Composting - Benefits, Siting, and Methods
Composting achieves two major objectives: it diverts organic materials from landfills resulting in reduced greenhouse gas emissions, and the application of compost improves soil health. Soils in San Diego County are typically poor, heavy in clay, and require amending with organic matter to improve physical structure. Compost returns important nutrients, including carbon, to agricultural soils and can improve crop yields and health while reducing dependency of chemical fertilizers. Applications of compost and mulch are considered best management practices (BMPs) because of their low tech and maintenance requirements, relatively low cost, and high effectiveness. Compost and mulch can be used for erosion control, weed suppression, slope stabilization, storm water treatment, pollution prevention, and to increase the water-holding capacity of native, irrigated, and agricultural soils (resulting in reduced water use).
Applying compost to soil ultimately increases the soil carbon content and results in overall net sequestration of atmospheric carbon into the soil and plant substrate. California Governor Jerry Brown’s 2015-2016 Healthy Soils Initiative recognizes the important nexus between composting (and waste diversion), soil health, water, and climate change.
“as the leading agricultural state in the nation, it is important for California’s soils to be sustainable and resilient to climate change. Increased carbon in soils is responsible for numerous benefits including increased water holding capacity, increased crop yields and decreased sediment erosion. In the upcoming year, the Administration will work on several new initiatives to increase carbon in soil and establish long term goals for carbon levels in all California’s agricultural soils.”
Economy and Jobs Potential in a Circular Economy
Locally produced compost also supports jobs and the local economy in ways that landfills cannot. In their excellent study, the Institute for Local Self-Reliance highlights that if the estimated 1 million tons* of organic materials disposed in Maryland were instead composted at small, medium, and large facilities and the resulting compost used within the state, almost 1,400 new full-time equivalent jobs could potentially be supported, paying wages ranging from $23 million to $57 million (2013 data). Conversely, when disposed in landfills and incinerators, this tonnage only supports 120 to 220 jobs.
*Note: this is the organic materials tonnage that the San Diego region produces and thus highlights the economic and jobs potential for our region.
Siting compost facilities, large or small, can be a sensitive issue and raise concerns. Improperly managed compost sites can emit foul odors, attract rodents and flies, have leachate problems and the general aesthetics of the facility can induce an “ick” factor. On the other hand, properly managed compost operations do not emit foul odors, do not attract vectors, and are aesthetically pleasing due to good housekeeping measures.
In part because San Diego has a history of mismanaged sites, and in part because composting has been regarded as a waste management activity similar to landfills, limited zoning ordinances make siting compost projects of all sizes difficult.
Limited zoning and land use rules and the high cost of fees for use permits disincentivize development of composting infrastructure. Land use codes generally allow composting of materials generated onsite. However, the art and science of composting requires the appropriate blends of carbon and nitrogen based feedstocks that might not be generated at the same location. Planning and development services staff require education, as they are often not familiar with composting principles or rationale for project design, and permit applicants pay additional review fees for the learning curve. Compost facility definitions can be vague, incomplete and even contradictory, resulting in confusion and wasted time. In theory, small projects should be the easiest to launch with minimal investment or resources, but such restrictions often make it financially infeasible for even the smallest of projects to launch.
Local land use rules also tend to disincentivize on-farm composting. While farms are typically allowed to compost material generated onsite, they are not guaranteed composting by-right to support their agricultural operations. This limits a farm's ability to acquire the appropriate blends of materials needed for a healthy compost operation, and diminishes the potential for farms to help divert organics from their local communities to grow their own healthy soil.