What Material for Non-Corrosive Pipes in Compost?

AI Thread Summary
The initial prototype of the anaerobic digester struggled to maintain the necessary temperature, prompting the idea to utilize heat from nearby compost bins. A proposed solution involves circulating fluid from the digester through pipes placed beneath the compost. Discussions highlighted materials for the piping, with options like plastic for cost-effectiveness and durability, and copper for its high thermal conductivity, though concerns about corrosion and cost were raised. Stainless steel was suggested but noted to be unsuitable in oxygen-poor environments. Overall, the focus remains on finding a practical and efficient material for heat transfer in this setup.
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I am trying to transfer heat from compost into anaerobic digestion tanks for maximum productivity from the methanogenic bacteria. The digestion tanks are to produce biogas.
So with our initial prototype for our anaerobic digester, we weren't able to sustain the right temperature inside the tanks. One idea we came up with is to use the heat from the compost bins that is only within 10-20 feet from our tanks. We plan to circulate the fluid inside the digestion tanks underneath the compost using a pump. So my question is, what is a material that has high thermal conductivity and would not rust or corrode underneath compost?

We put fruit peels, coffee grounds, paper dishes and bowls, vegetables, peoples leftover meals, and some other stuff i can't remember off the top of my head into the compost.
 
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In case of limited thermal transport the usual answer is the most common plastic pipe. The thermal conductivity is low, but it is cheap to extend the surface and (in normal circumstances) it has long lifetime. It is also easy to use.
Copper would also do (high thermal conductivity) but I don't know how it would fit with the compost. Copper is often considered to have some antibiotic properties. It is also not cheap and more vulnerable to movements (compost is expected to shrink and move).

Are you sure the compost heap can/will produce enough heat?
 
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Maybe use stainless steel piping? It is probably not cheap, though...

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Is there oxygen where those pipes run? Stainless steel should be avoided in places where it is not exposed to oxygen.
 
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anorlunda said:
Stainless steel should be avoided in places where it is not exposed to oxygen.
Interesting. Why's that?
 
See the below for a quick answer:
https://www.imetllc.com/training-article/stainless-steel-corrosion-resistant/
 
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Don't re-invent wheel this time around, look at the plastic piping used for under-floor heating. Lots of know-how on usage, inexpensive accessories & connectors.
;-)
 
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