Emissions and Health

Perhaps more hazardous than what you smell is what you don’t smell. Industrial composting can contribute to environmental pollutants that are harmful to public health.

Volatile Organic Compounds

As waste decomposes, it emits volatile organic compounds (VOCs)—carbon-based chemicals that evaporate at room temperature. Many VOCs—which may or may not smell—are also air pollutants. VOC concentrations are highest at the beginning of composting, when feedstocks arrive, are being ground up, and are starting to decompose. Humans get exposed to VOCs emitted from composting facilities by breathing contaminated air.

The following VOCs are common to decaying food scraps and grass clippings:

  • Terpenes
  • Alcohols
  • Acids
  • Esters of acids
  • Organic-sulfur compounds
  • Ketones
  • Dimethyl disulfides

The Washington State Department of Ecology conducted an air emissions study at a local composting facility (2011) and found a host of VOCs being emitted from the composting piles. Click here to learn more about those VOCs and specific information about their hazards.

Bioaerosols

Bioaerosols, or organic dust, result from the breakdown of organic matter. Made of microbes, plant and animal matter, fungi, viruses, and various toxins, some bioaerosols are pathogenic (cause health problems) and others are not. The smaller the bioaerosol particle, the greater the risk, as small particles can become trapped within lung tissue.

Although bioaerosols are always in the air from soil dust, natural breakdown of vegetation, and agriculture, they are likely to be found in higher volumes when organic matter is stirred up. At a composting facility, the following conditions can contribute to this:

  • Feedstocks being ground up
  • Piles being turned, especially when overly dry
  • Weather, like wind and heat
  • Physical layout of a facility—piles stored outside
  • Topography–facility is in a valley, which can trap bioaerosols
Studies on Bioaersols at Industrial Composting Facilities

Various studies have examined what boundaries should exist around industrial composting facilities, to maximize their neighbors' health and safety. As each site is different, a variety of boundary recommendations exist.

  • The Environment Agency in the UK has stated that any composting facility within 250m (820ft) of residential areas or workplaces require a permit and study to prove that their operations will not increase bioaerosol levels beyond acceptable levels.
    • Acceptable levels of bioaerosols for the following bacteria commonly present in composting:
      • Gram negative bacteria: 300cfu m3 (colony forming units per cubic meter of air)
      • Total bacteria: 1000cfu m3
      • Aspergillus fumigatus: 500cfu m3
  • A study at a composting facility in northern England found levels of bioaerosols that were equal with natural, background levels at a distance of 300m (985ft).
  • A study at a composting facility in New York found that emissions of bioaerosols from the facility caused an increase of bioaerosol concentrations 500m (1600ft) away in a residential neighborhood.
    • Researchers state that the health effects of these concentrations of bacteria are still unclear, though there may be an increased risk for people with immune system deficiencies.
  • A study in Germany detected low levels of bioaerosols and VOCs at a distance of 800m (2600ft) from the composting facility.
  • A study examining bioaerosol concentrations and health impacts to neighbors found concentrations 100-1000 times normal levels within 300m (1000 ft) of the facility.
    • Concentrations of microorganisms found within 200m (650ft) of the facility were at levels expected to elicit complaints of airway inflammation.
    • An association could be demonstrated between residential bioaerosol pollution <200m (650 ft) from the facility and complaints of irritated airways.
    • An association could be demonstrated between complaints and bioaerosol exposure of 5 years or more, suggesting that chronic exposure over long periods of time could cause negative health effects.

Monitoring and Testing

The atmospheric dispersal of toxins is not easy to monitor. Chemicals are released into the atmosphere and mix with other sources of pollution in the surrounding area.

Nonetheless, in a report on industrial composting produced for the California Integrated Waste Management Board, researchers suggest periodic air testing and monitoring to ensure that compost emissions are at safe levels for facility workers and the surrounding environment.

Specific recommendations include:

  • Exhaustive control of biological risks
  • Measure microorganisms in the compost and in the air (indoor)
  • Measure indoor concentrations of VOCs
  • Monitor levels of VOCs in workers
  • Provide protective measures to prevent exposure to VOCs and bioagents
  • Measure microorganisms and VOCs in the environment surrounding facilities
  • Periodically quality control compost in order to reject any that contains unsafe levels of biological or chemical agents
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