My compost pile is too cool

greendreamhomeFebruary 27, 2014

I have an Earth Machine, and I started composting in it a month ago, at the end of January. (Remember I'm in Phoenix, so it was in the 60's in the afternoon then, and it's in the 80's in the afternoon now.)

When I started I had nothing but dried leaves, and over the past month I've been adding all of our fruit and vegetable peelings and ends. I haven't added any grass clippings because we haven't cut the lawn.

At first I was adding green materials and mixing it up daily, but after asking about frequent turning here, I've been saving up the green materials and adding them every two to three days.

I always try to keep the pile the wetness of a wrung-out sponge.

For the first few weeks, I could feel that the center of the pile was very warm, but lately it hasn't felt very warm. I got a composting thermometer yesterday, and it read exactly 80 -- the very lowest reading before the materials are too cool to break down into compost.

Why is my compost pile too cool?

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Check for finished matl. at the bottom it might be time to harvest.
Or add some more browns along with the greens you have been adding, sounds like there may be too many greens.
Either way don't fret, eventually you will get compost even if the temp is at 80 or less. Experimentation & patience, each time you make compost you will get better. Hope that helps.

    Bookmark   February 27, 2014 at 10:27AM
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How full is it?

    Bookmark   February 27, 2014 at 10:55AM
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It's a third of the way full. I thought that if I made it too full, I would have trouble turning it, plus at the time I had so very much more brown than green matter (since the lawn was dormant) that I figured it was better to start smaller.

    Bookmark   February 27, 2014 at 11:21AM
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Even if the other parameters (C:N, Moisture, air) are perfect, you're not likely to create a lot of heat at that volume.


    Bookmark   February 27, 2014 at 11:29AM
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Natures_Nature(5 OH)

You have the wrong ratio of nitrogen(greens) to carbon(browns). In general, you need 25 parts carbon/browns( fall leaves, straw, woody dry plant material) to 1 part nitrogen/greens(grass clippings, veggie scraps, manure). Just imagine cutting the grass, bagging the clippings. For every full bag of grass clipping you dump in the compost, you should add 25 bags of leaves, or other dry brown carbon material.

    Bookmark   February 27, 2014 at 12:56PM
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"For every full bag of grass clipping you dump in the compost, you should add 25 bags of leaves, or other dry brown carbon material."

This is not correct. If one is talking about volumes, it's more like 2.5 bags shredded leaves to one bag fresh grass clippings. The volume of leaves will vary depending on the density (degree of shredding) of the product.


    Bookmark   February 27, 2014 at 1:04PM
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Natures_Nature(5 OH)


Thanks for catching that! Their pile definitely would be cool if you added 25 bags of shredded(thats critical) leaves, to a mere bag of grass.

    Bookmark   February 27, 2014 at 2:28PM
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"lately it hasn't felt very warm. I got a composting thermometer yesterday, and it read exactly 80 -- the very lowest reading before the materials are too cool to break down into compost. "

That's OK, just wait until May. :)

I do "cold composting" ... largish pile of whatever comes to hand, with a drip line to keep it wet, and although they seldom get blisteringly hot, things do decompose. It just takes longer

Here is a link that might be useful: Cold composting in Phoenix

    Bookmark   February 27, 2014 at 2:54PM
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joepyeweed(5b IL)

My compost pile is too cool also.

Its buried under about a foot of snow... ;-)

You need more greens... or yellows... pee on it....

    Bookmark   February 27, 2014 at 4:32PM
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Okay, so this is what I'm understanding so far:

1. I should have a larger pile

2. My current pile needs more greens, so that the ratio is approximately 2.5 to 1, with the 2.5 being browns. (By the way, my browns are all crushed up; we stomped them tiny so they could fit in metal trash cans.)

    Bookmark   February 27, 2014 at 4:51PM
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#2. Different ingredients have their own C:N ratio and can skew a pile if one tries to use a "one size fits all" formula. Here is a website that has a compost calculator that one can adjust the amounts of each ingredient. Caution: Its ingredients numbers are more like a guideline. For example, dry leaves can vary from 40:1 to 80:1 (and probably outside of that as well).


    Bookmark   February 27, 2014 at 6:56PM
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At 10.5 cubic feet capacity that compost does not have enough volume to generate much heat. The minimum volume I have found needed for the bacteria to generate much heats is 27 cubic feet.

    Bookmark   February 28, 2014 at 7:01AM
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Your compost is 'cool' because the conditions that will lead to hot or warm composting are not present.

Hot compost requires a number of things:
1) Large enough bin for heat retention. Your Earth Machine might better be described as a digester; rather than a compost bin suitable for hot composting if you desire. The info on the EM did not suggest it was promoted as a quick compost method.
2) small particles
3) optimal mix of greens and browns (C:N mixture). An example might be 1 pound finely shredded leaves with 1.5 pounds fresh grass.
4) Moisture in the right range.

I like a mesh bin four feet in diameter, and 24" or 30" tall. Cheap, $20 to make, easy to move, easy to turn. I mix it in one day, and with the right mix get a core temp of 130F to 160F (in the warmer months) two or three days later. Turn and add water as my compost thermometer suggests.

Nothing the matter with cold (or slower) compost. But some folks don't like to wait for it, and your post suggest you may be one of these folks.

    Bookmark   March 1, 2014 at 4:16PM
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There has been some miscommunication about the ratio of greens to browns. The ratio may be expressed in two ways -- by volume or by weight.

The ideal of the mixture is a C:N (carbon to nitrogen) ratio of 30:1. Volume is a rather imprecise method, I prefer the weight method.

Even the weight method is less than exact. A trash can full of spring grass from my yard will weigh differently than a trash can full of summer grass from my yard. And the C:N value of a mix of leaves from my yard will be different in September than it will be in November.

These number are estimates. Cornell Composting has a Handbook of C:N values that is the most thorough that I am aware of. When I first got my tumbler twelve years ago, the first batch of compost did not get hot. Using the provided compost thermometer, my bathroom scale, and putting it on a Excel spreadsheet, I got to a core temp of 160F.

I have not used the spreadsheet or scale in many years. The compost thermometer is still valuable.

There are some compost-related web sites that let you plug in two or three ingredients, and give you a value (an estimate, remember!). But if your bin or gizmo size is not large enough, the high temp generated by the activity will be lost.

Composting is not rocket science. But it is basic science.

If my grass is 20:1 and my mix of October leaves is 40:1, an equal mix might be around 30:1. In November my leaves might be 55:1, so more grass would be required.

    Bookmark   March 1, 2014 at 4:50PM
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floral_uk z.8/9 SW UK

GreenDreamhome - you could start by asking the question why do you want to compost? Is it to prevent organic materials from going to landfill and to have something good to add to your garden? Or is the perfection of the process itself your main goal?

By saying your compost is TOO cool you must be measuring it against something. So, too cool by what yardstick? Some of us cold compost and have done so happily for years. In the UK it is by far the commonest way people do it and there is very little hand-wringing over temperatures and ingredients. Heat is just not an issue. Personally, I have no interest at all in the process, only in the results. Your name implies you too are interested in the green aspects of composting. You can fulfil those absolutely fine even if your compost never warms up. Once you have started a series of bins or piles there is actually no waiting at all because there is compost ready pretty much constantly.

    Bookmark   March 2, 2014 at 6:23AM
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Robert: Apparently it IS rocket science. This is WAY too complicated.

FloralUK: Believe it or not, with all the reading I did before starting to compost, I never read the phrases "hot compost" and "cold compost." All the articles, and the people I talked to, referred to attaining and maintaining heat. They even talked about "compost starters." A few people in my neighborhood have a series of compost piles. The Earth Machine says that its compost is ready in about four months. Is that an indication of a "hot" or "cold" composting technique?

All I want is to create compost for my own garden. The only reason I'm in a hurry at all for my first batch is that I can't handle the additives in commercial potting soils, even the "green" ones. I've been screening my own dirt dug from parts of our yard that had been growing healthy grass, adding pure worm poo and topping the soil with crushed up leaves. So far our kale, geraniums and roses are growing nicely, and I think our herbs are okay.

    Bookmark   March 2, 2014 at 2:25PM
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Ok first & foremost making compost should be fun, not something to stress over. After all you are doing your own small part to assist mother nature & keeping green waste where it belongs - back in the ground.
Making compost is not for those in a hurry. Mother nature is in charge of decompostion whether in the woods or in an earth machine & she doesnt hurry. Your earth machine will heat up if you have the approx. C:N ratio. Above you mentioned crushed leaves are your browns. Perfect, crushed leaves are IMO the best brown. Greens, kitchen & yard waste (take the time to chop green matl. into small pieces). Now mix all that together, dump it all into the earth machine a bucket full at time watering as you go. (This is the only time matl. is added) Jam the lid on & walk away for 3 days. Then come back & notice how the lid goes on easy & how the pile has shrunk. Dig down a little & feel heat from within the pile. You can stir it a little & add water or do it when you come back to check in a couple more days. In any case mix & water when you notice the temp. going down. It is finished when the stuff you get out of the bottom is crumbly, smells good, has a few worms etc...Thats hot composting, matl. added one time only, requires some effort, but not much & its fun because finished matl. happens around 30 days. (sometimes less)
Cold composting is not being concerned for C:N ratio, little watering & mixing, adding matl. frequently. Compost will eventually happen.
I have two piles one hot one cold. I build my hot batches using the stuff I continually add to the cold pile & my kitchen waste.
So fill that earth machine. Go out & fiddle with it now & then, learn as you go. Look at the stuff as it decomposes, think of where you will put the finished matl. Once you get finished matl. you will be hooked...
Hope that helps & have fun :)

    Bookmark   March 2, 2014 at 3:36PM
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I've read over your posts GreenDream and you're doing exactly what I would advise someone to do if they were using a 'continuous feed' method (which does not need heat to work). It's perfect, and I recommend your method to most average homeowners.


P.S. The title should be changed to "My compost is WAY cool!"

This post was edited by pt03 on Sun, Mar 2, 14 at 16:31

    Bookmark   March 2, 2014 at 4:20PM
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Hot composting has no official definition that I know of. I'd call it composting when a new core temp rises to 130F to 165F in the summer, for a back yard composter.

I have leaves from oak, maple, and sweet gum trees. In the fall, there are a number of weeks from maybe September to Early November when I can simply shred (four times with my mower, once with chipper/shredder) the leaves and make a hot pile. My bins are mesh bins of hardware cloth about 4'x8' and 24" or 30" high.

This is composting as easy as I can make it. Core temps after three days rise to 130F to 150F. The bright color of the leaves even indicates when the best collection is.

Say my back was bothering me until the end of November. Then I would shed the leaves and put them in the bins until spring. Fresh spring grass would be cut and mixed in with the leaves. At this time the pile would become 'hot', or at least 'warm'.

My compost takes about three or four months to make, even when I start out 'hot'. The same ingredients might take a year if I made no effort to speed up things. People who become excited by '14 day compost' often become disillunioned in my experience. I used a tumbler at one time, but only for a year and a half.

Ask yourself the revelent question. Are you a patient person?

I don't see how one can go wrong with fall leaf compost.

    Bookmark   March 4, 2014 at 3:47PM
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Composting is easy, although some try to make it sound like rocket science. Perhaps this video from Growing a Greener World episode 225 could be of some help.

Here is a link that might be useful: GGW225

    Bookmark   March 4, 2014 at 4:40PM
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darth_weeder(z7 NY)


P.S. The title should be changed to "My compost is WAY cool!""

My compost has been way cool this past winter but I doubt there is much compost cooler than yours Lloyd

    Bookmark   March 4, 2014 at 6:51PM
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Just responding to some comments in the thread. Continuous feed composting can also be hot. If you compost all your kitchen scraps, it will probably get hot (mine does). The whole thing may not get hot at once, but once it attains critical mass, there will always be a hot zone, as long as you don't let it dry out. My compost bin this year kind of lagged due to lack of rain. I didn't check the temperature, but it was getting so full, I was afraid I would have to build another bin. But then it rained, it heated up big time. Now it is hot and shrinking faster than I can add stuff to it. If I lift the top layer, steam comes out. It is a four foot square bin. 4 feet = 1.2 meters. Not necessarily applicable to rotating composters, or at least I have no real experience with rotating composters.


    Bookmark   March 4, 2014 at 10:10PM
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toxcrusadr(Zone 6a - MO)

I have a similar bin and in winter, I have basically the same two ingredients: dry leaves and kitchen scraps. Rather than starting with a pile of browns and stirring up the entire pile every time new greens are added, I simply store the leaves OUTSIDE the bin, and layer some with each addition of kitchen scraps.

When the bin is full, lift it off the pile, set it down next to the pile and turn over/mix back into the bin. If there is finished stuff on the bottom, use it.

Keep adding layers, and when full again, more of the bottom layer will be finished. This is about the most efficient method if you only have one bin.

    Bookmark   March 5, 2014 at 4:04PM
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toxcrusadr, yes, I store dry leaves also. Although I was careless and let them get wet recently. But I have evergreen trees, so dry leaves can be gathered in spring, summer and fall in my climate.

    Bookmark   March 5, 2014 at 11:13PM
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toxcrusadr(Zone 6a - MO)

I used to store them in bags, but reading about leaf mold in this forum, I realized they should be left out in the weather to get a head start on composting. Now I put them in a wire mesh bin and grab a handful as needed for the compost pile. I also have some large mesh bins out next to the woods that will just be left as long as it takes to make leaf mold.

    Bookmark   March 6, 2014 at 10:36AM
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Thanks to everyone for your comments and suggestions. Toxcrusadr: That's the way I should have done my bin! I'm thinking of getting another, so I can have a "new" and "old" one.

I was going to try the suggestion of adding scraps only every three days, but I don't have room in the fridge to store all those scraps, so it will have to be every two days. Still, after adding more leaves, the center of my pile is definitely warm.

    Bookmark   March 11, 2014 at 10:42AM
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