- screened compost
- rectangular metal baking pans, or other suitable oven-proof container
- aluminium foil
- oven mitts
- cooling racks
- Preheat your oven to 150 °F (65 °C).
- Fill the baking pan, or pans, three quarters full, but no more than 10 cm (4 inches) high
- Cover pan with aluminium foil, crimping firmly along all edges to ensure as tight a seal as possible.
- Place in oven for 20 minutes.
- Remove the pan from the oven and check the temperature of the compost.
- If it has not reached a temperature of 65.5 °C (150 °F), replace the aluminium foil cover and place the pan back in the oven to continue cooking for another 10 – 15 minutes before checking the temperature again. Repeat this step until the compost has reached the correct temperature. When that temperature has been reached, replace the aluminium foil cover and place the pan back in the oven to continue cooking for an additional 30 minutes.
- If the compost has reached 65.5 °C (150 °F) after the initial 20 minute cooking time…replace the aluminium foil and put the pan back in the oven to continue cooking for another 30 minutes.
- If you are using a meat thermometer, you can place it in the compost…making very sure the tip is not touching the bottom of the metal pan…and carefully crimp the aluminium foil cover around it. Using a meat thermometer, you will not have to take the pan out of the oven repeatedly in order to check the temperature.
- When the compost has had it full allotment of cooking time…the 30 minutes after it has reached 65.5 °C (150 °F)…remove the pans from the oven and set on racks to cool.
- Once the pasteurized compost is fully cooled, you can use it to make up your potting soil mix.
Note: You can find the Potting Soil Recipes in “Garden Recipes” under “In the Garden” on the menu bar. You can also click on the quick link here.
Another note: Some people use their compost straight out of the bin when they are making up potting soil mix. We are “guilty” of this ourselves. However…and it is a big however…we hot compost in our bins…building the pile properly and keeping a close watch on the internal temperature of our compost to ensure it heats up to 65.5 °C (150 °F) and stays there. Hot composting is why we can have usable soil amendment in three months or less, depending on how many times we have turned the pile.
(For an optimum Compost Recipe, one which will hot process your compost, look in “Garden Recipes” under “In the Garden” on the menu bar. You can also click on the quick link here.)
There are some people who say they use “cold processed” compost in their potting soil mix and claim not to have had any problems. (Cold processed compost means the ingredients have just been piled into the bin without any intention of building up heat to kill the bad bacteria and fungi.)
Personally, I think they are dodging the bullet…like you potentially dodge flu bugs when you are in the grocery store or cooped up in the office. The fungi which cause “damping off” disease, for instance, can be present in the soil mix…so you are playing a game of Russian roulette. But that is just my opinion. It is ultimately your decision.
And yet another note: Pasteurizing soil in your oven could be a smelly project…one which could upset the cook in the family. If you prefer not to take any chances of introducing unwanted aromas into tonight’s serving of roast beef…you may want to consider building a solar oven, expressly for pasteurizing your compost.
There are any number of plans for a DYI solar oven project available on the Internet. Select one which fits your level of expertise, time allowance, and pocketbook. Unfortunately, I cannot personally recommend any, as I have not built a solar oven myself. But I know it can be done…so good luck!
Posted on February 2, 2017