Compost Temperature

arrowoodJuly 5, 2008

I am using a Compact ComposTumbler with some success. However, my temperature rarely gets above 120F. Most of my biomass is grass clippings, which I usually allow to dry and then use as my brown material. My green material comes from kitchen scraps, weeds, some green lawn clippings, and horse manure. Even with the horse manure, which gets the temperature to rise quickly, my temperatures seem to max out at 120.

At first I tried following the carbon/nitrogen recipes that came with ComposTumbler. This year I have been following some instructions I found on old postings of this forum. I put my brown material in (filling the tumbler 3/4 full or more since grass tends to take up a lot of room at first and then to reduce in volume very quickly). Then I gradually add my greens over the course of a week. Once my temperature exceeds 100F, I stop adding greens and give the tumbler only one or two turns each day as I monitor the temp. The forum post recommended not turning too vigorously until temperatures neared 140F, but my temps never get that high.

Is dried grass a sufficient brown material? Is there something else that I should be adding to get my temps up?

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I could get up to 160F with my Compact. I weighted all my ingredients with the bathroom scale and filled it full up the first day. My main ingredients were shredded leaves and fresh cut grass.

I now have seven mesh bins and do not use either my plastic bin (too small) or the tumbler (too much work). The mesh bins are made of 1/4" mesh hardware cloth, and are either 4' diameter and 18" or 24" high; or 4'x8' by 18-24" high.

    Bookmark   July 5, 2008 at 5:22PM
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Belgianpup(Wa/Zone 7b)

When you read about compost reaching 150-170F, people are usually referring to a pile that is at least a cubic yard.

While it may be possible to reach those temps with a ComposTumber, you're working with a container that holds slightly less than half a cubic yard.

I wouldn't worry about it too much. Just let it compost until it doesn't heat up anymore, and all the materials are no longer recognizable, and you should be set.

This is composting, not brain surgery on an infant. Agonizing over 'perfect' composting just raises your stress level. Relax. Let the microbes do the work. Have some lemonade.


    Bookmark   July 5, 2008 at 6:24PM
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"This is composting, not brain surgery on an infant." Sue, I think I now have a new saying.

Dried grass is still a green. Keep in mind it isn't the color that makes it a brown, it's the content. I use cardboard (lot's of starch in cardboard) and newspaper when I don't have leaves. This will help really get that compost going. It might take a day or two for it to start the first time, but after that use a little of that compost to start the next batch and it will get an even better start.

    Bookmark   July 6, 2008 at 8:32AM
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Thank you, everyone!

My problem when I started composting was using too much green material and it looks like I still have the same problem. I did know that color isn't the real indicator - brown horse manure is a "green," but I thought dried material made up "browns." I live in the middle of a farm field - with no trees - so dried leaves are tough to come by. I shred newspaper, but I can't imagine shredding enough to constitute all of my browns. I'll have to keep looking.

I'm not really stressed about getting perfect compost. The compost I have been getting has not been the "black gold" advertised by ComposTumbler, but it has been brown chunky stuff that tills into the soil pretty easily and makes good mulch when I use it as a top dressing. I'm just trying to learn - that's the fun of gardening!

    Bookmark   July 6, 2008 at 1:54PM
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My highest compost core heat numbers were about the same for both a smallish tumbler, and my 4' diameter mesh bin that is 24" high. Both were in the 160's, which ought to be high enough for everyone except those interested in starting a fire.

The main reason a 3-5 foot diameter or square pile is usually recommended, I think, is that the generated heat is retained longer in the larger size pile. Not hotter, just longer.

The reason that I weighted all ingredients when using the tumbler was to get the temp. up to advertising temp. I did the third or fourth time. After a year and a half, I switched over to mesh bins, which were bigger, cheaper, and easier.

    Bookmark   July 9, 2008 at 4:34PM
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"Greens" are your Nitrogen source that will feed the bacteria that will digest the Carbons (browns) and that is what stimulates the bacteria to get to work, what feeds them so they can work. If your temps do not go up then you are not adding enough "greens".

    Bookmark   July 10, 2008 at 7:25AM
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140 is a fine temp unless you are composting the "no-nos" like weed seeds, diseased plants, pet or people manure, meat, dairy, etc. Grass clippings are generally thought of as "green" but it does kinda depend on the type of grass and the stage at which it was cut since straw is definitely a brown since most of the nitrogen has already been used up in the grain.

If you want to experiment on how hot you can make compost, you could always pee in it.

    Bookmark   July 10, 2008 at 1:17PM
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