Composting is the actively managed process of decomposition of organic residuals to produce a material (COMPOST) to help grow plants and improve soil health.
The leaf and yard waste collected by the City is sent to contractors who employ various types of windrow processing techniques to produce compost suitable for use by the residents of the City.
The material is usually ground to a coarse size and formed into long triangular rows (windrows) which are usually 3 to 4 metres high.
The windrows are periodically turned using large automated windrow turners which straddle the piles. During the composting process the windrow is constantly monitored for oxygen and moisture content. The turning ensures the constant presence of needed oxygen. If moisture levels drop, water is applied during turning.
The actual decomposition of the material is carried out by micro-organisms (bacteria, fungi, etc.) and macro-organisms (mites, centipedes, worms, etc.)
Two main types of microorganisms are involved in composting. Lower temperature (mesophilic) bacteria rapidly decompose organic matter producing heat up to 38 oC. At this point they start to die off. High temperature (thermophilic) bacteria then take over and raise the temperature to approximately 70 oC. At this point they die off, the pile cools and low temperature bacteria again become active to degrade the remaining organic material.
It is important to note that during the high temperature decomposition phase harmful pathogens are destroyed making the finished compost safe for human handling and plant growth.
The finished compost is then stored in large piles for anywhere from 4 months up to a year to allow the compost to cure and ensure further decomposition does not occur.
The compost is tested by independent laboratories to ensure it meets Ontario Compost Quality Standards for AA Quality.
The cured compost is now suitable for applications where compost is useful and should be mixed at a ratio of 1 (compost) to 6 (soil).