Feeling the compost heat!

More compost excitment yesterday! The compost pile is steaming hot! Check it out:

Our compost is hot stuff! Nearly 130  Fahrenheit, which is over 50 degrees Celcius!

Our compost is hot stuff! Nearly 130 Fahrenheit, which is over 50 degrees Celcius!

Last week, the compost was all still in the first bin and there wasn’t much action in there. I hadn’t turned it after the winter, so it was mostly just fruit and vegetable scraps, really wet and packed together after sitting frozen all winter and getting pretty stinky. A few weeks ago, we got some hay as a carbon source, which I’ve been layering on and it’s started helping, but last week I decided it was time to turn it. When I went out during a free period, a teacher and student were out there, taking a bit of a ‘time out’ and checking out the garden. This boy has a challenging time taking part in regular classroom activities, and the teacher who works with him often takes him out to the garden for a breather. He’s really strong and really enjoys physical work, so he helped a lot a couple of weeks ago when we had soil delivered which had to be carried to the garden. He was keen on helping turn the compost too. He wasn’t a biggest fan of the smell, but put up with it pretty well. (I’m actually surprised by how well I put up with the stink too!) And we got all of the compost emptied from the first bin to the second bin, adding some soil and hay between layers along the way.

And, well, apparently what we did helped! Just a week later, the middle bin was way more decomposed than it had been (way fewer identifiable things) and less stinky. I was curious to know if it had heated up too, so I pulled out our new compost thermometer. Wow, was I excited when I saw it climb up to the top of the “active” phase temperature! During garden club, many of the students were excited to get to use a garden fork to mix the compost a bit. Some of the girls got excited about checking out the temperature too, and kept putting the thermometer in the bin. I think they thought it would get hotter with every turn of the fork, but I’m glad they were excited! They (and I) also thought it was pretty great that it was steaming when they dug it up. I was super glad that they garden club kids got into testing the temperature of the compost, instead of just giving me a funny look for getting excited about the steaming pile! 🙂

And if you don’t know why I’m so excited about the compost pile being hot, don’t worry. Until a few years ago, I didn’t know why it’s a good thing either. (In fact, I didn’t even know what compost would heat up at all…)  The compost thermometer shows three phases of composting: Steady, Active and Hot. We’re currently at the high end of the “active” zone. Composting happens pretty quickly in this phase and is done mostly by microorganisms – bigger things like worms can’t survive temperatures this hot. In the hot phase, things like weed seeds and pathogens are (hopefully) killed, so we’ll see if we get the pile that hot…

Happy growing (and composting)!


2 responses to this post.

  1. Posted by Sean Hooper on May 23, 2013 at 8:30 pm

    Awesome post! Any tips on where to do some reading on starting up a compost pile in the back yard? Is it necessary to have different bins? Or is it possible to maintain a single steaming pile?


  2. Hi Sean! I was mostly research 3-bin systems, but we just use one bin in the backyard and it works fine. Don’t think it heats up, though. I think that one of the keys to heating it up is mixing it fairly regularly – then you get air in there and get aerobic composting going on, instead of anaerobic (which can get stinky). I think it also has to be a certain size for it to head up. There’s tons of good compost info online – I like Rodale Institute, Mother Earth News, etc. I used this site a lot when I was starting the school compost programme – http://www.createyourowneden.org.nz – but it might be more school-focused rather than backyard. Happy composting! (And feel free to bombard me with more compost questions.)


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