feasibility and production costs of composting …...100,000 tons of broiler and turkey litter was...
TRANSCRIPT
© 2009 Poultry Science Association, Inc.
2009 J. Appl. Poult. Res. 18 :172–184 doi: 10.3382/japr.2007-00094
Feasibility and production costs of composting breeder and pullet litter with eggshell waste
N. P. Kemper *1 and H. L. Goodwin Jr. *†
* Department of agricultural economics and agribusiness, University of arkansas, 217 agriculture Building, Fayetteville 72701; and † Department of Poultry science and
Center of excellence for Poultry science, University of arkansas, POsC O-114, Fayetteville 72701
Primary Audience: Growers, Breeders, Poultry and Egg Processors
SUMMARY
Phosphorus runoff from the land application of poultry litter has become a concern in water-sheds in the Ozark Plateau region, prompting local growers to use alternative litter management practices. One option is the export of excess poultry litter from producers in nutrient-surplus watersheds to users located in areas where nutrient loads are not problematic. In 2006, nearly 100,000 tons of broiler and turkey litter was exported by BMPs Inc., a nonprofit corporation providing litter management services. However, breeder hen litter and pullet litter are rarely exported because there are limited outlets for these lower nutrient value litters. Another poultry industry by-product is eggshell waste from egg-breaking operations, most of which is currently landfilled at a cost of $25/ton. Composting was examined as an alternative method to con-vert litter and eggshell wastes into a marketable soil amendment, making use of the beneficial soil nutrients available in both; 4 blends and 2 production systems were analyzed. Process results indicated that during composting, the observed temperatures of each of the 4 blends were different, but all followed a similar trend throughout the production cycle. Functional group inventory and diversity analysis indicated that all blends fell within optimal ranges of microbial species, except for the ratio of aerobic to anaerobic bacteria; only blend 4 was within the optimal value for this parameter. Diversity values for each blend fell within the moderate diversity range (3 < d < 6.5). Maturity analysis results indicated that no blends were mature at 11 wk (index <50%) and could not safely be used in horticultural applications but could safely be used in field applications. Break-even analyses indicated that compost could be produced at an average cost (across the 4 blends) of $17.48 to $20.09/ton for systems 1 (small-scale) and 2 (large-scale), respectively.
Key words: composting , breeder and pullet litter management , eggshell waste
DESCRIPTION OF PROBLEM
Poultry production is highly concentrated in the Ozark Plateau region. A by-product of this
concentration is large volumes of poultry lit-ter (PL). Land application of PL has long been known to increase agricultural output; howev-er, a negative externality of land-applied PL is
1 Corresponding author: [email protected]
agricultural runoff. Recently, P runoff has be-come a concern in area watersheds, prompting researchers to identify alternative methods of litter disposal. A substantial number of growers will need to use alternative litter management practices to satisfy regulatory guidelines for nutrient application in nutrient-surplus water-sheds [1]. One attractive option is the nonprofit corporation BMPs Inc., established in March of 2005 to coordinate pick-up and transportation of litter from producers in nutrient-surplus water-sheds for distribution to users located in areas where excess nutrient loads are not problematic. Broiler and turkey litters have been the focus of export thus far. To date, limited outlets exist for hen and pullet litter. Breeder hen litter and pullet litter are typically lower in nutrient value than other types of litter [2] and are also more difficult to transport [3]. Approximately 55,000 tons of breeder hen and pullet litter was gener-ated in the Eucha Spavinaw Watershed and Il-linois River Watershed in 2004 [4]. Another by-product of the poultry industry is eggshell waste from area egg-breaking plants, most of which is currently landfilled. This waste consists primar-ily of CaCO3 [5]. Calcium in this form can be applied to the soil to increase soil pH. Proper pH management can have several benefits, in-cluding, but not limited to, 1) influencing the solubility of some essential plant nutrients; 2) reducing aluminum, which may be toxic and re-strict root and top growth (restricted root growth also reduces drought tolerance); 3) increased efficiency of P; and 4) improved nodulation of legumes, allowing for more N capture from the soil atmosphere [6].
Composting has been used successfully to convert agricultural and animal wastes such as poultry mortalities, PL, and hatchery waste into a value-added soil amendment product that is stable, a source of essential plant nutrients, and agronomically attractive [7, 8]. With the appro-priate blend of inputs, composting temperatures are sufficient to reduce or eliminate pathogens such as escherichia coli and salmonella [9]. Poultry litter as an input in composting has been shown to contribute to a more efficient elimina-tion of salmonella in compost [7].
Composting pullet and breeder litter with eggshell waste is not only a waste management alternative, but is also a means of producing a
horticulturally and agriculturally based resource. [10–12]. One attractive value-added market in the region for compost is the horticultural indus-try (nurseries, greenhouses, floriculturists, golf courses, etc.). Compost users in this industry have reported that the primary reasons for using compost were related to soil tilth, building the humus content of the soil, and increased plant growth [13]. However, the lack of information regarding the advantages and disadvantages of producing and marketing compost presents a barrier to compost adoption [13]. Sound produc-tion and financial information are needed to start a compost facility.
The objective of this study was 2-fold: 1) to identify an effective method of composting breeder hen and pullet litter with eggshell waste and other waste inputs into a marketable prod-uct, and 2) to estimate the production costs of each blend for 2 production systems. Four prod-uct blends were designed, inputs were combined accordingly, and the composting production cycle was completed. Through laboratory analy-sis at BBC Laboratories in Tempe, Arizona [14], the quality (microbial concentration, diversity, maturity, and stability) of each respective blend was assessed. Nutrient contents of each blend were based on the nutrient analyses performed at the University of Arkansas and USDA-Agri-cultural Research Service research laboratories [15]. Two hypothetical compost facilities were modeled to provide production budgets for po-tential operators.
MATERIALS AND METHODS
Inputs and Composting Process
Factors affecting the composting process in-clude levels of oxygen and aeration; nutrients; moisture; porosity, structure, texture, and par-ticle size; pH; temperature; and time [8]. Reci-pes for each blend were designed based on typi-cal C and N (C:N) ratios, moisture levels, and structure ratings (airflow potential) of all inputs (Table 1). Each blend had a beginning C:N ratio near 30; moisture levels were kept at approxi-mately 50% during the compost process. Egg-shell waste, breeder and pullet litter, hay, oak sawdust, unfinished compost, and clay (subsoil) were inputs in the 4 blends; proportions of each input were varied across the blends. Eggshell
KEMPER AND GOODWIN: COMPOSTING EGGSHELL WASTE 173
waste was obtained through Membrell LLC in Carthage, Missouri [16]. Membrell LLC pro-duces products derived from eggshells and egg-shell membranes. Before delivery, the shells were pulverized and dried (<10% moisture) and contained approximately 5 to 10% of the pro-tein membrane. Breeder and pullet litter was obtained from nearby growers. Square bales of rotten hay were obtained from a local farmer; hay offers a good structure for oxygenation and was selected as the primary C source over wood chips because it breaks down faster and more completely than wood chips. Unfinished com-post (the leftover materials cleaned off the sides of windrows), provided by Hostetler Compost-ing in Berryville, Arkansas, was added to blends 2, 3 and 4, a typical practice for established compost firms [17]. Clay (subsoil) was used for its odor-reducing properties and its beneficial contribution to building humus soil structure [17]. Water was added during the turning pro-cess to maintain moisture levels. The final input to each blend was a combination of 3 microbial inoculants.
The Advanced Composting System of Mid-west Bio-Systems Inc. [18] was used to manage each blend. The Advanced Composting System is a highly aerobic and controlled process with quality monitoring throughout. Controls include recipe formulation and aeration, and moisture decisions based on readings of temperature, CO2, and moisture. The ideal C:N ratio for com-post at the start is in the range of 25 to 30, and moisture content should be kept between 50 and 60% [8]. Temperatures are primarily controlled by the C:N ratio of the blend as well as by the replacement of CO2 with O2 during turning and the microbial activity, and should range from 130° to 140°F for at least 2 wk and then progres-sively decline [8].
A composting firm in Berryville, Arkansas, was contracted to produce the compost blends designed for this project. The operator provided the site, tractor, compost turner, water wagon, la-bor, and some of the inputs used in the blends. Although the combination of inputs in each blend varied, the process for managing each blend was the same. Because different materials decompose at different rates, all inputs besides eggshells were formed into rows (individually), turned, and watered (if too dry) as each input
was delivered. Ideally, all materials should break down at the same time once combined into rows, and the synchronized breakdown of materials should reduce the time required to finish the compost cycle and increase saleable output [17]. The process for combining inputs was designed to follow this progression: all inputs except the eggshells were combined and temperatures were allowed to reach a range of 130 to 140°F, and then the eggshells were added. By d 2, each blend had reached an internal temperature of more than 130°F. Because of a transportation is-sue, the eggshells were not delivered at this time. Another source of eggshells was not identified until wk 3, when Membrell LLC was contracted to deliver eggshells to the project site [19].
The eggshells from Membrell LLC had a drastically lower moisture content than the orig-inal eggshells to be used (<10 vs. 50% mois-ture). The delay contributed to the windrows be-ing kept at suboptimal moisture levels, and the hay became too dry and stopped decomposing. At wk 3, the eggshells, clay, and first application of inoculants (N-Converter) were incorporated into each blend according to the recipe. The N-Converter is meant to improve compost quality and increase the microbial population and diver-sity. Organic matter is broken down during this portion of the process by microbial processes and their resulting heat. Nitrogen is converted from NH3 to NO3. The N-Converter contains microbes best suited to break down organic mat-ter and convert the NH3 from NO2 to NO3 [18].
During wk 4 to 6, the windrows were turned every second or third day unless weather dictat-ed otherwise. The frequency of turning during this portion of the production cycle was to keep CO2 levels low and O2 levels high enough to promote the growth of microbial populations. In wk 6, the Humifier portion of the inoculants was added in a split application and was intended to aid in the humus buildup portion of the compost production cycle [18]. At this point, most of the organic materials had been broken down. The Humifier provides microbial species that help to convert the broken down organic matter into humic substances while increasing the microbi-al population diversity of the finished compost [18]. During the final part of the cycle, wk 7 to 9, activities slowed. The compost was turned only twice during wk 7 and only once during wk
JAPR: Research Report174
KEMPER AND GOODWIN: COMPOSTING EGGSHELL WASTE 175
Tabl
e 1.
Com
post
ble
nd re
cipe
s as
per
cent
age
of ro
w v
olum
e an
d w
eigh
t
Mat
eria
l
Ble
nd 1
Ble
nd 2
Ble
nd 3
Ble
nd 4
% o
f row
vol
ume
% o
f row
wei
ght
% o
f row
vol
ume
% o
f row
wei
ght
% o
f row
vol
ume
% o
f row
wei
ght
% o
f row
vol
ume
% o
f row
wei
ght
C so
urce
Hay
4011
339
329
4010
Saw
dust
74
74
53
74
Com
post
00
76
55
76
N so
urce
Bre
eder
litte
r13
1613
1616
217
8 P
ulle
t litt
er24
2024
1931
2719
15O
ther
Egg
shel
ls4
114
111
37
22 C
lay
subs
oil
1338
1336
1132
1336
C:N
ratio
3232
3032
Nut
rient
s, pe
r ton
of f
inis
hed
com
post
%lb
/ton
%lb
/ton
%lb
/ton
%lb
/ton
Tota
l N0.
613
0.7
140.
613
0.6
13To
tal P
1.0
201.
019
1.2
240.
918
K1.
019
1.0
211.
224
1.1
21C
a9.
318
69.
218
58.
617
312
.925
7
8 and 9, when the final portion of the inoculants (Finisher) was added. During this part of the cycle, short molecular chain humic substances extend to become long-chain varieties. Volatile substances are stabilized and the microbial pop-ulation expands. The Finisher was added at this point because it provides microbial species that help to continue to build humus soil structure, stabilize any remaining volatile compounds, and further add to the microbial population and its diversity [18].
During wk 10 and 11, activity at the site was limited to curing and sampling. Because of the delay in adding eggshells, the materials continu-ing to break down were sufficient to produce heat and CO2. The compost was allowed to cure for 2 wk under cover, with turning done once per week. During wk 11, two samples of each blend were taken and shipped to BBC Laborato-ries for the compost quality analysis portion of the study. Each of the 8 samples was made up of 10 to 12 subsamples, totaling approximately 2 quarts of total material per sample [20].
Compost Quality Analysis
BBC Laboratories performed 3 microbial tests for 1) functional group enumeration and di-versity analysis, 2) stability analysis, and 3) ma-turity analysis. In addition, pathogen testing for e. coli and salmonella was conducted. Table 2 includes information on the optimal ranges and ideal values for each of the quality components as well as on pathogen limits [14].
The functional group enumeration analysis indicated the number of viable microorganisms in a particular group. The 6 functional groups are summarized in Table 2. The diversity analysis estimated the total number of different types of microbes in each category. The maturity analysis refers to plant toxicity associated with the com-post. Immature composts contain more growth-inhibiting substances than mature composts and include salts, NH3, phenolic substances, heavy metals, and organic acids. Stability analysis re-fers to the degree to which composts have been decomposed into more stable materials and was measured by the amounts of CO2 produced or O2 used per unit per hour under conditions appro-priate for microbial growth. More stable com-post will have lower respiration rates than unsta-
ble compost (Table 2) [21]. Estimates based on the nutrient analyses of compost samples done at the University of Arkansas Soils Laboratory were used to estimate the nutrient content of the finished compost.
Break-Even Analysis
A break-even analysis examined 2 hypotheti-cal compost production systems using windrow composting. The production systems analyzed were similar to the one used in this study. System 1 had an input capacity of 5,000 tons of input; system 2 had an input capacity of 20,000 tons. The costs required for producing each compost blend included the total input costs, the total capital investment cost (land and improvement, equipment, etc.), the annual fixed [22] (own-ership) costs, and the hourly variable (operat-ing) costs. The compost systems were designed based on 2 objectives: 1) to minimize the capital investment, production costs, and time required, and 2) to maximize usable output. System 1 is a small-scale facility (5,000-ton input capacity using a 12-ft-wide windrow turner); system 2 is a large-scale facility (20,000-ton input capacity using a 17-ft-wide turner). Both systems screen all the finished compost and sell the product in bulk; system 2 was assumed to bag 25% of its compost into 2-ft3 bags. Production budgets were generated from these systems to provide useful information to entrepreneurs interested in starting a composting operation.
The composting systems were patterned af-ter existing commercial operations (such as the one used to produce the 4 blends) producing moderate- to high-quality compost suitable for a range of applications. Other information was synthesized from estimates of compost produc-tion systems made in previous studies [23–25]. Each system included 1) land requirements; 2) a production schedule; 3) a sketch of the produc-tion area layout as well as the materials prepa-ration area, retention pond, and buildings (if required); 4) a list of machinery and equipment requirements; 5) labor and equipment require-ments; and 6) summarized production budgets of the capital, fixed costs, and variable costs re-quired [26].
Table 3 summarizes the capital and land re-quirements, purchase price, and cost estimates
JAPR: Research Report176
KEMPER AND GOODWIN: COMPOSTING EGGSHELL WASTE 177
Tabl
e 2.
Com
post
qua
lity
anal
ysis
for e
ach
blen
d1
Item
Item
Uni
tB
lend
1B
lend
2B
lend
3B
lend
4
Path
ogen
scre
enSt
ate
limit
Det
ectio
n e
sche
rich
ia c
oli,
1 to
23
MPN
2 /g <
1,00
0 M
PN/g
>23
MPN
/g11
MPN
/g3
MPN
/g2
MPN
/g s
alm
onel
la, 1
/4 g
<3/
4 pe
r gN
egat
ive
Neg
ativ
eN
egat
ive
Neg
ativ
e
Func
tiona
l gro
upO
ptim
al ra
nge
Cou
nt A
erob
ic b
acte
ria 1
00 m
illio
n to
10
billi
on c
fu/g
dw3
Bill
ions
4.50
3.50
2.70
7.10
Ana
erob
ic b
acte
ria ≥
10:1
aer
obic
:ana
erob
icB
illio
ns4.
500.
210.
170.
26 Y
east
s and
mol
ds 1
to 1
00 th
ousa
nd c
fu/g
dwTh
ousa
nds
12.0
06.
405.
205.
80 A
ctin
omyc
etes
1 to
100
mill
ion
cfu/
gdw
Mill
ions
42.0
058
.00
150.
0012
0.00
Pse
udom
onad
s 1
thou
sand
to 1
mill
ion
cfu/
gdw
Mill
ions
4.90
6.50
2.00
7.60
N-f
ixin
g ba
cter
ia 1
thou
sand
to 1
mill
ion
cfu/
gdw
Thou
sand
s30
.00
14.0
08.
4018
.00
Tot
al sp
ecie
s div
ersi
ty H
igh
(>6.
5), l
ow (<
3)N
A4
5.9
4.6
4.3
6.2
Mat
urity
, % (p
hyto
toxi
city
)>5
0%49
42.5
32.5
50St
abili
ty,5 m
g of
O2/k
g (r
espi
ratio
n ra
te)
≤20
(hor
ticul
tura
l app
licat
ions
)32
2325
28<1
00 (f
ield
app
licat
ions
)32
2325
281 B
BC
Lab
orat
orie
s (Te
mpe
, AZ)
.2 M
ost p
roba
ble
num
ber/g
.3 C
olon
y-fo
rmin
g un
its/g
of d
ry w
eigh
t.4 N
A =
not
app
licab
le.
5 A m
easu
re o
f the
leve
l of o
xyge
n pr
esen
t, in
dica
ting
whe
ther
the
com
post
is st
ill a
ctiv
ely
brea
king
dow
n
for all components used in this study. Compost production was assumed to occur over a 6-mo season, with 3 mo required for storage and cur-ing; compost sales, delivery, marketing; and feedstock contracting, delivery, and prepara-tion would be annual activities. Each windrow was assumed to be turned 30 times before being covered for curing. Nine weeks was required to complete a batch, and all rows were combined at the end of the third week (2 rows combined into 1) and new windrows were formed at the same time, which resulted in 19 rows/acre complet-ed during the 6-mo season. Equipment used to produce the compost was assumed to operate at 90% efficiency [27, 23–25]. Land was assumed to have a purchase price of $2,050/acre [28], and improvements could be constructed for $7,200/acre [25]. The annual fixed costs included were straight-line depreciation on land improvements, machinery, equipment, general overhead items license and permitting, repair and maintenance, testing, and insurance.
Variable costs included those that varied with the output volume. Variable costs were based on equipment output capacities, production sched-ules, and packaging, if any (system 1 all sold in bulk; 25% of system 2 was bagged) [29]. Mate-rial costs included hay, oak sawdust, unfinished compost, breeder litter, pullet litter, eggshells, clay (subsoil), inoculants, and bags. Hay costs assumed the hay was rotten or spoiled and could be obtained at a discounted price equaling 10% of the average hay price ($6.20/ton [30]) plus a $4.00/ton hauling fee. Sawdust costs were $19.22/ton [25]. Unfinished compost was locat-ed on site and had zero material cost because the costs to produce this material were accounted for in the variable production costs. Breeder and pullet litter was budgeted at a cost of $4.00/ton for transportation and a $6.00/ton cleanout fee [3]. Eggshell waste had a transportation cost of $6.17/ton; this cost was observed in the delivery of materials for the 4 blends. Clay was budgeted at $0.91/ton. The inoculants required were bud-geted at $0.425/yd3 [31] and bags at $0.33/bag [25].
Variable machinery and equipment costs included fuel, lubricants, and repair expenses [23,25]. Costs estimates were updated by using 2005 Prices Paid Indices from the National Ag-ricultural Statistics Service [32]. Hourly labor
was budgeted at $12.23/h, the mean value for all farming, fishing, and forestry occupations, ob-tained from the Bureau of Labor Statistics [33]. System 2 was assumed to require a full-time manager to supervise and monitor the compost production facility and to implement market-ing plans; a $43,270 salary was assumed [34]. The specific requirements and costs estimates for each system are found in the following sec-tions.
RESULTS AND DISCUSSIONThe delayed delivery of eggshells affected
moisture and temperature. Because of the highly managed process used, the delay affected the quality of the end-product. Study results were perhaps negatively affected, and had the delay not occurred, the results would likely have dif-fered.
Process ResultsThe primary measures for monitoring the
composting process were temperature, CO2 pro-duction and removal, and moisture. Moisture management was done simply by daily inspec-tion of each blend, with moisture being kept near 50%. Figures 1 and 2 show the weekly average temperatures and weekly average CO2 concen-trations (before turning), respectively. The ob-served temperatures (all in degrees Fahrenheit) of each blend were different but followed a simi-lar trend throughout the compost cycle (Figure 1). Each blend had a temperature of greater than 150°F for the first 2 wk and declined thereafter. During wk 3, the average temperatures ranged from 137 to 144°F; wk 4 temperatures declined to 115 to 128°F. Near the end of wk 4, the wind-rows were reconfigured to help retain heat and allow for better utilization of the compost site. During wk 5, temperature remained fairly con-stant (115 to 130°F), indicating that this strategy was successful [35]. During subsequent weeks, average temperatures continued to decline; by wk 9, all blends had temperatures ranging be-tween 85 and 96°F, and by wk 11, at the start of the curing phase, all blends temperatures were in the ideal range (near 80°F). After 8 wk, com-post is typically ready for use in field applica-tions, but for safe use in containers as a fertil-izer and soil amendment, further curing may be required.
JAPR: Research Report178
KEMPER AND GOODWIN: COMPOSTING EGGSHELL WASTE 179
Tabl
e 3.
Cap
ital r
equi
rem
ents
and
cos
ts fo
r 2 c
ompo
st p
rodu
ctio
n sy
stem
s1
Item
Des
crip
tion
Uni
tU
sefu
l life
, yr
Syst
em 1
Syst
em 2
Qua
ntity
Cos
t%
Qua
ntity
Cos
t%
Cap
ital r
equi
rem
ents
Lan
dU
nim
prov
ed la
ndA
cre
—2.
485,
091
226.
4213
,165
22 C
ompo
st p
rodu
ctio
n ar
eaA
cre
—2.
054.
83 M
ater
ials
pre
para
tion
area
Acr
e—
0.25
0.58
Ret
entio
n po
nd a
rea
Acr
e—
0.18
0.43
Im
prov
emen
tsG
radi
ng (5
%) a
nd re
tent
ion
pond
Acr
e20
17,8
7978
46,2
3778
Sub
tota
l22
,970
100
59,4
0210
0B
uild
ings
Sto
rage
bui
ldin
g50
× 1
00 ft
Squa
re fe
et20
5,00
043
,026
31 S
cree
ning
and
bag
ging
faci
lity
50 ×
150
ftSq
uare
feet
207,
500
64,5
3947
Asp
halt
pave
men
t50
× 2
35 ft
Squa
re fe
et20
12,5
0029
,643
22 S
ubto
tal
00
137,
208
100
Mac
hine
ry a
nd e
quip
men
t T
ract
or, 1
-yd
load
er85
hor
sepo
wer
Each
201
42,2
5036
Tra
ctor
140
hors
epow
erEa
ch20
191
,900
16 W
indr
ow tu
rner
, PT
120
1,32
0 yd
3 /hEa
ch20
127
,940
24 W
indr
ow tu
rner
, PT
170
2,67
0 yd
3 /hEa
ch20
182
,950
14 F
ront
-end
load
er, s
kid
stee
r60
hor
sepo
wer
Each
101
20,0
0017
120
,000
3 F
ront
-end
load
er, 3
-yd
buck
et13
5 ho
rsep
ower
Each
101
103,
800
18 T
ruck
, dum
p be
d, u
sed
2-to
nEa
ch10
111
,400
101
11,4
002
For
klift
3,00
0-lb
lift
Each
101
9,85
22
Scr
een-
sepa
rato
r70
yd3 /h
rEa
ch10
112
9,75
022
Bag
ging
mac
hine
20 b
ags/
min
Each
101
72,0
0012
The
rmom
eter
sD
igita
l with
15-
s 36-
in. p
robe
Each
101
310
04
1,24
00
Vol
umet
ric C
O2 i
nstru
men
tD
igita
l with
36-
in. p
robe
Each
101
379
04
1,51
60
Wat
er p
ump
2 ho
rsep
ower
Each
101
2,24
92
12,
249
0 W
indr
ow c
over
13 ft
wid
e, v
ario
us le
ngth
sSq
uare
feet
1066
,823
14,0
8912
172,
810
36,4
346
Pal
lets
45 ×
48
in.
Each
103,
200
21,1
974
Sub
tota
l11
8,61
710
058
4,28
910
0To
tal c
apita
l inv
estm
ent c
osts
141,
586
780,
898
1 Bef
ore
inte
rest
and
tax.
Sys
tem
1 h
as a
n in
put c
apac
ity o
f 5,0
00 to
ns o
f com
post
, and
syst
em 2
has
a c
apac
ity o
f 20,
000
tons
.
The average weekly CO2 readings (Figure 2) indicated that microbial populations in each blend were thriving and breaking down materi-als. The CO2 readings were taken before turning to determine whether aerobic breakdown was being accomplished. Low readings (≤4%) could
indicate that anaerobic conditions had been es-tablished. The average CO2 during wk 1 ranged from 13 to 17%, indicating sufficient airflow to provide O2 to the microbes so materials could be broken down. During wk 2 to 5, average weekly CO2 readings remained between 15 and 20%.
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Figure 1. Weekly temperatures (before turning) of 4 compost blends. Temperature readings were taken only on the days when rows were turned.
Figure 2. Weekly CO2 concentrations (before turning) of 4 compost blends. Carbon dioxide concentrations were taken only on the days when rows were turned.
Readings on October 30 were very low (6, 4, 6, and 11% for blends 1 to 4, respectively), and it was suspected that in uncovering and starting to turn the windrows, the wind might have replaced the CO2 with O2 before an accurate reading could be taken. The following day, readings for all rows were above 20%, so the readings from October 30 were considered aberrant and were removed from the calculations. Average weekly CO2 for wk 6 ranged from 18 to 21%. Readings from wk 8 indicated that weekly average CO2 production was subsiding to levels below 10%. By wk 10, each blend was in the ideal range for finished compost (<8%).
Compost Quality Analysis Results
Results of the compost quality analysis are summarized in Table 2 [36]. Each blend was sampled twice and combined to find a mean value for each. All blends tested positive for e. coli but were within acceptable state limits for compost use in Arkansas [37]. The lowest levels of e. coli were found in blends 3 and 4. salmonella tests were negative for all blends. All blends fell within optimal ranges of micro-bial species enumeration, except for the ratio of aerobic to anaerobic bacteria; only blend 4 was within the optimal value for this parameter. The most aerobic bacteria were found in blend 4, but the values for all of the blends fell within the optimal range. Blend 1 had the highest measure of yeasts and molds (fungi). Nitrogen-fixing bacteria populations were the highest in blend 1, whereas blend 3 had the most actinomycetes and blend 4 had the most pseudomonads, which are important in helping plants make P available.
Total species diversity values for each blend fell within the moderate diversity range (3 < d < 6.5). The highest diversity value (6.2) was asso-ciated with blend 4, and blend 3 had the lowest. Each blend had high diversity values for yeasts and molds, pseudomonads, and N-fixing bacte-ria, whereas the diversity values of the other 3 functional groups fell into the moderate or low range. The maturity analysis results in Table 2 indicated that all blends were not yet mature (index <50%), although blend 4 approached the ideal range. These results were expected be-cause the blends needed to cure for several more weeks before use. After allowing all blends to
cure properly, each should be within acceptable levels of maturity. Accordingly, the stability analysis (respiration rate) results indicated that none of the blends was ready for use in horti-cultural applications but could be used in field applications. Blend 2 was the most stable at test-ing, but all blends had values of less than 35 mg of O2/kg. The nutrient analysis results are listed in Table 1.
Break-Even Results
System 1. System 1 was designed with an an-nual input capacity of 5,000 tons; composition by inputs is shown in Table 1 [38]. The finished product was assumed to total 4,540 tons or 6,053 yd3. All output was assumed to be screened and sold in bulk form. System 1 required 2.48 acres of land: 2.05 acres for compost production, 0.25 for materials storage and preparation, and 0.18 acres for a runoff retention pond (Table 3). A capital investment [39] of $141,586 was required for the necessary equipment comple-ment, with the largest expenditure being made for the 85-horsepower tractor ($42,250) [40]. Capital costs per ton of finished compost were $31.19 (Table 4). Total annual fixed costs were $12,629, with the greatest costs associated with the depreciation cost of machinery and equip-ment (58.6% of total). Useful life assumptions are listed in Table 3.
Annual variable costs were for materials, power for machinery and equipment, and labor to accomplish the production cycle. The cost of materials totaled $36,657, 54.9% of total vari-able costs (Table 4). Power requirements were the estimated time and power needed to com-plete all activities at the facility (tractor hours, for instance); annual labor requirements were estimated by using a factor of 1.2 (power re-quirements multiplied by 1.2 to estimate labor). This labor factor was used to account for the additional time required for job preparation, re-pair and maintenance, breaks, and transport time around the site. The cost of power estimates for machinery and equipment totaled $18,872, and 917.1 h of labor at $12.23/h totaled $11,216 in labor costs. Labor details for other activities are shown in Table 4. Total variable costs for system 1 were $66,745. The total cost for system 1 was $17.48/ton of finished compost.
KEMPER AND GOODWIN: COMPOSTING EGGSHELL WASTE 181
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Tabl
e 4.
Pro
duct
ion
cost
sum
mar
y (a
vera
ge a
cros
s 4
blen
ds)1
Cat
egor
yD
escr
iptio
n
Cos
t, $
Syst
em 1
Syst
em 2
Ann
ual f
ixed
cos
tsLa
nd a
nd im
prov
emen
ts89
42,
312
Bui
ldin
gs0
6,86
0M
achi
nery
and
equ
ipm
ent
7,39
944
,230
Gen
eral
ove
rhea
d4,
336
61,9
50To
tal f
ixed
cos
ts12
,629
115,
353
Ann
ual v
aria
ble
cost
sM
ater
ials
36,6
5717
1,34
1M
achi
nery
and
equ
ipm
ent
18,8
7249
,533
Labo
r11
,216
28,5
50To
tal v
aria
ble
cost
s66
,745
249,
424
Cap
ital i
nves
tmen
t per
ton
of fi
nish
ed c
ompo
stIn
itial
out
lay
for l
and,
impr
ovem
ents
, mac
hine
ry, e
tc.
31.1
943
.00
Cos
t per
ton
of fi
nish
ed c
ompo
stA
nnua
l fix
ed c
ost
2.78
6.35
Tota
l var
iabl
e co
st14
.70
13.7
3 M
ater
ials
cos
t8.
079.
44 A
ll ot
her v
aria
ble
cost
s6.
634.
30To
tal c
ost p
er to
n17
.48
20.0
91 C
osts
bef
ore
inte
rest
and
tax.
System 2. System 2 has an annual input ca-pacity of 20,000 tons; composition by inputs is shown in Table 1. The finished product was as-sumed to total 18,160 tons, or 24,213 yd3. All output was assumed to be screened, with 75% sold in bulk form and 25% bagged in 2-ft3 bags. System 2 required 6.42 acres of land: 4.83 acres for compost production, 0.58 for materials stor-age and preparation, 0.57 acres for 2 buildings (a bagged compost and equipment storage build-ing and a screening and bagging building), and 0.43 acres for a runoff retention pond (Table 3). A capital investment of $780,898 was required for the necessary equipment complement, with the largest expenditure made for the screening machine ($129,750) [41]. Capital costs per ton of finished compost were $43.00 (Table 4). To-tal annual fixed costs were $115,353, with the greatest costs ($61,950) associated with general overhead (53.7% of the total). The largest por-tion of the general overhead was for the full-time manager.
Annual variable costs were for materials, power for machinery and equipment, and labor to accomplish the production cycle. The cost of materials totaled $171,341, or 68.7% of total variable costs (Table 4). Annual labor require-ments were estimated by using a factor of 1.2. The cost of power estimates for machinery and equipment totaled $49,533, and 2,334.4 h of la-bor at $12.23/h totaled $28,550 in labor costs. Labor details are shown in Table 4. Total vari-able costs were $249,424, and the total cost was $20.09/ton of finished compost (Table 4).
CONCLUSIONS AND APPLICATIONS
1. Windrow composting can produce nu-trient-rich compost with thriving popu-lations of beneficial microbial species, effectively eliminating e. coli and sal-monella.
2. The per-ton compost production cost ranged from $17.48 to $20.09 for 4 spe-cific blends.
3. The N-P-K-Ca values of the compost produced (based on current fertilizer prices, August 10) ranged from $33 to $37/ton of finished compost. A US Envi-ronmental Protection Agency price sur-vey indicated a range from $26/ton for
landscape mulch to more than $100/ton for high-grade compost.
4. Process and economic results indicated that breeder hen and pullet litter, as well as eggshell waste, could be diverted to a composting system that would produce a value-added product.
REFERENCES AND NOTES
1. Goodwin, H. L., Jr., J. Hipp, and J. Wimberly. 2000. Off-farm Litter Management and Third-Party Enterprises. Foundation for Organic Resources Management, Winrock International, Little Rock. http://www.winrock.org/us_ programs/files/Off-Farm%20Litter%20Management%20report.pdf Accessed May 5, 2008.
2. Vandevender, K. Poultry Litter Nutrient Summary Information. Unpublished data collected by producers in Ar-kansas, Missouri, and Oklahoma from 1993 to 2000. Ana-lyzed by the University of Arkansas Agricultural Diagnostic Laboratory; summarized by Karl VanDevender, Arkansas Cooperative Extension Service, University of Arkansas, Fayetteville.
3. Goodwin, H. L., Jr. 2006. University of Arkansas, Fayetteville. Personal communication.
4. Goodwin, H. L., Jr., R. Carreira, K. Young, and S. Hamm. 2005. Feasibility Assessment of Establishing the Ozark Poultry Litter Bank. Arkansas Soil and Water Conser-vation District Project 03-900, October 2003–2005. http://arkansaswater.org/319/03-900.html Accessed May 5, 2008.
5. Long, D. 2007. Personal communication. http://www.membrell.net/
6. North Carolina Cooperative Extension Service. 1993. SoilFacts—Soil Acidity and Proper Lime Use. Publ. AG-43917. http://www.soil.ncsu.edu/publications/Soilfacts/AG-439-17_Archived/ Accessed Feb. 5, 2009.
7. Das, K. C., M. Y. Minkara, N. D. Melear, and E. W. Tollner. 2002. Effect of poultry litter amendment on hatch-ery waste composting. J. Appl. Poult. Res. 11:282–290.
8. Rynk, R. 1992. On-Farm Composting Handbook. No. 54. Northeast Regional Agricultural Engineering Service, Ithaca, NY.
9. US Environmental Protection Agency. 2008. Wastes—Resource Conservation—Reduce, Reuse, Recy-cle—Composting. http://www.epa.gov/compost/ Accessed May 5, 2008.
10. Gouin, F. 1995. Compost use in the horticultural in-dustries: Green industry composting. BioCycle Special Re-port. The JG Press Inc., Emmaus, PA.
11. Scheurell, S., and W. Mahaffee. 2002. Compost tea: Principles and prospects for plant disease control. Compost Sci. Util. 10:313–338.
12. Faucette, B., J. Governo, and B. Graffagnini. 2003. Compost pricing and market survey in Georgia. Biocycle 44:32–33.
13. Walker, P., D. Williams, and T. M. Waliczek. 2006. An analysis of the horticulture industry as a potential value-added market for compost. Compost Sci. Util. 14:23–31.
14. BBC Laboratories. 2006. Home page. BBC Labora-tories, Tempe, AZ. http://www.bbclabs.com Accessed May 2, 2008.
KEMPER AND GOODWIN: COMPOSTING EGGSHELL WASTE 183
15. During the composting process, there is typically a dramatic decrease in volume of the inputs used. This gener-ally results in an end-product that has a higher concentra-tion of nutrients, when compared with the nutrient content of the inputs used. This study did not measure the reduction in volume, although a reduction in volume was anecdotally observed and documented with photographs. However, nu-trient content estimates were made on a per ton of finished compost basis
16. Membrell LLC. 2007. 5335 South Garrison, Carthage, MO. http://www.membrell.com/
17. Midwest Bio-Systems Inc. 2006. Compost Workshop Manual. Workshop September 13–15, 2006, Sedalia, MO. Midwest Bio-Systems Inc., Tampico, IL.
18. Midwest Bio-Systems Inc. 2006. http://www.mid-westbiosystems.com
19. For the first 2 wk, each blend was kept below ideal moisture because the original eggshells were to be 50% moisture. This was planned to last for only 4 d; however, the trucking company contracted to haul eggshells for the project was unable to do so.
20. BBC Laboratories. 2006. Compost Sampling for Mi-crobiological Analysis: Instructions for Sampling and Ship-ping. BBC Laboratories, Tempe, AZ. http://www.bbclabs.com Accessed May 2, 2008.
21. Willson, G. B., and D. Dalmat. 1986. Measuring Compost Stability. BioCycle 27:34–37.
22. Fixed costs are estimated before interest and tax.23. Haith, D., T. Crone, A. Sherman, J. Lincoln, J. Reed,
S. Saidi, and J. Trembley. 2001. Co-Composter version 2a. Cornell University, Ithaca, NY.
24. Midwest Bio-Systems Inc. (MBS). 2006. ACS Com-post’s True Value in the Soil. http://www.midwestbiosys-tems.com/acs-value.html Accessed Feb. 5, 2009.
25. Safley, C. D., and L. M. Safley, Jr. 1991. Economic analysis of alternative poultry litter compost systems. De-partment of Agricultural Resources Economics, North Caro-lina State University, Raleigh.
26. Major cost items that a compost production facil-ity would need to produce compost are included, but some overhead items, such as office, machinery, supplies, legal services, and marketing costs, were omitted, as were interest and taxes. These costs can represent a substantial portion of a firm’s budget depending on various factors. Entrepreneurs should be aware of the costs excluded from this study.
27. In practice, operating at 100% efficiency is not real-istic, given variations in weather, feedstock availability, and timing of compost sales and delivery. The authors used 90% efficiency to allow for unforeseen circumstances that would not allow the “ideal” production cycle to be fulfilled.
28. USDA, National Agricultural Statistics Service. 2006. Mean Arkansas farm land value per acre FY2006. Land Val-ues and Cash Rents 2006 Summary. August 2006. http://usda.mannlib.cornell.edu/usda/nass/AgriLandVa//2000s/2006/AgriLandVa-08-04-2006.pdf Accessed Feb. 5, 2009.
29. To account for the decrease in volume, a 9.2% reduc-tion loss factor was assumed for both systems.
30. Average hay price for all hay is from USDA, Na-tional Agricultural Statistics Service. USDA, National Ag-ricultural Statistics Service. 2006. All Other Hay: Price per Ton and Value of Production, by State and United States, 2003–2005. Crop Values 2005 Summary. http://usda.mannlib.cornell.edu/usda/nass/CropValuSu//2000s/2006/CropValuSu-02-15-2006.pdf Accessed Feb. 5, 2009.
31. Pricing is $425 for the inoculant pack and is enough to treat 1,000 cubic yards.
32. USDA, National Agricultural Statistics Service. 2006. Prices Paid: Farm Machinery and Tractors, Unit-ed States, April 2000–2005. Agricultural Prices 2005 Summary. http://usda.mannlib.cornell.edu/usda/nass/AgriPricSu//2000s/2006/AgriPricSu-07-21-2006_revi-sion.pdf Accessed Feb. 5, 2009.
33. United States Department of Labor, Bureau of Labor Statisitics. 2006. May 2005 State Occupational Employment and Wage Estimates for State of Arkansas. May 24, 2006. http://stats.bls.gov/oes/2005/may/oes_ar.htm#b45-0000 Ac-cessed Feb. 5, 2009.
34. United States Department of Labor, Bureau of Labor Statisitics. 2006. May 2005 State Occupational Employment and Wage Estimates for State of Arkansas. May 24, 2006. http://stats.bls.gov/oes/2005/may/oes_ar.htm#b45-0000 Ac-cessed Feb. 5, 2009. Mean value for “First-Line Supervi-sors/Managers of Farming, Fishing, and Forestry Workers” from BLS.
35. Two windrows at the same stage of the production cycle are typically combined when volume has reduced. This allows the production facility to be used for more pro-duction by using less space. Instead of combining windrows (because each windrow is a different blend), each blend was simply folded on top of itself to create a windrow with half the length but twice the height. At this point, the same vol-ume was being produced on half the area.
36. Results from BBC Laboratories. BBC Laboratories. 2006. Functional Groups, Maturity, and Stability Measures of Compost. BBC Laboratories, Tempe, AZ. http://www.bbclabs.com Accessed Sept. 2006.
37. Arkansas Pollution Control and Ecology Commis-sion. 2006. Regulation No. 22: Solid Waste Management Rules. Arkansas Pollution Control and Ecology Commis-sion, Little Rock.
38. Averages across blends are presented in the break-even analysis to shorten the presentation.
39. System 1 is assumed to rent the 70 yd3/h screening machine.
40. All cost estimates are made before interest and tax. 41. Screening machine ownership would be required by
1) total time required and 2) frequency of screening.
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