Hot composter

[LesMiserable]

Has anyone here got any experience of using a hot composter? I have used a large compost bin for a few years now but not with much success. I mix the green and brown and wait, and wait. Then turn it all over and wait again, and wait again and after a couple of years I get a bit of useful compost with lots of unrotted hard bits.
My local authority can provide a subsidised hot composter, but they are still quite expensive.
The write ups look good with temperatures between 40 and 60 degrees centigrade allowing weed free compost to be made in just a few months.
Well, that's what the suppliers say. Is it really that easy?
Any views?

[toomanytommytoes]

If your compost pile isn't getting hot it's probably not big enough, too wet/too dry or the carbon:nitrogen ratio is off.

[ameno]

I don't have a hot composter, and I get compost within just a few months, anyway. I get three loads a year. A lot of the decomposition seems to be done by worms, judging by the sheer quantity of them in there, so obviously it never gets particularly hot, or they'd die.

The key is to fill it up as much as you can, as quickly as you can, then don't add any more.
Just turn it regularly (at least once a month, ideally more often), firm it back down after turning (if the air gaps are too large, it inhibits decomposition) and add water if it seems too dry (although personally I usually have the opposite problem, with lots of juices draining out of the bottom).
Also, cut everything up as small as you can (a shredder is very usually for this), especially woody stuff; I personally wouldn't add any woody item bigger than a finger nail.

I have actually inadvertently made a hot compost bin recently, though. I pollarded my cherry large tree about 3 weeks ago, and shredded all the prunings. The tree was already in full leaf, so these shreddings were a perfect mix of fleshy green stuff and more carbon-rich material, finely shredded and tightly packed. The sacks of shreddings become hot to the touch within hours of shredding them. Since combining them all (that is, tipping them into my compost bin) the material is now too hot to touch once you dig down a few inches.

Whether you have a hot bin or a cold one, the most important points for fast composting are:
-Cut everything as small as possible (this is probably the most important, in a way)
-Turn regularly
-Don't let it dry out

A good mix of green and brown is important, too, but unless you have it wildly skewed one way or the other (like 100% woodchip, or 100% grass clippings) then you actually have quite a lot of leeway on that. Too wet, too, tends to sort itself out, as long as the bin is set up such that excess water can drain off on its own.

[Mr Bones]

Hot composting's worth it if you can get enough material together in one go. Couple of very short clips hot composting on our lotty. One April 29th this year the other Dec 20th 2019 (sorry cant post direct to the individual pages)

[Penellype]

I bought a hotbin in 2013 because my compost area was too big and I wanted it to rot down faster. I also wanted somewhere to put food waste, which our council does not take. With a few caveats it is brilliant, and I wouldn't be without it.

The first and most important point is that you need to chop everything up small, but you also need to add "bulking agent" to provide sufficient air spaces. This is essentially chopped wood - I use bits of twigs or the chunky pieces sieved out of compost that I am using for carrots. You also need to add plenty of shredded paper, but although this counts as browns, it does not do the same job as the bulking agent. Everything needs to be mixed together, not added in layers. What you put in size wise will influence what comes out - your compost will have some unrotted bits in, the bigger the pieces that go in, the chunkier the compost will be. I have developed a system where I put garden rubbish into a trug, then chop it up using lawn edging shears and mix it before putting it in the composter.

The 2nd thing I discovered was that although the bin is supposed to stay hot all year, and they provide you with a bottle to fill with hot water to boost the temperature if it cools, this really doesn't happen in the winter. After several attempts to keep it hot, adding an aeration pipe (waste of time), emptying and refilling it (hard work) and adding the hot bottle every day, I decided it was best to let it be a hotbin (40-60C) during grass cutting months and a cooler wormery (around 25-30C) in the winter, as grass is the thing that really gets it hot. It still rots faster than an ordinary heap in winter. I still put food waste in it in the winter and I haven't had an issue with bad smell or rats, but do expect worms, mites, slugs etc to appear when it is cooler. White fluffy mould when it gets hot is normal.

The bin works best when 3/4 full or more. It is therefore best to dig out the bottom 1/4 or so when the bin is full rather than empty the whole bottom half to create a bigger space, unless you have a lot of garden waste to dispose of in one go.

The compost that comes out of the bottom is very wet and sticky, not at all the same as the crumbly stuff that comes out of an ordinary compost bin. It is fine if you are going to spread it on soil, and it is great straight out of the bin for potatoes, which love it. If you are going to use it for anything else it is better to store it for a while first. I therefore have an ordinary small compost bin into which I put the rotted hotbin compost plus any used compost from pots that are not potato/tomato, and this is stored through the year until I need it for my potato buckets. The compost is not suitable for sieving or sowing seeds when it first comes out of the hotbin. Anything that hasn't yet rotted can be put back in the bin.

Somethings don't rot. The most crucial thing you can put in a compost heap and not in the hotbin is soil, which will cool it down. You therefore shouldn't tip in pots of dead plants that have been grown in soil or compost with added grit, and you shouldn't add turf - both of these would be fine in an ordinary compost bin. Small amounts of soil on plant roots are ok as long as it isn't in a big lump. Leylandii clippings aren't great, although small amounts will rot if well mixed with everything else. This is the only garden waste apart from large branches that I send to the council recycling. Large amounts of moss need to be well mixed in too otherwise they form a mat that doesn't rot well. Avoid adding liquids. On the other hand, as long as the bin is running hot you can put in diseased material and pests, along with perennial weeds, although I would not add horsetail and definitely not Japanese knotweed if you are unlucky enough to have it. I add chicken bones, which don't rot but do add bulk and the cartilage and remnants of meat stuck to them rot down and help keep the bin hot. I wouldn't add big bones such as those from a leg of lamb. Fish bones disappear completely. Eggshells won't rot but are fine to add, teabags contain plastic so the bags themselves will not rot. I also add the contents of my hoover (but nylon fibre carpet dust won't rot down), and hair will rot as long as it isn't in a big lump. Tomato seeds will survive even 60C and tomato plants may appear as weeds in the compost but very little else will grow from it.

To sum up, chop everything as small as possible and mix well before adding, don't expect miracles in the winter, empty little and often and be prepared for sticky compost with some chunky bits in it that will need to dry out a bit for some purposes.