Manure has been used as a heating fuel for centuries in many parts of the world. With rising prices for oil, gas, electricity and other traditional home heating fuels, there is renewed interest in using manure as an inexpensive, renewable resource for home heating.
What is Manure?
Manure refers to the waste produced by livestock such as horses, cows, pigs, sheep, goats, chickens, etc. It consists of animal feces and urine along with bedding material such as straw or wood shavings.
Manure contains:
- Organic matter
- Plant nutrients like nitrogen, phosphorus, potassium
- Trace minerals
- Undigested material
- Bacteria and other microorganisms
It can be in solid or liquid form. Solid manure includes farmyard manure and chicken litter. Liquid manure refers to slurry and dirty water from washing down livestock housing.
Why Use Manure for Heating?
There are several key benefits to using manure for home heating:
- Renewable - Manure is a renewable fuel produced continuously on farms with livestock. It does not deplete finite resources like oil or gas.
- Low cost - Manure has little or no market value as a fertilizer. It is inexpensive compared to commercial heating fuels.
- Energy independence - Using manure from your own livestock provides free on-farm fuel and reduces dependence on external energy sources.
- Closed loop system - Manure can be used to produce heat and then the ash/biochar returned as a soil amendment. This closed loop reduces waste and pollution.
- Carbon neutral - Burning manure releases carbon dioxide but this is offset by carbon captured when growing livestock feed. So there is no net addition of CO2 to the atmosphere.
How Manure is Converted to Fuel
There are a couple methods for converting raw manure into a usable home heating fuel:
Composting
Manure can be composted or aged for 6 - 12 months. This allows the manure to break down, killing pathogens and weed seeds. Well-aged manure has these advantages as a fuel:
- Dry and easy to handle
- Higher energy content
- Low moisture so it burns efficiently
- Less smoke and smell when burning
The composting process converts the organic nitrogen in manure into stable organic matter and humus. This yields a better quality and more uniform fuel.
Pelletizing
Manure pellets are made by drying manure then forcing it through a pellet mill. The high pressure causes natural lignin in the manure to act as a binder. This yields firm, dense pellets.
Benefits of manure pellets:
- Higher energy density than raw manure
- Uniform shape and size burns evenly
- Low moisture content lights easily
- Handling and storage is easier
- Reduced odor and off-gassing
Pelletizing also sterilizes manure by heat and pressure. Pellets are typically made from chicken, turkey or hog manure.
Heating Systems for Burning Manure
Manure can be burned in several types of heating systems:
Outdoor wood boilers
An outdoor wood boiler consists of a firebox and heat exchanger located in an insulated shed outside the home. Water is heated by burning manure then piped underground to transfer heat inside.
Benefits:
- No indoor fire tending needed
- Manure odors and smoke vented outside
- Thermostatically controlled for convenient heating
Well-aged manure or pellets are recommended for outdoor boilers.
Indoor wood stoves
Wood pellet stoves designed for low-emission operation can burn manure pellets instead of wood. An exhaust system vents emissions outside.
Benefits:
- Low installation cost
- Convenient to operate and refuel
- Zone heating for just where you need it
Furnaces and boilers
A furnace or boiler with a manure hopper and auger feed system can provide whole house hydronic heating. Hot water or steam from the manure fire heats radiators, underfloor tubing, or forced air systems.
Benefits:
- Central heating for whole house
- High efficiency heat transfer
- Automated operation
An indoor or outdoor furnace can run on manure. Separating the firebox from living space contains odors and emissions.
Tips for Burning Manure Efficiently
Follow these guidelines for clean, efficient manure combustion:
- Use aged or pelletized manure with low moisture content
- Operate the burning device at high temperatures above 1400°F
- Provide adequate air supply and distribution in firebox
- Remove ash regularly to allow air flow
- Service equipment annually and inspect venting
- Don't overload the firebox
- Avoid idling - burn hot on a load of fuel
This ensures complete combustion, avoids smoldering, and reduces creosote buildup.
Is Burning Manure Safe?
With properly aged and pelletized manure, good combustion practices, and well-designed equipment, manure offers a safe, sustainable home heating solution. Here are some precautions:
- Aging destroys pathogens and reduces nitrogen content in manure that creates emissions when burned.
- Pelletizing allows high temperature drying that further reduces contamination risk.
- Venting systems remove smoke, particulates, and combustion gases from the home.
- Routine maintenance and cleaning of equipment prevents fouling and deterioration.
- Proper operation at high burn temperatures minimizes harmful emissions.
- Sourcing clean manure from healthy livestock fed quality feed reduces risks.
Follow equipment guidelines, allow manure to fully age, and operate the system properly to ensure safe, reliable heating.
Burning manure can provide an economical and sustainable solution for home heating needs. With some planning and preparation, manure's potential as a fuel can be harnessed without sacrifice to safety or indoor air quality.