Aerated Static Pile (ASP) Composting Technology
Virtually all organic materials will compost, that is decompose to rich humus like soil amendment product. The landscape industry has a long history with compost to improve soil fertility, texture and water holding capacity. Farmers use it in their barns as bedding and equestrian centers are using it to replace high cost straw and wood shavings normally used as bedding in the stalls. The question is, how long will it take to compost the raw feedstock materials and are there any environmental consequences?
Managed Organic Recycling has been designing and supplying equipment for the aerated static pile (ASP) composting technology since 2006. The process is very simple. Make a recipe with the proper carbon to nitrogen ratio (C:N), correct moisture content in the recipe mix to 60 percent and have adequate porosity (about 40 percent) to facilitate positive aeration in the pile. Generally, most feedstock materials require a bulking agent to achieve the correct mix (feedstock to bulking agent of 1:1 by weight is normally recommended as a starting point). Once the recipe is thoroughly mixed a pile is constructed over aeration plenums, a breathable membrane cover is placed on top of the pile and the process begins.
Microbiological (thermophilic bacteria) activity in the pile quickly increases the temperature in the pile to over 1500F. This high temperature destroys pathogens, such a fecal coliform, Salmonella, bacteria, enteric viruses and viable helminth ova. The process meets US EPA 503 regulations for a safe and sterile finished product. This takes about eight to ten days. After the pathogen requirements are met, temperatures are reduced so that the mesophilic bacteria can take over and decompose and stabilize the organic material and begin the curing process. This phase the ASP composting technology can take anywhere from four to eight weeks depending on the type of feedstock material.
The major environmental issues associated with the composting process and air and water impacts. The ASP process addresses these issues by using the micropore breathable cover that traps odors and volatile organic compounds (VOCs) that can impact air quality. The cover also prevents precipitation from entering the pile and combining with leachate that can impact water quality. The covers also facilitate temperature and moisture management in the pile which efficiency of the composting process.
In addition to its design services capabilities, MOR provides complete systems to private and public agency clients. A complete composting facility will include micropore compost covers (each cover is custom designed for optimum pile capacity), positive aeration system (including centrifugal fans and aeration plenums), leachate collection and treatment system and automated process control system (radio frequency temperature probes, computerized control of the blowers/fans to maintain a temperature set point throughout the composting process, and data logging for regulatory compliance). Most composting facilities elect to compost on a concrete pad to simplify material handling operations.
Capital as well as operation and maintenance costs (O&M) can vary widely depending on the size of the facility. Capital costs for large systems (over 100 yd3/day) $30,000/yd3/day of capacity to around $100,000/yd3/day for small systems, less than 10 yd3/week. O&M costs also follow a similar trend, averaging about $20/yd3 for the larger systems to about $75/yd3 for smaller composting facilities.
About the Author: John Bouey is the President of Managed Recycling. You can reach him at 510-316-4078 or at firstname.lastname@example.org Websites are morcompost.com and odorfreecompost.com.