Analyzing Compost Emissions From Washington
State Compost Facilities
David Erickson, Shelley Pressley, William Wallace, Matthew Erickson, Tom Jobson
REU Department of Civil and Environmental Engineering
Laboratory for Atmospheric Research
Objectives
Together with the Washington State Department of Ecology, Washington
State University is conducting a study to identify what volatile organic
compounds (VOCs) are being emitted from the different areas of the
compost facility and the associated flux rate for particular compounds.
Samples were collected from two compost facilities in Washington, one on
the west side and one on the east side of the state. Precipitation patterns
between these two regions are quite different and it is known that soil
moisture and temperature are important for controlling emissions.
Multiple samples were collected at each location for analysis by
certified laboratories and WSU. Results from the study will be
used by the Department of Ecology to assess if emissions from these
facilities cause a health hazard or are an odor nuisance. Another
outcome is that the compost facilities themselves could use this data
to help reduce their emissions by changing management practices.
The second technique being used to identify VOCs is Gas Chromatography
Mass Spectrometry(GC-MS). The GC-MS is used in combination with a
custom thermal desorption system using Tenax-GR for sample preconcentration (Fig. 1). Compound identification is based upon retention
time and mass spectral fingerprint. The mass spectrometer breaks the
molecules into ionized fragments and identifies them by matching to the
National Institute of Standards and Technology (NIST) mass spectral
library. It is unlikely that two compounds will have both the same mass
spectrum as well as the same retention time making it simple to identify
them. Mass spectra from 45-250 amu were collected.
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monoterpene fragment
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C4 benzenes
monoterpenes
toluene
phenol
other butenes
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C2 benzenes (C8H10)
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styrene
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benzene
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acrylonitrile
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Western WA: Unchopped day old waste/Can # 6900
butanol
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acetonitrile
propene
acetaldehyde
ethanol
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isoprene/furan
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acetone
acetic acid
dimethyl sulfide/ethyl mercaptan
water cluster
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10
GC-MS
methanol
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Hydrogen Sulfide
Figure 1: Eastern
Washington Site.
Workers taking
material from the
unchopped pile
and shredding it to
later be moved
into a windrow
Results from the PTR-MS analysis showed slightly elevated levels of methanol
and monoterpenes, the highest levels being 86.45 ppmv and 28.6 ppmv
respectively. The odor threshold of methanol is approximately 90 ppmv
Figure 3 illustrates the complexity of one of the samples collected from the
tipping area of the Eastern WA compost facility (units are in counts not
concentrations.
HONO
The VOCs from these canisters were analyzed using two different
methods, Proton Transfer Reaction Mass Spectrometry (PTR-MS) and Gas
Chromatography Mass Spectrometry (GC-MS). The PTR-MS is capable
of scanning and identifying a range of compounds by passing sample air
through a constant stream of hydronium ions (H3O+). Since VOCs usually
have a higher proton affinity than water vapor the extra proton is
transferred to the compound. The protonated proton then passes into a
quadrupole mass spectrometer (QMS).
H3O+ + R → RH+ +H2O
The QMS separates ions by mass to charge ratio (m/z) and measures ion
intensity in ion counts per second (Hz). The mass range studied was from
20-140amu. PTR-MS cannot specifically identify the compounds; the
mass spectrum is interpreted as an M+1 mass spectrum. Using data from
previous experiments, some compounds have been identified such as
methanol, dimethyl sulfide, toluene and monoterpenes.
HCHO
Few studies have been conducted looking at emissions from industrial
scale compost facilities. These facilities take a wide variety of organic
waste from grass clippings to bio-waste to old pizza boxes, where it is
shredded, mixed and allowed to sit in aerated piles (windrows) for multiple
weeks before it is degraded enough to be used as soil. Every step of the
composting process emits volatile gases: greenhouse gases (e.g CO2 and
CH4), odorous gases (ethyl mercaptan and H2S) and hazardous air
pollutants or air toxins (e.g. toluene and dimethyl sulfide). Residents near
compost facilities often complain about odors and are worried about VOCs
that could be hazardous to their health.
Results
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PTR-MS
Hz / MHz H 3O
Introduction
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m/z
Figure 4: PTR-MS mass spectrum of the unchopped pile sample. Many of the
compounds are tentatively identified based only on their m/z ratio.
Emissions from the covered windrows varied significantly between the two
sites. The ECS cover used in the Eastern Washington Site has approximately 4
times the level of monoterpenes but had approximately four times less
methanol than the Gore Cover used at the Eastern Washington Site.

Compounds that have been identified at high levels from the GC-MS are
dimethyl sulfide, α-pinene, toluene and various furans.

Various compounds that have the highest rates of emissions appear in either
the unchopped or freshly chopped piles at both sites. The emissions are
reduced in the primary aerated static piles (ASP) but increase as the ASP ages.
One of the more odorous compounds, H2S is shown in Figure 3.

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4
Hydrogen Sulfide
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Data Collection
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References
Kumar, Anju et al. “Volatile organic compound emissions from green waste
composting:Characterization and ozone formation.” Atmospheric
Environment 45 (2011): 1841-1848. Online
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Hz/MHz H 3 O
An Environmental Flux Chamber
technique was used to
collect samples. A flux chamber
was placed on the source material,
allowed to equilibrate using a
helium flush gas and 6L SUMMA
polished canisters were filled for
analysis in the lab. Samples
Figure 2: CE Schmidt filling a canister on the
were collected from the
unchopped vent at the Eastern Washington Site.
tipping area (where fresh
materials were delivered to the facility), the chopping area (where
materials were mechanically ground to reduce size and increase
surface area), windrows of various ages (piles that sit for extended
periods while being negatively or positively aerated until the materials
fully decompose), biofilters (tightly packed organic material that
scrubs VOCs from the aeration system) and leachate clarifiers
(collection ponds that hold the liquid run off from windrows).

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4
2
10
H2S Odor Threshold
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6
4
2
W.W Media Blank
E.W Media Blank
W.W Gore on Primary Compost
E.W ECS Cover Vent
E.W 13 Day Old Windrwo Dup.
E.W 13 Day Old Windrow
W.W Secondary ASP
W.W Primary ASP Dup.
W.W Primary ASP
E.W Fresh ASP No Cover
E.W Unchopped/Day Old Vent
W.W Fresh Chopped Compost
E.W Fresh Chop< 1 Day Old
W.W Finish Pile
E.W Finish Pile
W.W Primary Effluent Lagoon
E.W Leachate Clarifier
W.W Secondary Biofilter
W.W Primary Biofilter
E.W Primary Biofilter
1
Figure 5: 45% of the samples collected emit hydrogen sulfide at levels that are
above the odor threshold (the lowest concentration at which a person can detect an
odor). Hydrogen sulfide gives off an odor similar to rotten eggs.
Acknowledgments
Figure 3: Stage 1 shows the flow of sample air into the Tenax-GR.
Stage 2 shows how the air is filtered out of the Tenax-GR, through the GC column
and into the Ion Trap for analysis
Many thanks to John Cleary of the Washington State Department of Ecology
and Charles Schmidt, Ph.D., Environmental Consultant for filling the sample
canisters analyzed at WSU and sharing their findings for comparison with
our results.
This work was supported by the National Science Foundation’s REU
program under grant number 0754990