Positive Effects Culhane’s invention was fi rst used in countries where many people lived off the grid. And it’s had a major impact. Households using biodigesters 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 cut down for fuel. T at’s


good news because removing trees destroys wildlife homes and causes flooding. Biodigesters also keeps communities


cleaner. Because the biodigester is fed food scraps and other waste, less garbage lies around to attract flies and other wild animals. Dumping toilet waste in the biodigester keeps disease-causing microbes out of the water supply, too.


Reaching More Homes Culhane’s invention worked well in distant areas. So now he looks at areas where most people live on the grid. He made smaller biodigesters. T at way


households could have their own energy- producing systems. T is would reduce the use of fossil fuels. Culhane knows that a smaller biodigester


can’t produce all of the energy needed by a household in a lot of 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. T at can save on the amount of energy that needs to be purchased. So the carbon footprint of a household would get smaller.


‘Domestic Dragons’ Biodigesters have another advantage. T e rich, liquid fertilizer they produce can be used to grow plants. Culhane urges people to use it to grow food plants such as 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 pours fertilizer over the roots every day or so. T e gardens use very little space. People living in cities can put them on porches and rooſt ops. Culhane calls the biodigesters “domestic


dragons” for the flame they produce. He uses one in his own home. He believes strongly that they provide huge benefi ts. T ey reduce our carbon footprint. T ey


reduce air pollution and protect trees. T ey save money. T ey are easy and safe to use. T ey turn every bucket of garbage into odorless cooking gas and fertilizer for growing food without soil. Culhane says, “It is a win–win solution that gives me great hope for the future.”


WORDWISE


biodigester: an invention that uses 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


NOVEMBER—DECEMBER 2015 23


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