Dual GC Techniques Track Compost VOC Emissions

Some U.S. states have started requiring that food scraps be sent to compost facilities instead of landfills. That's good news for cutting down on landfill greenhouse gases, but it comes with a catch: compost can release its own mix of gases, some of which may be harmful to breathe or just smell offensive, which could be a concern for people's health. Because of this, there's a need for good ways to figure out exactly which gases compost is putting out and where they're coming from.

In response to this need, a joint study conducted by Lewis-Clark State College (Lewiston, Idaho) and the Department of Civil and Environmental Engineering, at Washington State University (Pullman, Washington) developed and employed a two-component compost sampling method consisting of a chilled impinger and pump apparatus to trap water-soluble volatile organic compounds (VOCs), and dual sorbent tubes to capture hydrophobic VOCs in yard and food/yard waste compost. VOCs were measured via headspace gas-chromatography with flame ionization detection (HS-GC-FID) and thermal desorption-gas chromatography–mass spectrometry (TD-GC–MS). A paper based on their efforts was published in the journal Atmosphere.¹

Why is Composting Important?

Farmers rely heavily on compost as fertilizer and to improve soil quality. Because it breaks down organic waste using oxygen rather than without it, composting is a more efficient option and is becoming more popular. More cities and towns are turning to composting since it relies on this oxygen-based breakdown, unlike landfills, where waste decomposes without oxygen and releases methane gas. Both landfills and compost piles raise concerns because they release greenhouse gases like methane and carbon dioxide, which contribute to global warming.^2-5

Why Does this Study Focus on Identifying the Specific VOCs that Compost Releases?

One downside of composting is that it can give off VOCs.^6-8 Because of the health and environmental concerns these gases raise, many cities have rules limiting VOC emissions from compost facilities or require these facilities to get air permits. A recent review⁹ found that compost facilities typically release somewhere between 6 × 10⁻⁵ and 1.7 × 10⁻³ kg of VOCs for every kilogram of wet material composted. Despite this, there is still little detailed data on exactly which VOCs compost releases, mainly because testing for them is time-consuming and costly, which inspired this study.¹

What Did the Study Find, and Why Do Those Findings Matter?

The researchers report that hotter compost piles give off more VOCs overall, with ethanol levels reaching as high as 27,000 ppm and methanol up to 3500 ppm. These piles also released notable amounts of pine- and citrus-scented compounds (alpha-pinene and D-limonene), each topping 1600 ppb. Piles mixing food and yard waste produced over a thousand times more methanol and ethanol than yard waste alone, though yard waste gave off a bit more of those pine/citrus compounds. Methanol levels exceeded safe indoor air guidelines, which could be a health concern.¹

The team believes that their research could be useful for tracking air pollution, setting emission benchmarks, and shaping regulations. For instance, the food/yard waste mix released noticeably more alcohol fumes, and steps like using biofilters or adjusting temperature and airflow could help cut those emissions. Knowing exactly which gases compost gives off can also help assess how much compost workers and nearby residents are exposed to, and what health risks that exposure might carry.¹

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References

1. Berger, S. K.; Morales, R. C.; McCown, K. et al. Analysis of Volatile Organic Compounds from Compost. Atmosphere 2025, 16 (5), 591. DOI: 10.3390/atmos16050591
2. Ho, T.T.K.; Tra, V.T.; Le, T.H.; Nguyen, N.K.Q.et al. Compost to Improve Sustainable Soil Cultivation and Crop Productivity. Case Stud. Chem. Environ. Eng. 2022, 6, 100211.DOI: 10.1016/j.cscee.2022.100211
3. Stentiford, E. I. Composting Control: Principles and Practice. In The Science of Composting; Springer, 1996; 49–59.
4. Abduli, M. A.; Naghib, A.; Yonesi, M. et al. Life Cycle Assessment (LCA) of Solid Waste Management Strategies in Tehran: Landfill and Composting Plus Landfill. Environ. Monit. Assess. 2011, 178, 487–498.DOI: 10.1007/s10661-010-1707-x
5. Sánchez, A.; Artola, A.; Font, X. et al. Greenhouse Gas Emissions from Organic Waste Composting. Environ. Chem. Lett. 2015, 13, 223–238. DOI: 10.1007/s10311-015-0507-5
6. Van Durme, G.P.; McNamara, B.F.; McGinley, C.M. Bench-Scale Removal of Odor and Volatile Organic Compounds at a Composting Facility. Water Environ. Res. 1992, 64, 19–27. Available online: https://www-jstor-org.uidaho.idm.oclc.org/stable/25044110?sid=primo (accessed on 2 February 2025).
7. Müller, T.; Thißen, R.; Braun, S. et al. (M)VOC and Composting Facilities: Part 1: (M)VOC Emissions from Municipal Biowaste and Plant Refuse. Environ. Sci. Pollut. Res. 2004, 11, 91–97. DOI: 10.1007/BF02979708
8. Schiavon, M.; Martini, L. M.; Corrà, C. et al. Characterization of Volatile Organic Compounds (VOCs) Released by the Composting of Different Waste Matrices. Environ. Pollut. 2017, 231, 845–853. DOI: 10.1016/j.envpol.2017.08.096
9. Nordahl, S. L.; Preble, C. v.; Kirchstetter, T. W. et al. Greenhouse Gas and Air Pollutant Emissions from Composting. Environ. Sci. Technol. 2023, 57, 2235–2247. DOI: 10.1021/acs.est.2c05846