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Hot compost or Cold Compost?

 
Siloe Oliveira
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Most of the compost I make ends up not heating up very much (partially from not having enough material around to provide the right balance). I would like to know if you usually get fast hot compost or slower cold compost, and how it performs in your garden. I made a video about what I've learned about composting over the years and I would like to get more insight into fellow gardener's personal experiences. Here's the video:
 
John Elliott
pollinator
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I like my compost cold. I don't want to kill any fungal spores that are going to build long term soil health. I'm in no hurry to get my biomass to break down quickly, in my sub-tropical climate things break down pretty fast and I'm always looking for more mulch materials.
 
Peter Ellis
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Location: Central New Jersey
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I do not think I have ever had a compost pile heat up. Probably tons of reasons, from not keeping them damp enough to not paying attention to the ratio of carbon to nitrogen to not turning sufficiently.
With the result that my compost piles take longer to become "compost" than those of people who are getting hot composting to work. Some times I wish it would happen faster, some times I would like to be able to stack functions and pull a yield (heat) from my compost pile to help out with something else (like warming my greenhouse), but mostly I have other things to do that are a higher priority for me than the balancing act to generate hot compost.

The product from my slow process seems to work just fine for growing plants.

and then there's the whole can of worms about how much of what you wind up releasing into the atmosphere and losing from your material when you hot compost.
 
Mountain Krauss
Posts: 130
Location: Northern California
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I don't worry about getting our compost hot. We live in a hot & dry environment, and I won't waste water trying to keep our piles moist in the summer. And I like that it doesn't get hot enough to kill the seeds in the pile; we get volunteer plants popping up all the time, creating plenty of free food for the chickens.
 
Lorenzo Costa
steward
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Location: Italy, Siena, Gaiole in Chianti zone 9
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I have friends that use the hot compost pile method, here in Italy we sometimes call it the Berkeley method. I guess it depends a lot on how much compost you need, on how many beds you have to put it. in some cases one must boost the fertility of new beds maybe on a fairly big scale and i think the big hot pile is more useful, probably on a home scale one can use a cold pile that takes longer. I guess that once the system is established and the beds in our vegetable garden are stable and rich and regularly mulched, or our food forests are stable you don't have to do big composting, and just compost the waste you actually produce like Siloe shows in his video. you just compost your normal produce of waste and don't have to work with nothing more so the cold composting can be more practical.
 
Druce Batstone
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I'm voting for hot compost but that's because I;
1. need lots for my patch (allotment),
2. don't like weeding,
3. don't like rats.

Our home has a cold bin that makes very nice compost over 12 months from kitchen scraps and leaves (without turning). Rats are a problem. The zillion papaya, tomato, pumpkin etc seedlings must be eliminated from the roses and other ornamentals.

That's my personal experience in answer to Siloe's request.

Now to debate points raised by the coldies;
(a) Hot composting is difficult
(i) insufficient materials
(ii) C:N ratio wrong
True, building a hot compost pile or bin needs at least 1 cubic metre of greens and browns - preferably shredded. The C:N ratio is not all that hard as roughly equal quantities of greens and browns will heat up just fine. I need to bring in manure for greens and sugarcane for browns. My most rapid rise in temperature was from ambient of 22 C (max) to 54 C in 19 hours.
(b) Losing stuff to the atmosphere
Biochar is known to reduce nitrogen losses in composting. Search for "Reducing Nitrogen Loss during Poultry Litter Composting Using Biochar" to find the definitive study. For more information on compost and biochar, I highly recommend reading http://www.intechopen.com/books/management-of-organic-waste/synergism-between-biochar-and-compost-for-sustainable-soil-amelioration
(c) Killing fungal spores
Somehow fungi appear in the cooling down and maturation phase in my bins - even after highs greater than 70 C. The synergism article quoted in (b) emphasises the importance of maturation. I use the presence of worms as a good indicator of compost maturity. The worms might be the inoculating agents.
(d) Uses too much water
A hotter pile will surely have a higher evaporation rate but I rarely have to add water even in summer with a daily maximum of 32 C and no rain. How could this be? Maybe because the outside of the pile is at the ambient temperature. Evaporation from within the pile condenses on the cooler outside material. Loss of water is also a function of time. The longer a pile sits the more it will dry.

Loved the video Siloe. Why not expand it to include R&D and commercial composting?


 
Tim Malacarne
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Location: South central Illinois, USA
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I guess I'll vote for the hot method, although I'm more inclined to think that the important part is that you do it at all... Either way is OK, either way has pros and cons. I can turn our hot pile with a tractor loader in about an hour usually. If I can get somebody to turn it while I water it, so much the better! About a month ago, a fellow I know, a farmer, came by and offered me 2 loads of spoiled silage and calf manure from his farm. I said sure, and showed him where to dump up at the neighbors place, where we'll do the composting. Neighbor or one of his big strong sons will haul horse manure from a horse farm down the road. If things are going well, and I have a little extra time, I'll grab some granite powder from the monument place, mix it in.... Turn it and wet it mebbe 5 or 6 times. Man, it's kinda fun in the cool of the early mornings, looks like the thing is on fire!

So hot works for me, produces plenty of decent compost for our gardens. I've recently thought about a cold pile. Meh, we'll see. Got nuthin' against 'em.

Best, TM
 
Tim Malacarne
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Location: South central Illinois, USA
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Say and, this is a really interesting and thoughtful discussion.

Thank you all!
 
John Saltveit
gardener
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Nice video Siloe,
I prefer hot/warm composting, partly based on my climate. We have very dry summers. If I can get mine to be hot, that means that millions/zillions of bacteria and other microbes are exploding through it. THey are the base food of the soil food web. Many of the other microbes eat them. If the compost has gotten hot at least once, then it will retain water many times better. I won't have to add water to it frequently, and when I mix it with new compost, it will retain the moisture too. I make compost tea out of my compost and I want the max microbes in it before I make it. In the fall, I use the super microbial compost to seed the leaves and wood chips I distribute through my garden and start my new compost pile for the year.
John S
PDX OR
 
Siloe Oliveira
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Thank you everyone for participating in the discussion. This has been very enlightening. It seems we have a split group with perhaps a bit more cold composters. This is definitely a topic I need to get more in depth with. Thanks to Druce Batstone for the link you provided. It is something I need to read, and your suggestion of expanding the video to include R&D and commercial composting is really good. I should do future episodes expanding this topic further. (This video was certainly barely an introduction)
 
Leila Rich
steward
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Location: Wellington, New Zealand. Temperate, coastal, sandy, windy,
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I basically cold compost.
I don't have a philosophy about it, I'm just lazy and rarely turn my heaps.
When I do, there's always a major increase in heat.
My compost is always a total pain to turn, as I chuck pretty much everything in without cutting it up,
so if I get excited and turn it, I might have to haul an old pair of jeans and an entire shrub into the next bin.
Did I mention I'm lazy?
Oh, and I like growing worms in my compost.
 
Michael Cox
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Location: Kent, UK - Zone 8
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Leila - sounds a bit like our heaps! I was spreading compost on the veggie beds a few months back and a whole pigs skull dropped out of the barrow from a hogroast last summer. When our chickens arrive the heaps will move to their new run, so I'm hoping they will do some of the work for us.
 
Peter Ellis
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Location: Central New Jersey
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There is no right or wrong here Just some differences. Differences in methods, processes and results. Some situations favor one approach, some favor another.
The end products are not quite the same, with hot compost product being more bacterial based and so grassland biased and cold compost (leaf mold) being more fungal and so more tree friendly.
Having both makes sense for a permaculture approach, let's you balance better, gives you the choice to optimize for a specific application.
 
Lorenzo Costa
steward
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Location: Italy, Siena, Gaiole in Chianti zone 9
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well said Peter Ellis, they don't exclude each other, I had never thought about the difference of the two and there relation to what plants favour one or the other, fungal based or bacterial based, thanks I'll keep this in mind.
 
Ronnie Ugulano
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Location: Zone 9, CA
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I've been vermicomposting for years, so I'm gonna say "cold". But I can't say one or the other is "better". I enjoy feeding my worms, and watching them work. Somebody else may get joy watching that thermometer hit high temperatures and seeing steam coming off the pile in cool weather.
 
Tim Malacarne
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Location: South central Illinois, USA
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That whole pig skull business made me laugh!

My final instructions are for direct cremation. I told my wife I'd like to be spread on the compost pile, she said, "It would be hard on the kids..."
 
I agree. Here's the link: http://stoves2.com
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