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Positive Effects Culhane’s invention was fi rst installed in countries where many people lived off the grid. And it’s had a major impact. Households using biodigestors no longer

need to burn wood for cooking, so air pollution is reduced. T at’s important because smoky fi res can cause health problems for people living around them. Fewer trees are now cut down for fuel.

T at means that deforestation—widespread tree removal—has slowed down around areas using biodigesters. T at’s good news because deforestation threatens wildlife habitats and causes fl ooding. Using biodigesters also keeps communities

cleaner. Because the biodigestor is fed food scraps and other organic waste, garbage is no longer around to attract fl ies, rats, or other wild animals. Dumping toilet waste in the biodigester keeps the waste from contaminating water supplies with disease- causing microbes.

Reaching More Homes Culhane saw how well his machine was working in remote areas. Now he is focusing on areas where most people live on the grid and have large carbon footprints. By designing smaller biogesters, more households can have their own energy-producing systems. T is reduces the use of fossil fuels. Culhane knows that the smaller biodigesters

can’t produce all of the energy needed by a household in the United States, Europe, or other areas on the grid. But replacing even a small amount of fossil fuel energy with biogas can make a big diff erence to the environment. For example, a biodigester might produce

just enough gas to cook with. Or it might provide enough energy to heat water for showers and baths. While it doesn’t sound like a lot, it still represents a signifi cant savings in the amount of energy that needs to be purchased. So the carbon footprint of a household gets smaller.

‘Domestic Dragons’ T ere’s another advantage to using a biodigester. T e rich, liquid fertilizer it produces can be used to grow plants. Culhane urges people to use it to grow food plants such as tomatoes and lettuce. T ese plants can grow without soil if they are nourished by the fertilizer. Culhane places plants in towers made of

recycled scrap materials. He puts netting inside the towers to support the plants’ roots. He pours fertilizer over the roots every day or so. Plants begin to grow. T ese gardens use very little space. People living in cities can put their tower gardens on patios, rooſt ops, and porches. Culhane calls the biodigesters “domestic

dragons” for the fl ame they produce. He uses one in his own home. He believes strongly that biodigesters provide an unending and sustainable supply of benefi ts. Biodigesters reduce our carbon footprint.

T ey reduce air pollution and deforestation. T ey are cost-effi cient. T ey are easy and safe to use. T ey turn every bucket of organic garbage into an hour or two of odorless cooking gas and a bucket of fertilizer for growing food without soil. Culhane says, “It is a win–win solution and explains why I live with such hope and optimism for the future.”


biodigester: a device that uses organic waste to produce a gas that people can use for energy

biomass: plant material and animal waste used as a source of fuel

carbon footprint: the amount of carbon dioxide and other gases released during a given period

grid: a network of wires that carries electricity


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