ResultsResults 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.

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.

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 ResearchIntroductionFew 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.

Data CollectionAn Environmental Flux Chambertechnique was used to collect samples. A flux chamber was placed on the source material,allowed to equilibrate using a helium flush gas and 6L SUMMApolished canisters were filled for analysis in the lab. Samples were collected from the 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).

PTR-MSThe 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.

GC-MSThe 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 pre-concentration (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.

AcknowledgmentsMany 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

Figure 1: Eastern Washington Site. Workers taking

material from the unchopped pile

and shredding it to later be moved into a windrow

ReferencesKumar, Anju et al. “Volatile organic compound emissions from green waste composting:Characterization and ozone formation.” Atmospheric Environment 45 (2011): 1841-1848. Online

ObjectivesTogether 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.

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

H2S Odor Threshold

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.

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Figure 2: CE Schmidt filling a canister on the unchopped vent at the Eastern Washington Site.

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