MAKING COMPOST

Eliminating the nuisance factor
Facility construction
Processing

 
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By Lynn McCracken Lucas

All municipal composting facilities, and most industrial plants with compostable waste streams,[1] must meet the same siting and construction standards established for commercial compost manufacturers.   Backyard and on-farm composting, because the materials composted are generated and used by the same family or entity, do not.   

In truth, there aren’t that many industrially-owned composting facilities, but a number of municipal operations dot the landscape.  However, since the primary motivation behind these operations is usually finding a better disposal method than land application or landfills, through-put and space requirements take a back seat to capital investment and operating costs.

In both categories, open-air windrow operations dominate, but some municipalities opt for operations under roof to provide more control over the weather or totally indoors to make the operation invisible and facilitate odor management.  Yard waste-only operations are almost always outdoors.  It’s the municipality or industrial concern composting large volumes of biosolids or other challenging materials that’s most likely to use a roof and walls.

Outside of the backyard or on-farm setting, almost all composting facilities are required to follow a few basic rules governing facility construction, regardless of the composting method employed.

A.  Set-backs and buffers.  While specific distances will vary from state to state and city to city, the exact spot where the composting operation will sit on the property is governed by rules and regulations.  Whether processing indoors or out, the distance between the active composting area and property lines, neighbors, groundwater, wells, lakes, streams, and wetlands will all factor into the final shape and location of the pad or building. 

Groundwater surveys (determining direction of flow), as well as archeological and endangered species determinations, may be needed before state permit writers will even consider an application.    Title searches to identify possible past-use contamination and geological surveys may also be required as part of the site assessment.

Use state and local site requirements as a checklist when making land purchases for composting facilities.  Finding a site with a good spot for a composting pad does not mean it’s a good location for a facility.

B.  Pads and floors.  Areas for raw materials storage and active composting must be constructed with pads and floors that prevent leachate from seeping down to groundwater or running off into rivers and streams. Minimum construction standards usually call for surfaces to have an impermeability rating of 10^-7.  This level of protection may be achieved through the use of one or more materials (clay, ash, concrete, synthetic liners) with a total rating that meets or exceeds this standard.  Systems must also be in place to collect and manage leachate.  Usually these systems incorporate berms, troughs, sloping floors and/or sumps.  Rainwater falling on materials storage and processing areas must also be collected and treated on-site or a discharge permit will be required.

C.  Buildings.  Provided buildings meet local construction codes and do the job for which they were intended, regulations don’t micro-manage the design of composting buildings.  You’ll need to tell them what you’re going to build, why you’re building it that way, what goes in it and where, and how everything works together.  Local jurisdictions may require things like sprinkler systems or air filtration systems for enclosed processing buildings.

TIP: Composting tends to create a corrosive environment.  Prolong the useful life of girders and other susceptible surfaces with protective coatings.