycle assessment of milk production a comparison of conventional and organic farming Swedish Institute for Food and Biotechnology Report Nr 643 Conant RT J Six amp K Paustian 2001 Land use effects on soil carbon 39actions in the southeastern United States I Management intensive ver5us extensive grazing unpublished Colorado State Univ Nat Res Ecol Lab Follett RF JM Kimble amp R Lal 2001 The Potential of US Grazing Lands to Sequester Carbon and Mitigate the Greenhouse Effect Lewis Publishing Wash DC 437 pp Holmes CW 1999 An Outline of Dairy Production Systems in New Zealand Massey Univ Unpublished Mimeo IPCC 1996 Climate Change 95 Impacts Adaptations and Mitigation of Climate Change Scienti cTechnical Analyses Cambridge Univ Press IPCC 2000 Good Practice in Inventory Preparation for Agricultural Sources of Methane and Nitrous Oxide httpwwwipcch Johnson D E A Seidl amp H Phetteplace 2001 Methane nitrous oxide and carbon dioxide emissions from US beef production systems In Energy Metabolism in Animals Eur Ass Anim Prod Pub No 103 pp 161164 Johnson D E AF Seidl amp HW Phetteplace 2000a Livestock system greenhouse gases Effects of practices and policies on emissions and economic returns Final report to US EPA Wash DC Johnson D E H Phetteplace amp M Ulyatt 2000b Variations in proportion of methane of total greenhouse gas emissions 39om US and NZ dairy production systems Proc 2quotd International Methane Mitigation Conference Novosibirsk Russia USEPA p 249 Johnson DE GM Ward amp G Bemal 1997 Chapt 32 Biotechnology mitigating the environmental effects of dairying Greenhouse gas emissions In Milk Composition Production and Biotechnology Biotechnology in Agricultural Series No 18 Welch R et al Edit CAB International pp497 51 1 Lal R JM Kimble RF Follett amp CV Cole 1998 The Potential ofUS Cropland to Sequester Carbon and Mitigate the Greenhouse Effect Ann Arbor Press Chelsea MI 128 pp Lambert MG DA Clark AD Mackay amp DA Costall 2000 Effects of fertiliser application on nutrient status and organic matter content of hill soils N Z J Agric Res 43 127139 LIC 1999 Dairy statistics Livestock Improvement Corp Hamilton NZ Mosier A C Kroeze C Nevison O Oeneme S Seitzinger amp 0 van Cleemput 1998 Closing the global N20 budgetznitrous oxide emissions through the agricultural nitrogen cycle Nutr Cycling in Agroecosy 52225248 MWBNZ 1999 Compendium NZ Farm Production Statistics Meat and Wool Econ Service of NZ Wellington NZ NRC 1996 Nutrient Requirements of Beef Cattle 739h ed National Academy Press Wash DC NRC 1989 Nutrient Requirements of Dairy Cattle 6 ed National Academy Press Wash DC Pirnentel D 1980 Handbook of Energy Utilization in Agriculture Ed D Pirnentel CRC Press Boca Raton FL RLEP 1998 Proc Ruminant Livestock Ef ciency Program Edits ConneelyD and M Gibbs US EPA Robertson GP E A Paul amp RR Harwood 2000 Greenhouse gases in intensive agriculture contributions of individual gases to the radiative forcing of the atmosphere Sci 28919225 Russell JM 1999 Personal communication NZ Dairy Research Inst Palmerston North NZ Sherlock RR C Muller J M Russell amp RJ Haynes 1992 Inventory information on nitrous oxide Ministry of Environment NZ Velthof GL amp O Oenema 1997 Nitrous oxide emission from dairy farming systems in the Netherlands Netherlands J Agric Sci 45347360 Ward G M K G Doxtader W C Miller amp D E Johnson 1993 Effects of intensi cation of agricultural practices on emission of greenhouse gases Chemosphere 2687 Wells CM 1998 Total energy inputs as indicators of agricultural sustainability Dairy industry case study In Mander NK amp REI l Sims Eds Energy for Our Country Opportunities for the 215t Century Sustainable Energy Forum Wellington NZ Pp1 14 124 Wilcock RJ JW Nagels HHE Rodda MB O Connor BS Thorrold amp JW Barnett 1999 Water quality of a lowland stream in a New Zealand dairy farming catchment NZ J Marine Freshwater Res 33683696 COZ Production for dairy systems C02 Production C02herd 103 kg C02head 103 kg CO2Jmilk glkg COZImil39ksotids kg 002 103 kglha 002 Sources 103 kg Fertilizer including time Fuel Inseclicidelherbicide Irrigation Machinery o Embodied Total cropping Fuel milking equipment Fuel feed processing Fuel transportation feed or animals Total luel for term operation Embodied equipment Embodied buildings Embodied fences Total embodied farm energy excl cropping Total C02 sources CA Percent GHGNet WI Percent GHGNet C02 C02 Equival 002 Equival 02 Equiva Equival 296 177 39 329 462 289 482 352 39 335 684 1892 190 224 246 660 250 155 003 405 296 26 at total 223 137 407 226 567 834 248 314 707 99 00 1800 2921 372 190 44 606 384 155 004 539 407 40 of total 718 149 US Mean 351 202 648 268 Mean 398 530 69 167 1242 2406 281 207 145 633 317 155 003 472 351 SD 78 034 168 263 029 SD 119 252 42 237 789 728 128 24 143 38 95 00 001 78 of total 180 134
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