Nutrient and Carbon Balance during the Composting of Deep Litter

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  • (Received 11 September 1998; accep

    During the storage of solid animal manure, biological transformation of nitrogen (N) and carbon (C) may

    increase the temperature from 60 to 703C, i.e. composting. Composting may cause emission losses of ammonia(NH

    3) and carbon dioxide (CO

    2). Furthermore, plant nutrients may leach from the compost heaps. During

    a composting period of 197 day from September 1997 to April 1998, emission of NH3, nitrous oxide (N

    2O),

    methane (CH4) and CO

    2was measured using dynamic chambers covering three heaps of deep litter from

    a house with dairy cows. Leaching of nutrients during composting was determined. Denitri"cation wasestimated as N unaccounted for in an N mass balance. The heaps were either mixed once after 30 days,compressed initially or left untreated. Compacting the heap caused a temperature increase from 10 to 50}603C.The temperature increased from 30 to 403C in the heap being mixed. From both the compacted and mixed heap,the cumulative ammonia volatilization was 0)2 kgN/t corresponding to between 2)6 and 3% of the total N. Halfof this amount was lost from the untreated heap in which the temperature only increased marginally in the "rstdays after the start of the experiment. Cumulative CO

    2losses were 33 (19%), 20 (12%) and 17 kg C/t (10%) from

    the litter mixed after 30 days, compressed deep litter and untreated deep litter, respectively. Emissions of N2O

    and CH4

    were low. Nitrogen losses due to leaching were (0)8% of the initial N. Total nitrogen losses due todenitri"cation, NH

    3emission and leaching was from 5 to 19% of the initial N, the lowest from mixed and the

    highest from untreated litter.( 1999 Silsoe Research Institute

    1. Introduction

    Solid manure amounts to about 20% of the Danishmanure (Poulsen & Kristensen, 1998). Farmyard manureconstitutes the majority of solid manure; however, anincreasing interest in loose housing systems built withsolid #oors strewn with straw for welfare reasons will infuture increase the amount of deep litter (Andersen et al.,

    feed and fertilizers, thus, a reduction in the loss of N fromagriculture is needed to maintain the plant production ontraditional farms. In organic farming, N is mainly pro-vided by N-"xing leguminous plants, and as large a partas possible of this N has to be transferred in manure fromthe grazed "elds to "elds in rotation. E$cient use ofmanure-N for plant production is, therefore, very impor-tant if plant production is to be maintained in bothJ. agric. Engng Res. (1999) 74, 145}153

    Nutrient and Carbon Balance duri

    S. G. Somm

    Research Centre Bygholm; Danish Institute of Agricultural Sciences, DDenmark; e-mail: Sven

    Article No. jaer.1999.0446, available online at http://www1999). It is the policy of the Danish government that10}20% of Danish agriculture should be farmed in agree-ment with the rules for organic farming. This will contri-bute to an increased production of solid manure, asorganic farmers tend to have animals on deep litter.

    During storage, 20}40% of N in deep litter may belost, mainly though gaseous emission (Karlsson & Jep-pson, 1995; Eghball et al., 1997). The Danish governmentintends to reduce the amount of N imported to farms in

    0021-8634/99/100145#09 $30.00/0 14ng the Composting of Deep Litter

    er; P. Dahl

    epartment of Agricultural Engineering; P.O. Box 536, 8700 Horsens,G. Sommer@agrsci.dk

    ted in revised form 29 May 1999)

    .idealibrary.com ontraditional and organic farming systems.Composting processes and gaseous emission of oxi-

    dized and reduced nitrogen has been measured duringcomposting of municipal litter or livestock manure beingturned frequently, often several times each week (Hell-man et al., 1997; Martin & Dewes, 1992). However, thereare few studies of nutrient losses from deep litter duringcomposting. During storage, the deep litter will start tocompost and organic farmers will enhance the composting

    5 ( 1999 Silsoe Research Institute

  • li

    process by mixing the heap once after one month, be-cause they believe that composting improves the fertilizervalue of organic manure.

    Gaseous emission of N of C and leaching losses ofN and P during composting of deep litter has beenquanti"ed in this study. A movable dynamic chamberwas used to determine gaseous losses, and liquid from thecompost was collected for the purpose of estimatingleaching losses of nutrients. Furthermore, the loss ofN caused by denitri"cation was estimated as a di!erenceby means of a mass balance. Techniques for reducing thelosses were developed and tested.

    2. Material and methods

    2.2. Dynamic chamber

    The dynamic chamber consists of a mobile chambercovering the storage during measurements, a ventilatorfor suction of air through the chamber, and equipmentfor measurement of gas, temperature and wind velocity.A "eld laboratory placed close to the experimental areaprovided the supply of electricity (340 V AC) to the venti-lators and instruments for measurement of gas emission.

    The three mobile chambers on wheels had the dimen-sions: height, 1)6 m; width, 2 m; and length 4 m. Thechambers were made of marine plywood and mountedon a metal frame, with only one gable closed by plywood,the opposite end being open for facilitating the chambersto be moved over the heaps, and connected to a station-ary gable placed at the end of the sealed surface. The

    S. G. SOMMER; P. DAHL146TabQuantity and composition of stored deep litter from housing of dauntreated. Volume of the deep litter heaps being 3, 32 and 36 m

    Sampling Treatment Amount,occasion t

    DM Ash Ntotal

    Initial Untreated 0)720 422 (1) 61 (1) 8)4 (0)3)Compressed 0)980 379 (50) 52 (6) 7)5 (1)1)Mixed 0)660 409 (11) 59 (2) 8)3 (0)1)

    End Untreated 0)810 214 (9) 46 (2) 6)0 (0)2Compressed 0)990 229 (5) 55 (4) 6)5 (0)3)

    2.1. reatments

    Gas emission and leaching losses of nutrients weremeasured during 197 days, composting in three pilot-scale heaps of deep litter from the housing of dairy cows.The litter was stored in heaps with a length of 3)7 m,width of 1)9 m and height of 1)3 m on a sealed surface(length of 4m, width of 2 m), with collection of runo! toclosed containers buried in the soil. The amount andcomposition of the deep litter used for composting isgiven in Table 1. In the experiment from 29th September1997 to 14th April 1998, the deep litter was mixed bytreating the material three times with a manure spreaderon the "rst day of the experiment. Immediately after thistreatment, three portions of the litter were stored underthe following conditions: (1) compressed once duringstorage, (2) mixed once by turning the heap manuallyafter 30 d, and (3) untreated.Mixed 0)810 202 (3) 46 (3) 6)4 (0)4)

    DM, dry matter; TAN, total ammoniacal nitrogen.e 1ry cows. The deep litter was compressed, mixed after 30 days and3, respectively. (Standard deviation in bracket for two samples)

    Composition, g/kg

    TAN NO3 P K C

    0)54 (0)03) 0)20 (0)00) 1)43 (0)03) 13)5 (0)1) 177)9 (0)9)0)63 (0)04) 0)13 (0)04) 1)21 (0)20) 12)0 (1)3) 160)3 (24)2)0)60 (0)04) 0)25 (0)04) 1)40 (0)02) 13)7 (0)5) 172)4 (4)8)

    0)21 (0)02) 0)00 (0)00) 1)16 (0)04) N.D. 85)98 (6)1)0)26 (0)02) 0)00 (0)00) 1)31 (0)07) N.D. 91)65 (4)3)

    gable on the chambers had an opening for incoming air.A steel tube (length of 2 m, inner diameter of 0)40 m) witha ventilator was connected to the stationary gable. A rec-tangular metal frame was mounted on the sealed surfaceperpendicular to the stationary gable. The dimensions(length of 4 m, width of 2 m) of the frame allowed it to "tclosely with the chambers when mounted. Air was drawnthrough the chamber by the ventilator, enabling mea-surements of the #ux of gases to and from the chamber.

    Air#ow through the dynamic chamber was measuredwith cup anemometers in the steel pipe, the air#ow ratescould be adjusted from the "eld laboratory. Air temper-ature and the temperature 0)40 m above the bottom ofthe deep litter heap was measured with PT100 and ther-mocouple sensors (Kontram A/S, DK-Copenhagen). Thesensors were connected to a datalogger (DatatakerDT200, Data Electronics Ltd, Australia).

    One-quarter of an hour before a measurement, thechambers were moved over the deep litter heap and "xed0)23 (0)02) 0)00 (0)00) 1)17 (0)05) N.D. 79)20 (3)0)

  • to the stationary gable. When measuring emissions ofNH

    3, the wind speed was adjusted to 3 m/s; and when

    measuring emission of N2O, CH

    4and CO

    2, the wind

    speed was adjusted to 1)2 m/s. Atmospheric NH3

    of air#owing into the chambers and from each chamber wasdetermined with two active denuders (Ferm, 1979) ateach sampling occasion. For the analysis of CH

    4, N

    2O

    and CO2, four gas samples of 55 ml were taken with

    syringes both at the inlet of the chamber, and from thesteel tube 30 cm from the gable on each measuring occa-sion. The samples were stored as described below for gassamples taken from the deep litter heap. The emissionwas calculated as the di!erence in the #ux between theincoming and outgoing gases. Determination of emissionwas stopped in January 1997 after 87 days, because nogas emission could be detected in January. Concentra-tions of gas in and emissions from the heaps were deter-mined twice on the "rst day, once each day from day 2to 6, twice per week from week 2 to 5, once each weekfrom week 6 to 8 and once every fortnight from week9 to 12.

    2.3. Gas-phase composition

    For the determination of CH4, N

    2O, CO

    2and oxygen

    (O2) gas samples were collected from the centre of the

    deep litter heaps by modifying the technique of Petersenet al. (1998). The two ends of a #exible, but rigid plastictube with an internal diameter (i.d.) of 10 mm and con-taining four holes, 2 mm in diameter, per cm length wereconnected to two 2 m lengths of gas-tight Te#on tubes(i.d. 2 mm). The Te#on tubes were connected to a dia-phragm pump (Model 5002, ASF GmbH, Germany).A silicone tube was inserted into the rigid tube, but after2}3 weeks no air samples could be collected, and on day30 the silicone tube was removed from the rigid plastictube in the heap that was mixed after 30 days. A septumfor gas sampling was located immediately after the dia-phragm pump, continuously circulating air through thetubes during an experiment. Four samples of 60 ml weretaken at each sample collection with syringes. The gassamples were transferred to 5 ml glass bottles "tted withbutyl rubber septa. When transferring a sample to the glassbottle, an extra needle was inserted through the rubber sealand the bottle was #ushed with 45 ml of the gas in thesyringe; then the needle penetrating the septum was re-moved and the 15 ml remaining in the syringe was injected.

    2.4. Nutrient composition

    COMPOSTING OAt the initiation and the conclusion of the experiment,two samples each of 2 l of organic material were takenfrom each heap. Samples of liquid (0)5 l) leaching fromthe dung heap were taken when the containers werenearly full and emptied. The samples of organic materialand liquid were stored at !183C.

    Before analysis, the organic material was thawed to03C and the sample of 2 l was "nely chopped with a cut-ting machine. Representative subsamples of about 500 gof the chopped material were then cut into small piecesand from this material 100 g was taken for analysis. Allmanure samples were analysed for dry matter (DM), ashcontent, total C, Kjeldahl N (N

    505!-), total ammoniacal

    nitrogen (TAN), NO~3, P and K.

    2.5. Analysis

    2.5.1. AmmoniaThe concentration of ammonia in the air from the

    background and from the dynamic chamber was deter-mined by active denuders (Ferm, 1979). An active de-nuder consists of a glass tube (length 500 mm, innerdiameter 7 mm) coated on the inside with oxalic acid,through which air is drawn at a "xed air#ow. A dia-phragm pump provides suction and a critical ori"ceadjusts the air#ow to exactly 0)9 l/min through the de-nuder. All NH

    3#owing into the tube is absorbed by the

    oxalic acid. After exposure, the amount of NH3absorbed

    in the tubes was determined, by dissolving the coating in5 ml water and analysing NH

    3concentration using

    a QuickChem 4200 (Lachat Instruments WI, USA).

    2.5.2. Methane, nitrous oxide, carbon dioxide and oxygenNitrous oxide and CH

    4were measured on a Hewlett-

    Packard (5890, series II) gas chromatograph with anelectron capture detector and a #ame ionization detector.It was equipped with a 1)8 m]3 mm column withporapak Q 80/100 for N

    2O; with Ar/CH

    4(95/5) used as

    carrier gas at 30 ml/min; and temperatures of injectionport, oven and detection were 110, 40 and 3203C, respec-tively. Methane was isolated with a 1)8 m]3 mm columnwith poropak N 80/100; He was used as a carrier gas at30 ml/min; and temperatures of injection port, oven anddetection were 110, 40 and 2703C, respectively. Oxygenand CO

    2were measured on a Varian 3350 gas chromato-

    graph equipped with a thermal conductivity detector. Itwas equipped with a 1 m]3 mm column with MolecularSieve 5A 60/80 for isolating O

    2and a 2 m]3 mm Haysep

    R 80/100 for CO2. The carrier gas was He at a #ow rate

    of 30 ml/min, and the temperatures of oven and detectorwere 30 and 1903C, respectively.

    147F DEEP LETTER2.5.3. Nutrient compositionTotal ammoniacal nitrogen and NO~

    3in the solid

    manure were extracted in 1 M KCl for 30 min, "ltered

  • before analysis with a QuickChem 4200 #ow injectionanalyser (Lachat Instr. WI, USA). Dry matter was deter-mined after drying at 1053C for 24 h, and ash content at5503C for 4 h. Total C was determined by dry combus-tion (Leco model 521-275), K by #ame photometry(FLM3, Radiometer) after incineration and dissolving inacid, and P was measured colorimetrically (Spectronic1001, Braush & Lomb) after incineration and dissolvingin acid, and a colouring reaction with ammonium molyb-date vanadate. Total nitrogen was analysed usingthe Kjeldahl method and a Kjellfoss 16200(Copenhagen, DK). Total-nitrogen, P, K, TAN and NOv

    3in the leachate from the dung heap were determinedwithout extraction.

    2.6. Calculations

    The average NH3

    concentration Catm

    in g NH3-N/m3

    in the air passing through two Ferm tubes used at eachsampling occasion was calculated by the following equa-tion:

    Catm

    "(C1#C2!2C3 )

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