If your compost pile is generating heat, then I say it is working. more than if it is not warm to hot in the middle.

As the average temperature drops the bacteria that will digest your materials wil slow down, although my compost piles have stayed quite active, warm because of that activity, in the center of the pile during the winter.

Your compost thermometer will tell what is going on if you have one. Why turn a pile over to discover what is going on when a compost therm can be inserted in just a second. Mine was $15 at a good garden store ten years ago (just the basic 18" model), probably $20 by now.

I added my neighborhood leaves to my large mesh bins shortly after they fell. Maple, oak, and sweet gum were mower-shredded three times and put into the piles with a little water. Core temps were 110 to 135F for weeks with a little turning.

Actually I was really asking if anyone knows what is happening to compost during the winter. When its not decomposing is anything good going on or is it just kind of sitting there? I know that at the bottom the leaves look water logged but its dried out at the top. Will worms still migrate into the compost during this time? Does anyone know chemically or physically what is happening?

Soil bacteria and other decomposers are like most animals - when it gets colder, their biological functions slow down. When it gets cold enough, then just shut down and wait for warmth. I put up piles of chopped leaves in the fall. When the snow melts soon,all the leaf pieces will be pretty well identical to the way I left them in November.

Nothing scientific to add but my 2 Compost Tumblers are about 1/3 full now and were just short of completely stuffed last fall. I only turned them about once a month since Nov.

Well, dug around the compost piles today, 40 degrees out, and was pleased that they're no longer balls of solid ice. There's actually pockets of small redworms, almost dormant, among the chunks and layers. When things warm up they'll get really active and work the piles down to the good stuff. Finally.

Agree with all above who say it will simply compost more slowly - and if frozen, much more slowly.

The freezing-and-thawing, however, will help in the process of breaking things down once it thaws and the bacteria, worms, etc., get active again. What happens is that the freezing will break down cell walls and some internal structures in the composting material that are good natural defences. So everything being equal, you'll probably see a burst of compost activity as it thaws and gets warm again. So in a sense the freezing will slow things down, but also make things ready for quick composting in spring.

One caveat though - things will probably settle in the process and may create pockets without air, leading to anaerobic conditions - meaning smelly bits. Water might pool in areas and with the settling make the anaerobic bits worse. Stirring things up and mixing the compost will help and should get things back to normal.

I remember reading about the biological process of the various organisms in a compost pile. I wasn't reading for that purpose so I did not intentionally "study". What I gathered from the reading is: There are many different organisms that work the pile. Each organism thrives at a different temperature range. They're all good. And it explained, to me, why a long-composting pile ... like that which I find along my fence line where leaves, dead plant matter and grass clippings gather unhindered is so vitally rich in nutrients for the plants. (I dug this up and used it in my planter. Best soil I have.)

It read that most the organisms don't die in colder (or hotter) temperatures, but they either slow down or move on to another area that is more suitable. Quite fascinating. The reading helped me understand one of the major reasons why turning too frequently hinders composting. When doing so, I'm moving the organisms to a spot they cannot thrive. It's like removing the plate in front of my children at the dinner table and hiding it. It takes time for them to find it, again. This is telling me that I cannot make the perfect compost pile, only nature can. All I can do is try to help.

Because of this reading, I deliberately placed some compost materials along that fence line where these organisms exist naturally giving them more to eat. Then, I left it alone.

Most of us are more interested with the type of organisms that break down in near-perfect environment with higher temperatures because it composts fast and because these quickly destroy bad things like disease.

If you leave any compost alone, in time it will become rich and healthy. But it can take a long time. By "long time" I'm saying at least two years. I'm like most. Don't have time to wait. (I play it safe and put any known diseased stuff off the property.)

I'm not well versed in plant disease pathogens. Likely, I'll end up throwing some bad stuff in the pile without realizing it until later.

If that happens I'll know to just leave it alone ... for a long time ... while starting another pile somewhere else. Still, the rich nutrient-dense material from good compost is designed to make plants withstand disease. That's why I go organic. Some things ya just can't control. Instead, I want healthy plants who can fight for themselves.

These are why "any compost is good".

Now, if I can just grow a garden as well as building some composts.....

Good stuff

If the C:N ratio of the material you put in to compost is close to that 30:1 and the moisture level is about right and not too wet or too dry and there is adequate volume, the bacteria that will digest that material will stay active. There are bacteria, thermophilic, that function best at different temperatures so how active they are determines what the internal temperature of your compost pile is more then the ambient air temperature.

So as we start another winter, has anyone seen any good articles about what is happening in the compost pile during the cold months? I'm always looking to learn more and understand better the processes that breaks down my compost.

The link below may explain what I have been telling you better.

Here is a link that might be useful: composting in winter

If I was compost, I would be huddled under a blanket watching the game this time of year, drinking tea and/or bourbon.

It's 2F outside this morning. Brrrr!

"Actually I was really asking if anyone knows what is happening to compost during the winter. When its not decomposing is anything good going on or is it just kind of sitting there? ... Does anyone know chemically or physically what is happening?"

The Four Stages of Compost

1) mesophilic phase
2) thermophilic phase
3) cooling phase
4) stabilization phase
Some articles break it down into three stages instead of these four.

If your compost pile is optimal as for as size of pile, particle size, balance of greens/browns (C:N ratio), and in the right range of moisture:

Mesophilic bacteria start work, microorganisms give off heat. Around 111F, both mesophilic and thermophilic are active. In the transition zone of 111 to 126F, thermophilic bacteria begin to predominate. Much heat is produced, but most composters do not favor temps over 160F. I often reach my high compost core temp two to three days after making a pile.

The high heat begins to decline, even with turning and watering. The larger woody pieces remaining are attacked by fungi, worms, and sowbugs.

These numbers are hardly set in concrete. Cornell uses 105 to 141F for the thermophilic range! And as I recall they used different numbers in different articles by different authors.

If you want pictures of these microorganisms, I think the small book "Easy Compost" by Brooklyn Botanic Garden has them.
No doubt a number of websites as well.

Winter will slow things down, but probably won't stop the process. Is it worth the effort? I think that depends on whether your climate has periods of thawing inside the frozen winter months. I am willing to turn the pile in above-freezing periods, but not willing to break up frozen parts of the pile.

Some folks might say any extra effort in winter is too much work. But I find that turning my low piles over in winter a few times is less work than my tumbler (in the summer).