An important step in site development is deciding what types of feedstock material will be initially be accepted, as well as potential for the future. The list of materials, and their possible sources is large and diverse. Most municipal programs accept leaves and yard trimmings from residential and public properties. Food scraps from residential properties are the next most commonly accepted material in municipal programs.
Depending on the local community, other feedstock materials could include:
- Biosolids from wastewater treatment
- Animal manure
- Food processing residuals
- Commercial businesses
- Institutions (e.g., schools)
- Industrial entities
Important properties of feedstocks include moisture, carbon and nitrogen content, physical characteristics, and level of contamination (physical and/or chemical). The degradability of a feedstock will directly influence how the material is received and the selection of the compost process operations.
The type and amount of feedstock material often dictates the regulations that apply. In most states, the regulatory requirements are relaxed for certain materials that are not highly degradable (e.g., leaves). Conversely, regulatory requirements are more stringent for highly degradable materials (e.g., biosolids).
How much organic waste is there? A critical component in developing a facility is understanding how many tons per year (TPY) of each feedstock will be received – and need to be processed. Estimates can be developed, based on waste audits and waste composition studies, to answer the following questions:
- Volume: how much organic material is in the targeted waste stream?
- Diversion potential: how much of that organic material can feasibly be collected and composted?
With estimates of type and quantity of feedstocks in hand, and converting tonnages to volumes (cubic yards per year and per season), the following items must be considered to develop an initial estimate of the required site size:
- Space requirements for incoming feedstock, curing and finished compost
- Technology selection (static pile, windrows, ASP, in-vessel, etc.) and space needs for active composting, considering:
- How do moisture, nutrient content, and particle size affect handling?
- How does the feedstock recipe (mix of incoming materials) impact processing choices?
- Area needed for setbacks, buffers and water management
- Space needs for other operational considerations such as gatehouse, scale, office and internal roads
Resources and Links:
Feedstocks and Recipes, Clemson University
Compost Feedstock, LSU Ag Center