The Difference Between Hot, Cold, and Warm Compost Piles

comments (2) March 20th, 2012

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ChrisMcLaughlin Chris McLaughlin, contributor
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Photo by Pretty Poo Eater under the Creative Commons Attribution License 2.0.


No matter how much time you have (or the length of your attention span), there's a composting style for everybody. World-renowned "hot" or "fast" compost pile, is exactly what it sounds like; core temperatures can range from 113 degrees to 160 degrees. "Warm" composting and the "hybrid" pile doesn't get as hot, nor break down as quickly, but it's respectable and requires very little attention. Then again, if you just want to toss it and fugheddaboutit, that works just as well, albeit it takes the longest amount of time to decompose.


All three composting styles need four ingredients: equal amounts of greens (think grass clippings, kitchen scraps, etc) and browns (think dried leaves, straw, etc), as well as water and oxygen. They'll be their best if they're built touching the bare earth. Naturally occurring micro and macro organisms will quickly be drawn to your pile, which is exactly what it needs to get things cooking. All types will need air and water, also.


There are several ways to keep air in a pile, but for simplicity's sake, the easiest way is to turn it. You could use a pitchfork and turn the pile over or move the pile from one place to a spot right next to it. It should be turned once or twice a week -- or never depending on how fast you'd like it to break down. It's how you balance the basic four ingredients -- greens, browns, moisture, and oxygen -- that determines whether you have a hot, cold, or warm (hybrid) compost pile.


Hot Composting Tips

  • A hot compost pile needs at least 3' X 3' X 3' in order to heat up and ideally, even a bit wider and taller. Between 3' and 6' tall and deep is a good rule of thumb. Hot pile temperatures range anywhere from 113 degrees to 160 degrees and you can have compost in about eight weeks.
  • Try to build a hot pile "all at once." Once you have a nice-sized pile going, don't add anymore to that one and just work it until it's broken down (finished) into fluffy, earthy, humus. Periodically adding more materials to the pile will add more decomposing time.
  • Turn (aerate) this pile a couple of times per week to get things hot in there. Don't try to rush it any faster by turning everyday; the bacteria have to have some time to do their thing.
  • 4. Keep the moisture steady. Get water into the pile as you're turning or moving it. I like to have a garden hose handy and I water things down after I've moved a few forkfuls of organic matter. Remember, not sopping wet, just thoroughly damp like a wrung-out sponge.


Cold Composting Tips

  • "Cold" or "passive" compost piles break down slowly at temps that are 90 degrees or lower. At these kick-back temperatures, you'll have garden gold in about six months to a year or more. It'll depend upon the season and what you're tossing in there. Still, who cares? Where's the fire, right?
  • This is the no-work composting system. Toss your greens and brown together, willy-nilly, add some water once in a while (or never), aerate now and again (or never), and Mother Nature is still going to do what she's great at; decompose.
  • A cold pile is one that you may want to keep hidden because it does take so long to break down, you may consider it unattractive. There's also the chance that this type of pile could potentially become smelly -- especially if you never give it oxygen (aerate).
  • Cold piles have a certain desirable quality, however. High temps in a hot compost pile kill off certain fungi and bacteria that help suppress soil-borne diseases in the vegetable garden. These beneficial microbes are left intact in the humus produced by a cold pile.


Warm (Hybrid) Composting Tips

  • I have to admit that I started gave those compost piles which are "halfway" tended, the moniker "hybrid" or "warm" because I had no idea how else to describe them. This is the composting technique that I use most of the time.
  • This is a happy medium compost pile that's neither ignored nor pampered. I start it out as if I were building a hot pile. I add lot of green and brown material in equal parts. I wet it thoroughly and toss it around making a great mix.
  • But after that, I turn it once about every couple of weeks. At that time, I'll add some water, as well. It gets just enough love to keep things smelling nice and moving forward, but it might take 8-14 weeks to break down.

posted in: compost

Comments (2)

JadaE writes: Hey Chris! Question: How much coffee is too much?? I know tomatoes like a slightly acidic soil, and I know coffee grounds are good for acid. Starbucks has as much as I need at any given time! How much would be reasonable for my raised bed?

Thanks!
BTW, I'm reading "Idiot's Guide to Composting" as we speak (or type?)...but thought I'd ask the author here! :)
Posted: 10:43 am on April 24th
MikeTheGardener writes: Personally I am a fan of trench composting. For me, composting could not be easier than this format. Although I do have a compost pile and a compost bin, trench composting still ranks #1 in my book.
Posted: 10:46 am on March 26th
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