The City of Whitehorse operates an excellent organic waste program for their community. They use an aerated windrow composting process, where the material is aerated and turned 8-10 times during the composting process. The screened product undergoes laboratory testing, but also quality testing at their facility before it is sold. The video below provides a short overview of their program.
The City of Whitehorse is fortunate in that their location and climate does not require that the composting process be inside a building or that they require covers over the windrows. There are a number of reasons why they can produce a quality compost using a simple open aerated windrow infrastructure:
- There is not much precipitation in Whitehorse, allowing the composting material to maintain a moisture content of 60% or less. (The risk of objectionable odours during the composting process increases when the moisture content of the composting or curing material increases above 60%).
- In addition to the community yardwaste and food waste, the operators add woodchips during the blending process to ensure adequate porosity in the composting material. (The risk of objectionable odours increases when there is not enough air-filled porosity in the composting material to allow oxygen to enter the material).
- The windrows are actively aerated to provide oxygen concentrations of 15-18%, which minimizes the production of anaerobic and odorous compounds.
- They have the time and space to turn and mix the material adequately during the composting process, usually 4-5 times during active composting, and another 4-5 times during curing.
- The composting process is at the landfill, where the small amount of odour, usually mostly from the material being received and before blending, does not have a significant impact on the surrounding community.
- The design of the aerated windrows is such that if there was the potential for objectionable odour production early in the composting process, the aerated windrows could be easily covered with a layer of finished compost or wood chips as a biofilter layer to reduce the odour.
The video above demonstrates how the aeration works in these large aerated composting windrows, allowing the City of Whitehorse to compost their organic material effectively with minimal odour during the composting process.
Adequate aeration during active composting minimizes the potential for lingering odour during the curing process, and in the finished compost. In addition, the size of the curing piles are limited to 15 ft high and 30 ft wide and are turned regularly to ensure that the curing material does not become anaerobic.
Before being marketed, the compost is screened to < 1/4″ using a stainless steel trommel screener. The compost is tested for quality parameters at an independant laboratory, and tested at the facility for weed seeds and phytotoxicity.
The City of Whitehorse operates one of the best run composting processes that I have seen with residential organic waste!
Cautionary statement: In areas receiving higher precipitation, both the active composting and curing compost should be covered. The potential odour increases when the moisture content increases above 60%. Its also more difficult to obtain a high quality compost in higher rainfall areas if the process is not covered.