On 03/09/2018 14:23, Judith in England wrote:
A friend of mine is using an old microwave to sterilise soil before
using for cuttings/seeds etc. in his greenhouse.

Is it worth doing?

Will it kill off "good things" as well as bad?

Any comments?

Steralising soil should do just that STERALISE it, that means killing
off every living thing in it as well as dormant life forms.
I have used a microwave to steralise soil to add to potting compost and
it works well as long as you let it cook and remember to cover the top
so the cooking is even.
You can't cook all that much in a batch but you can do it quite quickly
and a microwave isn't that expensive to run.
But do it in an outbuilding and not in the kitchen, not everyone likes
the smell of steralised soil.
As for the reason to steralise soil. You use it in a compost miz to make
a compost similar to the old John Innes composts - a mix of soil, sharp
sand or crushed grit and peat.