alternative poultry litter storage for improved
TRANSCRIPT
233
Transportation of poultry litter out of nutrient limited watersheds such as the Illinois River basin (eastern Oklahoma) is a logical solution for minimizing phosphorus (P) losses from soils to surface waters. Transportation costs are based on mass of load and distance transported. Th is study investigated an alternative litter storage technique designed to promote carbon (C) degradation, thereby concentrating nutrients for the purpose of decreasing transportation costs through decreased mass. Poultry litter was stored in 0.90-Mg conical piles under semipermeable tarps and adjusted to 40% moisture content, tested with and without addition of alum (aluminum sulfate). An additional study was conducted using 3.6-Mg piles under the same conditions, except tested with and without use of aeration pipes. Samples were analyzed before and after (8 wk) storage. Litter mass degradation (i.e., loss in mass due to organic matter decomposition) was estimated on the basis of changes in litter total P contents. Additional characterization included pH, total nutrients, moisture content, total C, and degree of humifi cation. Litter storage signifi cantly decreased litter mass (16 to 27%), concentrated nutrients such as P and potassium (K) and increased proportion of fulvic and humic acids. Th e addition of aeration pipes increased mass degradation relative to piles without aeration pipes. Nitrogen volatilization losses were minimized with alum additions. Increases in P and K concentrations resulted in greater monetary value per unit mass compared with fresh litter. Such increases translate to increased litter shipping distance and cost savings of $17.2 million over 25 yr for litter movement out of eastern Oklahoma.
Alternative Poultry Litter Storage for Improved Transportation and Use
as a Soil Amendment
Chad J. Penn,* Jeff ery Vitale, Scott Fine, Joshua Payne, Jason G. Warren, Hailin Zhang, Margaret Eastman, and Sheri L. Herron
The poultry industry is economically important in east-
ern Oklahoma, serving as a major source of employment in
rural areas and often as a more profi table alternative to traditional
agricultural enterprises in the region. Approximately 48.2 million
birds (USDA–NASS, 2007) were produced in Oklahoma during
2007 (USDA–NASS, 2007). Poultry feeding operations are sup-
ported by the import of animal feed containing nutrients such as
nitrogen (N), phosphorus (P), and potassium (K); these nutrients
are then exported from the farm in the form of agricultural prod-
ucts (meat, eggs, etc.). However, much of the nutrients imported
with the feed will remain on the farm in the form of manure
(Nord and Lanyon, 2003; Slaton et al., 2004), which is termed
litter when mixed with bedding used in the poultry production
house. Manure management remains an ongoing challenge to the
industry as a result of this on-farm nutrient accumulation.
Poultry litter is typically land applied to pasture or crop land,
being a good source of N, P, K, and micronutrients (McGrath et
al., 2010). Historically, litter was applied to supply plant available
N (PAN) which results in an overapplication of P relative to plant
needs (Reddy et al., 2008; Eghball and Power, 1999). Continuous
application of poultry litter to plants at PAN rates has been shown
to cause an increase in soil test P (STP) beyond agronomic opti-
mum (Sistani et al., 2004; Maguire et al., 2008). For Oklahoma,
this optimum is 32.5 mg kg−1 Mehlich-3 P (M3-P). One conse-
quence of increased STP is a greater potential for nonpoint trans-
port of P to surface water bodies through overland fl ow (Johnson
et al., 2004; Daniel et al., 1994). Input of P into surface waters
can cause eutrophication (Williams et al., 1999; Boesch et al.,
2001). Eutrophication is characterized by excess plant growth and
oxygen depletion in water and can result in algal blooms, taste
and odor problems, and fi sh kills. Th is not only reduces attractive-
ness for recreation but creates water quality concerns for drinking
water supplies.
Th e link between STP and increased potential transport of P to
surface waters has led to regulations regarding the land application
of animal wastes such as poultry litter. In Oklahoma, for example,
soils within “nutrient limited watersheds” (such as the Illinois River
basin) possessing M3-P values >150 mg kg−1 are not permitted to
Abbreviations: FA, fulvic acid; HA, humic acid; HI, humifi cation index; ICP–AES,
inductively coupled plasma atomic emission spectroscopy; M3-P, Mehlich-3 P; MAS,
magic angle spinning; NH, non-humic; NMR, nuclear magnetic resonance; PAN, plant
available N; PLTM, poultry litter transport model; STP, soil test P; WSP, water soluble P.
C.J. Penn, J. Vitale, S. Fine, J. Payne, J.G. Warren, H. Zhang, and M. Eastman, Oklahoma
State Univ., Stillwater, OK 74078; S.L. Herron, BMPs Inc. Assigned to Associate Editor
Xiying Hao.
Copyright © 2011 by the American Society of Agronomy, Crop Science
Society of America, and Soil Science Society of America. All rights
reserved. No part of this periodical may be reproduced or transmitted
in any form or by any means, electronic or mechanical, including pho-
tocopying, recording, or any information storage and retrieval system,
without permission in writing from the publisher.
J. Environ. Qual. 40:233–241 (2011)
doi:10.2134/jeq2010.0266
Published online 3 Dec. 2010.
Received 14 June 2010.
*Corresponding author ([email protected]).
© ASA, CSSA, SSSA
5585 Guilford Rd., Madison, WI 53711 USA
TECHNICAL REPORTS: WASTE MANAGEMENT
234 Journal of Environmental Quality • Volume 40 • January–February 2011
receive P applications. For non-nutrient limited watersheds,
soils with >200 mg kg−1 M3-P are only permitted to receive a
maximum P application equal to plant P removal rates (USDA–
NRCS, 2007). Much of the Oklahoma poultry production is
located in the eastern portion of the state where nutrient limited
watersheds are abundant (Britton and Bullard, 1998).
Over the past two decades, the continuous application of
litter on poultry farms’ soils has led to a build-up of M3-P,
at times exceeding 150 and 200 mg kg−1. Because of current
regulations that prevent further P application, there now exists
a need to move the poultry litter off -farm (Van Horn et al.,
1996; Collins and Basden, 2006). Marketing poultry litter
outside of impacted watersheds to nutrient-defi cient areas
off ers one solution to the litter surplus problem associated
with high production areas. In Oklahoma, areas outside of
these nutrient-dense watersheds are typically composed of soils
that are nutrient poor, low in organic matter and pH, result-
ing in overall poor quality; such soils would benefi t most from
litter applications (McGrath et al., 2010; Adeli et al., 2009).
However, transportation cost is the biggest obstacle to move-
ment of litter to nutrient-defi cient areas (Payne and Smolen,
2006). A study conducted in Alabama determined that litter
can only be cost-eff ectively transported up to 263 km from
the production facility. Th is study showed that the 29-county
region could not utilize the amount of litter produced (Paudel
et al., 2004). Cost-share programs have been successfully
implemented in both Arkansas and Oklahoma to help defray
litter transportation costs. However, the longevity of these pro-
grams is uncertain.
Poultry litter transportation costs are based on mass of
load and distance transported. One potential solution to help
decrease the cost of litter transportation and allow for greater
hauling distances is reducing litter mass. Traditional compost-
ing of animal manure will cause a mass reduction of 30 to 50%
(Eghball et al., 1997; Rynk, 1992) due to organic carbon (C)
oxidation to carbon dioxide (CO2). However, traditional com-
posting of litter is not always a viable option because it is a
time-, energy-, and labor-consuming process, in addition to
application of C-rich materials intended to decrease N volatil-
ization. An increase in the C-to-N ratio occurs due to the typi-
cal application of materials with C-to-N ratio higher than the
litter (i.e., “bulking agents”); this increase in C:N makes the
material less desirable as an agronomic fertilizer by reducing
the PAN content of the material. Since litter value (monetary)
is currently based on the amounts of N, P, and K contained in
“as is” litter, any increase in nutrient concentration and reduc-
tion in moisture content will increase litter value on a weight
basis and increase the effi ciency in which nutrients could be
transported (Carreira et al., 2007). Th e increase in value would
allow for greater transport distances per unit mass of litter. In
addition, a decrease in litter mass or increase in P concentra-
tions via drying or organic matter decomposition would simply
reduce the total mass of material needed to be transported.
Th us, there lies a need to reduce litter mass and increase
nutrient concentrations with little monetary and labor inputs
for the purpose of reducing litter transport costs and increas-
ing hauling distances. Th e objectives of this study were (i) to
determine to what degree an alternative litter storage process
designed to promote C degradation would decrease mass and
aff ect litter properties, including nutrient concentrations and
carbon forms, and (ii) to conduct an economic analysis of this
storage process in the context of transporting litter from poul-
try-dense watersheds to areas defi cient in soil P.
Materials and MethodsPoultry litter was collected during cleanout of commercial
broiler houses located on the Oklahoma–Arkansas border.
Th e collected broiler litter was transported to Oklahoma State
University research stations, where it was stored over a period
of 60 d for two separate studies: a small- and a large-scale study
involving 0.90 and 3.6 Mg litter per pile, respectively. Broiler
litter was obtained in March 2007, 2008, and 2009 for the
small-scale study conducted in Haskell, OK; litter obtained
in 2009 was also utilized for the large-scale study in Perkins,
OK. Average temperatures in March and April for Haskell were
11.5 and 16.3°C, and 9.6 and 14.8°C for Perkins. All litter
piles were established the same day in which litter was obtained
from a poultry production house cleanout.
Two treatments were established for the small-scale study:
“normal” and “alum”-treated litter. Year was the blocking
factor. For normal litter, an electronic postal scale was used to
weigh out 0.90 Mg of litter in 45.3-kg increments and adjusted
to a moisture content of 0.4 g g−1 in a 132-L plastic trash can.
After mixing, moisture adjusted litter was then poured onto
the ground, forming a conical shaped pile located under an
open-sided storage building. Th e litter pile was then covered
with a polyethylene tarp (0.13 mm thickness and 4 threads
cm−1 in a horizontal and vertical direction) and staked to the
ground. After 30 d, the pile was uncovered and mixed with a
shovel before re-covering with the tarp. Sixty days after litter
piles were established, the piles were uncovered again and
mixed for the purpose of taking several composite samples for
chemical analysis. For the alum treatment, an identical pro-
cess was repeated for a second litter pile using the same initial
litter source, except that aluminum sulfate (alum) was mixed
by hand in the plastic garbage can at a 10% rate (based on dry
mass) before moisture adjustment.
For the large-scale study conducted in 2009, duplicated
conical piles were constructed with and without aeration pipes
and litter was not turned at any time. Th e aeration pipes were
meant to provide oxygen to the degrading litter, remove reac-
tion products, and allow degradation to occur without the
need for periodically turning the pile. Perforated polyvinyl
chloride pipes (10.1 cm diam., 1.27 cm diam. perforations)
were horizontally laid on the ground in the shape of a cross in
which each of the four pipes extended 2.13 m from the center.
In addition, a single vertical pipe connected to the four hori-
zontal pipes extended upward 1.98 m from the center (0.45 m
above the top of the pile). Litter was poured onto the center
of the pipe network using a front end loader on a tractor. 3.6
Mg of litter was used for all piles, which was approximated by
calibrating the average mass of litter delivered by one full front-
end bucket load. Litter moisture content was adjusted to 0.40
g g−1 for all piles by spraying a hose for a calculated time period
(based on fl ow rate and mass of litter in bucket) onto the litter
as it was slowly poured out of the front-end loader. Th e hose
nozzle was calibrated to deliver the desired fl ow rate. Piles
Penn et al.: Alternative Poultry Litter Storage 235
were covered with a tarp as described for the small-scale study.
Hortplus Model G Temperature probes (Hortplus, Hastings,
NZ) were placed 60 cm into the litter piles.
For both storage studies, tarps were removed after 60 d and
litter samples were collected from throughout the pile; six sam-
ples (0.5 kg each) per composite and three composite samples
per pile were collected. Composite samples were analyzed as
described below with results averaged among each pile.
Chemical AnalysisAll degraded and fresh litter samples were analyzed to deter-
mine the eff ect of degradation on mass reduction, carbon
forms, nutrient content, and nutrient solubility. Percentage
mass reduction (percentage of initial litter mass that was
degraded) was calculated on the basis of the increase (relative
to fresh litter) in concentration of a nongaseous, easily recover-
able, and plentiful element (P and K). Total P and potassium
(K) were determined on air-dried litter by the USEPA 3051A
acid digestion method (Leytem and Kpomblekou-A, 2009),
with analysis of solutions for P and K by inductively coupled
plasma atomic emission spectroscopy (ICP–AES; Th ermo
Scientifi c, Waltham, MA).
Litter pH was measured with a pH probe using a
solid:solution ratio of 1:5 and an equilibration time of 15 min.
Total C and N were analyzed on fi eld moist samples with a
LECO Truspec dry combustion analyzer (Nelson and Sommers,
1996). Ammonium and nitrate were determined on fi eld
moist samples by extraction with 1 M KCl (1:5 solid:solution
ratio) using a 30-min reaction time followed by fi ltration with
Whatman #42 fi lter paper (Whatman, Piscataway, NJ) and
subsequent colorimetric analysis with a LACHAT (LACHAT
Instruments, Milwaukee, WI). Water soluble phosphorus
(WSP) was determined on fi eld moist samples by shaking with
deionized water at a 1:100 ratio for 1 h followed by fi ltration
with Whatman #42 fi lter paper and P analysis by ICP–AES.
Fresh and degraded litter samples (fi eld moisture) from the
small-scale study were fractionated for C forms using the method
of Ciavatta et al. (1990). Th e purpose of this analysis was to
determine the eff ect of the degradation process on C forms. After
extraction of total C, the procedure separated and quantifi ed C
pools into two groups: “non-humifi ed” (NH) and humic acid
(HA) plus fulvic acid (FA) (“humifi ed fraction”). Th e humifi ca-
tion index (HI; Ciavatta et al., 1990) was calculated from Eq [1]:
HI = NH/HA+FA [1]
Th erefore, a lower HI indicates a more humifi ed organic material.
In addition, selected samples (2007 normal fresh litter and
degraded litter) were analyzed by quantitative 13C solid-state
nuclear magnetic resonance (NMR) after grinding dried samples
into a fi ne powder. Th is analysis provides a semiquantitative view
of organic matter functional groups. Based on the functional
group composition and relative amount, one can gain informa-
tion about the nature of the organic matter analyzed. Our inten-
tion was to determine if NMR could detect changes in the degree
of aromaticity of the litter after storage and decomposition to
complement data from the C fractionation technique previously
described. A greater degree of aromaticity is indicative of C stabil-
ity. Th e NMR spectra were obtained by the method of Mao et
al. (2000), except deconvolution was not conducted. All spectra
were taken at 75.694 MHz on a Varian/Chemagnetics CMX II
spectrometer (Varian Corporation, Palo Alto, CA) and referenced
to separately acquired spectra of tetramethylsilane (0 ppm). Direct
polarization spectra were taken at 13-kHz spinning speed with a
2.5-mm magic angle spinning (MAS) probe using a 10-s delay
between scans, 77-μs echo delay, 90° pulse width of 3.6 μs, and
10,000 scans. Spinning side bands were not evident at this sig-
nal-to-noise level and so were not included in the analysis. Four
regions of each spectrum were integrated (0–50, alkyl; 50–110
O-alkyl; 110–160 aromatic; 160–220, carboxyl and carbonyl).
Th ese integral regions were corrected with factors obtained from
integration of the same regions in two CP/T1–TOSS experiments
with T1C fi lter times of 500 μs and 10 s. CP/T
1–TOSS spectra
were acquired at 4.5 kHz spinning speed with a 7.5-mm MAS
probe, with 1-s delay between scans, 0.5-ms contact time, 6.5-μs
proton 90° pulse width, and 7.4-μs carbon 90° pulse width.
Economic AnalysisA poultry litter transportation model (PLTM) was constructed to
evaluate the economic benefi ts of degraded litter compared with
fresh litter by utilizing the results of the small-scale storage study.
Th e PLTM projects litter movements by minimizing shipping
costs between source and destination, that is, poultry producers
supplying litter and farms demanding the contained nutrients.
Th e cost of transporting chicken litter (TRNSP COST) from
source i to destination j is given by the following equation:
TRNSP COST ij ij ijt ijti j t
D C Q X=∑∑∑ [2]
where Dij is the distance from i to j, X
ijt is the binary decision vari-
able that determines whether litter is shipped in year t (Xijt = 0 no
shipment, Xijt = 1 shipment), Q
ijt is the quantity of litter shipped
in year t, and Cij is the unit cost of transporting litter from i to j in
year t. In Oklahoma, this requires moving litter from the eastern
part of the state, where poultry operations are concentrated, to
producers in the central or western part of the state, where crop
and hay production is primarily located. In addition to the trans-
portation costs, handling and application costs are also included in
the model for poultry litter. When combined with the transporta-
tion costs from Eq. [2], the total cost of transporting, handling,
and fi eld applying poultry litter is given by the following equation:
TOTAL COST
( )ij ij ij ij ijt ijti j t
D C H A Q X= + +∑∑∑ [3]
where Hij and A
ij are the handling and fi eld application costs for
poultry litter for each unit of poultry litter shipped from i to j.Constraint relationships were included in the model to
ensure compliance such that the accumulated soil P levels from
applied litter were held under 32.5 mg kg−1. Using similar
notation to Eq. [2], the P constraint equation is given by the
following inequality:
soili t
PHOS for all ijt ijtX Q P j≤∑∑ [4]
where PHOS is a coeffi cient that relates the quantity of litter
applied at site j in year t to the long-term accumulation
236 Journal of Environmental Quality • Volume 40 • January–February 2011
of P in the soil and soilP is the upper limit on soil P levels.
Optimum soil test P concentration for agronomic production
in Oklahoma is 32.5 mg kg−1 (M3-P soil extraction; Mehlich,
1984). For P demand and crop production, it was assumed
that no P would leave the farms receiving litter; this provided
a “worst-case scenario” for moving litter. Th e increase in soil
test P with litter applications was estimated using relationships
developed for Oklahoma soils (Davis et al., 2005).
Economic benefi ts were determined by the cost savings in
applying equivalent nutrient levels from poultry litter versus
commercial fertilizer sources according to the following equation:
NPK NPKBENEFITS PRCijt ijti j t
Q X= Φ∑∑∑ [5]
where ΦNPK
is the transformation coeffi cient governing the
content of NPK per unit of litter, and PRCNPK
is the vector of
N, P, and K prices. Th is valuing approach also enabled a direct
comparison between conventional and degraded poultry litter.
Poultry litter demand was estimated based on its use as a sub-
stitute for N, P, and K from commercial fertilizer. Poultry litter
applications were applied in the model on the basis of observed
crop and hay acreage at the county level (USDA–NASS, 2009)
and achievement of 32.5 mg kg−1 M3-P, which established an
aggregate demand for P. Current average soil P levels were esti-
mated using soil test samples from Oklahoma State University’s
Soil Testing Laboratory, which contains records of 65,000 soil
samples. Consistent with Carreira et al. (2007), poultry litter was
valued using commercial fertilizer prices to establish nutrient
prices for N, P, and K (Oklahoma State University NPK, 2010).
Table 1 was then used to value poultry litter on a weight basis
(i.e., the estimate of ΦNPK
) based on the measured concentrations
of N, P, and K in the poultry litter. Transportation, handling,
and fi eld application costs used in the economic model (Eq. [3])
were obtained from Carreira et al. (2007), with values of Cij =
$0.10 Mg−1 km−1, Hij = $18.73 Mg−1, and A
ij = $ 7.72 Mg−1.
Th e transportation model was solved by maximizing the
diff erence between the BENEFITS and COSTS equations
subject to maintaining soil P levels within the prescribed limits
dictated by Eq. [3]. Th e General Algebraic Modeling Systems
(GAMS) software package was used to fi nd the optimal solu-
tions to the transportation modeling formulation given by Eq.
[2–5]. Results were then linked to the Arc-Maps GIS system
(GIS Arcview, ESRI, Redlands, CA) where maps were created
to present results of the transportation fl ows.
Statistical AnalysisTh e small-scale litter storage study was a randomized complete
block design, with year as the blocking factor (3 yr) and two
diff erent treatments; normal litter and alum-amended litter.
Th e large-scale litter study was a complete randomized design
with two diff erent treatments: no aeration and passive aeration.
For both studies, ANOVA was conducted to determine if there
were signifi cant diff erences among chemical properties (p =
0.05) between the fresh litter (Day 0) and degraded litter (Day
60). Th e statistical procedure was conducted with SAS software
(SAS Institute, 2003) using the PROC GLM command.
Results and DiscussionTh e broiler litter collected each year of the study were typical in
pH, dry matter content, total C, N, and P, and WSP (see “pre-
Table 1. Percentage mass reduction and litter characteristics (dry weight basis) before and after initiating the degradation storage process both with and without the addition of aluminum sulfate.
Litter treatment DM† % mass reduction‡ pH TC§ TN§ NH4
NO3
WSP§ HI¶
——————————————— g g−1 ——————————————— ———————— mg kg−1 ————————
2007
Pre-degraded 0.68 – 8.6 0.41 0.044 8,976 1128 4078 1.49
Normal degraded 0.72 23.2 8.5 0.33 0.041 8,307 371 4861 0.94
Alum degraded 0.73 26.9 8.0 0.35 0.043 14,804 303 2049 0.89
2008
Pre-degraded 0.65 – 8.8 0.55 0.053 8,879 2117 3536 1.50
Normal degraded 0.65 15.9 8.9 0.44 0.047 7,882 439 5025 1.13
Alum degraded 0.64 18.1 8.1 0.40 0.052 14,833 1031 2727 1.15
2009
Pre-degraded 0.64 – 8.4 0.33 0.044 10,457 133 2184 1.53
Normal degraded 0.60 19.8 8.9 0.31 0.042 6,938 139 3043 1.29
Alum degraded 0.69 24.1 8.0 0.26 0.043 15,351 183 1375 1.35
Averages
Pre-degraded 0.66 – 8.6 0.43 0.047 9,437 1126 3266 1.51
Normal degraded 0.65 19.6 8.8 0.36 0.043 7,709 316 4310 1.12
Alum degraded 0.69 23.0 8.0 0.34 0.046 14,996 506 2050 1.13
LSD# ns 2.7 0.37 0.07 0.0031 1,796 ns 913 0.25
† DM, dry matter content.
‡ Percentage of the initial litter mass (not including added aluminum sulfate) that was degraded; calculated based on changes in concentration of a
non-gaseous and recoverable element (phosphorus) after degradation.
§ TC, total carbon; TN, total nitrogen; WSP, water soluble phosphorus.
¶ HI: humifi cation index. non-humic carbon/(fulvic acid + humic acid). A lower index indicates a greater degree of humicfi cation.
# Least signifi cant diff erence for the average values at P = 0.05; ns, not signifi cant.
Penn et al.: Alternative Poultry Litter Storage 237
degraded” litter in Tables 1, 2, and Fig. 1). All litter properties
were well within the range reported for broiler litter (Kaiser et
al., 2009; Silva et al., 2009).
Small-Scale Litter Storage PilesTh e small-scale (0.90-Mg piles) litter storage technique suc-
cessfully resulted in a signifi cant decrease in dry matter for
both normal and alum-treated litter; percentage mass reduc-
tion ranged from 18.1 to 26.9 (Table 1). Clearly, the dry matter
reduction can be attributed mostly to organic C decomposition
(Table 1) and subsequent loss as CO2 gas, with some reduction
resulting from N volatilization. Th is caused an average mass
reduction of 19.6 and 23% for normal litter and alum-treated
litter, respectively (Table 1). If we consider the decrease in litter
mass, then the C reduction expressed as a percentage
of the pre-degraded litter C content would be 32.7
and 33.2% for normal and alum-treated litter, respec-
tively. Warren et al. (2008) also found similar results
for normal and alum amended (10% dry weight)
poultry litter that was incubated in cups (0.30 g g−1
moisture adjusted, 25°C) for 93 d in a laboratory.
After 63 d, the authors found that 16 and 29% of the
litter dry matter had been lost from normal and alum-
amended litter, respectively.
Th e increased dry matter loss from alum-amended
litter may be an indirect eff ect of pH. Initially, a
10% alum application rate to litter is expected to
decrease pH 1 to 3 units, resulting in a pH of about
4 to 6 (Moore et al., 1999; Moore and Miller, 1994).
Although the pH of alum-amended litter tends to
increase after several weeks of equilibration, the fi nal
pH of alum-amended litter will still be signifi cantly
lower than normal litter (Table 1). Th e lower pH of
the alum-amended litter is probably having an impact
on litter microbial populations, which in turn is
causing diff erences in carbon degradation/utilization
among the litter treatments. For example, Cook et al.
(2008) showed that alum additions to poultry litter
shifted the microbial populations from mostly bacte-
rial to fungi. Since fungi are more eff ective at utiliz-
ing lignin-based carbon sources compared to bacteria
(Paul and Clark, 1996), this could have an impact
on the decomposition of litter components such as
rice hulls and wood chips and would also explain the
observed increases in litter degradation (i.e., mass reduction)
for this study.
Although the fi nal total N concentrations in the degraded
litter were similar to pre-degraded litter (Table 1), this equates
to 26 and 16% total N losses from the degraded normal and
alum-amended litter, respectively, when the mass reduction
is considered. Presumably, the loss of N was due to ammonia
(NH3) volatilization since leaching of water and surface runoff
was not possible as the piles were covered and kept under a
roof. Various studies have shown that composting litter results
in appreciable losses of N (Henry and White, 1993; Hansen et
al., 1989; Kithome et al., 1999). DeLaune et al. (2004) found
that composting litter lost 42 to 44% of initial total N via NH3
volatilization when litter was windrowed and turned weekly
Table 2. Impact of aeration on the litter degradation storage process. Average percent mass reduction and litter characteristics are presented on a dry weight basis before and after initiating the degradation storage process.
Litter treatment DM† % mass reduction‡ pH TC§ TN§ NH4
NO3
WSP§ Total P
g g−1 ——— g g−1 ——— ——————— mg kg−1 ———————
Pre-degraded 0.63 – 8.9 0.33 0.044 7584 1285 1762 17,236
Degraded: no aeration 0.67 14.9 8.8 0.22 0.040 6153 120 2052 20,267
Degraded: aeration pipes 0.77 23.0 8.8 0.24 0.037 3946 185 2273 22,399
LSD¶ 0.08 4.65 ns 0.04 0.013 970 204 ns 712
† DM, dry matter content.
‡ Percentage of the initial litter mass that was degraded; calculated based on changes in concentration of a nongaseous and recoverable element
(phosphorus) after degradation.
§ TC, total carbon; TN, total nitrogen; WSP, water soluble phosphorus.
¶ Least signifi cant diff erence at P = 0.05; ns, not signifi cant.
Fig. 1. Average total phosphorus and potassium concentrations before and after the degradation storage process among normal and alum treated litter. ** indicates signifi cant diff erences between fresh and degraded litter at P = 0.01.
238 Journal of Environmental Quality • Volume 40 • January–February 2011
for 92 d. Th e N loss values for the current study are lower
than those reported for traditional composting presumably
because litter piles were covered with semipermeable materials
and turned only once, thereby slowing the loss of NH3 gas.
As expected, the alum-amended litter reduced N losses during
degradation relative to normal litter due to acidifi cation of the
litter, thereby preventing NH4 deprotontation and subsequent
NH3 gas formation (Moore et al., 1996).
Due to the concentrating eff ect of the mass reduction (i.e.,
C degradation), there is an accompanying increase in the con-
centration of nonvolatile nutrients (Warren et al., 2008; Tiquia
and Tam, 2002). An example of this concentrating eff ect is
shown in Fig. 1 for P and K. Warren et al. (2008) also showed
that litter amended with moisture followed by 63 d of labora-
tory incubation increased total P from 17,500 to 23,600 mg
kg−1. For their study, this 34% increase in total P concentration
corresponded well with their measured decrease in litter mass.
Although litter moisture content was initially adjusted
to 0.40 g g−1 for the storage process, there was no diff erence
in fi nal dry matter content after 8 wk of degradation com-
pared with the fresh pre-degraded litter (Table 1). In addition
to a greater concentration of total nutrients, the degraded
normal litter also possessed a signifi cantly higher concen-
tration of WSP compared with the fresh pre-degraded litter
(Table 1), suggesting that the former may better serve as a
plant nutrient source. However, alum-treated litter did not
release soluble P during degradation; in fact, alum-treated
litter possessed lower WSP concentrations compared with
fresh litter (Table 1). Application of alum to litter has clearly
been shown to reduce soluble P concentrations by adsorbing
phosphate onto newly formed amorphous Al oxides/hydrox-
ides and precipitation of Al phosphate mineral (Peak et al.,
2002). In addition, alum amendments to litter will also pre-
vent the mineralization of phytic acid due to the formation of
Al-phytate (Warren et al., 2008).
With degradation of litter C, there was also a shift in the C
fractions as evidenced by the HI; a lower HI value indicates a
more “humifi ed” or degraded material (Table 1). Essentially,
the degraded litter possessed a greater concentration of HA
plus FA and less non-humic C compared with the fresh pre-
degraded litter, causing a decrease in the HI (Table 1). Petrussi
et al. (1988) also showed a decrease in the HI for swine, cattle,
and sheep manure after composting with earthworms. Among
composting lignin-cellulostic wastes, the degree of humifi ca-
tion was found to be a good indicator of compost maturity as
organic materials further degraded with time (Mondini et al.,
2006). Th e degraded litter in our study possessed a HI simi-
lar to urban compost (Ciavatta et al., 1990; Gigliotti et al.,
1999). Th e greater degree of humifi cation in the degraded litter
compared with fresh pre-degraded litter was also somewhat
evident by the lack of malodors and darker color of degraded
litter. Although not statistically signifi cant, the NMR analysis
suggested that the degraded litter possessed a higher ratio of
alkyl:o-alkyl groups compared with pre-degraded fresh litter
(0.31 vs. 0.26, ± 0.09) and a higher degree of aromaticity (ratio
of aromatic to nonaromatic functional groups; 0.22 vs. 0.20,
± 0.06). An increased ratio of alkyl:o-alkyl and aromaticity
indicates a greater degree of humifi cation (Inbar et al., 1990;
Simpson et al., 2008).
Th e application of more humifi ed organic materials to soils
may provide additional benefi ts, including enhanced soil qual-
ity. For example, Fernandez et al. (2007) applied composted
sewage sludge to a sandy loam for 3 yr and found that com-
posted sludge increase soil humic acid percentage and degree
of polymerization compared with a thermally dried sludge and
chemical fertilizer treatment.
Large-Scale Litter Storage Piles
and the Eff ect of AerationInternal pile temperatures ranged from 40 to 55°C during
the storage test period, thereby achieving thermophilic tem-
peratures (>40°C). Th e large-scale litter storage piles resulted
in mass degradation similar to the 0.9-Mg litter storage piles
(Tables 1 and 2) and laboratory-incubated litter after 63 d
(Warren et al., 2008). However, the addition of passive aeration
via perforated pipe network within the pile caused a signifi cant
increase in mass reduction compared with piles without aera-
tion pipes (Table 2; 8.1% point increase in mass reduction rela-
tive to nonaerated piles). Again, this mass reduction occurring
from C degradation resulted in an increase in concentration of
nonvolatile nutrients such as P (Table 2). Similar to the small-
scale piles the degraded litter contained lower total C, total N,
NH4, and NO
3 compared with fresh pre-degraded litter. Water
soluble P also increased for the degraded litters, although this
was not statistically signifi cant (Table 2).
Th e piles aerated through use of the perforated pipe signifi -
cantly increased percentage mass reduction due to the ability to
provide more oxygen to microorganisms that oxidize organic C
(Lau et al., 1992; Leton et al., 1983). Among composting facil-
ities, aeration has been shown to decrease the active decompo-
sition time (Sartaj et al., 1997; Finstein et al., 1980). Aeration
helps to produce an odorless end product, high temperatures
required for the inactivation of pathogens and weeds, and
remove waste gases, excess heat, and moisture (Rynk, 1992;
Leton and Stentiford, 1990).
Poultry Litter TransportationEqual dry matter contents of degraded and fresh poultry
litter, plus an increase in total P and K concentrations with
only a small decrease in total N concentrations, resulted in a
degraded litter with a greater economic value than conven-
tional litter. Phosphorus and K can be transported at lower
costs when shipped as degraded litter rather than conven-
tional fresh litter. On a standard truck unit carrying 21.7 Mg
of litter (70% dry matter), degraded litter would be able to
deliver 337 kg of P, signifi cantly more than the 266 kg deliv-
ered by nondegraded litter, assuming P concentrations deter-
mined in the small-scale study (Fig. 1). Based on a typical
shipping distance of 80 km, degraded litter would increase
economic benefi ts by $180.96 per haul due to higher nutri-
ent concentration. Th ere would also be a substantial increase
in the break-even distance over which litter could be prof-
itably transported. Degraded litter could be transported up
to 416 km, 82 km further than conventional litter’s break-
even distance of 334 km, based on current N, P, and K values
(Oklahoma State University NPK, 2010).
Penn et al.: Alternative Poultry Litter Storage 239
Degraded litter would also result in more effi cient and eff ec-
tive movement of P out of nutrient limited watersheds. Results
of the PLTM (developed from results of the small-scale litter
study; Fig. 1) indicate the optimal allocation of Oklahoma’s
annual production of 149,659 Mg of poultry litter over a 25-yr
period (Fig. 2). Within the fi rst 6 yr, the seven major poultry-
producing counties in the Illinois River watershed would have
produced and applied enough P on their soils to meet agro-
nomic P requirements within their respective county. Once
this occurs, those major producing counties will need to export
poultry litter to counties further west. Because of lower trans-
portation costs and a greater break-even shipping distance,
degraded litter would have a larger market area and would sat-
isfy a larger proportion of P demand than conventional litter
(Fig. 2). After 10 yr, the PLTM projects that degraded litter
would be able to access producers in 10 additional counties
compared with conventional litter (Fig. 2). Th e most signifi -
cant eff ect of degraded litter appears after 20 yr. At this time,
conventional litter would reach its break-even distance at
which further hauling would cost more than the litter nutrient
value and shipping poultry litter would therefore no longer be
profi table. However, degraded litter would remain economi-
cally viable for the next 25 yr. As a result, an additional seven
counties would be supplied with poultry litter. (Fig. 2).
Fig. 2. Results of the poultry litter transportation model illustrating (a) poultry litter demand, (b) annual supply, and potential transport of (c, e) fresh litter and (d, f) degraded litter 10 and 25 yr in the future.
240 Journal of Environmental Quality • Volume 40 • January–February 2011
Poultry litter would generate economically important ben-
efi ts over the next 20 to 25 yr (Table 3). Degraded poultry
litter would provide the largest impact, reaching $66.4 mil-
lion over a 25-yr period. Th at impact is generated by shipping
3.67 million Mg of poultry litter over an average distance
of 200 km. Conventional litter would generate an economic
impact of $49.2 million, $17.2 million less than degraded
litter, and corresponding to a diff erence of 34.9% compared
with degraded litter (Table 3). Conventional litter off ers less
economic potential than degraded litter since it is more costly
to ship, ultimately limiting its ability to reach wayward points
to the west. Over its 20 yr economic life, conventional litter
would ship 3.06 million Mg of poultry litter, 19.8% less than
degraded litter.
ConclusionsAlthough the alum-amended litter displayed a mass reduction
up to 26.9% due to carbon degradation, when the mass of the
aluminum sulfate added to the litter is taken into account, the
net mass reduction is only 15.3%. Th is makes the normal litter
storage (i.e., without alum) process more effi cient in net mass
reduction compared with alum-amended litter. In addition,
the cost of alum should be considered, approximately $343
Mg−1, not including shipping (Rex Johns, General Chemical,
personal communication, 2010).
Th e proposed technique for litter degradation, with or
without the use of aeration pipes, has distinct advantages over
traditional composting processes in the context of litter trans-
port. Th e simplifi ed system requires much less time, labor, and
cost compared with traditional composting in that litter does
not need to be turned on a weekly basis and N losses are mini-
mized. Overall, the process simply involves addition of mois-
ture (target of 0.40 g g−1) to litter while moving it into a conical
shaped pile (with or without a network of perforated pipes),
covering with a polyethylene tarp, and if aeration pipes are not
utilized, optionally turning the litter once after 30 d and re-
covering, allowing for 30 more days of degradation.
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TimeConventional litter Degraded litter Percent increase Conventional litter Degraded litter Percent increase
Litter delivered Economic benefi ts
yr —————————— Mg —————————— —————————— $ million ——————————
5 730,149 730,149 0 21.9 27.3 24.7
10 1,460,210 1,460,210 0 36.4 44.8 23.5
15 2,190,314 2,190,314 0 44.0 55.9 27.0
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