City Compost shelf life


How long is the community distributed bagged 13kg compost good for,if I’m storing it in an unheated garage?


Thank you for contacting the Toronto Master Gardeners concerning the long term storage of compost.

Compost is nutrient rich and full of life. It improves the soil and feeds roots. Ideally, compost should not be stored for years since it starts to degrade once the decomposing process has passed its peak. Most resources state that compost should be utilized within 3-4 months to get the most benefit from the compost. However, compost can be used even after that. Over time, the nutrients in the compost break down further or escape the compost. This process occurs rather slowly, so you likely won’t have to worry about it too much if you plan on storing it over the winter.

The biggest concern with storing compost is moisture, which can lead to nutrient breakdown, rot and fungus. So as long as the place where you plan to store it is dry, out of the sun, with some ventilation, as in your unheated garage there should be no problem with storage.  As you mentioned, the city’s compost comes in large 13kg bags, since you are storing the compost for a while it is best to cut the tops of the bags open to easily monitor the moisture in the bag. You can then use close pegs to reseal the bags to prevent evaporation.

For additional information on compost please refer to a few of our archived posts here.