Proceedings available at: http://www.extension.org/67663 Recent research has shown that over half of nitrogen excreted by chickens is lost into the atmosphere via ammonia volatilization before the litter is removed from poultry houses. Large quantities of particulate matter and volatile organic compounds (VOCs) are also emitted from animal rearing facilities. During the past decade we have developed and patented an acid scrubber for capturing ammonia, VOCs and dust from air exhausted from poultry and swine barns. The objectives of this project were; (1) to re-design the scrubber to improve the ammonia removal efficacy, (2) conduct full-scale testing of the scrubber under controlled conditions at various ventilation rates, (3) evaluate the cost, practicality and efficacy of various acids for scrubbing ammonia, and (4) install scrubbers on exhaust fans of poultry houses located in Virginia and Arkansas and measure the efficiency of ammonia removal from the exhaust air. The efficiency of ammonia removal by the scrubber varied from 55-95%, depending on the type of acid used, air flow rate, and the internal scrubber configuration. This technology could potentially result in the capture of a large fraction of the N lost from AFOs, while simultaneously reducing emissions of bacteria, dust, and odors, which would improve the social, economic, and environmental sustainability of poultry and swine production.

1. Development of an Acid Scrubber for
Reducing Ammonia Emissions
from Animal Rearing Facilities
Philip Moore, USDA/ARS
Rory Maguire, Virginia Tech
Mark Reiter, Virginia Tech
Jactone Ogejo, Virginia Tech
Robert Burns, Univ. of Tennessee
Hong Li, Univ. of Delaware
Dana Miles, USDA/ARS
Michael Buser, Oklahoma State Univ.

2. • According to the EPA the biggest source of atmospheric
NH3 in the U.S. is animal manure, with poultry reportedly
contributing 27% of the total (Battye et al., 1994).
• Atmospheric ammonia contamination can lead to
environmental problems, such as particulate matter less
than 10 microns, excessive nitrogen loading into the
aquatic environment and soil acidification.
• The ammonia emission factor for 50 day old broilers is
around 45.5 g NH3/bird (Moore et al., 2011).
• Over half of the N excreted by broilers is lost to the
atmosphere via ammonia before the litter is removed from
the barns.
Problems caused by ammonia volatilization

3. 45.5 g NH3/bird total loss or 37.4 g N/bird
Typical ammonia losses from broilers
In Arkansas, where 1.1 billion broilers are
grown each year, this would result in annual
emissions of 50 million kg of NH3 which has a
fertilizer value close to $100 million dollars.
We need to convert this waste to worth.

4. 33.5 lbs NH3/day-house
Average daily ammonia losses during the flock

5. Fertilizing pastures with N from scrubbers
• In some watersheds, growers cannot apply litter because
of soil test P thresholds and must purchase commercial
fertilizer to meet the N needs of their pasture.
• If we could develop a scrubber that would trap an
average of 5 lbs N per day, then the grower would
recover 1825 lbs N/unit/year.
• Assuming the grower has 2 units on each chicken house
and a total of four houses, then he/she could recover
14,600 lbs N/year. This would be almost enough N to
supply 150 lbs N/acre to 100 acres of pasture.
• Air and water quality would also greatly benefit.

6. Wet scrubber for controlling ammonia and dust
• Our unit has been conducting research on ammonia
scrubbers on and off for about a decade. Currently we
have one patent on these scrubbers (Moore, 2007) and two
more in the pipeline. These scrubbers would work best on
houses that use 2-4 minimum ventilation fans during the
cooler months of the year.

7. • Cheap – The first scrubber we built cost less than $1,000.
• Small – The original scrubber had a 5’ x 5’ footprint.
• Simple – There was one pump; no heaters or cool cells.
Pros of our original scrubber

8. • Acid use was high. Dust from poultry houses contains
manure, which has a high alkalinity. More than half of
the acid was wasted neutralizing the dust.
• There were large losses of acid and nitrogen via mist.
• In extremely cold weather the contents of the reservoir
would freeze.
Cons of our original scrubber

9. Although it had problems, the original
scrubber did make the NRCS webpage!

10. Our second version consisted of two scrubbers; the first was a water scrubber
which captured most (>99%) of the total dust. The second was an acid scrubber.
However, acid and N losses were still occurring even there were no “leaks”.
It was ugly…but it worked!
acid scrubber dust scrubber

11. • Data from this scrubber showed N levels in the reservoir
would build up to a certain point, then decline, even
though the pH was still low.
• When an acid containing sulfate was used in the acid
scrubber the concentration of sulfate would slowly
decline throughout the growout, indicating a leak was
occurring.
• However, we could not find a conventional leak. So we
concluded that the losses were occurring as a fine mist.
Apparent leaks in the scrubber

12. • A fine mist may only equal one drop per second.
• 1 drop per second = 3 ml/minute
• 180 ml/hr
• 4,320 ml/day
• 224.6 L/growout for 50 day birds
• Reservoir volume = 360 L
• At that rate 62% of the acid and N is lost.
Mist collection is essential

13. • Exhaust air from broiler houses is warm, however,
depending on the growth cycle of the birds any one fan
may not run very often.
• Acids and acid/salt mixtures tend to have a lower
freezing point than water, however they will still freeze.
• To avoid this problem heaters were installed in both the
dust and acid scrubber.
Internal heater is also essential

14. Objectives:
• Re-design the scrubber to improve efficiency.
• Conduct full-scale testing at various ventilation rates
under controlled conditions.
• Evaluate the cost, practicality and efficacy of various
acids for scrubbing ammonia.
• Build and install scrubbers on poultry farms in AR, DE,
PA and VA and measure ammonia, dust and VOC
emission reductions.
This research was funded by USDA/ARS and by grants from USDA/NRCS and
the National Fish and Wildlife Foundation.

15. The current version has
two scrubbers; one for
dust and the second for
ammonia.
The shells are made out
of fiberglass. Each has
a 360 L reservoir.
These scrubbers are
made for minimum vent
fans in order to get the
most N per dollar spent
(Melse et al.,2006).
Dust
scrubber
Ammonia
scrubber

16. The dust scrubber can hold
up to 8 rows of wooden
slats at 45 degree angles.
Our design goal was to
keep static pressure below
0.3”.
If this is exceeded, then
rows of slats can be
removed, as needed.
Wood is much cheaper than
plastic or fiberglass.

17. A simple float switch is used to control the water level.
An inexpensive submersible pump is used to recirculate the water.
To avoid freezing, a heating element was included in the current design.

18. The ½ HP pump used in the dust
scrubber delivers 22 gal/min.
120 volts, 6 amps.
Little Giant 6EN-CIA-SFS.

19. • Acid scrubbers used in Holland and Germany use
nozzles to scrub ammonia.
• However, if the solution used for scrubbing is being
recycled, these nozzles will inevitably clog, due to the
large amount of particulate matter in the exhaust from
poultry houses.
• Using nozzles also results in fine droplets, which will
enhance the loss of nitrogen as mist.
Dutch and German scrubbers use nozzles

20. To avoid these problems
we chose a simple
delivery system of large
orifices (0.040”) which
results in a water
curtain.
The distances between
these holes are 2” near
the pump, 1.5” in the
middle third and 1” apart
on the far side of the
pump.

21. This system can be run for several flocks without clogs. However, if they do
occur, they can be unclogged in less than a minute with a long-handled brush.

22. The dust scrubber has a screen above the reservoir to catch feathers and
very large particulate matter (including rats, cats, etc.).
feather
trap

23. Acid tolerant heaters are made by Vulcan Industries. They turn on at 38
degrees and have 120 degree limit switch.
If all of the heaters and pumps are working simultaneously the maximum
electrical use will be 24 amps.

24. A 1/3 HP magnetically driven
pump is used in the acid
scrubber. It’s expensive ($500),
but can withstand extremely
acidic conditions, such as
concentrated sulfuric acid.
When the pump is not running,
the acid drains back into the
reservoir, reducing the risk of
frozen pipes during winter.
It will deliver 14 gal/min and uses
3.4 amps.
IWAKI MD-100RCT

25. Plastic cool cell material was
was enclosed in a stainless
steel frame on the exhaust end.
Although this material is an
effective medium for acid
scrubbing it also helps with mist
collection.
It is on hinges, allowing for easy
access into the scrubber.
Made by GEA
(Polypropylene Humipacking)

26. We have tested various
configurations, including
dual cool cells. This setup
can remove >95% of the
NH3 at airflows of 5,000 cfm
with 25 ppm NH3. However,
we think cleaning and other
maintenance would be very
difficult with this design, so
we are only using one layer
of cool cell material.

27. • The main criteria for ammonia scrubbers set forth by
NRCS is the pressure drop should be less than 0.3”.
• Initial research was conducted to determine how slat angle
affects static pressure (SP) and air flow.
• The goal was to determine the angle that would maximize
particle collisions with a wet surface while minimizing
pressure drop.
• We also evaluated how the number and arrangement of
slats, water curtains and cool cells would affect pressure
drop and air flow.
Preliminary design studies

28. FANS
unit
variable speed
poultry house
fan
plenum
dust
scrubber
acid
scrubber
Preliminary testing of the new scrubber was conducted by attaching a variable
speed fan to the scrubber via a plenum. This fan was capable of airflows up to
20,000 cfm. Air flow was measured with a FANS unit. Static pressure was
measured with a Setra 2601MS1 differential pressure sensor.

29. 0 10 20 30 40 50 60 70 80 90
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Slat Angle (degrees)
StaticPressure(incheswater)
one row of slats in dust scrubber
60 Hz
40 Hz

30. 0 10 20 30 40 50 60 70 80 90
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
22000
Angle of slat (degrees)
Airflow(cfm)
60 Hz
40 Hz
one row of slats in dust scrubber

31. 0 2 4 6 8 10 12 14 16
0
0.05
0.1
0.15
0.2
Number of slats in dust and acid scrubber
StaticPressure(incheswater)
no cool cell, no water curtain
one cool cell, no water curtain
one cool cell, one water curtain
one cool cell, two water curtains
one cool cell, three water curtains
two cool cells, three water curtains
fan setting = 40 Hz
current configuration

32. • We evaluated the effects of water, a neutral salt (calcium
chloride), five acid salts (alum, aluminum chloride, ferric
chloride, ferric sulfate, and sodium bisulfate) and four
strong acids (sulfuric, hydrochloric, nitric and
phosphoric) on ammonia reduction.
• Rates of each acid were equivalent to 2 liters of
concentrated sulfuric acid (up to 19 lbs material for some
salts).
• Each acid was tested for three runs that were two hours
each at two fan speeds; (1) 40 Hz – which resulted in
airflows of about 5,000 cfm, and (2) 60 Hz – 8,000 cfm.
Acid Testing

33. Anhydrous ammonia was metered into
a distribution system located in front of
the fan. The amount entering the
system was varied, as needed, to
achieve 25 ppm in the plenum.
All personnel involved in this research
wore respirators equipped with
ammonia cartridges.

34. During each run airflow
was measured using a
FANS Unit.
Ammonia was introduced
via a distribution system
directly in front of the fan.
Ammonia concentrations
entering and leaving the
scrubber were measured
every five minutes during
the two hour trials using
an Innova 1412.

37. At 5,000 cfm, air residence time in scrubber = 3 seconds
1.5 seconds in the acid scrubber.

38. Stainless steel star
samplers were used
to sample intake and
exhaust air.

39. Five whatmanFive whatman
36 filters were36 filters were
placed on aplaced on a
frame duringframe during
the initial testingthe initial testing
to evaluateto evaluate
acid/N loss viaacid/N loss via
mist. Mistmist. Mist
losses werelosses were
small.small.

40. 0 2 4 6 8
0
5
10
15
20
25
30
35
Time (hours)
Ammoniaconcentration(ppm)
sodium bisulfate (PLT) in acid scrubber
Intake
Exhaust
60 Hz 40 Hz 60 Hz 40 Hz

41. 0 2 4 6 8
0
5
10
15
20
25
30
35
Time (hours)
Ammoniaconcentration(ppm)
Intake
Exhaust
Water in acid scrubber
40 Hz 60 Hz 40 Hz 60 Hz

42. • Water is cheap! It can scrub ammonia from air as long as
the pH is below about 8.
• If a corn grower was irrigating with acid well water, then it
would be easy to devise a system where fresh water was
constantly trickled into the dust and “acid” scrubber before
being discharged into a pond or reservoir.
• If the residence time in the scrubber was equal to an hour
of fan time, then the N concentration would increase to 50-
100 mg N/L, which would help meet N needs of the crop.
• Disadvantage of water alone – amount used would require
a pond, which may require a permit (Reg 5 in AR).
Could water scrubbers be the most sustainable?

43. 0 2 4 6 8
0
500
1000
1500
2000
2500
Time (hours)
Ammoniaconcentrationinacidreservoir(mgN/L)
Water
PLT
y = 14x + 43
R = 0.74
y = 278x + 97
R = 0.97
2
2

44. 0 2 4 6 8
0
2
4
6
8
10
Time (hours)
pH
Water
PLT
NH3 + H+
 NH4
+

45. 0 1 2 3 4 5 6 7
-5
0
5
10
15
20
Run number
AmountNcapturedbytapwaterindustscrubber(g)

46. 6 7 8 9 10 11
-5
0
5
10
15
20
Initial water pH
AmountNcaptured(g)
y = -3.8x + 43
R = 0.40
2

47. water calcium sodium aluminum aluminum ferric ferric
0
20
40
60
80
100Ammoniareductioninexhaust(%)
40 Hz (~5,000 cfm)
60 Hz (~8,000 cfm)
C
A
AB
ABCABC
D
D
a ab
bc
de
cde
f
f
chloride bisulfate chloride sulfate choridesulfate

48. water sulfuric hydrochloric nitric phosphoric sodium
0
20
40
60
80
100Ammoniareductioninexhaust(%)
40 Hz (~5,000 cfm)
60 Hz (~8,000 cfm)
cde
de de
e
de
f
ABC ABC
C
CC
D
acid acid acid acid bisulfate

49. -20
0
20
40
60
80
100
120
140
160NitrogenCaptured(gN/hr)
40 Hz (~5,000 cfm)
60 Hz (~8,000 cfm)
water
f
f
cd
abc
a
abc
ab
E
E
CD
AB
ABC ABC
A
calcium sodium aluminum aluminum ferric ferric
chloride bisulfate chloride sulfate choridesulfate

50. -20
0
20
40
60
80
100
120
140
NitrogenCaptured(gN/hr)
water
40 Hz (~5,000 cfm)
60 Hz (~8,000 cfm)
ABCD
D
CD
BCD
CD
E
cd
e
de
bcd
cd
f
sulfuric hydrochloric nitric phosphoric sodium
acid acid acid acid bisulfate

51. Scott Becton, one of my
technicians, has played
a key role in designing
and assembling the
scrubbers.
So far we have built 6
of the new scrubbers (4
in VA and 2 in AR).
This year we will build 5
more, which go to farms
in AR, DE, and PA.
Carpenter, electrician, mechanic, plumber, and ventilation

52. Conclusions
• The re-designed scrubber does a good job of removing
ammonia from air, even at high flow rates. The goal of
keeping pressure drop at less than 0.3” was met.
• Acid salts of Al and Fe worked better per mole of H+
than
strong acids or sodium bisulfate (PLT). However, we
believe Al and Fe hydroxides will clog the cool cell.
• Due to the inherit danger of strong acids, we have decided
to use PLT in our future research. It is sold as a litter
amendment to poultry growers, so it is readily available.
It is also relatively easy to dissolve.
• Water may be the most sustainable scrubbing solution.
However, the volumes needed will require a pond and

53. Future Plans
• Four ammonia scrubbers will be attached to the sidewall
fans of a broiler house in Madison County, AR.
• We will evaluate the efficacy for reducing ammonia,
particulate matter and VOCs.
• We will also measure how much PLT, water and
electricity is used by the scrubbers, as well as how much
N is captured. A cost-benefit analysis will be performed.
• Data on the efficacy to scrub ammonia will also be
collected on farms in DE, PA, and VA.
• We will also evaluate water as a scrubbing solution, but it
may only be cost-effective on farms irrigating crops.