Making Thermophilic Compost

There are many ways to compost – thermophilic, static and vermi (worm) among the aerobic types. In the past, I’ve done static and vermi with good, and poor, results. After learning about the thermophilic method in the Soil Food Web Foundation Courses a year ago, I’ve been itching to give it a shot, thinking it would be quick and easy. Let’s just say, I learned a few things.

What is Thermophilic compost?

Thermophilic compost (or simply thermo) is a hot composting method. As microorganisms consume compost materials, heat is generated increasing the temperature of the center and killing disease and seeds. Because the temperature gets so hot so quickly, the materials break down rather quickly. If proper temperatures are maintained, thermo compost can be prepared in accordance with organic standards.

The starting materials are important for thermo compost, as well as the amount of high nitrogen materials to start the composting and increase the temperature. Sufficient high nitrogen materials are necessary if it’s cold outside, but too much can make the pile get too hot too fast and turn anaerobic. Additionally, green materials are needed as bacterial food and brown materials for the fungi. Protozoa and nematodes will find their way into the pile once the bacteria and fungi are present.

First attempt

Before I could start, I needed reasonable outdoor temperatures and sufficient inputs (sufficient in both quality and quantity). 

Reasonable outdoor temperatures took some time. Spring in Ottawa was a bit of a tease this year, making brief appearances before shying away and letting winter have another go. Mid-April looked promising and with that in mind I started organizing my inputs. I had been squirreling away inputs for a bit. Coffee grounds and meat waste were stowed in the freezer, the remains of a pine tree cut down in the fall tucked in the garage, and toilet paper rolls stashed everywhere. Fortunately, it got me off to a good start. I had to source some high nitrogen materials and save all my kitchen waste for a couple of weeks but in the end, I had enough of each type of starting material to make a small pile with the pre-calculated ratios. 

Adding starting materials

After gathering all my starting materials, buckets for measuring, a tarp for mixing and securing my chicken wire frame, I was ready to start. 

I used 5 gallon buckets to measure each type of starting material based on my pre-calculated ratio and threw everything onto the tarp to thoroughly mix. I remembered when I was doing this that some starting materials (green and brown material) should have been wet beforehand to maintain proper moisture in the pile. It was a bit late to properly soak everything, but I added plenty of water in the mixing to ensure everything was nice and wet. After all the materials were thoroughly mixed I piled it into the wire frame, stuck thermometers in, covered it with a tarp and left it alone to compost.

Temperature and Moisture

I was happy to find the temperature quickly climbed to 135F by the next day. This was perfect as the pile should be at 131F (or higher) for 72 hours days before being turned (if it reaches higher temperatures it can be turned sooner). Unfortunately, it was still April and winter made a final brief appearance at this point, dropping outdoor temperatures to freezing. After only 48 hours (24 hours at 131+), the temperature of my pile dropped to 120F. On day 4 (~96 hours) when it dropped down to 100F I realized it probably wasn’t going to get hot again so I decided to execute the first turn. It was about this time that I had reservations about the success of this pile, but I forged on. It was also around this time that I remembered I was supposed to check the moisture of the pile when I checked the temperature…oops. 

As it turned out, it was quite a terrible compost pile. After the first turn, the temperature of the pile increased and the moisture evaporated leaving the pile dry; adding water created pockets of supersaturation and pockets of dryness instead of a uniform moisture. Both of this led to low oxygen conditions and allowed detrimental organisms to thrive. Before turning the pile for the second time I started to see actinobacteria (non beneficial bacteria). But, the third increase in temperature compounded the existing problems and by the end there was actinobacteria everywhere. 

Under the microscope

Out of curiosity, I wanted to see just how bad things were. The first assessment showed plenty of actinobacteria and oomycetes (non-beneficial fungi) along with an abundance of bacterial feeding nematodes (that was a good thing!); the second assessment showed fewer nematodes and more fungi, but still lots of actinobacteria and oomycetes. I didn’t consider it a complete flop given the presence of some beneficial microorganisms, but not enough of a success to actually use and relegated it to starting material for the second pile. 

Lessons learned

Ensure proper moisture levels from the beginning, and check the moisture regularly!

Published by juliamdupuis

Green Angel Sustainability Consultant. Environmental Chemist. RRU MEM Graduate.

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