You didn't give a definition of what you envision really hot to mean. The hottest I've obtained is 162F and most tutorials say that the common microbes in composting can begin to destroy themselves over the 160 mark so any hotter than that is counterproductive. I like the 140-155 range.

How to get hot? Well, there are the basics, food, water, shelter and air. The microbes are living creatures so they need these basics to create large amounts of heat.

Food: They need carbon for fuel and nitrogen for reproduction (and boy do they like to re-produce!). The 'ideal' ratio is 30:1 but heat can be generated within a C/N range. Most tutorials talk about 25:1 to 40:1. The further one is away from the 'ideal' will be a factor in how long the heat generation will last and the peak heat obtained. One also needs a substantial enough volume of food to generate the number of microbes required to generate the heat. Being well mixed and smallerish particles (shredded leaves) are also extremely helpful.

Water: Most sites mention a range of 40-60% moisture. Once again, if one is at the lower end, any heat generation will lead to moisture loss so it is easy to fall below the recommended levels. Even distribution throughout the pile is better than having wet and dry areas.

Air: or more precisely, oxygen. Once again there is a range but anything below 5% O2 restricts aerobic consumption.

Shelter: Protection from the elements. Wind is a cooling event. Rainfall (or in the case for us poor Canadians on the tundra, snowfall) can have a cooling effect. A large enough pile can also be thrown into this category because the outside of the pile is, in effect, an insulator for the microbes on the inside. There are some graphics available online that show the core of a pile being the hottest with decreasing temperatures as one gets closer to the outside.

How long it stays hot depends on the volume of food and all these other factors but it is not an endless thing. All piles eventually move out of the optimum heat producing range in some category. This isn't a bad thing, it just means different organisms are now doing the decomposition work.

I have never used an activator so I don't know much about them.

Kinda basic, but that's my view on hot composting.

Lloyd

I like to cheat and use lots of manure mixed with leaves or cardboard with the right amount of water and a tarp over it heats pretty quick
I also find good sized piles are much easier to get hot in my opinion

You could add lots of UCG, or smaller amounts of seed meals (I've used soyameal) or blood meal to help speed heating.

OK, all the nonsense aside, if you want your compost pile to heat up, then first of all you have to have something in compost to make it happen.
You are going to add the usual, the kitchen scraps, the grass clippings, and at this time of season, all the dead plants that kick the bucket the first hard frost that visits. My own garden, that happened last night...and all the stuff went into the compost as much as I think the pile is in a balanced form.....that is nitrogen, phosphurus items...the greens, the browns.

Grass clippings, because they fill all the nooks and crannies of the pile surface, if left for a few days, will heat up a pile as good as anything.
But....its autumn, the days are getting shorter, the nights longer...the sun's going down, the warmth of summer is fast going down hill. So what warmth you get in your pile wont be there very long in the future.

But, piles should not be left just covered in order to prevent oxygen from getting into the interior....that's sometimes thought to be the only way heat will be retained.....don't let it out.
But, the opposite is true, keep turning the pile about every week....or so...get oxygen in there and your pile will heat up. More to the point, the oxygen will help the materials break down because it generates aerobic action.

To help a pile break down---if you appreciate that in the process of breaking down, nitrogen is used. So make it a habit to throw a couple handfuls of the granular fertilizer into the pile to let it help the process.

All the usual stuff you think of from the garden and the kitchen, will, in the end, provide you with good compost if you give it time. You cant rush a compost pile....you can help the process, but it takes time to bring it about.
Forget the couple months from fresh to end result....think instead 6 months to a year.

There are materials, chemicals, that you can buy in nurseries, garden centres, and large box stores. They usually go by a name that suggests it can speed things up.
They might do a little faster action, but generally they are not worth the money.

Pretty soon, as the temperatures go down, the action will stop; once the temperature in the interior gets down to below 45ºF, and it wont resume until temperatures go back up again. This though is not a reason to stop adding.
Add everything right through winter....even if it just sits...its better there than throwing it away.
And as soon as the temps rebound, the action will resume and you've given it something to work on .
In the north, compost piles regularly turn to a block of ice because they have so much moisture locked inside.

You can help prevent this happening for a time by putting a cover over the pile, reducing the amount of snow/rain/snowmelt from entering the pile and causing it to be too wet, which, it itself, will causae slow-downs.

I think Lloyd gave a pretty good outline. The others gave a lot of good advice, also, but I thought his post was particularly good.

If you read through a bunch of the threads here, you'll get a good feel for what you need.

You want a mixture of different materials, with some being high in nitrogen (N) and some high in Carbon (C). Some people like to use the terms greens for the high N materials and browns for the high C materials. I do that sometimes, as well, because it's convenient, but sometimes I dislike those terms because they're misleading. Some greens are brown in color, like Used Coffee Grounds (UCG) or some manures. Basically, if something is higher than 30:1 C:N it's a brown or carbon source and if it's lower than that, it's a green or nitrogen source, regardless of color.

You're aiming for a C:N ratio of 30:1, which is supposed to be the ideal. Note that that ratio is C:N, and not greens to browns. I usually start with approximately equal amounts of greens and browns. If it stinks, I add more browns and/or turn it. If it's not heating up, I add more greens and/or add water and/or turn it. I don't have problems with too much water, but too much water can cause it to stink, also. You want enough water for it to be about as damp as a wrung out sponge.

I agree with Jeannie on the products you'll see that claim to be activators. There's no need for them. There are bacteria and fungi everywhere that will decompose the contents of your compost, so buying something isn't necessary.

Adding granular fertilizer will heat it up if there's not enough N in the mix, but if you get a good mix of other material, you won't need to do that. Some people prefer to use only "natural" ingredients in their compost. Some people will also tell you that compost should only contain things that you got for free. You can probably get by with things that you get for free and without adding any granular fertilizer, but if you're low on browns and want to buy a bag of pine bedding, or if you want to toss in a handful of fertilizer, that's completely up to you.

A lot of people will say that you need a minimum of 1 cu yd to generate heat, but my bin is less than half that size and I've gotten hot compost batches pretty regularly.

If you can get the right mix of ingredients, moisture and air and you turn it at the right times, you can theoretically get compost in less than a month. But I don't look at it as a race, so if it takes several months, that's fine also.

Some people will also let it sit and cure for several months after it has cooled off. I used to think that was a complete waste of time, but some of what I've read more recently makes me think it has some merit, especially if you're using the compost in a vegetable garden.

One thing to remember is that it's almost impossible not to make compost out of compostable materials. It might take you longer than you want, it may smell bad at times, but in the end, IALBTC (It...

Lloyd's response covers most of what you need to know.
A few comments to add:
If you want a continuous pile versus a batch pile, you need to have a continuous supply of feedstocks. "Browns" (carbonaceous) material can be stockpiled, ( I still have some of last year's leaves that are also slowly making leaf mould) but greens can't.
Piles smaller than a yard need more finesse with C:N ratios and distribution as well as particle size. Large piles are more forgiving in their makeup.
If you have steady feedstocks, winrows are easier to manage than piles though they dry faster.
Letting compost age has the benefit of worm contribution once the hot stage is over. There will be large volume reduction.

I pick up coffee grounds at a local coffee shop 2 to 3 times a week. They're soaking wet and heavy. I add them all winter, with copious amounts of leaves and straw, and the pile usually doesn't freeze. It doesn't get real hot because I refuse to stay out in the cold to flip it regularly. I might flip it once or twice during the winter season if we get an occasional "warm day", i.e. up around 40 degrees with not too much wind.

Adding pumpkins and straw bales collected in the neighborhood after Halloween will help, too.

Karen

Good post. Can someone here tell me why meat is forbidden? Is that just an animal problem thing (e.g. the little fellers in there looking for scraps?) or does it have to do with composition and, ahem, decomposition? I had a roundabout with my partner about this the other night regarding some rice with small bits of chicken in it. I was inclined to chuck it in on the basis that the percentage of chicken to the total pile was miniscule. Others in the household were aghast!!!??
thanks

Rats! I hate rats!

Forbidden might be a bit strong, perhaps "not recommended" would be better. But in your specific case, small bits in a large volume, probably not an issue especially if the pile is hot and it's mixed in.

Lloyd

I agree w/Lloyd on the chicken and rice. Although at my house it would be lunch the next day (if still edible) and only go in the compost if it went 'round the bend.' I once put an entire turkey carcass into a fresh 1 cu yd pile after Thanksgiving and it composted just fine. Course that was cool weather and a hot pile, I might not do it in the summer for fear of odors etc. Small amounts, any time.

Hot pile? 1 cu. yd. minimum, good mix, damp with moisture, enough air. Pretty simple.

The freezer went out once at my house and a steak went bad. I threw the whole steak in and covered it well with lots of high carbon material and made sure it was in the center of the bin for a week or so. The compost temp was around 150-160 for the entire time and there was no trace of the steak when I turned it.

For small bits like the chicken and rice, I think you're fine in just about any case (although I'd still make sure it's well covered). For larger pieces of meat, I'd only do it if you have a compost thermometer and can be sure the compost gets to 145 and stays there for at least 3 days.

Mulchie meat is far from forbidden it is just not highly recomended for beginners

in your case it would be just fine this summer I composted several raccons and woodchucks in a large pile that held almost 160 degrees for several weeks it was a large pile and it was eaisy to get them under a few feet of material
in a week it will eat things like that right up without any odor

To make your compost pile heat up you need a mixture of material with the right C:N ratio, about 30:1 Carbon to Nitrogen with the particle size close to not too big and just moist enough with ample air. As the bacteria digest your material, the most activity will be in the center of the pile, they will generate heat and the faster they work they more heat they will generate, to a point. As the food and moisture begin to "run out" (be digested) that activity will slow down and there will be a decrease in the heat being generated and if you turn your pile at this point the bacteria will once more, providing conditions are what they like, work diligently and generate some more heat, bit probably not as much as initially (less food available). You should be able to do this several times seeing lower peak heat each time as the food is less available. Too much water (which excludes air) can inhibit the process just as too little moisture will.
You can have all the right "stuff" but if the particle size is too large you will not see the heat generated by the bacteria since they will be working much slower, although they will be working. Too much moisture can also inhibit the process, the material needs only be moist and not wet, far too many people start out thinking the material needs to be close to soaking wet nad it does not. It took me quite some time to understand that running the water hose into the compost pile while I was building it was counterproductive, and that water running out from under the compost pile was doing nothing to help.

Keep it simple at first.

1) Right size bin. I like 4' diameter; 24" or 30" high.
2) Right mix of finely shredded materials. Simple is 1.5 pounds of fresh cut grass to 1 pound of dry finely shredded leaves.
3) Water and air added as needed. For air you just turn it over.