Still Image from Back to Eden Film.
WHAT IS A Wood chip compost heating SYSTEM?
If you are a Back to Eden Gardener, you have probably witnessed how wood chip piles begin to steam and feel warm to the touch as they decompose after only a matter of days! But did you know that the center of these wood chip piles reach temperatures capable of heating water and air up to 140°F? We aren't talking about burning wood chips as a fuel for fires. We are talking about harnessing the natural heat generated from the composting process of wood chip piles. We have discovered an age-old heating method that enables you to heat your two story home, greenhouse, warehouse, or bath and shower water using composting wood chip piles!
Photograph from Jean Pain's Book, Another Kind fo Garden.
JEAN PAIN INVENTOR OF COMPOST HEATING SYSTEM
Jean Pain was an inventor from the south of France born in 1928 who discovered a brilliant way to harness the heat produced by composting wood chip piles as an off-grid heating source! He created a highly efficient method of producing 100% of his own energy needs using nothing but wood chips! Not only can his method help reduce your energy bills, it also can help you grow food year round by heating your green house or indoor growing room.
Jean Pain’s system was able to heat water at a rate of 4 L per minute. That’s almost 1 gallon per minute of hot water produced with nothing but the heat from composting wood chip piles. That kind of heat output surpasses the capabilities of many modern water heaters! Jean Pain proved his system could satisfy his daily needs for heat and hot water from clothes washing to bathing and indoor heating. How to Build A wood CHIP HEATING SYSTEM
All you really need to build a simple wood chip compost heating system is a large pile of wood chips and lots of polyethylene tubing. You’ll also want a wood chip compost soil thermometer to test how hot your pile is getting inside. Some people use horse manure in addition to the wood chips in their pile. Manure is another great heat producing resource that is often readily available and free to your wood chip compost pile. Of course depending n your needs you may want to build a slightly more advanced system.
Photograph from Jean Pain's Book, Another Kind fo Garden.
Usually your pile will start with a compressed layer of compost followed by a layer of coiled tubing followed by a layer of compressed compost until you reach the desired height. When creating a wood chip pile for the primary purpose of generating heat, it is ideal to compress the wood chip pile together into a condensed mass. This will create anaerobic bacteria which conducts more heat in the pile. In our gardens, we try to avoid too much anaerobic bacteria by allowing naturally occurring air space during decomposition. However, in wood chip compost piles used for the purpose of a heating system we want to compress the air space out of the pile. We can accomplish this sufficiently by creating a cylindrical container for the compost pile. Jean Pain used chicken wire to hold the pile in a more upright, tall formation which allows the gravity to condense the air out of the center of the pile. Many people also add hay barrels as a final perimeter for their wood chip compost piles. The key to harnessing the best heating results from your pile is to use plenty of tubing material, coiling it throughout the wood chip compost pile. For example, for a 6ft x 6 ft compost pile you will need about 300 feet of 1 inch diameter tubing. The concept is actually very simple!
Jean Pain's Book, Another Kind fo Garden.
WOOD CHIP Compost WATER HEATER
The design of your system will depend on if your goal is to heat water or to heat a space with hot air. An open loop system means the input is attached to your tap water, and the output is hot water. This is the most is a simple design, capable of providing 140°F tap water for six months at a rate of 4 liters per minute from a large wood chip compost pile.
If you are building a wood chip compost heating system for the purpose of heating water, you will also need a metal water heating tank. This is placed inside the center of the wood chip compost pile and then the pile is wrapped with the plastic tubing. As you can see in the diagram below, it works best to contain the water heater in the center of the pile in a simple construct of wire mesh and wood stakes in order to ensure the water tank is hugged closely with the compost material. 
WOOD CHIP WATER HEATER SYSTEM SUPPLIES
ADDITIONAL SUPPLIES FOR Green House & Home HEATING:
HeatING GREENHOUSE WITH Wood CHIP COMPOST
Does the thought of wood chips make you feel warm and fuzzy? In fact, wood chips literally can make you and your winter veggies stay warmer year round! Why waste your money buying expensive electric or gas heaters to keep your winter crops from freezing when you have free wood chip piles generating 140 degree temperatures at no cost!?
If you haven't already laid wood chips down on the soil in your backyard garden, farm or green house then this is the first thing we recommend you do for over-wintering vegetables. This will help insulate the soil and the decomposition of the wood chips will generate heat that helps plants grow more readily in colder temperatures. The thicker the wood chips, the more heat they will generate. Keep this in mind to avoid burning any plants. Some people heat their green house with very simple methods of compost heating. This can involve digging trenches in between rows of vegetables and adding fresh compost to decompose in place, generating heat at the soil level. A wood chip compost pile on its own left in an enclosed space will help generate some amount of heat during the decomposition process. However, wood chip pile left inside a contained space runs the potential risk of combustion if not turned and watered regularly. However, by far the hottest temperatures occurring in wood chip compost piles are at the core of the pile. Therefore harvesting the core heat to bring to the surface as Jean Pain teaches is much more effective in achieving higher heat output.
Heating Your HOME FOR FREE USING COMPOST
Of course, using the same heating system design that warms your green house can be highly effective for also heating your home. An artist living in Nova Scotia named Franz Fraitzel recently made headlines in the news for having put to use the forgotten concepts of Jean Pain by creating a furnace capable of heating an entire two story warehouse in the snow using free wood chip piles! He is applying the same principles of harnessing heat from wood chip piles pioneered by Jean Pain. Franz then used a converted industrial furnace to blow the heat into his workshop combined with donated materials and polyethylene tubing. He says he turned his industrial furnace heating bill totaling $600 / month into a one time investment of $1,000 for a lifetime of free heating. In addition to being a cheaper option for heating it is also uses renewable resource from wood chips from tree trimmings. Not only does this system offer a reduced impact on the environment it also provides a self sufficient heating source during power outages. One wood chip heating pile of the scale that Franz is using can last for up to a year of producing sufficient heat before needing to be refueled with a fresh wood chip pile!
Photograph of Fraitzel’s wood chip heating system by Carsten Knox/CBC
recycle composted wood chips in gardens
After your wood chip pile has composted for up to a year, the composted wood chips should be removed from your heating system and a fresh wood chip pile for your heating system should be built for the coming winter. However, make sure you don’t let the composted wood chips go to waste! Remove the composted wood chips and add them to your garden beds in the fall. If the composted wood chips have turned into anaerobic compost they will smell like ammonia and be very wet. In this case, you should mix in some fresh wood chips and nitrogen to help the compost return to an aerobic state which means it has sufficient oxygen present and isn't overly acidic. Simply layer fertilizer, recycled wood chip compost and fresh wood chips on your garden bed and after a few months the soil will be noticeably enriched. Your plants will love it in the spring and your soil will absorb the nutrients from the compost tea that is created all winter as they break down.  Photograph by Dana Richardson, Back to Eden Gardening.
For more details on how to build your compost powered heater there are many great plans, videos and articles available online!
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Dana Richardson & Sarah Zentz, Producers of Back to Eden Film
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