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8/13/2019 CN Balance Deep CompostingNutrient and Carbon Balance During the Composting of Deep LitterNutrient and Car
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J. agric. Engng Res. (1999) 74, 145}153
Nutrient and Carbon Balance during the Composting of Deep Litter
S. G. Sommer; P. Dahl
Research Centre Bygholm; Danish Institute of Agricultural Sciences, Department of Agricultural Engineering; P.O. Box 536, 8700 Horsens,Denmark; e-mail: Sven G. [email protected]
(Received 11 September 1998; accepted in revised form 29 May 1999)
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
) and carbon dioxide (CO
). Furthermore, plant nutrients may leach from the compost heaps. During
a composting period of 197 day from September 1997 to April 1998, emission of NH
, nitrous oxide (N
O),
methane (CH
) and CO
was 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 was
estimated 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 kg N/t corresponding to between 2
)6 and 3% of the total N. Half
of this amount was lost from the untreated heap in which the temperature only increased marginally in the "rst
days after the start of the experiment. Cumulative CO
losses 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 N
O
and CH
were low. Nitrogen losses due to leaching were (0)8% of the initial N. Total nitrogen losses due to
denitri"cation, NH
emission 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 Danish
manure(Poulsen & Kristensen, 1998). Farmyard manure
constitutes the majority of solid manure; however, an
increasing interest in loose housing systems built with
solid #oors strewn with straw for welfare reasons will in
future increase the amount of deep litter(Andersenet al.,
1999). It is the policy of the Danish government that
10}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 be
lost, mainly though gaseous emission (Karlsson & Jep-
pson, 1995;Eghballet al., 1997). The Danish government
intends to reduce the amount of N imported to farms in
feed and fertilizers, thus, a reduction in the loss of N fromagriculture is needed to maintain the plant production on
traditional farms. In organic farming, N is mainly pro-
vided by N-"xing leguminous plants, and as large a part
as possible of this N has to be transferred in manure from
the grazed "elds to "elds in rotation. E$cient use of
manure-N for plant production is, therefore, very impor-
tant if plant production is to be maintained in both
traditional and organic farming systems.
Composting processes and gaseous emission of oxi-
dized and reduced nitrogen has been measured during
composting of municipal litter or livestock manure beingturned frequently, often several times each week (Hell-
manet al., 1997;Martin & Dewes, 1992). However, there
are few studies of nutrient losses from deep litter during
composting. During storage, the deep litter will start to
compost and organic farmers will enhance the composting
Article No. jaer.1999.0446, available online at http://www.idealibrary.com on
0021-8634/99/100145#09 $30.00/0 145 1999 Silsoe Research Institute
8/13/2019 CN Balance Deep CompostingNutrient and Carbon Balance During the Composting of Deep LitterNutrient and Car
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Table 1Quantity and composition of stored deep litter from housing of dairy cows. The deep litter was compressed, mixed after 30 days anduntreated. Volume of the deep litter heaps being 3, 3'2 and 3'6 m
3, respectively. (Standard deviation in bracket for two samples)
Sampling Treatment Amount, Composition, g /kgoccasion t
DM Ash Ntotal TAN NO3 P K C
Initial Untreated 0)720 422 (1) 61 (1) 8)4 (0)3) 0)54 (0)03) 0)20 (0)00) 1)43 (0)03) 13)5 (0)1) 177)9 (0)9)Compressed 0)980 379 (50) 52 (6) 7)5 (1)1) 0)63 (0)04) 0)13 (0)04) 1)21 (0)20) 12)0 (1)3) 160)3 (24)2)
Mixed 0)660 409 (11) 59 (2) 8
)3 (0
)1) 0
)60 (0
)04) 0
)25 (0
)04) 1
)40 (0
)02) 13
)7 (0
)5) 172
)4 (4
)8)
End Untreated 0)810 214 (9) 46 (2) 6)0 (0)2 0)21 (0)02) 0)00 (0)00) 1)16 (0)04) N.D. 85)98 (6)1)Compressed 0)990 229 (5) 55 (4) 6)5 (0)3) 0)26 (0)02) 0)00 (0)00) 1)31 (0)07) N.D. 91)65 (4)3)Mixed 0)810 202 (3) 46 (3) 6)4 (0)4) 0)23 (0)02) 0)00 (0)00) 1)17 (0)05) N.D. 79)20 (3)0)
DM, dry matter; TAN, total ammoniacal nitrogen.
process by mixing the heap once after one month, be-
cause they believe that composting improves the fertilizer
value of organic manure.
Gaseous emission of N of C and leaching losses ofN and P during composting of deep litter has been
quanti"ed in this study. A movable dynamic chamber
was used to determine gaseous losses, and liquid from the
compost was collected for the purpose of estimating
leaching losses of nutrients. Furthermore, the loss of
N caused by denitri"cation was estimated as a di!erence
by means of a mass balance. Techniques for reducing the
losses were developed and tested.
2. Material and methods
2.1. reatments
Gas emission and leaching losses of nutrients were
measured 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!to
closed containers buried in the soil. The amount and
composition of the deep litter used for composting isgiven inTable 1.In the experiment from 29th September
1997 to 14th April 1998, the deep litter was mixed by
treating the material three times with a manure spreader
on the "rst day of the experiment. Immediately after this
treatment, three portions of the litter were stored under
the following conditions: (1) compressed once during
storage, (2) mixed once by turning the heap manually
after 30 d, and (3) untreated.
2.2. Dynamic chamber
The dynamic chamber consists of a mobile chamber
covering the storage during measurements, a ventilatorfor suction of air through the chamber, and equipment
for measurement of gas, temperature and wind velocity.
A "eld laboratory placed close to the experimental area
provided 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. The
chambers were made of marine plywood and mounted
on a metal frame, with only one gable closed by plywood,
the opposite end being open for facilitating the chambers
to be moved over the heaps, and connected to a station-
ary gable placed at the end of the sealed surface. The
gable on the chambers had an opening for incoming air.
A steel tube (length of 2 m, inner diameter of 0 )40 m) with
a ventilator was connected to the stationary gable. A rec-
tangular metal frame was mounted on the sealed surface
perpendicular to the stationary gable. The dimensions
(length of 4 m, width of 2 m) of the frame allowed it to "t
closely with the chambers when mounted. Air was drawn
through 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 measured
with 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 of
the deep litter heap was measured with PT100 and ther-
mocouple sensors (Kontram A/S, DK-Copenhagen). The
sensors were connected to a datalogger (Datataker
DT200, Data Electronics Ltd, Australia).
One-quarter of an hour before a measurement, the
chambers were moved over the deep litter heap and "xed
S . G . S O M M E R ; P . D A H L146
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to the stationary gable. When measuring emissions of
NH
, the wind speed was adjusted to 3 m/s; and when
measuring emission of N
O, CH
and CO
, the wind
speed was adjusted to 1)2 m/s. Atmospheric NH of air
#owing into the chambers and from each chamber was
determined with two active denuders (Ferm, 1979) at
each sampling occasion. For the analysis of CH
, N
O
and CO
, four gas samples of 55 ml were taken with
syringes both at the inlet of the chamber, and from the
steel tube 30 cm from the gable on each measuring occa-
sion. The samples were stored as described below for gas
samples taken from the deep litter heap. The emission
was calculated as the di!erence in the #ux between the
incoming and outgoing gases. Determination of emission
was stopped in January 1997 after 87 days, because no
gas 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 2
to 6, twice per week from week 2 to 5, once each week
from week 6 to 8 and once every fortnight from week
9 to 12.
2.3. Gas-phase composition
For the determination of CH
, N
O, CO
and oxygen
(O
) gas samples were collected from the centre of thedeep litter heaps by modifying the technique ofPetersen
et al. (1998). The two ends of a #exible, but rigid plastic
tube with an internal diameter (i.d.) of 10 mm and con-
taining four holes, 2 mm in diameter, per cm length were
connected 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 after
2}3 weeks no air samples could be collected, and on day
30 the silicone tube was removed from the rigid plastic
tube 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 the
tubes during an experiment. Four samples of 60 ml were
taken at each sample collection with syringes. The gas
samples were transferred to 5 ml glass bottles "tted with
butyl rubber septa. When transferring a sample to the glass
bottle, an extra needle was inserted through the rubber seal
and the bottle was #ushed with 45 ml of the gas in the
syringe; then the needle penetrating the septum was re-
moved and the 15 ml remaining in the syringe was injected.
2.4. Nutrient composition
At the initiation and the conclusion of the experiment,
two samples each of 2 l of organic material were taken
from each heap. Samples of liquid (0)5 l) leaching from
the dung heap were taken when the containers were
nearly full and emptied. The samples of organic material
and liquid were stored at !183C.Before analysis, the organic material was thawed to
03C and the sample of 2 l was "nely chopped with a cut-
ting machine. Representative subsamples of about 500 g
of the chopped material were then cut into small pieces
and from this material 100 g was taken for analysis. All
manure samples were analysed for dry matter (DM), ash
content, total C, Kjeldahl N (N
), total ammoniacal
nitrogen (TAN), NO
, P and K.
2.5. Analysis
2.5.1. Ammonia
The 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, inner
diameter 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"ce
adjusts the air#ow to exactly 0)9 l/min through the de-
nuder. All NH#owing into the tube is absorbed by the
oxalic acid. After exposure, the amount of NH
absorbedin the tubes was determined, by dissolving the coating in
5 ml water and analysing NH
concentration using
a QuickChem 4200 (Lachat Instruments WI, USA).
2.5.2. Methane,nitrous oxide,carbon dioxide and oxygen
Nitrous oxide and CH
were measured on a Hewlett-
Packard (5890, series II) gas chromatograph with an
electron capture detector and a #ame ionization detector.
It was equipped with a 1)8 m3 mm column with
porapak Q 80/100 for N
O; with Ar/CH
(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 m3 mm column
with poropak N 80/100; He was used as a carrier gas at
30 ml/min; and temperatures of injection port, oven and
detection were 110, 40 and 2703C, respectively. Oxygen
and CO
were measured on a Varian 3350 gas chromato-
graph equipped with a thermal conductivity detector. It
was equipped with a 1 m3 mm column with Molecular
Sieve 5A 60/80 for isolating O
and a 2 m3 mm Haysep
R 80/100 for CO
. The carrier gas was He at a #ow rate
of 30 ml/min, and the temperatures of oven and detectorwere 30 and 1903C, respectively.
2.5.3. Nutrient composition
Total ammoniacal nitrogen and NO
in the solid
manure were extracted in 1 M KCl for 30 min, "ltered
147COMPOSTING OF DEEP LETTER
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before analysis with a QuickChem 4200 #ow injection
analyser (Lachat Instr. WI, USA). Dry matter was deter-
mined after drying at 1053C for 24 h, and ash content at
5503C 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 in
acid, and P was measured colorimetrically (Spectronic
1001, Braush & Lomb) after incineration and dissolving
in acid, and a colouring reaction with ammonium molyb-
date vanadate. Total nitrogen was analysed using
the Kjeldahl method and a Kjellfoss 16200
(Copenhagen, DK). Total-nitrogen, P, K, TAN and NO
in the leachate from the dung heap were determined
without extraction.
2.6. Calculations
The average NH
concentrationC
in g NH
-N/m
in the air passing through two Ferm tubes used at each
sampling occasion was calculated by the following equa-
tion:
C"
(C#C
!2C
)