2660
Energy & Fuels 2006, 20, 2660-2665
Multi-utilization of Chicken Litter as Biomass Source. Part I.
Combustion
Nathan Whitely,† Riko Ozao,†,‡ Ramon Artiaga,†,§ Yan Cao,† and Wei-Ping Pan*,†
Institute for Combustion Science and EnVironmental Technology, Western Kentucky UniVersity,
Bowling Green, Kentucky, 42101
ReceiVed September 24, 2005. ReVised Manuscript ReceiVed May 28, 2006
Chicken litter disposal is a major economic and pollution concern. Poor waste management practices lead
to air and water pollution. To produce a useful renewable resource for energy, optimal conditions for combustion
were studied. Three samples differing in particle size were obtained from the chicken litter by drying, milling,
and sieving, each at a recovery of (A) larger than 150 µm in size, 87.5%; (B) between 150 and 45 µm in size,
6.3%; and (C) below 45 µm in size, 6.3%. Sample A showed the highest calorific value (5 300 BTU lb-1)
12 320 kJ kg-1) and lowest ash content (ca. 25%), whereas sample C showed the lowest calorific value (2 900
BTU lb-1 ) 6 740 kJ kg-1) and highest ash content (ca. 54%). Evolved gas analysis (EGA) techniques, including
thermogravimetric-mass spectrometry (TG-MS) and TG-Fourier transform infrared (TG-FTIR) were used to
identify off-gases. Kinetic analyses using thermogravimetric analysis (TGA) were also performed to find that
the combustion process proceeds in four stages (where E represents the activation energy): (I) release of
absorbed water and ammonia stemming from ammonium salts (room temp (RT) ) 150 °C), E ) 61.72 kJ
mol-1; (II) devolatilization (150-350 °C), E ) 71.43 kJ mol-1; (III) char precombustion (350-500 °C), E )
148.5 kJ mol-1; and (IV) rapid char combustion (500-650 °C), E ) 157.6 kJ mol-1. In stage III, the combustion
is retarded because N concentration is high.
Introduction
Commercial chicken production is one of the largest agricultural industries in the United States. Over 16 million tons of
chicken were produced within the United States during 2003,
with nearly 85% of that chicken being consumed within the
continental United States.1 In addition, chicken surpassed beef
as the most consumed meat in the United States in 2003, with
the average American consuming over 43 kg of chicken
annuallysover one-third of total meat consumption.2 As
individuals begin to become more health-conscious in their
choice of diet, the amount of chicken consumption will increase
by an estimated 5% per year. In commercial chicken production,
flocks of ∼25 000 chickens are raised in large houses spanning
up to 12 000 square feet of area.3 The chickens are raised and
harvested in 5-7 weeks, and to promote hygiene within the
flock, chicken houses are lined with bedding material, primarily
composed of wood chips in thicknesses of up to 15 cm, which
acts as an absorbent to remove excess moisture from the urine
and feces of the flock. The wood chip and fecal matter mixture
is termed litter and must be removed from the house floor
* Corresponding author. Tel.: +1(270)745-2272. Fax: +1(270)7452221. E-mail: wei-ping.pan@wku.edu.
† Western Kentucky University.
‡ Present address: SONY Institute of Higher Education, Atsugi, Kanagawa 243-8501, Japan. E-mail: ozao@ei.shohoku.ac.jp.
§ Present address: Department Ingenieria Industrial II, Universidade da
Coruna.
(1) Poultry yearbook compiled by the United States Department of
Agriculture Economic Research Service. http://www.ers.usda.gov/Data/sdp/
view.asp?f)livestock/89007/&arc)C.
(2) Food availability spreadsheets compiled by the United States Department of Agriculture Economic Research Service. http://www.ers.usda.gov/
Data/foodconsumption/mtpoulsu.
(3) North, Mack O. Commercial Chicken Production Manual; The Avi
Publishing Company, Inc.: Westport, CT, 1984.
periodically to promote good health and hygiene among the
flocks. Classically, chicken litter is spread onto agricultural land
or composted in massive mounds as a means of disposal.
Composted chicken litter is a significant threat to local and
global air quality due to the release of methane and ammonia.
At the local level, poorly managed chicken litter stockpiles can
cause large effluents of malodorous compoundssprimarily
ammoniasthat reduce air quality.4 Chicken litter composting
also can cause large methane releases, from the bacterial
decomposition of various compounds in the litter material.5-7
Spreading chicken litter as a fertilizer that is high in N and
phosphorus (P) content provides a suitable, economic, and
convenient supplement to inorganic fertilizers. However, overusage and neglect in proper fertilization and waste management
practices have led to major water pollution concerns regarding
chicken litter. Nitrogen is the limiting reagent of the chicken
litter mixture when applied to cropland; thus, plant producers
spread the chicken litter in quantities to meet the crops N
requirements. Furthermore, this practice results in an excess of
Pspresent as phosphatessapplication to the land. The excess
P and N is quickly transported by runoff water into the
neighboring rivers, lakes, and streams.8,9 Accumulation of P,
N, and other plant nutrients into bodies of water is a natural
(4) Siefert, R. L.; Scudlark, J. R.; Potter, A. G.; Simonsen, K. A.; Savidge,
K. B. Characterization of Atmospheric Ammonia Emissions from a
Commercial Chicken House on the Delmarva Peninsula. EnViron. Sci.
Technol. 2004, 38, 2769-2778.
(5) Brodie, H. L.; Carr, L. E.; Cardon, P. Poultry Litter Composting
Comparisons. Biocycle 2000, 41, 36-40.
(6) Georgakakis, D.; Krintas, Th. Optimal use of the Hosoya system in
composting poultry manure. Bioresour. Technol. 2000, 72, 227-233.
(7) Rao, P. P.; Seenayya, G. World J. Microbiol. Biotechnol. 1994, 10,
211-214.
(8) Sharpley, A. N. Identifying sites vulnerable to phosphorus loss in
agricultural runoff. J. EnViron. Qual. 1995, 24, 947-951.
10.1021/ef0503109 CCC: $33.50 © 2006 American Chemical Society
Published on Web 07/12/2006
Combustion of Chicken Waste
aging process known as eutrophication; however, anthropogenic
eutrophication is a serious problem resulting in accumulation
of large concentrations of specific plant nutrients in a relatively
short amount of time. When anthropogenic eutrophication
occurs, algae present within the water reproduce excessively
under aerobic metabolism, effectively using large quantities of
the water’s dissolved oxygen. Accounts of destruction to the
aquatic ecology due to anthropogenic eutrophication within the
United States have been reported.10 Increasing occurrences of
these outbreaks will compel the Environmental Protection
Agency (EPA) to regulate the amount of chicken waste used
per acre on agricultural land based on the local soil characteristics, weather conditions, and proximity to water systems.11
Much research has shown that chicken litter having calorific
values equivalent to low-rank coals (on the order of 5 000 BTU
lb-1 ) 11 600 J g-1)12,13 can be combusted to generate energy.14
Pilot studies have been executed to develop small reactors that
will provide electricity to power chicken houses through burning
chicken waste.15-17 Other research has shown that many useful
chemicals and materials can stem from the thermal degradation
of chicken waste.18
The possibilities of using chicken litter as a resource for
energy are studied. Animal waste such as poultry litter is defined
as “biomass”. Numerous studies have been made so far on the
combustion of biomass and kinetic modeling. For instance, there
is an overview by Nussbaumer;19 Gani et al.20 provide fundamentals of combusting low-rank coal mixed with biomass.
Furthermore, thermogravimetric analysis (TGA) has been used
in studying biomass char combustion reactivities for FBC,21 cocombustion of coal-sewage sludge mixture,22 and kinetic
(9) Sharpley, A. N.; McDowell, R. W.; Kleinman, P. J. A. Phosphorus
loss from land to water: Integrating agricultural and environmental
management. Plant Soil 2001, 237, 287-307.
(10) Geiselman, B. Okla. Farmers Polluted Water, Lawsuit Alleges. Waste
News, Dec 24, 2001, p 5; Business Source Premier, Aug 15, 2004.
(11) Ritchie, James D. Water, EPA, and You, July 2002; Today’s Farmer,
Aug 15, 2004, http://www.mfaincorporated.com/todaysfarmer/index.asp.
(12) Plasynski, S. I.; Goldberg, P. M.; Chen, Z.-Y. Using Animal Waste
Based Biomass for Power and Heat Production while Reducing Environmental Risks. Presented at 19th Annual International Pittsburgh Coal
Conference, Pittsburgh, PA, Sept 23-27, 2002.
(13) Miller, B. G.; Miller, S. F.; Scaroni, A. W. Utilizing Agricultural
By-Products in Industrial Boilers: Penn State’s Experience and Coal’s Role
in Providing Security for our Nation’s Food Supply. Presented at 19th
Annual International Pittsburgh Coal Conference, Pittsburgh, PA, Sept 2327, 2002.
(14) Davalos, J. Z.; Roux, M. V.; Jimenez, P. Evaluation of poultry litter
as a feasible fuel. Thermochim. Acta 2000, 394, 261-266.
(15) Stranahan, S. Q. Farmers Face a Big Stinking Mess. Fortune, Apr
1, 2002, pp 32-34; Academic Search Premier, Aug 15, 2004.
(16) Strutt, J. Fowl Source of Supply for New Power Scheme. The
Australian, Dec 13, 2002, p 4; Newspaper Source, Aug 15, 2004.
(17) McNeill, R. Study of Poultry Litter as Power Source of Interest to
Oklahoma Farmers. The Daily Oklahoman, Apr 17, 2004; Newspaper
Source, Aug 15, 2004.
(18) Shinogi, Y.; Kanri, Y. Pyrolysis of plant, animal and human waste:
physical and chemical characterization of the pyrolytic products. Bioresour.
Technol. 2003, 90, 241-247.
(19) Nussbaumer, T. Combustion and Co-combustion of Biomass:
Fundamentals, Technologies, and Primary Measures for Emission Reduction.
Energy Fuels 2003, 17, 1510-1521.
(20) Gani, A.; Morishita, K.; Nishikawa, K.; Naruse, I. Characteristics
of Co-Combustion of Low-Rank Coal with Biomass. Energy Fuels 2005,
19, 1652-1659.
(21) Adanez, J.; deDiego, L. F.; Garcia-Labiano, F.; Abad A.; Ananades,
J. C. Determination of Biomass Char Combustion Reactivities for FBC
Applications by a Combined Method. Ind. Eng. Chem. Res. 2001, 40, 43174323.
(22) Folgueras, M. B.; Diaz, R. M.; Xiberta, J.; Prieto, I. Thermogravimetric analysis of the co-combustion of coal and sewage sludge. Fuel 2003,
82, 2051-2055.
Energy & Fuels, Vol. 20, No. 6, 2006 2661
Figure 1. Sample preparation procedure.
Table 1. Summary of Sample Identifications
sample ID
particle size distribution
A
B
C
mill
particles over 140 mesh (>150 µm)
particles between 140 and 325 mesh (45-150 µm)
particles below 325 mesh (<45 µm)
possessing all particle sizes
modeling of coal blends.23 They show that TGA is useful for
detecting mass change and for mathematical modeling; however,
to completely exploit the full potential of chicken litter
combustion, the chicken litter must be well-characterized.
Accordingly, the combustion process was studied by TGA
and kinetic analyses, and the mechanism by which the chicken
litter decomposes was thoroughly studied by multiple modes
of evolved gas analysis (EGA), including thermogravimetricmass spectrometry (TG-MS) and thermogravimetric-Fourier
transform infrared spectroscopy (TG-FTIR) for combustion.
Experimental Section
Sample. Figure 1 shows the sample-preparation procedure.
Approximately 10 kg of chicken litter was collected from a local
commercial chicken production facility. Great care was taken
in collecting a representative sample by collecting equal volumes
of litter from the different parts of the litter pile. The sample
was divided into metal trays and air-dried at 80 °C for 24 h.
After air-drying, the sample was milled using a Retsch SM1
rotary cutting mill. The chicken litter was passed through a 12.5
mm screen to break down large aggregates of manure, followed
by another pass through the mill using a 4.0 mm screen. The
milling process served to homogenize the sample so that
repeatability within subsequent testing could be achieved. To
further homogenize the sample, the milled chicken waste sample
was divided in half using a hand riffle. The hand riffle randomly
divides the sample into two equal portions, where one is
discarded and the other is passed through the riffle once again.
The litter sample was passed through the riffle until the
remaining sample filled a 64 oz bottle. Although milling and
riffling processes decreased the gross heterogeneous nature of
the sample, some minor heterogeneity remained with regard to
particle size. The sample was then divided into three particlesize distributions using sieves of 140 and 325 mesh. Table 1
describes the composition of the samples used for the remainder
of the experiments.
Chicken Litter Characterization. The chicken litter samples
were characterized using American Society for Testing and
Materials (ASTM) method D5373 for carbon, hydrogen, and
nitrogen using a LECO CHN-2000. Likewise, sulfur was
(23) Vamvuka, D.; Pasadakis, E.; Kastanaki, E. Kinetic Modeling of Coal/
Agricultural By-Product Blends. Energy Fuels 2003, 17, 549-558.
2662 Energy & Fuels, Vol. 20, No. 6, 2006
Whitely et al.
Figure 2. TGA curves for all the samples in air at a heating rate of 20
deg min-1.
determined instrumentally using a LECO SC-432 in accordance
with ASTM D4239. Instrumental procedures for proximate
analysis were used following ASTM method D5142 and
utilizing a LECO TGA-601. The gross calorific value was
determined using a LECO AC-350 bomb calorimeter following
ASTM D5865. A Rigaku RIX-3001 XRF (X-ray fluorescence)
was used to determine the major and minor elemental composition following ASTM D4326.
Thermogravimetric Analysis (TGA). About15-20 mg of
each of the samples were subjected to TGA runs using TA
Instruments Hi-resolution TGA 2950 under air (Airgas compressed air (breathing grade), Type I, Grade D, 21% O2 certified)
at a flow rate of 50 mL min-1. The results obtained at a heating
rate of 20 °C min-1 for all the samples are shown in Figure 2.
For kinetic analysis, the samples were also run at heating rates
of 2, 5, 10, and 20 °C min-1.
In kinetic analysis, the rate of reaction dR/dt, where R is the
mass fraction, is assumed to be described by two separable
functions of temperature F(T) and fraction f(R):
Figure 3. Percent conversion of sample A with time at different
temperatures.
(4)
different β, from which Z and E can be obtained from the slope
and the intercept of 1/T.
Kinetic analysis was made first by curve fitting to logistic
functions24 to mathematically separate the reactions, and then
by assuming first-order independent parallel reaction, where
applicable, in the temperature from room temperature to 1000
°C. Consequently, the activation energy E and preexponential
factor Z were obtained. Furthermore, by analyzing the reaction
occurring at temperatures >500 °C, change in percent conversion with time was estimated at various temperatures to obtain
the optimum condition of combustion. The results are given in
Figure 3.
Thermogravimetry-Mass Spectrometry (TG-MS). Approximately 10 mg samples were analyzed by TA Instruments
2960 simultaneous differential scanning calorimeter (DSC)thermogravimetric analyzer (TGA) (SDT) interfaced to a Fisons
VG Thermolab mass spectrometer (MS) by means of a heated
capillary transfer line. The capillary transfer line was heated to
120 °C, and the inlet port on the mass spectrometer was heated
to 150 °C. The Fisons unit is based on quadrupole design
operating at a pressure of ∼1 × 10-6 Torr. The sample gas
from the interface was ionized at 70 eV, and a mass range of
1-150 amu was scanned. Breathing-quality air at a flow rate
of 50 mL min-1 served as the carrier gases to the MS. Purges
(30 min) preceded the heating programs, in which the samples
were heated from room temperature to 1000 °C at a rate of 20
°C min-1. The MS continually samples the outgas, generating
a temperature (or time) resolved MS spectrum for each of the
individual masses.
Thermogravimetry-Fourier Transform Infrared Spectroscopy (TG-FTIR). The samples were analyzed by a DuPont
951 TGA interfaced to a Perkin-Elmer 1600 series FTIR with
a permanent 1 in. silicon transfer line. Approximately 25 mg
litter samples were heated from room temperature to 1000 °C
at heating rate of 20 °C min-1 in TGA. Breathing-quality air at
a flow rate of 100 mL min-1 provided the combustion
atmosphere. The purge gas carried the decomposition products
from the TGA through an 80 mL sample cell with KBr crystal
windows. The cell was placed in the FTIR scanning path for
detection of the decomposition products. Wrapping the IR cell
in heat tape held at 150 °C and the increased flow rate compared
If the function f(R) is constant for the entire reaction, the
left-hand side plotted against 1/T yields straight lines for
(24) Cao, R.; Naya, S.; Artiaga, R.; Garcıa, A.; Varela, A. Logistic
approach to polymer degradation in dynamic TGA. Polym. Degrad. Stab.
2004, 85, 667-674.
dR
) F(T)f(R)
dt
(1)
The temperature dependence of the reaction rate function F(T)
is generally described by the well-known Arrhenius equation
F(T) ) Z exp
(-E
RT )
(2)
where R is the universal gas constant, E is the activation energy,
and Z is the preexponential factor. In TGA, the runs are made
under constant heating rate dT/dt ) β. Thus, eqs 1 and 2 can
be rewritten and combined to give
-E
dR Z
) exp
f(R)
dt β
RT
( )
(3)
TGA runs differing in heating rate, i.e., in different β, are
obtained to determine the kinetic parameters Z and E from the
linearized transformation of eq 3:
ln
Z
-E
dR/dt
) ln +
β
RT
f(R)
()
Combustion of Chicken Waste
Energy & Fuels, Vol. 20, No. 6, 2006 2663
Table 2. Summary of As-Received Proximate Analysis, CHN, S, and Gross Calorific Value of Litter Samples
sample
moisture (wt %)
ash (wt %)
volatile matter (wt %)
C (wt %)
N (wt %)
H (wt %)
S (wt %)
BTU (lb-1)
mill
A
B
C
10.59
10.43
11.43
9.44
26.58
25.27
34.62
53.85
54.72
54.43
49.25
34.83
29.09
30.66
26.13
16.75
3.44
3.35
4.74
3.68
5.11
5.07
4.69
3.35
0.80
0.76
1.28
1.24
5166
5299
4281
2915
Table 3. Summary of Major and Minor Element Data for Litter Samples
wt %
sample
SiO2
Al2O3
Fe2O3
CaO
MgO
Na2O
K2O
P2O5
TiO2
SO3
mill
A
B
C
9.83
7.23
11.45
31.29
1.36
1.02
1.82
3.64
0.58
0.44
0.74
1.26
3.72
4.29
4.32
3.49
1.26
1.21
1.88
1.99
1.61
1.73
1.59
1.22
3.34
3.44
3.63
3.41
4.23
4.54
5.71
4.75
0.06
0.03
0.09
0.33
1.91
1.89
2.54
2.51
to the TG-MS experiments are required to limit condensation
of high-boiling evolved products. The FTIR scans the frequency
range of 4500-450 cm-1 at ∼25 s intervals providing temperature (or time) resolved FTIR spectra. To monitor the evolution
of single gas moieties, the TG-FTIR data could be treated such
that single frequencies of the FTIR spectra were monitored,
generating plots of absorbance at a single frequency as a function
of time.
Table 4. Kinetic Parameters for the Temperature Regions I-IV
stages
preexponential factor
log Z (min-1)
activation energy E
(kJ mol-1)
I (RT ) 150 °C)
II (150-350 °C)
III (350-500 °C)
IV (500-650 °C)
8.423
6.199
10.43
11.00
61.72
71.43
148.5
157.6
Sample Description. The mill sample that contains all
particle sizes is approximately composed of 87.5% (volume
percent) sample A, 6.25% sample B, and 6.25% sample C.
Visual inspection of the litter samples indicates that sample A
is primarily composed of wood-chip bedding material and
sample C is composed of soil material. Sample B appears to be
an intermediate between the two extremes.
The as-received proximate analysis, CHN, S, and gross
calorific value of the four chicken litter samples are shown in
Table 2. The ash content of the litter samples is shown to
increase with decreasing particle size; however, the calorific
value and the volatile matter show an opposite trend, having
the highest values for the larger particle sizes. Collectively, the
ash, volatile matter, and the calorific value are indicative that
the composition of the chicken litter resembles low-rank coal.25
By comparing the calorific and ash contents of sample A and
the mill sample, one can deduce that removing particles under
140 meshssamples B and Csfrom the mill sample effectively
acts to increase the productivity of the litter by increased energy
content and a smaller ash content. The calorific value of the
mill and sample A is similar to that of lignite.25 The elemental
analysis shown in Table 3 as wt % in the litter supports the
conclusions made from the proximate analysis. Sample C is
comprised of 31.3% SiO2 by weight. The astounding concentrations of inorganic compounds such as SiO2, Al2O3, Fe2O3, and
TiO2 suggest that sample C is primarily composed of soil matter.
TGA. Figure 2 shows the TG curves of the samples obtained
in flowing air. By curve separation according to the method of
Cao et al.,24 it has been presumed that the mass loss occurs in
four steps in the following temperature ranges: (I) room
temperature to 150 °C; (II) between ca. 150 and 350 °C; (III)
between ca. 350 and 500 °C; and (IV) between ca. 500 and
650 °C. The small mass loss found at temperatures >600 °C is
attributed to mineral decomposition.
The mass loss in temperature region I is approximately the
same (∼10 wt %) for all of the samples. It is likely that
desorption of moisture and volatile gases occurs in this region
for all of the samples, and hence, the rate equation should be
the same for all the samples. The final mass % obtained on
heating to 1000 °C is in fair agreement with the ash content
above; the final mass % obtained by TG is ∼2% lower than
those obtained by combustion testing, showing mass loss still
occurring in the temperature range of 750-1000 °C on all
samples.
From the similarities in composition and the TG curves, it
has been found that sample A represents the original milled
sample. Thus, sample A is used for further study as a model
sample for the original milled sample. Sample C contains much
silica and alumina, and it can be considered as a starting milled
sample diluted by thermally stable oxide minerals.
In temperature region II, it is hypothesized that rapid
devolatilization and subsequent oxidation, overlapping at some
places, take place. That is, pyrolysis and oxidation take place
conjointly. In particular, the maximum rate of reaction, i.e., the
peak temperature for the derivative weight curve (DTG), is lower
by 30 °C than the peak observed by DSC. That is, mass loss
occurs first, with oxidation occurring shortly thereafter. Thus,
in this temperature region, the presumption of independent
reactions may not be applied; hence, the kinetic values are
provided with lower reliability.
In temperature region III, a plateau is observed in DTG, that
is, the reaction rate is constant in this region. Diffusion and
starting combustion of char, may be the rate-determining step.
This region may be regarded as a precombustion or an
introductory region26 and may be combined with region IV. In
temperature region IV, mass loss ascribed to very rapid char
combustion takes place.
Table 4 shows the preexponential factors and activation
energies obtained by kinetic analysis of temperature regions
I-IV. The results are in fair agreement with the case of cocombustion of sewage sludge,20 which also contains ∼40 wt %
ash. A typical coal has an activation energy of ∼60 kJ mol-1
in this temperature range, and the coal transformations involved
in this stage are presumed to be devolatilization, ignition of
volatiles, and reaction at the surface.22 Thus, because of high
N present in the sample, ignition of volatiles and reaction at
the surface are retarded, and this accounts for the high activation
(25) Nomura, M.; Suzuka, T. Modern Industrial Chemistry; Kodansha
Scientific: Tokyo, Japan, 2004; pp 71-72.
(26) Chen, Y.; Mori, S.; Pan, W.-P. Estimating the Combustibility of
Various Coals by TG-DTA. Energy Fuels 1995, 9, 71-74.
Results and Discussions
2664 Energy & Fuels, Vol. 20, No. 6, 2006
Figure 4. Overlay of the derivative weight curve (DTG) with selected
MS intensity measurements (m/z 44, 32, 18) for sample A.
energy for stage III in the present sample. Further, by the kinetic
analysis described in the section on TGA above, it was
calculated that the char combustion is completed in ∼1.5 s at
700 °C (Figure 3). This value is close to the burnout time for
char calculated by Ross et al.27 However, the present calculation
is made on the hypothesis that the sample size is very small,
and that the reactions occurring at lower temperatures, such as
water desorption, devolatilization, and partial oxidation, are
completed. Furthermore, for practical applications, isothermal
runs by heating in an infinitesimal short time up to higher
temperatures are necessary. The process of pyrolysis is,
therefore, studied in detail and reported elsewhere.28
TG-MS. Because the TGA data indicates that the four
samples are composed of the same compounds at different
concentrations, the TG-MS data was only studied on samples
A and C, which represent the extreme organic and mineral
compositions, respectively. Monitoring the identity of the
evolved gases allows development of generalized decomposition
mechanisms characteristic to each of the four mass-loss events.
Figure 4 is an overlay of the derivative weight curve (DTG)
with selected intensity measurements from the MS for sample
A. The DTG measures the rate of weight change and peaks
within this curve, which indicates regions in which the sample
is decomposing. Water (m/z ) 18) evolves in three different
stages. The first correlates to bound water, while the following
two water evolutions are due to devolatilization and combustion
of organic matter. The carbon dioxide (m/z ) 44) evolutions
occurring simultaneously with the second and third weight losses
are indicative of devolatilization and char combustion, respectively, which is representative of the predictive behavior of highcarbon content materials. The decrease in oxygen intensity (m/z
) 32) supports the idea of char combustion of carbonaceous
materials from the material and the solid decomposition products
from devolatilization.
Figure 5 shows the equivalent TG-MS data for sample C.
This figure shows that samples A and C behave similarly;
however, the evolutions of carbon dioxide, water, and oxygen
are much weaker in sample C than in sample A. The disparity
of the intensity in the evolution profiles can be attributed to the
significant difference in the percentage of organic material
composing each of the samples. Although samples A and C
contain considerable amount of N, MS is not effective for
identifying the oxides, because numerous m/z numbers apply
(27) Ross, D. P.; Heidenreich, C. A.; Zhang, D. K. Devolatilisation times
of coal particles in a fluidised-bed. Fuel 2000, 79, 873-883.
(28) Whitely, N.; Ozao, R.; Cao, Y.; Pan, W.-P. Energy & Fuels. Multiutilization of Chicken Litter as a Biomass Source. Part II. Pyrolysis. 2006,
20, 2666-2671.
Whitely et al.
Figure 5. Overlay of the derivative weight curve (DTG) with selected
MS intensity measurements (m/z 44, 32, 18) for sample C.
Figure 6. Change in absorbance for bands at 2359 (CO2), 3016 (CH4),
and 965 cm-1 (NH3) of the FTIR spectra obtained for the gas evolved
while heating sample A.
for NOx. Furthermore, the detection of S and P was unsatisfactory, which is described elsewhere.28
Figure 6 was generated by monitoring single frequencies in
the time-resolved FTIR spectra of sample A. Carbon dioxide
CO2 (g), methane CH4 (g), and ammonia NH3 (g) were
investigated by monitoring the IR absorption bands at 2359 cm-1
(C-O asymmetrical stretching vibration), 3016 cm-1 (C-H
symmetrical stretching vibration), and 965 cm-1(N-H out-ofplane stretching vibration) of the FTIR spectra, respectively.
NH3 and CH4 have mass numbers of 17 and 16, respectively,
and cannot be clearly distinguished from H2O (principal
spectrum at m/z 18). However, by IR, it can be clearly seen
that NH3 appears in four evolutions, two occurring below 215
°C as a result of the first weight loss and two occurring in
conjunction with devolatilization and char combustion, respectively. The latter two would be related to the fragmentation of
organic matter. CH4 is mainly found at temperatures higher than
>200 °C, presumably as fragments generated by devolatilization. The carbon dioxide emission profile observed in Figure 6
is in good agreement with that obtained by MS (Figure 4).
Figure 7 shows that sample C releases significantly less CH4;
also, from Figures 6 and 7, it can be understood that sample C
shows that the ratio of the relative absorption intensity at
temperatures ca. 250 °C with respect to that at higher temperatures is reversed as compared with the case for sample A. This
suggests that the NH3 evolution at lower temperatures can be
attributed to the mineral matter, or ammonium salts, and that
NH3 at high temperatures is released by fragmentation of organic
Combustion of Chicken Waste
Figure 7. Change in absorbance for bands at 2359 (CO2), 3016 (CH4),
and 965 cm-1 (NH3) of the FTIR spectra obtained for the gas evolved
while heating sample C.
matter. However, further study is necessary for determining the
functionality of N.
Conclusions
Chicken litter was examined by a wide variety of ASTM D05
methods and was found to possess ∼20% moisture, with the
Energy & Fuels, Vol. 20, No. 6, 2006 2665
air-dry loss being ∼10%; a calorific value similar to a lowrank coal (∼5300 BTU lb-1 ) 12 320 kJ kg-1); and an ash
value of ∼25%.
Dividing the chicken litter into fractions based upon the
particle size was shown as a physical means to alter the values
of the calorific value and the ash content.
On heating in air, chicken litter was found to decompose by
four stages as follows (where E denotes activation energy
obtained by kinetic analysis):
I. Release of absorbed water and ammonia stemming from
ammonium salts (room temperature (RT) ) 150 °C), E ) 61.72
kJ mol-1;
II. Devolatilization (150-350 °C), E ) 71.43 kJ mol-1;
III. Char precombustion (350-500 °C), E ) 148.5 kJ mol-1;
IV. Char combustion (rapid) (500-650 °C), E ) 157.6 kJ
mol-1.
The higher activation energy for temperature region III as
compared with a typical coal is presumably due to the increased
presence of N, which retards combustion.
Acknowledgment. This work is supported by the USDA-ARS
Project No. 6406-12630-002-02S.
EF0503109