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Microwaving compost?

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Tee Gee:
Over the years I have read articles here about sterilising compost using a microwave  and after a quick search I canít find any that specifically describes how to do it e.g. cooking times (if that is the correct description) relative to the quantities being sterilised?

We are replacing our old microwave oven because the turntable does not turn, but all the other facilities work OK so I thought I might give it a try.

The ovens power is 800 watts.

Do any of you have any tried and tested methods of how to go about it?

I just want to ensure that I donít zap the compost too much as I know from experience what this can do to foodstuff.

I look forward to you recipes! 


We were given a microwave which had a fault with the grill so I've using it for compost making. This method I use has not been researched but it seems to kill weed seeds.

I use 3 of the trays Chinese take aways use filled with compost for 4 minutes if seed  compost and 3 minutes if potting. The take away trays have been in use for several years which is good as I don;t eat Chinese take aways.

Compost here grows weeds so I looked up how to sterilise it and found this on the Gardening Know How website.   I've done it a couple of times for seeds which are really small or take their own sweet time to germinate:-

Sterilizing Soil with a Microwave Another option to sterilize soil is to use the microwave. For the microwave, fill clean microwave-safe containers with moist soilĖ quart size with lids are preferable (no foil). Add a few ventilation holes in the lid. Heat the soil for about 90 seconds per every couple pounds on full power. Note: Larger microwaves can generally accommodate several containers. Allow these to cool, placing tape over the vent holes, and leave until ready to use. Alternatively, you can place 2 pounds (1 kg.) of moist soil in a polypropylene bag. Put this in the microwave with the top left open for ventilation. Heat the soil for 2 to 2 1/2 minutes on full power (650 watt oven). Close the bag and allow it to cool before removing.

Read more at Gardening Know How: Tips To Sterilize Potting Soil, Garden Soil And Soil For Seeds

Good question.

Good answers.

Thanks all.

I forgot to mention that I have to check the compost first for insect and worm life!


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