California’s compost industry has had many challenges these past years. Below are some of the more significant operational challenges. Please see Responses to Challenges for extensive information on Best Management Practices, odor assessment tools, and more.


Odor is the number one operational challenge that threatens sites in California. Due to the encroachment of residential and commercial properties, all sites, with the exception of a few agricultural sites, will need to explore a strategy of odor minimization. To better understand odors and odor investigations, the following information is provided:


Air Quality Management District's and Air Pollution Control Districts have been proposing and adopting rules to reduce the emissions from compostable material handling. The most important emissions from composting operations are volatile organic compounds (VOC). VOCs react in the atmosphere with oxides of nitrogen (NOx) to make ground-level ozone a criteria pollutant. VOCs can also react with ammonia (NH3) to create fine particulates (alternatively referred to as particulate matter or PM) another criteria pollutant. Odors are generally a nuisance, not a health risk to the community.


Fires are an increasing problem at sites handling green material, wood, lumber and other compostable materials. Estimating pile size and amount of material on site is complicated but when piles are properly managed, it will reduce the possibility of fires. This page provides practical information on fires and their prevention at sites handling compostable materials.


There are many types of contamination, including municipal solid waste in green material and a previous problem of persistent herbicides such asclopyralid, in green material. Sudden Oak Death is a biological contaminant and is also a threat to composting.

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