The best and most appropriate operating practices (best management practices) are utilized to avoid negative impacts, such as odor. The Comprehensive Compost Odor Response Project (C-CORP) Report contains a comprehensive literature review on the best management practices for composting and valuable basic information on the science of the composting process. The C-CORP report provides practical tools for LEAs and operators to conduct site assessments to minimize odor impacts and effectively respond to odor complaints.

The following tables summarize the mitigation measures presented in the full C-CORP Report.

  • Table 12 (page 135 of report)
    This table lists processing operations where odors can occur and provides possible mitigation measures to resolve the odor problem. Each mitigation measure is listed as a management approach. Table 13 has links from odors to the appropriate numbered mitigation measure to resolve the identified odor.
  • Table 13 (page 138 of report)
    This interactive table provides odor descriptors and links to specific possible mitigation measures by feedstock and operation for a specific odor compound.

The operational challenges assessment procedure (OCAP) is another tool that was developed to assist local enforcement agencies and operators in the assessment of a compost facility, site or operation's management practices to address key operational challenges. The OCAP assessment will help identify an operational practice that may have caused an odor or other operational concern. The procedure also provides guidance so that those operational practices that may have caused an undesired consequence can be changed. Experience has shown that if the undesired impacts are not minimized, there is a higher potential for increased nuisance complaints and subsequent enforcement actions that can even result in facility closures.

The mitigation strategies for most types of odors are provided below and have been summarized from the C-CORP report.

Mitigation Strategies

Odors During Receiving:

  • Mix materials upon receipt (increase material porosity).
  • Stockpile bulking agent or high carbon amendments as receiving basin.
  • Stockpile bulking agents or high carbon amendments for unexpected deliveries.
  • Consider blanketing odiferous materials with a six inch to one-foot layer of bulking agent, high carbon amendments, or finished compost. (water lightly to reduce odor releases).
  • Reject odorous loads if possible (or add odor absorbing material at the originating location, such as sawdust to a load of manure).
  • Aerate receiving floor.
  • Incorporate wet or odorous loads directly into actively composting windrows.
  • Expedite material processing.
  • Increase collection frequency.
  • Consider blanketing odiferous materials with a six inch to one-foot layer of bulking agent, high carbon amendments, or finished compost (water lightly to reduce odor releases).

Odors During Grinding (when the odor is a terpene):

  • Add light misting of water or odor neutralizer to grinder at discharge points
  • Consider grinding green materials with woodier materials.

Odors During Mixing:

  • Create windrows/piles that are sufficiently blended.
  • Combine materials to achieve a high C:N ratio (greater than 30 to 1).
  • Mist water or odor neutralizer at dust generation points.
  • Create piles with good porosity.

Odors During Composting:

  • Turn regularly to re-invigorate the composting process.
  • Avoid over-watering windrows but maintain sufficient moisture.
  • Make smaller windrows to increase passive aeration.
  • Consider blanketing odiferous materials with a six inch to one-foot layer of bulking agent, high carbon amendments, or finished compost. (water lightly to reduce odor releases).
  • For mercaptans and sulfur, adopt forced aeration.

Odors During Curing:

  • Decrease curing pile size (height).
  • Increase processing time prior to moving to curing.
  • Review moisture content of in-process compost.
  • Screen after curing to maintain porosity.
  • Aerate curing piles.

Odors at the Site:

  • Clean aisles of spilled material. (Particularly at the end of each day).
  • Mechanically sweep paved areas at the end of each shift.
  • Apply water and/or neutralizer to reduce dust during dry conditions.

Odors in Runoff Water:

  • Review national pollutant discharge elimination system (NPDES) procedures to minimize storm water contact with organic materials.
  • Remove particles from water draining into storm water retention basin.
  • Filter storm water through a filter berm or sock.

Best management practices (BMP) will also assure a top quality compost product. There are many guidance documents that offer information on BMPs for a compostable materials handling site. The On-Farm Composting Handbook by Robert Rynk is a comprehensive guide on basic compost processes.

Odor control and other effective integrated best management practices are discussed in Dr. Eliot Epstein’s Planning, Design, and Operational Factors that Affect Odor Control at Composting Facilities. Odor treatment by may be done by use of odor masking agents, deodorizers or biofiltration.

Effective odor and fire control measures must be implemented. CalRecycle is aggressively researching worthwhile odor mitigation procedures. CalRecycle’s (now CalRecycle) ash study found that certain amounts of high carbon wood ash are effective in reducing odors as is the addition of lime. CalRecycle conducted another BMP emissions reduction study at Tierra Verde Industries in Irvine in November 2002, evaluating various feedstock mixtures and aeration practices. Currently, CalRecycle is funding a San Diego State University research project, which is evaluating the most effective best management practices for reducing emissions by examining operating controls including feedstock blends, pH, moisture, additives and aeration practices. Additionally, CalRecycle is developing guidance to reduce the occurrence of fires at compostable material and other waste and debris handling sites.

Excellent best management practices that if used will avoid odor emissions are provided in many of the odor impact minimizations plans (OIMP).

Compostable Materials Home