Composting Food and Vegetable Waste to Minimize Odour and Leachate

One of the challenges with composting food and vegetable wastes is the their high moisture content – they contain 80-90% water. If we want to reduce the risk of odour and leachate during composting, we must reduce the moisture content to about 60%, which requires a lot of bulking agent – 2-4 times the volume of the organic waste! This is particularly a challenge in cases where there is not a lot of wood waste or yard waste available to use as bulking agent!

Our 200 L insulated bin that we call the “magic box” provides insight in how food and vegetable waste can be successfully composted on the small scale, as well as providing insight on the principles of composting that can be applied on the large scale. Given that its been 10 years since we designed the award winning compost facility for Lafleche Environmental in Moose Creek Ontario, there are a number of improvements that can be realized!  (http://www.transformcompostsystems.com/blog/2015/09/26/solid-waste-association-of-north-america-honors-canadian-composting-facility-lafleche-environmental/)

In this 200 L bin, we composted 420 L of vegetable waste having a moisture content of 87%, along with approximately 120 L of yard waste. We accomplished this by grinding the vegetable waste to reduce the volume by 50%, and decreasing the particle size to speed up the decomposition. We then added the vegetable waste over a two week period, to allow the excess moisture to evaporate and maintain moisture contents optimal for composting.

There was minimal odour from the process, and no leachate. Temperatures reached 70 C, and the bin self aerated to maintain optimal oxygen concentration. The resulting compost after the 5 week process was 55%, and contained no odour.

The learning outcomes were that food and vegetable waste can be successfully composted on the small scale with minimal infrastructure, and that the principles of moisture evaporation can be adapted to a larger scale process. The process again verified that when we have optimal aeration rates for food and vegetable waste composting, we must mix the material almost on a weekly basis to prevent preferential air pathways and inconsistent drying!

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