how hot to compost?

Just starting making our own compost, and wondering how hot it has to get to kill off any seeds. I don't want volunteer strawbabies & tommytoes ( or weeds ) coming up in the beds. Do you actually take the temperature, and how? or just hope for the best?

The pros bake the compost in an oven before they use it. My wife worked for the school board on the garden crew, the crew boss had 2 green thumbs and cured the compost before using it, killing any seeds and drying the stuff in the process. You can do that too in your own oven if you want.
If you are using a hot composting method, the seeds are usually destroyed when the pile hits above 120 degrees, turn the pile and add moisture if it goes above 150 degrees. How can you tell how hot it is? I really don't know. I'd throw in a thermometer in the middle of the pile and then take it out after 20 minutes and see what the temperature is (if the thermometer goes that high).

If you are using cold composting, you are basically throwing in browns and greens then topping it off with kitchen scraps and leaving it untouched for 2 or 3 years. I don't know about the seeds with this method, I'd probably put a batch in a turkey roaster, pop it in the oven at 150 for 30 minutes or so and be careful it doesn't catch fire or explode.

Good Question. I was just wondering the same thing, hence my post on "Garden is in!" I just decided to start hot composting since I had three empty aluminum garbage cans. I filled two with layers of my take from my friend's farm. I have been turning it every couple of days, since it has been cold. Will increase to once a day when it starts to get some sun. Just wondering if this will work and what others have been doing to hot compost, other than the expensive barrels.

related question - if one has homemade compost and wants to kill any weeds in it - would laying it on a tarp in the hot sun for a few hours have the same effect as putting in the oven? i dislike the idea of putting dirt in my oven - and esp. scared of the possibility my dirt could explode (per ayanefan's post).

I started a new hot compost pile last week. I'm thinking it' getting close to 110F . It's hot in the middle of the pile, I can leave my hand in there for a bit before it gets too warm. To kill weed seeds takes between 120F - 150F. these temps can be achieved with layering your various compost ingredients. Make sure you have a good source of nitrogen to get the heat cranking. I made approx 4 cu. ft pile with lawn debris, winters kitchen scraps, coffee grounds, chopped leaves, 15 pounds of fresh poultry litter, dried blood. turning every few days, I should have some usable compost in another week or 2.

G'day kimbies,

I'd be a bit worried about baking compost the finished product as it would probably kill all the good microbs that it has in it.
I use 3 x compost bins all at various stages. If you get the right combination of materials your compost pile will get very hot and kill most seeds however some tomatoes seeds will still survive but you just let them grow a bit then pull them out and re-compost them.

Cheers, Peter.

The compost bin I have is a 4 foot diameter circle, 4 feet high; according to a TV show I watched last year, this is the critical mass for composting as it has enough weight when it's full to start cooking. I added brown mulched leaves at the bottom, green grass clippings at the top and drizzled it with lots of raw vegetation from the kitchen. It took 4 days before you could really feel the heat. My problem is that I did not add enough moisture in the mix to keep the cooking going, this is what I'm doing now; turning every day and adding water to the dry areas. It's coming along but there are a lot of flies buzzing around.

The other method I heard of from Betty Kennett, CBC Saint John green thumb, is to take the same 3x3 or 4x4 bin, fill it with as much vegetation you can and then at the end of the year, just leave it, don't touch it at all. Next year start a new bin and then do the same the year after that. On the 4th year, the first bin will have nothing but great compost you can use in your garden. Empty that one and then start filling up the first bin and enjoy some wonderful rotted muck!

I'm not sure if the latter method works well in warm climates but you may just ask the operator of a plant and garden nursery what they would recommend in your area.

I asked my wife why Mark (her boss on the garden crew) cooked the soil. She said it's because he had no backup at the time in case something went wrong with the soil. He started cooking the compost because of blight in the area that turned all his flowers he planted at the schools into white, powdery mildew. After he cooked his soil, he never had a problem and it seemed to make the plants perkier. As for the microbes, as soon as you add water and the soil starts to breathe the microbes will start repopulating in no time.