Agricultural Innovations

In-House Composting in High-Rise, Caged Layer Facilities

Richard T. Koenig

Washington State University, Pullman

Introduction

Manure handling, storage, and disposal are common 

problems facing poultry producers in the United 

States. Fly and odor control, urban encroachment, a limited 

nearby land base for manure disposal, and increased regulatory pressures necessitate the development of alternatives 

to traditional scrape and haul systems. 

One alternative for high-rise layer facilities is to compost 

manure inside of the buildings housing laying hens. Research showed that the addition of a carbon source coupled 

with frequent aeration of compost in a layer house produced temperatures high enough to inhibit fly reproduction 

in the material. 

In-house composting offers promising solutions to common 

problems faced by egg producers. Since manure can be 

treated within the layer facility, odors associated with manure disturbance and handling when cleaning out a building are reduced. Fly control is achieved with heat, thereby 

reducing the need for pesticides. In addition, a more uniform and marketable compost product is produced, which 

greatly reduces the need for a nearby agricultural land base 

for manure disposal. Research conducted by others [1] also 

has shown that the final weight and volume of material 

produced are at least 35% lower after in-house composting 

compared to traditional systems where poultry manure accumulates undisturbed. 

This article summarizes the in-house composting process 

and relevant research findings from a Western SARE pro

(Introduction continued on page 2)

Inside this fact sheet:

# Introduction

# High-Rise, Caged Layer Facilities

# An Overview of In-House Composting

# Managing Compost Inside Poultry Facilities

# Economic Evaluation

# SARE Research Synopsis

# References

SARE Agricultural Innovations are based on 

knowledge gained from SARE-funded projects. 

Written for farmers and agricultural educators, 

these peer reviewed fact sheets provide practical, 

hands-on information to integrate well-researched 

sustainable strategies into farming and ranching 

systems. The articles are written by project 

coordinators and published by SARE.

Continental U.S. and areas with similar climate and high

-rise, caged layer poultry production systems. This SARE 

research was conducted in the western U.S., but similar 

research has been done in Pennsylvania, Maryland and 

Georgia.

GE O G R A P H I C RA N G E :

Fact Sheet Practical applications for

sustainable agriculture

PDF available at www.sare.org/publications/factsheet/pdf/04AGI2005.pdf

Sustainable Agriculture Research & Education

F. Dean Miner, Jr.

Utah State University Extension, Provo

Bruce E. Miller

Utah State University, Logan

Matt D. Palmer

Utah State University Extension, Tooele

County Extension Agent Dean Miner sifts through 

composted poultry manure. 

Photo by Gary Neuenswander
In-House Composting in High-Rise, Caged Layer Facilities SARE 2

ject in Utah for producers interested in 

adopting the process on their farms. Additional information on in-house composting can be found on the Internet and 

in the publications cited in this article.

High-Rise, Caged Layer 

Facilities

The standard structure design for highrise, caged layer facilities involves housing poultry in offset-stacked cages in the 

upper floor of the structure. Manure 

from the cages is directed with plastic 

sheeting into the storage area below 

(Figure 1). Manure may accumulate for 

several months or more before buildings 

are cleaned out. 

Automated fans housed in the lower portion of the structure control ambient temperatures in the cage area by 

drawing air in through evaporative cooling screens located 

in the roof and expelling it through the walls in the manure 

storage area. The fans also serve to vent ammonia and 

other gasses from the building, and to accelerate manure 

drying. Fly control is normally achieved by supplying a 

feed-based larvicide to laying hens coupled with topical 

applications of insecticides on the manure as needed to 

control outbreaks. Odor and fly complaints are commonly 

associated with the clean-out process when accumulated 

manure is disturbed for loading and transport.

An Overview of In-House 

Composting

Composting is possible inside high-rise facilities using 

equipment sized to fit in the manure accumulation area 

of the structure. Cooperators at the sites where this 

SARE research was conducted used a Brown Bear 

model 24C compost turner [2] fitted to a skid-steer drive 

unit to aerate the materials (photo A). The skid-steer is 

the same power unit that, when fitted with a loader 

bucket, is used to remove material from the buildings. 

To prepare for a compost cycle, a carbon source such as 

straw or sawdust is spread on the floor after cleaning out 

a building. Manure is allowed to accumulate on the carbon bed for 2 to 4 days before forming the material into 

windrows with the turner. The material is turned 

(aerated) every two to four days, depending on the size 

of windrows and material temperature. 

Aerating promotes rapid decomposition by microorganisms. The metabolic heat produced by the microorganisms 

is capable of generating temperatures in the compost above 

the lethal limit for fly larvae (110 oF). Aerating also rotates 

fresh manure into the center of the pile where high temperatures kill new fly larvae. Material is removed when the 

volume exceeds the operational capacity of the turner.

In-house composting differs from traditional composting. 

Since manure is being added continuously, the product at 

the end of a cycle is not finished compost. However, as a 

result of frequent mixing and partial decomposition, the 

material is more uniform and has a lower moisture content 

and less odor than fresh poultry manure. If desired, finFigure 1. Schematic of a high-rise layer structure. Fans in the wall of the structure draw air out under negative pressure (suction). This pathway of air flow 

serves to vent ammonia and other gasses out of the structure, minimizing exposure of poultry.

Photo A. A Brown Bear 24C compost turner [2] fitted to a 

skid-steer drive unit turns compost inside a high-rise layer 

structure.
In-House Composting in High-Rise, Caged Layer Facilities SARE 3

ishing can occur outdoors in a conventional composting 

system, or partially composted material can be landapplied without finishing. Practitioners should check 

with state and local officials regarding regulations on composting facilities and compost quality standards before 

marketing the products of this process as compost.

An essential component of in-house composting is the 

negative pressure ventilation system that vents ammonia 

and other gasses from the composting area. This reduces 

the exposure of poultry and employees to potentially toxic 

gasses produced during composting. High concentrations 

of harmful gasses may still be present in the composting 

area, so employees working there should be equipped with 

appropriate monitoring and respiratory safety devices. Also, practitioners 

should be aware of impending air 

quality rules designed to regulate ammonia emissions from poultry farms. 

Careful attention to composting conditions, particularly the carbon to nitrogen (C:N) ratio of the material, can 

limit ammonia emissions. There is 

also some evidence (cited later) that 

chemical amendments can be used to 

reduce ammonia volatilized from composting manure.

Managing Compost 

Inside Poultry 

Facilities

Details on composting processes and 

methods are outside the scope of this 

article but are presented elsewhere in 

comprehensive manuals [3]. Two of 

the most important factors for successful in-house composting are the appropriate C:N ratio and moisture content 

of the material. Carbon to nitrogen 

ratio should be in the range of 20:1 to 

40:1, with moisture contents in the 

range of 40 to 65% by weight. Practitioners are encouraged 

to purchase a comprehensive reference on composting 

methods, and to periodically have samples of material analyzed to compare results to desired ranges and make adjustments as necessary.

Carbon requirements

Initial research showed that high composting temperatures 

could be achieved in-house using relatively low rates of 

carbon material (200 to 600 lbs per 1,000 square feet of 

floor area, [4, 5]) (Figure 2). The resulting C:N ratio of the 

compost, however, was approximately 10:1, much lower 

than recommended for optimum composting. Composting with a low C:N ratio contributes to high rates of ammonia gas evolution and atmospheric ammonia concentrations inside the layer facility. While using less carbon extends the length of time compost can accumulate before 

the volume exceeds the capacity of the turner, the resulting 

high rates of ammonia volatilization are not sustainable 

from an air quality perspective.

Increasing the amount of carbon used to produce a target 

C:N ratio of 20:1 to 40:1 will reduce ammonia volatilization. Formulae are available to calculate the exact amount 

of carbon necessary to achieve a target C:N ratio, knowing 

the characteristics of the manure and carbon source material [3]. Higher C:N ratio carbon sources are desirable, as 

they reduce the total amount of carbon required. Depending on the source, from 1/3 to 2 pounds of carbon per 

pound of manure would be required for an optimum C:N 

ratio with in-house composting.

22 24 26 28

30

40

50

60

70

Low volume (not turned on day 24)

High volume (not turned on day 24)

*

0 10 20 30 40 50

0

10

20

30

40

50

60

70

Low volume

Days after windrow formation

High volume

Temperatuire (oC)

Time (days)

*

[

Temperatuire (

oC)

Figure 2. Daily compost temperatures measured during a seven-week in-house cycle. The treatments consisted of high and low initial volumes of composting material. 

Arrows indicate when compost was turned. The horizontal line represents the lethal 

limit for fly larvae (43 oC = approximately 110oF). The * indicates when certain replications of the treatments were not turned on day 24. Data from Miner et al. (2001) 

[5].
In-House Composting in High-Rise, Caged Layer Facilities SARE 4

According to published research, a single laying hen produces approximately 0.058 lb manure per day (41% moisture equivalent) [6]. The C:N ratio of layer manure averages 8.5 [4, 5]. Using this information, together with data 

on the carbon source and the formulae cited above, the 

total amount of carbon needed for a given number of birds 

and length of time composting will occur can be calculated. Research [1] also suggests that as much as 35% of the 

manure decomposes during in-house composting, so some 

adjustment in the amount of manure may be warranted 

when forecasting carbon requirements.

Since manure is added continuously over time, all of the 

carbon should not be added at the beginning of an inhouse composting cycle. Divide the carbon into three or 

more separate applications made at regular intervals during 

a cycle. For example, in a six-week cycle, add approximately 33% of the carbon at the beginning of the cycle, 

33% after two weeks, and the final 33% after four weeks.

Turning frequency

Research demonstrated the importance of turning frequency on maintaining compost temperatures above the 

lethal limit for fly larvae. Results showed that critical temperatures could be achieved by turning the material once 

every 2 to 3 days (Figure 2). Missed turning events resulted in a rapid drop in temperatures below the critical 

value (see insert graph in Figure 2). Regular monitoring of 

compost temperatures is critical to determine when to aerate the materials. An inexpensive compost thermometer 

should be purchased to monitor windrow temperatures. 

Temperature monitoring also can be used as a troubleshooting tool. If temperatures do not reach critical values 

for fly control after a turning event, check compost moisture content and C:N ratio and compare to desired ranges 

cited above or in handbook references[3]. 

Average compost temperatures increased over time as the 

total volume and insulating capacity of the material increased (Figure 2). However, frequent turning is still necessary to ensure that fresh material deposited on top of the 

windrows is rotated into the pile and heated to kill fly larvae. Flies develop from egg to adult stages in as little as 

nine days under ideal conditions. Therefore, ensuring that 

all manure is rotated into compost piles at least once every 

nine days is critical for successful fly control.

Composting manure from young poultry 

(pullets)

Composting manure from pullets was less successful in 

research. Compost failed to reach critical temperatures for 

fly control despite more frequent turning and supplemental carbon additions. The failure of composting with pullet 

manure was attributed to a higher moisture content compared to layer manure. Additional research on pullet manure composting is warranted. Increasing the rate of carbon may further promote successful pullet manure composting.

Moisture content

In the arid climate where this research was conducted, the 

moisture content of in-house compost declined to as low as 

30% by weight during summer months [4, 5], well below 

the acceptable range of 40 to 65% [3]. Critical temperatures 

for fly control were still achieved with this low moisture 

content. Although studies in 

which water was added to 

composting materials were 

not conducted, supplemental 

water may increase composting temperatures in situations 

where the moisture content of 

material declines below critical levels.

Compost moisture content 

was higher in winter than in 

summer due to higher relative 

humidity, lower ambient 

temperatures and reduced 

operation of ventilation/

cooling fans in the buildings 

during winter. More frequent turning and the addiUtah egg producer Mike 

Shepherd holds composted 

poultry manure. Photo by 

Gary Neuenswander

Research demonstrated the importance of turning frequency to maintain high compost temperatures.
In-House Composting in High-Rise, Caged Layer Facilities SARE 5

tion of higher rates of carbon during winter are recommended to accelerate drying and promote higher material 

temperatures.

Fly control

The farmer cooperators on this SARE research project 

were able to discontinue using a feed-based larvicide and 

shift to topical applications of an insecticide when needed 

as long as the material was managed appropriately to maintain high temperatures. Fly outbreaks, though infrequent, 

did occur when equipment broke down and turning schedules could not be maintained. 

Similar success in controlling 

flies with in-house composting 

has been reported by other researchers [7].

Ammonia volatilization 

and control

One of the main challenges with 

in-house composting is the accumulation of high levels of ammonia and other gasses inside layer 

houses and venting of these gasses from the facility. Active biological decomposition coupled 

with the low carbon to nitrogen 

ratio and frequent turning of the 

material contributes to higher 

ammonia levels than in high-rise 

layer facilities where manure accumulates in static beds. Monitoring showed that atmospheric 

ammonia in the composting area 

peaked well above safe levels for 

humans and poultry when the 

compost was being turned (Figure 

3). Atmospheric ammonia was also 

higher in winter when fan use to 

cool buildings was reduced. Ammonia concentrations in the cage area were less than 50% 

of the concentrations in the composting area due to air 

flow patterns created by operation of the ventilation system [8]. 

There are several options to manage atmospheric ammonia 

during in-house composting. Practices that conserve nitrogen and reduce ammonia volatilization are the most desirable and environmentally sustainable solutions. Using 

rates of carbon calculated to maintain optimum C:N ratios 

will increase ammonia assimilation by microorganisms and 

reduce ammonia volatilization. Chemical amendments 

such as aluminum sulfate also have the potential to reduce 

ammonia volatilization from in-house compost [9], but 

more research remains to be done in this area. To reduce 

exposure in the short term, facility personnel where this 

research was conducted would over-ride the automated fan 

system for 15 to 30 minutes to vent ammonia when compost was being turned. It is recommended that facilities 

using in-house composting invest in ammonia gas sensors 

to prevent exposure of workers and poultry to high levels 

of atmospheric ammonia. In light of impending air quality 

regulations, practitioners of in-house composting also are 

cautioned to adopt practices that reduce ammonia emissions from poultry facilities.

Economic Evaluation 

Cooperators on this project reported cost savings associated with reduced pesticide use for fly control, removal of 

less material from the buildings at cleanout, and the proTime (minutes after 13:30)

0 500 1000 1500 2000 2500 3000 3500 4000 4500

NH3 Concentration (ppm)

0

10

20

30

40

50

60

}

~90 minutes

Figure 3. Ammonia concentrations over time in the manure storage area of a highrise layer structure during in-house composting. The peak concentration occurred 

during a compost turning event. The –— line indicates the 8 hour human health exposure limit. The — — line indicates the 10 minute human health exposure limit. 

Data are from Koenig et al. (in press) [9].
In-House Composting in High-Rise, Caged Layer Facilities SARE 6

duction of a higher value and saleable product. Additional 

costs were incurred for turning the compost. Based on partial budget analysis including these costs, annual savings 

equaled $6,000 per building per year. Total annual savings 

at a 330,000 laying hen facility was approximately $30,000. 

This was equivalent to a 65% reduction in costs associated 

with pesticides and manure removal and disposal. Overall, 

the greatest cost reduction was realized from reducing the 

amount of pesticide used. The savings offset the costs of 

new compost turners and other equipment required for inhouse composting in less than three years. Additional opportunities were created to use waste cardboard and egg 

shells from a cracking operation as a carbon source and amendment, respectively, to the compost.

SARE Research Synopsis

The goal of SARE research project Inhouse composting in high-rise, caged 

layer facilities was to develop operational parameters for in-house composting. Specific objectives were to: 1) 

evaluate carbon source, rate, and turning frequency variables for their effects 

on compost temperatures; 2) evaluate 

amendments and process controls to 

reduce ammonia volatilization from 

composting manure; and 3) conduct a 

partial budget economic analysis of inhouse composting relative to traditional 

methods of handling and disposing of 

poultry manure. 

The research was initiated in 1998 at a 

330,000-layer egg farm and later expanded to a second facility of similar size. Both farms were 

located in central Utah and featured high-rise, caged layer 

buildings. Each building housed approximately 65,000 laying hens. The manure accumulation area in each building 

was divided into multiple quadrants and treatments applied to separate quadrants in a randomized complete 

block experiment design. Each treatment was replicated 

three times within a building. 

Two trials were conducted to evaluate the effect of carbon 

rate and turning frequency on compost temperatures. Trials indicated that initial carbon rates of 200 to 600 lbs per 

1,000 square feet of floor area were adequate to achieve 

critical temperatures for fly control as long as material was 

turned at least once every three days during early stages of 

composting. Wheat straw and sawdust were equally effective as carbon sources.

Trials demonstrated the importance of turning frequency 

to maintain high compost temperatures. Temperatures 

peaked on the day of turning and declined rapidly thereafter. A turning frequency of once every two to three days 

was essential to maintain high in-house compost temperatures in layer manure. We also found that rotating fresh 

manure with live larvae from the surface to the interior of 

the pile enabled heat to kill the larvae. Longer intervals 

between turning events could be used later in the composting cycle when higher volumes of compost 

were present.

In-house composting with manure from 

young birds (pullets) was generally unsuccessful due to the higher moisture content of 

pullet compared to layer manure. Two additional trials were completed evaluating the 

effects of turning frequency (three or six 

days per week) and carbon rate (400 or 800 

lbs/1,000 square feet of floor area) on composting pullet manure. Results indicated that 

increasing the turning frequency could accelerate pullet manure drying and increase 

compost temperatures. Doubling the rate of 

carbon was less effective than increasing 

turning frequency.

In all of these studies, the C:N ratio of composting material was in the range of 10 to 12:1 

throughout a cycle. Composting with low 

C:N ratios generated high levels of atmospheric ammonia within the poultry facilities. 

While no reductions in egg production or increases in bird 

mortality were noted, high ammonia levels were a health 

concern for workers and poultry. 

Initial efforts to control atmospheric ammonia were focused on documenting the spatial and temporal variability 

of ammonia inside high-rise facilities during composting. 

Atmospheric ammonia levels were shown to vary spatially 

within the buildings, with higher concentrations found 

near the center of the building away from ventilation fans. 

Concentrations frequently exceed 25 ppm ammonia (the 

upper limit for eight-hour exposure of workers) in the manure storage area. Atmospheric ammonia concentrations 

were approximately 50% lower in the cage area. Spikes in 

atmospheric ammonia exceeding 35 ppm (the upper limit 

for 10-minute exposure) occurred immediately after a 

Researchers found annual 

savings of $6,000 per hen 

house per year.

Ohio State University 

Photo Library
In-House Composting in High-Rise, Caged Layer Facilities SARE 7

References

1. Thompson, S.A., P.M. Ndegwa, W.C. Merka and A.B. Webster. 2001. Reduction in layer manure weight and volume 

using an in-house layer manure composting system under field conditions. Journal of Applied Poultry Research 10:255-

261.

2. Brown Bear Corporation, Corning Iowa: http://www.brownbearcorp.com/

3. Rynk, R. (Ed). 1992. On-Farm Composting Handbook. Publication #54 of the Northeast Regional Agricultural Engineering Service (NRAES).

4. Miner, F.D., R.T. Koenig and B.E. Miller. 2000. In-house composting in high-rise layer facilities. Journal of Applied 

Poultry Research 9:162-171.

5. Miner, F.D., R.T. Koenig and B.E. Miller. 2001. The influence of bulking material type and volume on in-house composting in high-rise, caged layer facilities. Compost Science and Utilization 9:50-59.

6. Lorimor, J.S. and H. Xin. 1999. Manure production and nutrient concentrations from high-rise layer houses. Applied 

Engineering in Agriculture 15:337-340.

7. Pitts, C.W., P.C. Tobin, B. Weidenboerner, P.H. Patterson and E.S> Lorenz. 1998. In-house composting to 

reduce larval house fly, Musca Domestica L., populations. Journal of Applied Poultry Research 7:180-188.

8. Koenig, R.T., F.D. Miner, Jr., B.E. Miller and J.D. Harrison. Spatial and temporal variability of atmospheric ammonia 

during in-house composting in high-rise, caged layer facilities. Compost Science and Utilization (in press).

9. Koenig, R.T., M.D. Palmer, F.D. Miner, Jr., B.E. Miller and J.D. Harrison. 2005. Chemical amendments and process 

controls to reduce ammonia volatilization during in-house composting in high-rise, caged layer facilities. Compost Science and Utilization 13:141-149.

SARE Fact Sheet #04AGI2005

compost turning event and lasted for less than 60 minutes. 

Ammonia levels also increased over time as compost volumes increased. In a series of laboratory and limited inhouse trials, process controls and chemical amendments 

such as aluminum sulfate showed potential to reduce ammonia volatilization from composting poultry manure. 

This fact sheet is based on a SARE-funded project. 

For more information, please visit www.sare.org > 

Project Reports > Search the database 

for project # SW00-040