Compost Hot Water Heaters

For those of us who have successfully composted in the past, we know that a properly made compost pile produces a substantial amount of heat. In fact, when the pile stops creating heat it is usually done “cooking” and ready for the garden.

We focus a lot on leveraging technology to become more resilient. So what can we learn from a Frenchman who died over three decades ago?

A lot!

What is a Compost Water Heater?

Simply put, it’s a giant pile of compost with tubing that is coiled throughout the compost pile and then filled with water. The water within the tubing heats up substantially (and relatively quickly).

Compost Water Heater

Jean Pain in the process of building a compost water heater

Jean Pain was a French innovator who lived in southern France from 1930 until his passing in 1981. He was able to create a compost-based energy production system that was capable of producing 100% of his energy needs.

Using compost alone, Jean was able to heat water to 140°F. He used this water for washing, cooking and heating his home. We aren’t talking about a small amount of water either. His system was able to heat water at a rate of 4 L per minute; or almost 1 gallon per minute.

Many of our modern hot water heaters can’t even boast figures that impressive.

The work he did is still viable today. Sometimes known as Jean Pain Composting or the Jean Pain Method, we can learn a lot from the work of this Frenchman about resiliency.

Interestingly enough, just about all of Jean’s work is in French. There are English translations available around the Internet, however, so with a little bit of research we can take advantage of Mr. Pain’s successes as one of the early innovators of modern resiliency.

If you are interested in learning more about the work of Jean Pain, check out the book entitled “Another Kind of Garden.” It is translated from the original French so it is a little hard to read, but the information is extremely interesting and we could all learn a thing or two from his work.

How Does it Work?

It may seem unbelievable that a simple compost pile filled with anaerobic bacteria could heat water to temperatures hot enough to scald skin. It is, however, entirely possible and easily replicated at home.

You only need to search YouTube for a few minutes to find thousands of videos detailing variations of Jean Pain’s design being used in towns and cities around the world.

We all know that compost piles generate heat as part of the decomposition process. How much heat? A large, well balanced (nitrogen/carbon), and aerate compost pile can get up to 120-140 degrees for as long as six months, depending on the size of the pile.

As mentioned, the basic idea behind a compost water heater is that tubing is coiled throughout the compost pile and then filled with water, which in turn is heated by the compost pile.

As the below image illustrates, cold water goes into the coiled tube and hot water comes out. Not only that but it’s also possible to extract methane gas from the compost pile, which can then be used for cooking or heating.

Thermal compost pile

Recommended Videos

To give you a glimpse of what a real-life compost water heater is capable of, here’s Ben Falk at Whole Systems Design in Vermont showing off their first generation compost water heater:

They used a mix of wood chips and horse manure to build this compost water heater, and got hot water with temperatures of 140 – 145 degrees Fahrenheit (~ 60 degrees Celcius). Not bad.

Testing the first generation of Jean Pain woody-compost water-heating mound at Whole Systems Design’s Vermont hill farm. We are now 2 months into testing our first mound and the results are astounding with hot water able to be harvested from the mound at a rate of about 1 gallon/minute at 120 F continuously, or cycles of 145F water harvested in 30 gallon amounts. We will be using this mound to make soil for the gardens and fruiting perennials on the farm and for in-soil bed heating of our greenhouse for season extension.