With only minor modifications, biogas can be used to fuel a conventional tank-type gas water heater, thereby allowing the biogas home producer to get hot water ‘off the grid’. Heating your water without using nonrenewable energy sources not only saves money, it helps rid the environment of pollution caused by the run-off from livestock farming and the methane gas produced at landfill sites.
Biogas is a renewable energy source created by the natural processes of fermentation and decay. A typical home biogas unit consists of a digester (or fermentation tank) and a gas holder. The digester is usually a short cylinder with a feeder tube on one side into which the homeowner pours dung or other specific types of organic waste. As the waste ferments, the biogas is then siphoned off and collected in the holding tank. Nutrient rich slurry is drained out a separate pipe once the biogas is extracted from the manure and this slurry by-product can then be used as fertilizer or garden compost.
A conventional gas water heater is made up of an insulated water storage tank with a pipe that feeds cold water into it and a pipe that runs hot water out of it to your sink, shower, and washing machine. Under the tank is a gas burner that is kicked on by a thermostat to keep the water in the tank evenly hot. A relief valve on the side of the tank controls the pressure inside the tank.
On one side of the gas water heater is a gas supply line, a gas shut-off valve, and a gas burner control. In order to use biogas that you produce at home to heat hot water, you will need a modified hot water heater that is set up to burn methane gas, which is the main ingredient in biogas but is not present in LP or natural gas that you pay to burn.
Some areas of the United States are already using biogas in ordinary daily applications. Much of the biogas currently used for gas hot water heaters and for electricity production comes from the methane produced at landfills and at dairy farms. You may already live in an area where biogas is produced by your public utility.
Biogas is also being successfully used in third world countries such as India, where animal waste is a normal part of daily life. In foreign countries where home biogas production has caught on, it is typically used for cooking and for electricity production, not to fuel gas hot water heaters but there is no reason it cannot be used this way.
If you own livestock, using biogas to fuel your hot water heater may be an excellent option for you, and many resources can be found online that will help you get started and help you decide how to best use the waste products you have on hand.
