Learn to build a DIY anaerobic digester to turn biomass into clean, renewable biogas energy.
About five years ago, writer and renewable energy aficionado
Warren Weismann was researching ancient Greece for his novel when he
stumbled across information that the Greeks had built anaerobic digesters to produce
methane. He then read about similar archaeological evidence in ancient Syria and China. But it was the modern biogas
boom in China that got him
most excited and distracted him from his writing career: Tens of millions of
home-scale biodigesters have been built in China over the last century, with
the pace of construction still accelerating. Warren wanted one for himself.
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After a few years of further research, including conversations
with colleagues in India and
Nepal, where small-scale
biogas production is prevalent, Warren
modified traditional designs to create a plan for his own 700-gallon biodigester.
He was living at Maitreya Ecovillage, a threeblock community and
green-building-oriented neighborhood near downtown Eugene, Oregon.
After building his first biodigester last year, he’s become increasingly
excited about the possibilities for home-scale biogas, and has established Hestia
Home Biogas to build biodigesters locally and consult on biodigesters across
Back from Obscurity
Biogas has been used for lighting for at least a century,
and possibly millennia. But it was mostly abandoned in the United States
after cheap and abundant fossil fuel was harnessed in the early 20th century.
Home-scale biodigesters have remained on the sidelines in the developed world,
but are poised for a comeback as interest in a replacement fuel increases.
There are good reasons to consider building biodigesters for
a community, small farm, or even home. Biodigesters yield two products that are
extremely useful for the home and garden—high-nitrogen compost and flammable gas.
Biodigesters anaerobically (without air) break down organic
matter in a slurry held in a tank. The nitrogen remains in the composted slurry
as ammonia, a vital plant nutrient. The flammable gas produced by biodigesters
is about twothirds methane and one-third carbon dioxide—very similar to natural
gas—making it a good cooking fuel. Cooking requires intense direct application
of heat on demand, and renewable options for accomplishing this are limited.
Solar energy is dispersed and not consistently available, making solar cooking challenging,
and burning wood contributes to particulate pollution and further depletes
diminishing resources in the developing world. Cooking is not a huge consumer
of energy in the industrialized world, but doing it more sustainably is challenging. Unlike cooking with solar electricity,
biodigesters can be assembled with readily available materials by a handy homeowner.
Any type of propane or natural gas stove will run on biogas. For maximum
efficiency, propane stoves will require a larger air inlet.