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Successful Manure & Waste Management
Heat Recovery From Composting
March 24th, 2009 by peter
Heat is the natural byproduct of the biologic process that we call “composting”. It is not at all uncommon to see pile temperatures well above 140 degree Fahrenheit, sustained for several weeks.
Quite often, I am asked the question, “Can I recover some of the heat from my compost pile?” The simple answer is “Yes”, but then we must also answer the questions “How can this be done easily and inexpensively?”
Gregg Twehues at Stone Barns Center in Tarrytown, New York, has been experimenting with heat recovery from his O2Compost Micro-Bin system with a good deal of success. In Gregg’s case, he wanted to use the recovered heat to warm seed trays in their propagation house as a means of reducing their overall power consumption. Stone Barns Center has extensive greenhouses and they grow organic herbs and vegetables year round for use at Blue Hill, a world renowned four-star restaurant located on-site: www.bluehillfarm.com.
With his first test, Gregg used a long coil of plastic irrigation tubing buried in the Micro-Bin, and he was able to heat the circulated water to 84 degrees Fahrenheit for approximately 5 days. In his second test, he “sweetened” the mix by adding high nitrogen feedstocks and he was able to extend the hot phase of composting to nearly 3 weeks. In future tests, he plans to add 30 feet of copper tubing to the coil to improve heat transfer to the water.
This seems to be a growing area of interest. O2Compost was recently contacted by the Soil and Water Conservation District in Alaska to help develop a method of heating greenhouses in conjunction with composting horse manure and other feedstocks at temperatures below minus 20 degrees Fahrenheit, for weeks on end. This could be our ultimate challenge – we’ll keep you posted.
4 Responses to “Heat Recovery From Composting”
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Rather than using pex pipe (irrigation grade) could a less expensive material such as garden grade hose be used?
Yes, garden grade hose can also be used for heat recovery, but because rubber doesn’t transmit heat very efficiently, the flow of water will need to be quite slow to allow time for it to warm up. I will be experimenting with copper tubing (50 feet @ $125)and while expensive, I believe it will be very efficient.
What about copper tubing with the aluminum “scales” (Heating Grade” Although it would not be in a roll, and it would be harder to clean out, I would think that the heat transmission would be extremely effective.
It is also priced about the same as copper piping.