You can nuke em in the microwave for 90 seconds per kilogram (2.2 pounds) on full power. You will stink up your house this way. Or you can put small quantities in a 5 gallon bucket and pour boiling water over it. If you don't know what you are doing it could back fire. You gotta get the medium to about 180 degrees for 30 min, then cool. The medium cant go over 200 degrees. High temperatures may produce plant toxins in the medium which will kill your plants. So you have to do it just right. Thats why I personally don't sterilize.