Compost Temperature: Is your compost hot enough?

Compost Temperature:  Does it really matter?  :: Five Little Homesteaders

picture via Joi Ito on flickr

Compost.  We really should all be composting.  It’s great for the environment.  It’s great for your garden and there are so many different ways to go about it.

If you’re lucky enough to have a yard, then a compost pile is a pretty simple and easy way to go.  My husband wrote a post over a year ago about our simple 3-bin composting system.  He talks, in his post, about the importance of heat in a healthy composting system, but never get into the importance of actual, specific temperature.

Is your compost pile hot enough?  What is your compost temperature?  Do you know?  Do you care?  Should you care?

Compost Temperature: Why do we care?

To put it simply, yes, you should care about the temperature of your compost pile.

Checking and monitoring the temperature of your compost pile is important in order to ensure that enough heat builds up to kill off weeds, their seeds, disease, parasite and the like.

How does this happen?

When provided enough nitrogen, bacteria and fungi within in the compost pile will grow and reproduce rapidly – thus breaking down and decomposing the organic material and producing heat.  You want this growth and reproduction  because you want the material to break down and give you nutrient rich compost.


Compost Temperature: What should it be?

To ensure that your pile has composted properly, it needs to reach the desirable range of 140 degrees to 160 degrees for 10 to 15 days.

However, watch out.  Some piles can get REALLY hot and reach temperatures at or above 180 degrees.  When piles get this hot, they may spontaneously combust.  In order to prevent this, monitor your piles temperature and aerate it when if it reaches 165 degrees.  The simplest way to aerate the pile is to turn it.  This also ensures that pile is getting hot evenly and all the material is being decomposed at the same rate.

In a perfect world, a pile would be aerated by turning it at least 5 times during the 10-15 day range.

How do know what the temperature is inside the pile?

The easiest way is by procuring a compost thermometer.  (See the ones pictured below.)

Simple and cheap, a compost thermometer is good thing to keep on hand to give you the piece of mind you need to be sure that you’re compost temperature has reached and stayed where it needs to.


Compost Temperature: What if mine never reaches the right temp?

On the opposite spectrum from combusting, some compost piles might never reach the desired range.  If you’re pile never reaches 140-160 degrees, you cannot be sure that pathogens and weeds seeds have been destroyed.  This can (and probably will be) bad news for next season’s garden when you spread this fresh compost on it.

In this case, your pile needs more nitrogen rich material.  This includes things like fresh grass, plants in the legume family and fresh manure. (See!?  Those chickens in your backyard are good for more than just eggs!)

What are your thoughts?  Do you measure the temperature of your compost?

To be honest, I don’t own a compost thermometer but I DO check the temperature of my pile with my hand and we do regularly turn the pile.  So far so good!  However, if we ever start having problems, I will definitely invest in a thermometer.



picture via Joi Ito on flickr




  1. We don’t have a compost thermometer either. But it gets pretty hot and we’ve not ever had a problem. We also like to get used coffee grounds from Starbucks. When ever we’re in town we stop and see if they have any available.

  2. I bought a compost thermometer a while back. It has been fun to keep track of soil and compost temperature. I have had a hard time getting my compost much over about 145. In the summer it seems I have too much dry material and not enough green nitrogen rich material to heat it up.

  3. Kathy Barnett says:

    I live on the Wa. Coast where we get a lot of rain. My compost pile is in the shade and never seems to get hot. I turn it frequently add veggie scraps, gas clippings and leaves. What else can I do to compost quicker? Should I have the compost on a didn’t area?
    Newer at composting

  4. There are actually tow different compost “philosophies” and two different ways of composting, mutually exclusive: if you compost the way you describe you indeed get a nutrient-rich, weed seed free compost, but it is then naturally devoid of any “higher” organisms such as worms etc. We usually don’t go this route, and hence prefer a low/normal/soil temperature compost. While the above described bacteria then largely have to give way to those bacteria who decay stuff at lower temperatures (there, generally speaking, are always bacteria that have a certain optimum temperature, at which they will thrive to the extent of breeding at sometimes the tenthousand-fold rate than at lower or higher temperatures; q.v. milk, when heated slowly, can go sour in an instant when it crosses that “magic threshold” and hence our body reacts with fever against bacterial infections, as the bacteria that harm our body generally thrive at 37 degrees centigrade (body temperature) and a few degrees above they don’t do as well thus keeping them in check and making our immune system’s task much easier). That said, if you want a compost that is rich in worms, you cannot go the high-temperature route. Instead you have a lot of worms, “worm tea” and an excellent soil structure. Since worms tend to also eat weed seeds you will not necessarily have unwanted growth when you spread it, but, as I said, this way of composting is a totally different philosophy and I think both should be considered in parallel, depending on what needs you have.

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