Heat distribution compost pile

Hello!

For a long-term project I intend to build aerated compost piles.  Since I need an efficient way to get pasteurized compost
I would like to know what the heat distribution within a compost pile looks like.

Maybe you know from experience
For example, if I have a cylindrical pile 4 ft in diameter and 4 ft tall. Imagine the pile reaches 70°C (140°F) in the center.

Can you estimate at what distance from the ambient environment there is still a temp of 60°C? for instance, if the ambience has 20°C .

I  would like to make a cylindrical bucket made out of mesh within the cylindrical pile (which is held together by a mesh too) which I could just lift like a
bag so I get only the pasteurized part.

Thanks for an answer!

I did some digging because I swore I saw a heat graph of a compost pile before and luckily I found it again. (Source)

While I do not fully understand the context, it appears the temperature drops off quickly once it doe start dropping towards the edges.

Hi Vera , that sounds like a interesting project!

In a compost pile, the center is usually the hottest, around 70C, and the temperature drops as you move outward. Typically, around 1-2 feet from the center, the temperature can still be around 60C. It’s smart to use mesh to lift out the pasteurized part!

That should work well for getting the right compost.

Timothy Norton wrote:I did some digging because I swore I saw a heat graph of a compost pile before and luckily I found it again. (Source)

While I do not fully understand the context, it appears the temperature drops off quickly once it doe start dropping towards the edges.

When looking at the graph one can see that the outermost 10°C contour line is about 1 m away from the 60°C contour line. So at 1 m height  you'd  need to get 1 m into the pile from all sides to reach the 60°C core.

So thanks this graph provides some notion about heat distribution within the pile.

Vera Carrera wrote:Can you estimate at what distance from the ambient environment there is still a temp of 60°C? for instance, if the ambience has 20°C .

Yes, it is possible to predict temperature fairly accurately if you have a consistent recipe and can manage the environment and how the pile is constructed.  This is described in Chapter 4 of The Mushroom Cultivator: A Practical Guide to Growing Mushrooms at Home, by Paul Stamets and J.S. Chilton.  The temperature a compost pile reaches, including the shape of the heat profile map and how close to the edge reaches pasteurization temperature (inches vs feet), depends on several factors, but you can learn to control them.

I've measured temperature in dozens of piles over years, tried pasteurizing in a bucket (albeit not mesh) within a pile, and dabbled with ways of adding air.  I primarily do a passive center-feed hot composting method advocated by Joe Jenkins (see pg227 here), year-round from -27F to 100F in an arid and somewhat windy area, and I can control and adjust the temperature in those piles to within about 10F.  I would recommend using a compost thermometer to help you get familiar with your recipe, the impact of how you construct the pile, and to provide you with the final confidence you may be looking for.  In my experience, protection from wind and a foot of straw insulation on all sides, bottom, and top can help ensure predictable temperatures for a consistent recipe.  Also protect from excess rain if applicable.

Aerated Static Piles, such as O2 Compost, use forced air to give you some degree of after-build temperature control as an additional option.

Are you looking at no turn aerobic composting or a turned pile type system?

I have been studying to do no turn aerobic and how to make it work and pasteurize.  Very little information out there on it.

But there is a you tube video on a guy in alaska heating a small green house with totes of compost.  What he found was the compost was doing a poor job of heating the greenhouse.   The totes were something like a 4 ft cube and he got to measuring things and found he was basically only using half his fuel(the compost)  Basically the skin of the pile wasn't heating because it was cooling too fast.  The outer 6 inches was basically not doing anything.  4 ft x 4 ft x 0.5 ft x2 for 4x4x1+3x4x1+2x2x1=32 cubic feet is nearly totally inactive from 64 total cubic feet possible.  The semi cure he found there was to pack 4 totes in a in a tight square and insulate around it on all sides.

That got me to thinking of how to combine areas of interest.  If the no turn pile on an oversize pallet was put in an insulated box mounted on a bit of a hill with a solar thermal panel mounted below it going thru a folded path collector to prevent back flow.  Double pane glass tops out at between 140 and 150 degrees according to the collector info and since the pile needs to cook for a year. Load in late june or early july so the solar collector is heating during the best possible time.  Combine with the thermophilic reaction from the pile and it should be possible to bring it up to 140 degrees and hold it for a pasturization time.  The pile should cook for 6 weeks on its composting heat.  Since I suspect it won't stay warm enough thru the winter to keep the worms active the thinking is to put it over one of the air vents for the drain tile system as they steam all winter long.

Hello there, it is so cool that people actually do this "center based" conpisting. I wasn't sure if this is an odd idea but apparently it makes sense for certain applications.

It will depend on how much heat is generated and how it is lost. Ideally, the starting materials are of the right porosity, density, moisture content, pH, C:N ratio. The pile will be insulated on the side and air flow travels from the bottom to the top, providinright amount of oxygen without drying the pile up. It's difficult to achieve that, but in this video the composting specialist showed a setup with imperfect numbers and still made it to work with controllable forced air.