Biogas at Home


| 10/22/2014 8:28:00 AM


Tags: biogas, waste management, home power, Warren Weisman, Oregon,

As we head out the door on our road trip to the 2014 Mother Earth News Fair in Topeka, Kansas, I wanted to give an idea of how much energy can be generated at home using biogas while using the example of our home biogas digesters we will be exhibiting at the event. Home biogas and solar – both photovoltaic electric and solar thermal – would complement one another quite well. Biogas provides excellent, clean burning fuel for year-round cooking energy and a small amount of stand-by electric, while PV can do the heavy lifting for electric and solar thermal for heating and hot water.

2m3sideview

Just as solar panels depend on the amount of available sunlight, the amount of biogas that can be produced depends on the amount of organic waste available. A typical American household with a lawn or garden will generate enough energy to cook three meals a day. Our two cubic meter (525 gallon) home digesters are intended to be fed between 10 and 30 pounds of mixed waste per day, such as table scraps and garden waste, animal manure, grass clippings and tree leaves. This works out to be between a third and a full 5-gallon bucket per day, depending what temperature they are operated at. The units are fully insulated and have a heat exchanger filled with pet-friendly glycol beneath the digestion chamber intended to connect to an evacuated tube solar heater. Naturally, a wintertime hoop house would help improve performance.    

Operating

Temperature (degrees F)

Daily Waste

Energy Equivalent per Month

(25 pound LPG cylinders)

55°

10 pounds

LPgbottle

75°

20 pounds

LPgbottleLPgbottle

100°

30 pounds

LPgbottleLPgbottleLPgbottle

Under the lid is the key to Hestia’s simple operation, indicator lines show when the water level is too high (yellow arrow) and too low (blue arrow). Normal operating water level will be between these two lines. If you cannot see any lines, you know it is time to remove liquid biofertilizer; if you can see two lines, you know to add some water.

2m3lidinletlines

This baffle separating the inlet from the digestion chamber serves a further function as a built-in pressure relief system. If gas is allowed to build up for a few days, say, during a family vacation, the gas will push down the water level in the digestion chamber until it “burps” out through the inlet. Eliminating the need for any pressure relief valves that could become clogged and ensuring a failsafe pressure relief.




Crowd at Seven Springs MOTHER EARTH NEWS FAIR

MOTHER EARTH NEWS FAIR

Sept. 15-17, 2017
Seven Springs, PA.

With more than 150 workshops, there is no shortage of informative demonstrations and lectures to educate and entertain you over the weekend.

LEARN MORE