[acs symposium series] understanding greenhouse gas emissions from agricultural management volume...

Chapter 26

Quantification and Mitigation of GreenhouseGas Emissions from Dairy Farms

Hamed M. El-Mashada,b,c and Ruihong Zhang*,a

aBiological and Agricultural Engineering Department,University of California, Davis

bAgricultural Engineering Department, Mansoura University,El-Mansoura 35516, Egypt

cCurrent address: Agriculture and Environmental Sciences Department,Lincoln University, Jefferson City, Missouri 65101

*E-mail: [email protected]

Agriculture activities are major emission sources of greenhousegases (GHGs) such as carbon dioxide (CO2), methane(CH4) and nitrous oxide (N2O). About 18% of the globalanthropogenic GHGs are emitted from livestock productionactivities including land use. This chapter reviews the sourcesand quantities of GHG emissions on dairy farms. The methodscommonly used for measuring and quantifying GHG emissionsare presented and compared. Various mitigation strategiesfor reducing GHG emissions from dairy farms are discussed.These strategies include improved animal management relatedto animal breeding, animal housing, animal waste handling,and land application of animal manure. Potential uses ofmanure as a feedstock for the production of valuable productssuch as energy, fertilizers, chemicals and other materials arealso presented. Some critical research needs are identified inthe areas of mathematical modeling of GHG emissions andmitigation and in developing different technologies for manuremanagement and utilization.

© 2011 American Chemical Society

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In Understanding Greenhouse Gas Emissions from Agricultural Management; Guo, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

Introduction

Human activities emit many gases including greenhouse gases (GHGs) suchas carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The emissionsof greenhouse gases lead to global warming (1) . The major sources of the GHGsare energy supply, transport, industry, and agriculture sectors. The emissionof CO2 increased by about 80% from 1970 to 2004, due to the vast increasein energy consumption in industrial sectors (2). In 2004, agricultural activitiesand deforestation accounted for about 31% of the global anthropogenic GHGemissions in terms of CO2 equivalent (2) . Agriculture is the greatest contributorof N2O and CH4, accounting for about 60% and 50% of global anthropogenicemissions of the two gases, respectively (3) . The emissions of CH4 and N2Ofrom major agricultural activities from 1990 to 2008 are shown in Figures 1 and2. Livestock production activities, including land use, account for about 18% ofthe global anthropogenic GHG emissions (4). The main sources for the emissionsof CH4 and CO2 from dairy cows are enteric fermentation and respiration. Thestored manure is another significant source (5). However, animal respirationis not considered as a net source for the CO2 emissions, because animal feedpreviously sequestered atmospheric CO2 during plant growth (4). The emissionrates of different compounds depend on animal species, feeding practices, typeof confinement facility, manure management system (e.g., hadling and storage),and land application practices (6). The changes in the emissions over years wereattributed to the dynamics of the animal population and the changes in feed qualityand digestibility (7). The increase of CH4 emissions over years was also attributedto the increase in liquid manure application that has higher emissions than solidmanure. Agricultural soil management activities such as fertilizer application andother crop practices represented the major source of N2O emissions. There wasno significant difference in N2O emissions during this priod of time due to therelatively constant amount of nitrogen applied to soils. In addition to the sourcesshown in Figures 1 and 2, CH4 and N2O from field burning of the agriculturalresides represented respectively, about 0.5% and 0.2% of the total emissions ofthese compounds. Moreover, agricultural sources emit small amounts of CO2from the combustion of the fossil fuels to operate agricultural equipment.

The total emissions of GHGs from agricultural activities in the U.S. wereestimated to be 427.5 Tg CO2 eq in 2008, representing 6.1% of the total emissionsin the U.S. (7). The contribution of major emission sources is shown in Figure3. Greenhouse gases emitted from dairy farms include the net emissions of CO2plus the emissions of CH4 and N2O (9). Based on a life cycle analysis of milkproduction, CH4 represents 50% or more of GHG emissions from milk production(10). Emissions of N2O represent 27% -38% of the total emissions while CO2emissions represent only 5-10% of total emissions.

In this chapter, sources of GHGs (CH4 and N2O) in dairy farms, andquantification methods and mitigation strategies to alleviate their negative impacton the environment are discussed. According to Clemens et al. (11), ammonia isnot considered a greenhouse gas because of its short lifetime in the atmosphere,but its deposition induces N2O formation elsewhere.

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Figure 1. Total and major sources of CH4 emissions from agricultural activitiesin the U.S. from 1990 to 2008 (7). These calculations were based on a global

warming potential of 21 for CH4 (8).

Figure 2. Total and major sources of N2O emissions from agricultural activitiesin the U.S. from 1990 to 2008 (7). These calculations were based on a global

warming potential of 310 for N2O (8).

Figure 3. Emissions of CH4 and N2O from agricultural sector in the U.S.A. in2008 (7).

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Sources of Greenhouse Gas Emissions on Dairy Farms

A dairy farm is a complex system consisted of some subsystems such aslivestock, manure management, soil and crops (12). Dairy farming contributes toglobal warming directly through the emissions resulted from on-farm activitiesand indirectly through emissions from energy use, purchased goods and other Nemissions (13). In the model developed by Rotz et al. (9), the emission sources ofGHGs from a dariy farm were divided into primary and secondary sources (Figure4). Primary sources include different farm activities (i.e., feed production, animalmaintenance and manure handling). Secondary sources include the productionof fuel, electricity, machinery, fertilizer, pesticide and other materials used indifferent farm activities. It can also include emissions involved in the productionof replaced animals if any.

Emission Sources of Methane and Carbon Dioxide

Animals are a major source of CH4 and CO2 emissions on dairies. While CH4is produced under anaerobic conditions, CO2 is produced and emitted from animalfarms under both aerobic and anaerobic conditions as a result of the microbialdecomposition of organic matter (14). However, the CO2 emissions from animalsand their manure do not contribute to the long term increase in atmospheric CO2as it is part of carbon cycle that takes place over a short time period (6, 14).

Enteric fermentation is a major source of CH4 emissions. Methane isproduced by the methanogenic archaea present in rumen. Archaea are singlecell microorganisms genetically different from bacteria as they have genes andmetabolic pathways that are close to those of eukaryotes. About 6% –10% of thetotal gross energy consumed by a dairy cow is converted to CH4 and released viathe breath (15). This can be interpreted to an annual emission of 91-146 kg/head.The emissions of CH4 and CO2 were measured from a tie-stall farm housing 118lactating cows (16). Emission rates of CH4 and CO2 were 552 and 5756 L/d percow, respectively after subtracting the emissions from manure that were measuredto be 35 and 381 L/d per cow, respectively. The factors affecting the emissions ofboth CH4 and CO2 from animals are animal type, body weight, dry matter intake;and feed digestibility (17–20).

In addition to enteric fermentation, emissions of CH4 and CO2 take place frommanure collected on floors and in storages. The factors affecting the emissions ofCH4 and CO2 from manure on floors are manure handling, frequency of manureremoval, feed characteristics, weather conditions, and surface area (9, 21, 22). Thefactors affecting the emissions of CH4 and CO2 frommanure storage are amount ofmanure, type of manure storage, weather conditions, and the presence of storagecover (9, 23). Massè et al. (24) studied emissions of CH4 from manure storage at10 and 20 oC for 370 days, and concluded that frequent removal of manure in thesummer would significantly reduce CH4 emissions from manure storages.

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Figure 4. Sources of GHG emissions on farm (adapted from (9)).

Emission Sources of Nitrous Oxide (N2O)

Soils are the major sites for N2O emissions (6). While CH4 and CO2 areproduced via anaerobic degradation of organic matter, N2O is produced vianitrification and denitrification (25). CO2 is also produced during the aerobicdecomposition of organic matter when present in air or in soil. Among the factorsaffecting these two processes are degradable carbon and nitrogen, presenceof oxygen, application rate of nitrogen fertilizers and soil conditions such asmoisture content, ammonia content, pH, temperature, redox potential and physicalproperties of soils that affect gas diffusivity (26–30) . Soil with poor drainagehas more N2O emissions when nitrogen sources are available for nitrification anddenitrification. Moreover, manure application to cropland during the growingseason has less emissions of N2O as compared with manure applied to lands inthe absence of crops (6). This might be due to nitrogen uptake by plants. Thecharacteristics of manure, application time and rate, soil type, and crop type areamong the important factors affecting the emissions of N2O from manure appliedon grassland (31). Animal type is an important factor affecting the emissions ofN2O from manure due to the differences in manure compositions that resultedfrom the differences in diets, feed conversions and manure management (31).

In addition to the emissions from soils, N2O could be emitted from crust layersformed on the surface of manure storage, stacked solid and semisolid manure,bedded pack manure on barn floors, and unpaved dry lot surfaces (9). The factorsaffecting the emissions from these sources are surface area, temperature, rainfall,characteristics of crust layer, manure characteristics (e.g., pH, C/N ratio), storageduration and manure treatment technology applied if any (e.g., (32)). No N2O isformed and emitted when crust layer does not exist at the surface of liquid manurestorage (33).

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Quantification of Greenhouse Gas Emissions

Emission Factors

Quantification of the emission rate and total emissions of GHGs at thefarm level is an important step before developing and implementing mitigationstrategies, in order to focus on the sources of large emission sources (3). Themost common approach used for estimating the emissions of different compounds(e.g., CH4, NH3, and N2O) from animal farms is emission factors. They arederived based on the emission measurement data from a set of defined animalfeed operations to obtain an average emission value, for each compound, peranimal unit or per unit of production (34).

Table I. Emission factor of CH4 (kg C animal-1 yr-1) from entericfermentation of different animals

Source Emission factor References

Dairy cows 76.5 (40)

75.0 (39)

99.7 (41)

88.5 (42)

Heifers 47.3 (40)

52.9 (41)

42.0 (42)

Calves 36.8 (40)

13.1 (39)

36.8 (41)

35.3 (42)

Young cows 46.6 (39)

Bulls 58.3 (41)

56.3 (42)

Beef cows 54.0 (42)

Steers 35.3 (42)

Horses 9.8 (42)

Sheep 6.0 (42)

Goats 6.0 (42)

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Several methods are being applied for measuring emissions from dairy farms.Johnson and Johnson (35) discussed the basics, advantages and disadvantagesof each method. The are two common methods for quantifying emissions froma dairy farm. The first method is to measure short term air samples taken fromemission sources using enclosure techniques or tracer gas methods. The secondmethod is to use respiration chamber sampling systems such as whole animalchambers, head boxes, or ventilated hoods and face masks. A measurementsystem consists mainly of sampling system, measurement device and a mean ofdata acquisition and storage (36). Near infrared sensors, including photo-acousticand direct optical absorption sensors are commonly used for measuring theconcentrations of CO2, CH4 and N2O (37). The most common techniques formeasuring CH4 content in air are infrared spectroscopy, gas chromatography,mass spectroscopy, and tunable laser diode techniques. For direct measurementsof gas concentration, measuring devices are installed on site either directly atthe sampling location or at different locations. In the latter case, sample tubesand switch valves are used to transfer air sample to the measuring device (37).Samples could also be collected in gas tight bags and containers such as canistersand then sent off site for analysis. Tremblay and Massè (38) used respirationchamber approach to quantify CH4 emissions from a herd of 21 cows over 24 hper day for a period of one year. Using pure CH4, in the absence of animal, theaccuracy of CH4 recovery was found to be within ± 4.6% during 15 calibrationtests. Hensen et al. (39) estimated emission factors of CH4 and N2O from a 1200m3of slurry storred in Wageningen, Netherlands to be 11 g CH4 day-1 m -3 and0.014 g N2O day-1 m -3, respectively. Some emission factors of CH4 from entericfermentation and emissions factors of CH4 and N2O from manure management(handling, storage, and land application) for different animals are shown inTables I and II. As can be seen from these Tables, different emission factors werereported depending on farm and weather conditions. Dairy cows have the highestCH4 emission factors among other animal species.

Using a single emission factor for estimating the emissions of CH4 entails alarge error in emissions calculations for farms located in a small region (24).Thisis due to the differences in farm size, dynamics of herd, farm management andmanure handling systems. There are substantial uncertainties in the estimation ofGHG emissions from agricultural systems in general using emission factors (43).They include the insufficient understanding of the system and its interactions,variability in weather conditions and the validity and the distribution of possibleoutcomes. Emissions are also dependent upon farm management, rations, animalage and weight (e.g., (9)). Therefore, process-based emission models are superiortools for estimating emission rates and total emissions by including the factors thataffect emission dynamics (34, 44). The U.S. Environmental Protection Agency(USEPA) recently funded a project for measuring the emissions of different gasesfrom animal feeding operations (AFO). The study is called National Air EmissionsMonitoring Study (NAEMS). It is a two-year study of emissions from differentanimals AFO. Eight dairies are being studied in several states. Emissions aremonitored from barns and frommanure lagoons. The agency anticipates finalizingthe emissions estimating methodologies in June 2012. The NAMES study isexpected to provide reliable data on the emission rates of different GHGs under

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different weather conditions and farm practices. More information on the NAEMScan be found on http://www.epa.gov/airquality/agmonitoring/basicinfo.html. Theresults of the NAEMS could be also used to validate mathematical models for theestimation of GHG emissions.

Modeling of Greenhouse Gas Emissions

The GHG emission models are used for selecting cost-effective mitigationstrategies. They can also be used in extension and teaching (45). There are twoapproaches that can be used for modeling the emissions of GHGs on animal farms.The first is empirical and the other is mechanistic approach. Both types of modelsallow the calculation of emissions of different GHGs as a function of certain inputvariables. The empirical models are derived based on experimental data that arecollected under different conditions. In this approach, regression equations arederived to correlate the emissions of different GHGs with some of the factorsaffecting the emissions. These models are generally black box models where theprocesses (physical, biochemical, and mass transfer ) that control the emissionsare not distinguished rather the effects of these processes are lumped in certainvariables that drive the emissions. Empirical models are limited to the range ofexperimental conditions used to derive the models and do not allow the possibilityof changing certain input variables that influence specific processes that involvedin generation source, and transportation of GHGs from the source to the atmospher.

On the other hand, the mechanistic approach depends on understandingdifferent processes (physical, biochemical, and mass transfer) that govern thegeneration and transportation of different GHGs. Mechanistic models are usuallyderived using mathermatical equations including differential equations andlaws of physics, chemistry and mass transfer. However, in some instants (e.g.,absence of understanding of a certain process), mechanistic models can includesome empirical models. Mechanistic models for simulating GHG emissionsfrom dairy farms are usually divided into submodels. These submodels mayinclude submodels for emissions from animals, housing, manure storage and landapplications (Figure 5). Many input parameters can be included in mechanisticmodels so that it would be possible to accurately predict the emissions of differentGHGs. Mechanistic models in some cases are superior over empirical models.This is because validated mechanistic models can be applied to predict theemissions under a wide range of variables that affect the emissions of GHGs. Usersof validated mechanistic models can analyze the influence of different weatherconditions, farm designes, farm management, manure handling and manureapplication systems. With using detailed and validated mechanistic models, itcould be possible to develop cost effective and practical mitigation strategies forGHGs on the whole farm or for the sources that cause major emissions. Kebreabet al. (46) concluded that mechanistic models are more accurate when estimatingthe national emissions of CH4 from enteric fermentation. This is due to the factthat these models are based on the mathematical representation of biochemicalprocesses involved in ruminal fermentation. Moreover the chacteristics of animaldiet is an important input parameter for these models. The main drawback ofmechanic models is that they are more complex, contain more mathematical

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questions contain more input parameters, and require more time and mathematicaland modeling skills to develop as compared to empirical models.

Table II. Emission factors of CH4 (kg C animal-1 yr-1) and N2O (kg Nanimal-1 yr-1) from manure management

Type of animal CH4 emission factor N2O emission factor References

Dairy cow 7.1 114.7 (41)

27.0 -- (42)

Bulls 3.4 57.6 (41)

0.8 -- (42)

Beef cow 0.8 -- (42)

Suckler cow 2.0 33.6 (41)

Heifer 2.2 39.8 (41)

27.0 -- (42)

Beef heifer 0.8 -- (42)

Calve 1.4 26.2 (41)

0.8 --- (42)

Steers 0.8 --- (42)

Horses 1.1 --- (42)

Sheep 0.1 --- (42)

Goats 0.1 --- (42)

Models are usually used for quantifying CH4 emissions from entericfermentation (46). Models based on fermentation balance or feed characteristicshave been used to estimate CH4 production from animals (35). Mechanistic (e.g.,(47)) and empirical models (e.g., (48)) were used for calculating CH4 emissionsfrom enteric fermentation. Sommer et al. (20) developed a mathematical modelfor prediction of CH4 and N2O emissions during handling and use of liquidmanure. Their results showed that N2O and CH4 emissions from cattle slurrycould be reduced by 71% if slurry is anaerobically digested. A whole farm modelcalled DairyWise was developed by Schils et al. (12), which can be used topredict the changes in farm management. The model can accurately predict theflow of materials and nutrients inside a farm. It can also predict the exchange ofthese resources between the farming system and the surroundings. The model hasa submodel for estimating the GHG emissions from dairy farms using emissionfactors from Dutch emission inventories. The emission from enteric fermentationwas calculated based on an emission factor per each dry matter uptake. Emissionfrom manure was separately calculated from stored manure and from manureexcreted during grazing.

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Figure 5. Important input parameters and processes involved in mechanisticmodels.

Strategies for Mitigating the Greenhouse Gas Emissions

Emissions reductions of gaseous compounds from animal farms could beachieved using different approaches such as nutritional management, modificationof design of animal housing and manure storage, end-of-pipe air treatment, andanimal manure treatment and management (49). Three scenarios were reviewedfor the reduction of GHG emissions by Casey and Holden (50): improve milkproduction from cows so that fewer animals could supply the national milk quota,

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slaughter as many non-milk producing animals (i.e., slaughter scheme), andcombination of use of efficient cows with extensive management and eliminationof non-milking animals. The third scenario achieved the lowest GHG emissions.Emissions from enteric fermentation could be reduced by 28-33%. While the firstand second scenarios could reduce the emissions by about 14-18% and 14-26%,respectively.

Weiske et al. (51) discussed different measures for GHG mitigations in dairyfarms: optimizing lifetime efficiency of dairy cows, frequent removal of manure,anaerobic digestion of manure, and improved manure application techniques.Anaerobic digestion with capturing the produced biogas was considered as one ofthe effective mitigation measures for methane and and nitrous oxide emissions.This approach can eliminate CH4 emissions by converting it to energy source andtherefore reduce the fossil fuel consumption on farm. It can also prevent N2Oformation by restricting oxygen, a precursor for nitrification of NH4+ to N2O.

The control of the emission of a certain compound from manure mightenhance the emission of another compound or even of the same compounds atanother state of management (32) . For example, although anaerobic digestionreduces CH4 emissions, the low total solids of the digestate facilitate its infiltrationinto the soil, which reduced NH3 emission after application. However, theincreased pH and NH+4 content during digestion increases the potential of NH3emissions.

Mitigation of Methane Emissions

Mitigation of Emissions from Enteric Fermentation

Mitigation strategies for CH4 emissions from enteric fermentation werereviewed and are shown in Table III (15). The choice of a mitigation strategydepends on farm size, farm location, availability of resources and economicissues. Improving feed conversion efficiency and reducing the number of animalcould reduce CH4 emissions from the enteric fermentation (41). Increasing grainand soluble carbohydrates in animal ration decreases CH4 emissions as a resultof decreasing acetate concentrations (52). This is due to the fact that acetate is amain intermediate product for methane production.

Mitigation of Methane Emissions from Manure Storage

Controlled anaerobic digestion of manure can reduce GHG emissionsdirectly by the reduction in CO2 equivalent emissions and CO2 saving by biogasenergy that displaces fossil fuels and indirectly by reducing the nitrogen fertilizerproduction and use (41). Moreover, digested slurry emitted less GHGs duringstorage than untreated slurry (11). Anaerobic digestion could reduce up to 90% ofCH4 emissions from manure storage (20).

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Table III. Strategies for mitigating enteric CH4 emission (15)

Categories of mitigationstrategies

Subcategoriesof mitigationstrategies

Measures

Animal breeding - Improving feed conversionefficiency with using low feedintake,- Breeding ruminants with lowerCH4 production.

Animal manipulationAnimalmanagementsystem

- Reducing the number ofunproductive animals on a farm,- Extended lactation in dairying,- Applying novel productionsystems.

Forage quality - Feeding forages with low fiber andhigher soluble carbohydrates,- Changing from C4 to C3 grasses,- Addition of grain to forage dietincreases starch and reduces fiberintake,- Grazing on less mature pastures.

Plant breeding andplants secondarycompounds

- Increasing lipids and condensedtannins in forages,- Improve the digestability of feeds.- Increasing plant saponins andcondensed tannins concentration indiets.

Diet manipulation

Dietarysupplements

- Addition of yeasts, dietary oils,enzymes, dicarboxylic acids (e.g.,fumarate, malate, and acrylate).

Biological controlstrategies

- Inhibition of methanogenesis (e.g.,using bacteriophages),- Redirecting H2 to propionateproducers or acetogens,- Using bromochloromethane,chloroform and monesin asinhibitors for CH4 formation.

Rumen manipulation

Vaccination - Development of vaccines tocontrol methanogens.

Covering manure during storage and applying solid-liquid separation werealso found to be effective methods for mitigation of GHG emissions. Chadwick(53) studied the effect of compaction and covering during storage of farm yardmanure on the emission of NH3, CH4 andN2O. The results showed that compactionand covering significantly reduced emissions of NH3 and N2O. No significantdifferences were found on emissions of CH4 from digested slurry in storages withor without a straw cover (11). However, using wooden cover reduced the emission

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significantly. The effect of mixing manure with straw on GHG emissions wasstudied by Yamulki (54). Results showed that adding straw could be a promisingstrategy for reducing GHG emissions. The author attributed the reduction to thelowered mineralization at high C/N ratio and the increased aeration at the lowermoisture content that resulted from the addition of straw.

Amon et al. (32) studied the effects of solid-liquid separation with compostingof solid fraction, anaerobic digestion, slurry aeration and straw cover on emissionsof CH4, NH3 and N2O from liquid manure storages for 80 days and after manureapplication under field conditions. Ammonia emission after land application of theliquid fraction of mechanically separated manure was lower than that of untreatedmanure. However, a large amount of ammonia was emitted during compostingof the solid fraction. CH4 emissions after land application were small with alltreatments as compared with the emission during storage. Mechanical separationof solid fraction decreases the CH4 emissions by about 42%. During storage thelowest CH4 emissions were measured from the anaerobically digested manure dueto the fact that most of the biodegradable organics were consumed during digestionprocess. The amount of manure remaining for land application after emptying thestorage had a considerable effect on CH4 emissions as it can be a source of adaptedinoculum for CH4 production (24). Therefore, frequent cleaning of manure storagecould be a strategy for reducing the emissions of CH4. Cleaning manure storageassures the reduction of the amount of remaining manure that could carry enoughinoculum for the new manure added to storage.

Mitigation of Nitrous Oxide Emissions

Many strategies are being applied for mitigation of the emissions of N2O.The selection of a mitigation strategy depends on farm size and farm practice(e.g., type of manure storage and manure handling and processing). Managedgrasslands are the main source of N2O emission in dairy farming systems (55).Mitigation of N2O emission from these grasslands could be achieved by improvednitrogen fertilizer management, improved grassland management and improvedmanagement of livestock production. Improve nitrogen management (e.g.,reduction of ammonia volatilization and use corn silage) could achieve up to70% reduction of N2O emissions from dairy farming systems. Corn silage haslow concentrations of total protein, and therefore low amounts of nitrogen couldbe excreted when animal is fed corn silage (56). Application of nitrificationinhibitor (e.g., dicyandiamide) in grazed pasture soil significantly decreased N2Oemissions from animal urine patches by 56–73% (57). The nitrification inhibitorslows down the rate of the conversion of NH4+ to NO2 and NO3, and thus to N2O(58). Therefore, nitrification inhibitors reduce N2O emissions from nitrificationand denitrification processes (59).

Table IV summarizes potential mitigation measures for N2O emissions(15). Some of the measures are based on improving nitrogen recycling inanimal systems and producing genetic modified animals. Such measures includeincreasing the frequency and distributed area of urine either with feed or geneticmanipulations; decreasing the concentration of nitrogen in urine and increasingurination frequency by addition of salts that increase the water intake; and feed

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additions such as condensed tannins that protect the degradation of proteins inanimals. Other measures are based on reducing emissions from soils such ascontrolling the rate and timing of applications of animal manures and nitrogenfertilizers; injecting and incorporation of animal manure in soils; application ofnitrification inhibitors; irrigation and drainage management; and grazing on wetsoils. Emissions of N2O could also be reduced by breeding plants that use nitrogenmore efficiently, thus producing high energy to protein ratios. Aerated and strawcovered manure had the highest N2O emission during storage (32). After landapplication, digested slurry had the lowest emissions of N2O as compared withother treatments due to the low dry matter contents. Using impermeable coversfor manure storage could inhibit N2O emissions by depriving oxygen inside thestorage (11). Lower emissions of CH4 and N2O were found when applying dairyslurry to dry soils as compared with wet soils (31). Lower emission of N2O wasalso measured during summer than during spring due to the greater plant uptakeand increased ammonia volatilization in warming weather conditions.

Table IV. Strategies for mitigation of N2O emission (15)



Measures

Fertilizersand manureapplications

- Controlling the source, rate andtiming of application of manure andN fertilizer,- Selection of application technique(e.g., injection of manure couldincrease the direct emissionsof N2O but can decrease theindirect emissions of N2O dueto the reduction of ammoniavolatilization),- Adjusting the moisture content ofsoils before application,- Application of N fertilizer at leastthree days after manure application.-

Nitrificationinhibitors

- Applying nitrification-inhibitors-coated fertilizers and spraynitrification inhibitors such asnitrapyrin and dicyandiamide,- Feeding inhibitor to animals,- Breeding plants that secrete naturalnitrification inhibitors from theirroots.

Soils

Continued on next page.

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Table IV. (Continued). Strategies for mitigation of N2O emission (15)



Measures

Grazingmanagement

- Restricting grazing on wet soils,- Reducing grazing time andN-fertilizer application rates.

Irrigation anddrainage

- Irrigation through dry seasons,- Reducing water logging ofpastures,- Well drained soils is denitrifiedless efficiently than waterloggedsoils.

Animal breeding - Genetic modification to improvethe N conversion efficiency withinthe rumen,- Produce animal with morefrequent urination that leads to lessN concentration in urine,- Produce animal that walk whileurination that leads to greater urinespread.

Animals

Animal diet - Balancing the protein-energyratios,- Using high sugar varieties ofryegrass,- Addition of condensed tanninsextracts,- Salt supplementation increaseswater intake and thus reducingthe urinary N concentration andincreases the urination events.

Plants Plant breeding - Forages that use Nmore efficiently,- Forages that have a higherenergy-to-protein ratio,- Producing forages with high tannincontents.

Alternative Uses of Animal Manure To Mitigate Greenhouse Gas Emissions

Effective development and implementation of new technologies foralternative uses of animal manure are expected to result in significant reduction ofGHG emissions from manure sources. Different products can be produced frommanure (Figure 6). Alternative uses of animal manure can be in three categories:(1) conversion and use as an energy source, and (2) conversion to value-addedproducts and (3) innovative and emerging products (60).

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Figure 6. Alternative uses of dairy manure for energy and value-added products.

Many technologies and strategies already exist for converting animal manureinto energy and other valuable products and new technologies are also beingdeveloped with better efficiencies and/or new products. The current statusof various manure treatment technologies are reviewed in various literature,including reports produced by USEPA (60) and San Joaquin Valley Dairy ManureTechnology Feasibility Assessment Panel (61). Research and developmentare needed to apply these technologies to the processing of dairy manure anddevelop stable and high quality products to meet consumer demand. In orderto successfully produce and market the products derived from dairy manure,concerted effort is needed on several fronts, including technology developmentand demonstration, market development and testing, and policies. The overallenvironmental impact of alternative uses needs to be assessed when pursuing themaximum economic benefits.

Odor and pathogen free are the basic requirements for manure derivedproducts. Various technologies need to be applied to transform the manure orits constituents into desirable products. Emissions and effluent management forthese manure processing facilities must be carefully controlled to minimize theenvironmental and public health impact. Energy products that can be derivedfrom dairy manure include heat and biofuels, which include gaseous, liquid orsolid fuels. Gaseous fuels include syngas produced from thermal gasificationand biogas from anaerobic digestion. Liquid fuels include alcohols producedfrom fermentation and thermal oil from pyrolysis or hydrothermal liquification.Solid fuels are densified products such as pellets made from fibers. Based on thefacts that animal manure has complex chemical compositions and high moisturecontent, biogas production via anaerobic digestion processes appears to be the

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most energy efficient choice. Biogas is typically 50-70 % CH4 with the restmainly being CO2 and small quantities of moisture and other compounds. Byremoving moisture, CO2 and impurities, biogas can be upgraded to biomethane,a product equivalent to natural gas. The biomethane can be supplied to theexisting and future natural gas distribution systems. For dairy manure to becomeeffective feedstock for thermal processes, such as combustion and gasification,the manure needs to be dried to lower the moisture content to less than 50%.Manure collected from corals and solids separated from freestall manure could bemore suitable. Alcohol production from the fibers separated from dairy manurecould have good potential as they contain up to 70% cellulose and hemicelluloses.As the technologies for producing alcohols from lignocellulosic materials becomemore efficient and cost competitive, manure fibers may have increased values asfeedstock supply for alcohol production. Manufacturing solid fuel such as pelletsand briquettes from manure fibers for biomass power plants could see increasedinterest in the future.

The value added products include fertilizer, feed, chemicals and biobasedindustrial products. Manufacturing high quality fertilizer products from rawmanure or the effluent of other manure processing operations (e.g. anaerobicdigesters) requires specially designed technologies to meet the nutrient andproduct specification of fertilizer industry. Up to 50% of nitrogen and othernutrient elements are tied up in organic compounds in the manure as excreted.Manure treatment is normally needed to transform these elements into inorganicforms so that they become readily available when they are provided to theplants. Composted dairy manure has been well recognized as an excellent soilamendment and fertilizer. It can be also used as bedding materials for animals orgrowth media for mushroom. The nutrients contained in the liquid streams aremore challenging to manage as they are mixed with salt elements. Developingnew technologies to separate nutrients from salts is necessary in order to develophigh value fertilizer products. Using dairy manure as feed additives is practicedin some countries. Pathogens transfer, health risk, public relations, and nutrientdigestibility are concerns that will need to be addressed. Dairy manure is anexcellent nutrient source for growing various microorganisms for production ofenzymes, various chemicals (e.g. volatile fatty acids), and microbial products (e.g.single-cell protein and algae). This is relatively a new research area. The mostabundant components in the dairy manure are fibers. These fibers are now calledanimal-processed fibers (APF) (62). The fibers separated from raw manure or theeffluent of other processes, such as anaerobic digesters, could be used in animalbedding and potting soil or could be potentially become a valuable supplement inthe paper, pulp, and wood industries for manufacturing fiber-derived compositeproducts (e.g. fiberboard, particleboard, floor tiling, and siding) and as a bindingagent in adhesives, industrial tape and masonry patching materials (62).

In the past, most of the research and development effort has been focusedon energy production and fertilizer applications of dairy manure. As regulatoryand market based incentives for production of bioenergy and biobased productsbecome stronger driving forces, new opportunities have emerged and continueto expand for dairy and other biobased industries to invest in the developmentand deployment of various biorefinery technologies and business strategies for

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creating multiple revenues from dairy manure so that dairy manure could trulybecome a valuable resource, rather than a waste for disposal. This will requirethe dairy industry to re-evaluate current manure handling and managementsystems, make necessary changes in the manure collection methods and developand implement new processing technologies in order to meet the consumerrequirements for supplying dairy manure either as a biomass feedstock orproducts.

Summary and Conclusions

Greenhouse gas emissions from dairy farms are considered to be one of themajor air quality problems facing the dairy industries. The main sources of GHGemissions on farms are enteric fermentation and manure during storage and afterapplication to lands. Effective mitigation strategies are needed to alleviate thenegative effects of these gases on the environment. Quantification of the amountof GHG emissions is the first step towards developing cost effective mitigationstrategies. The most common methodology for estimating GHG emissionsfrom dairy farms is to use emission factors. This approach is seriously limitedbecause emission factors do not normally account for the dynamics of GHGemissions associated with the changes of both farm management and weatherconditions. Some mechanistic models have been developed to estimate GHGemissions under different farm management and weather conditions. However,validation of these models is still lacking. More research is needed for furtherdevelopment of these models to calculate emissions from different sources,animal feeding and manure management practices and under different weatherconditions. Many strategies were identified in the literature for mitigation of CH4and N2O emissions. These include genetic improvement of animals to increasefeed conversion efficiencies of animals, producing high quality feeds with highenergy to proteins ratios, dietary supplements, manure treatment technologies,and manure and soil additives. The mitigation potential and effectiveness of theseproposed mitigation measures should be evaluated under various managementscenarios. Mathematical models can play a substantial role in this regard. Thefollowing research needs can be identified for further development of science andtechnologies for creating and realizing the values from animal manure:

1. Identifying and developing markets for dairy manure derived productsand understanding the requirements for manure properties andcharacteristics in order to supply the manure as a valuable biomassfeedstock.

2. Developing literature, publications and educational programs to marketdairy manure effectively as designer products.

3. Developing innovative manure collection and processing methods formeeting the requirements of different consumer requirements for dairymanure or manure derived products.

4. Conducting both basic and applied research and demonstratingcommercial scale manure conversion and biorefinery technologies:

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- Pretreatment processes to make the manure solids morebiologically degradable;

- Advanced high-rate anaerobic processes for biomethaneproduction and integrated waste management;

- Lignocellulosic fermentation for alcohol production;- Solid fuel production and structural material manufacturing

from manure solids;- Thermochemical biomass-to-liquids (BTL) processes for

making renewable diesels, gasolines, alcohols, and otherfungible products;

- Advanced integrated biochemical and thermochemicalbiorefineries for improved yields and reduced cost;

- Advanced separation techniques for nutrient-salt separation;- Advanced separation techniques for fiber and other component

separation;- High quality solid and liquid fertilizer products; and- High quality growth media products for plants and

microorganisms.

References

1. United Nations Framework Convention on Climate Change (UNFCCC).Kyoto Protocol to the United Nations Framework Convention on ClimateChange; FCCC/CP/L7/Add.1, 10 December 1997; UN, New York, NY.

2. Intergovernmental Panel on Climate Change (IPCC). Climate Change 2007:Synthesis Report, Core Writing Team, Pachauri, R. K., Reisinger, A., Eds.;Geneva, Switzerland, 2007; p 104.

3. Intergovernmental Panel on Climate Change (IPCC). IPCC FourthAssessment Report: Climate Change 2007: Mitigation of Climate Change.Metz, B., Davidson, O. R., Bosch, P. R., Dave, R., Meyer, L. A., Eds.;Cambridge University Press: Cambridge, United Kingdom and New York,2007.

4. Steinfeld, H.; Gerber, P.; Wassenaar, T.; Castel, V.; Rosales, M.; Haan, C. de.Livestock’s Long Shadow; Environmental issues and Options; 2006; URLhttp://www.fao.org/docrep.010/a0701e/a0701e00.htm.

5. Hamilton, S.W.; DePeters, E. J.; McGarvey, J. A.; Lathrop, J.; Mitloehner, F.M. J. Environ. Qual. 2010, 39, 106–114.

6. Spellman, F. R.; Whiting, N. E. Environmental Management of ConcentratedAnimal FeedingOperations; CRCPress, Taylor&Francis Group: NewYork,2007.

7. Unitd States Environmental Protection Agency (USEPA). Inventoryof US Greenhouse Gas emissions and Sinks: 1990 – 2008; URLhttp://www.epa.gov/climatechange/emissions/downloads10/US-GHG-Inventory-2010_Report.pdf.

8. Intergovernmental Panel on Climate Change (IPCC). Greenhouse GasInventory Reference Manual; Revised 1996 IPCC Guidelines for National

511

Dow

nloa

ded

by P

EN

NSY

LV

AN

IA S

TA

TE

UN

IV o

n Ju

ne 1

9, 2

012

| http

://pu

bs.a

cs.o

rg

Pub

licat

ion

Dat

e (W

eb):

Oct

ober

11,

201

1 | d

oi: 1

0.10

21/b

k-20

11-1

072.

ch02

6


Greenhouse Gas Inventories, Vol. 3 (Paris, France, 1997); URLhttp://www.ipcc-nggip.iges.or.jp/public/gl/invs6.html.

9. Rotz, A. C.; Montes, F.; Chianese, D. S. J. Dairy Sci. 2010, 93, 1266–1282.10. Food and Agriculture Organization (FAO). Greenhouse Gas Emissions from

the Dairy Sector a Life Cycle Assessment; 2010; URL http://www.fao.org/docrep/012/k7930e/k7930e00.pdf .

11. Clemens, J.; Trimborn, M.; Weiland, P.; Amon, B. Agric., Ecosys. Environ.2006, 112, 171–177.

12. Schils, R. L. M.; de Haan, M. H. A.; Hemmer, J. G. A.; van den Pol-vanDasselaar, A.; de Boer, J. A.; Evers, A. G.; Holshof, G.; van Middelkoop, J.C.; Zom, R. L. G. J. Dairy Sci. 2007, 90, 5334–5346.

13. Schils, R. L. M.; Verhagen, A.; Aarts, H. F. M.; Kuikman, P. J.; Šebek, L. B.J. Global Change Biol. 2006, 12, 382–391.

14. Unitd States Environmental Protection Agency (USEPA). Emissions FromAnimal Feeding Operations; EPA Contract No. 68-D6-0011; 2001; URLwww.epa.gov/ttnchie1/ap42/ch09/draft/draftanimalfeed.pdf.

15. Eckard, R. J.; Grainger, C.; de Klein, C. A. M. Livestock Sci. 2010, 130,47–56.

16. Kinsman, R.; Sauer, F. D.; Jackson, H. A.; Wolynetz, M. S. J. Dairy Sci.1995, 78, 2760–2766.

17. Chianese, D. S.; Rotz, C. A.; Richard, T. L. Trans. ASABE 2009, 52,1313–1323.

18. Wilkerson, V. A.; Casper, D. P.; Mertens, D. R. J. Dairy Sci. 1995, 78,2402–2414.

19. Monteny, G. J.; Groenestein, C. M.; Hilhorst, M. A.Nutr. Cycl. Agroecosyst.2001, 60, 123–132.

20. Sommer, S. G.; Petersen, S. O.; Møller, H. B.Nutr. Cycl. Agroecosyst. 2004,69, 143–154.

21. Sommer, S. G.; Sherlock, R. R.; Khan, R. Z. Soil Biol. Biochem. 1996, 28,1541–1544.

22. Sherlock, R. R.; Sommer, S. G.; Khan, R. Z.; Wood, C. W.; Guertal, E. A.;Freney, J. R.; Dawson, C. O.; Cameron, K. C. J. Environ. Qual. 2002, 31,1491–1501.

23. Chadwick, D. R.; Sneath, R. W.; Phillips, V. R.; Pain, B. F. Atmos. Environ.1999, 33, 3345–3354.

24. Massè, D. I.; Masse, L.; Claveau, S.; Benchaar, C.; Thomas, O. Trans ASABE2008, 51, 1775–1781.

25. Monteny, G. J.; Bannink, A.; Chadwick, D. Agric., Ecosys. Environ. 2006,112, 163–170.

26. Eichner, M. J. J. Environ.Qual. 1990, 19, 272–280.27. Maag, M. Mitt. Dtsch. Boden. Ges. 1990, 60, 205–210.28. Parton, W. J.; Holland, E. A.; Del Grosso, S. J.; Hartman, M. D.; Martin, R.

E.; Mosier, A. R.; Ojima, D. S.; Schimel, D. S. J. Geophys. Res. 2001, 106(D15), 17403–17419.

29. Parton, W. J.; Mosier, A. R.; Ojima, D. S.; Valentine, D. W.; Schimel, D. S.;Weier, K.; Kulmala, K. E. Global Biogeochem. Cycles 1996, 10, 401–412.

512

Dow

nloa

ded

by P

EN

NSY

LV

AN

IA S

TA

TE

UN

IV o

n Ju

ne 1

9, 2

012

| http

://pu

bs.a

cs.o

rg

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ion

Dat

e (W

eb):

Oct

ober

11,

201

1 | d

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0.10

21/b

k-20

11-1

072.

ch02

6


30. Johnson, J. M. F.; Franzluebbers, A. J.; Weyers, S. L.; Reicosky, D. C.Environ. Pollut. 2007, 150, 107–124.

31. Chadwick, D. R.; Pain, B. F.; Brookman, S. K. E. J. Environ. Qual. 2000,29, 277–287.

32. Amon, B.; Kryvoruchko, V.; Amon, T. ; Zechmeister-Boltenstern, S. (2006).Agric., Ecosys. Environ. 2006, 112, 153-162.

33. Chianese, D. S.; Rotz, C. A.; Richard, T. L. Appl. Eng. Agric. 2009, 25,431–442.

34. National Research Council (NRC). Air Emissions from Animal FeedingOperations: Current Knowledge, Future Needs; The National AcademiesPress: Washington, DC, 2003

35. Johnson, K. A.; Johnson, D. E. J. Animal Sci. 1995, 73, 2483–2492.36. Saha, S.; Islam, M. T.; Hossain, M. Z. J. Eng. Appl. Sci. 2006, 1, 26–32.37. Teye, F. K. Ph.D. dissertation, Faculty of Agriculture and Forestry, University

of Helsinki, Finland, 2008.38. Tremblay, F. J. B.; Massè, D. I. Can. Biosys. Eng. 2008, 50, 721–728.39. Hensen, A.; Groot, T. T.; van denBulk,W. C.M.; Vermeulen, A. T.; Olesen, J.

E.; Schelde, K. Agric., Ecosyst. Environ. 2006, 112, 146–152.40. Van Amstel, A. R.; Swart, R. J.; Krol, M. S.Methane, the Other Greenhouse

Gas. Research and Policy in the Netherlands; RijksInstituut voorVolksgezondheid en Milieu: Bilthoven, 1993.

41. Kaparaju, P.; Rintala, J. Renew. Energ. 2011, 36, 31–41.42. Division Environment Canada; URL http://www.ec.gc.ca/pdb/ghg/

1990_00_report/acknow_e.cf.43. Gibbons, M.; Ramsden, S. J.; Blake, A. Agric., Ecosyst. Environ. 2006, 112,

347–355.44. Zhang, R.; Mitloehner, F.; Rumsey, T.; El-Mashad, H. M. ; Li, C.; Salas, W.;

Rotz, A.; Hafner, S.; Montes, F.; Arogo, J.; Xin, H.; Ni., J. Process BasedEmission Models for Predicting Gaseous Emissions from Animal FeedingOperations; White paper for Agricultural Air Quality Task Force, 2009.

45. Schils, R. L. M.; Olesen, J. E.; del Prado, A.; Soussana, J. F. Livestock Sci.2007, 112, 240–251.

46. Kebreab, E.; Johnson, K. A.; Archibeque, S. L.; Pape, D.; Wirth, T. J. AnimalSci. 2008, 86, 2738–2748.

47. Baldwin, R. L.Modeling Ruminant Digestion and Metabolism; Chapman &Hall: London, U.K., 1995.

48. Intergovernmental Panel on Climate Change (IPCC). 2006 IPCC Guidelinesfor National Greenhouse Gas Inventories; IGES, Hayama, Kanagawa, Japan;URL http://www.ipcc-nggip.iges.or.jp.

49. Melse, R. W. Ph.D. dessertation, Wageningen University, The Netherlands,2009.

50. Casey, J. W.; Holden, N. M. Agric. Syst. 2005, 86, 97–114.51. Weiske, A.; Vabitsch, A.; Olesen, J. E.; Schelde, K.; Michel, J.; Friedrich, R.;

Kaltschmitt, M. Agric., Ecosys. Environ. 2006, 112, 221–232.52. Chase, L. E. Methane emissions from dairy cattle. In the Proceedings of

Mitigating Air Emissions from Animal Feeding Operations Conference, IA,May 2008.

513

Dow

nloa

ded

by P

EN

NSY

LV

AN

IA S

TA

TE

UN

IV o

n Ju

ne 1

9, 2

012

| http

://pu

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eb):

Oct

ober

11,

201

1 | d

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0.10

21/b

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11-1

072.

ch02

6


53. Chadwick, D. R. Atmos. Environ. 2004, 39 (4), 787–799.54. Yamulki, S. Agric., Ecosys. Environ. 2006, 112, 140–145.55. Velthof, G. L.; van Beusichem, M. L.; Oenema, O. Environ. Poll. 1998, 102,

173–178.56. Rotz, C. A. J. Anim. Sci. 2004, 82 (E. Suppl.), E119–E137.57. Di, H. J.; Cameron, K. C. Biol. Fert. Soils 2006, 42, 472–480.58. Amberger, A. Commun Soil Sci. Plant Anal. 1989, 20, 1933–1955.59. Di, H. J.; Cameron, K. C. Aust. J. Soil Res. 2008, 46, 76–82.60. Unitd States Environmental Protection Agency (USEPA). Alternative

Technologies Uses of Manure; URL http://www.epa.gov/npdes/pubs/cafo_report.pdf.

61. San Joaquin Valley Dairy Manure Technology Feasibility Assessment Panel;URL www.arb.ca.gov/ag/caf/dairpnl/dairypnl.htm.

62. Sims, B. Biomass Mag. 2007, 11, 36–41.

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