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I have a wheelbarrow half full of spent compost from my potted winter tomatoes.
I usually scatter it on any vacant beds, but I was wondering if I could reuse it as potting compost.
As it was used for tomatoes it could harbour blight spores or any other nasty spores or pest eggs, but if I were to sterilise it with microwaves, do you think it would be OK?
I have an old working microwave oven that would hold 2 or 3 litres at a time, as it would only take a minute or two it wouldn't be that arduous, and if I replenished the John Innes with seaweed dust I could have cheap potting compost for ever more.
Is there a catch?

Odsox wrote: ↑Sat Jun 22, 2019 1:03 pm Is there a catch?

Dunno - you try it and tell us.

Would overwintering outside kill the blight spores?

I'm not very knowledgeable about blight. We've never had it! Not even in sunny Manchester. I think we're too far north here.

I'm more concerned about what else you'd kill, microwaving it. All the beneficial bacteria etc wouldn't survive either presumably.

Green Aura wrote: ↑Sun Jun 23, 2019 1:35 pm I'm more concerned about what else you'd kill, microwaving it. All the beneficial bacteria etc wouldn't survive either presumably.

I don't know how they produce potting compost nowadays, but years ago potting compost was always sterilised.
Before the "invention" of soil less (peat) compost, I remember making my own by steaming ordinary sieved garden soil over a Baby Burco.
Unsterilised potting compost would have been chock full of viable weed seeds
That was a few years ago mind

Having used it for a season though there should be some living organisms, shouldn't there?

I don't know how much it matters. As long as your soil is full of the good stuff I'm sure you can get away with your compost.

I'm not sure it would last for ever more. There'll ba a lot less comes out than went in, by the time you've got all those tomato roots out.

If you are just looking for something that plants will stand up in then it will be fine - the nutrients will be depleted and the "bugs", both good and bad, will probably be killed also. However, these can be replaced simply by mixing in with a proportion of "good" compost and the appropriate nutrients.
GA, I doubt that winter chill or freeze will kill all the spores etc. They are carefully designed to survive the normal vagaries of climate.
Our research here(about turning weeds into compost) indicates temperatures above 65c continuously for a minimum of 48 hours is neded to be confident; in short normal composting processes cannot be relied on the destroy weed seeds. To qualify through, we were looking at huge quantities of mixed material as would be collected by a council in a "green" recycling program.

footnote - tomato seeds! Do your worst you simply cannot kill tomato seeds.

Weedo wrote: ↑Sun Jun 23, 2019 11:18 pm Do your worst you simply cannot kill tomato seeds.

Oh crivens, yes! We've had them sprout in places we couldn't imagine. Having said that, we usually leave them - any additional tomato plants always welcome. It's that other nightshade, the spud, that drives me wild sprouting where they're not wanted. That's why I took potatoes out of my rotation into a dedicated bed.

Green Aura wrote: ↑Sun Jun 23, 2019 1:35 pm I'm not very knowledgeable about blight. We've never had it!

We have a blight warning in effect from today, so I will probably get it. But the potato plants have just about finished growing so won't lose any crop.
For blight (Smith Period) you need temperatures above 10c and humidity above 90% for 2 days. I suspect that you living the other side of the Arctic circle, you never see temperatures above 10c, that's why you don't get blight.

Cheeky.