feasibility and production costs of composting …...100,000 tons of broiler and turkey litter was...

© 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


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



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.



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%.


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.



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.


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.


feasibility and production costs of composting …...100,000 tons of broiler and turkey litter was...

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