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Methane Digesters (Large)

This sewage sludge digester fermenter facility, sewage treatment plant works, produces methane biogas as a bi-product.

Agricultural, industrial, and human digestion processes create an ongoing (and growing) stream of organic refuse. Without thoughtful management, organic wastes can emit fugitive methane gases as they decompose. Methane creates a warming effect 34 times stronger than carbon dioxide over one hundred years.

One option is to control decomposition of organic waste in sealed tanks called anaerobic digesters. They harness the power of microbes to transform scraps and sludge and produce two main products: biogas, an energy source, and solids called digestate, a nutrient-rich fertilizer. The digestion process unfolds continuously, so long as feedstock supplies are sustained and the microorganisms remain happy.

When produced at industrial scales, biogas can displace dirty fossil fuels for heating and electricity generation. When cleaned of contaminants, it can be used in vehicles that would otherwise rely on natural gas. On the solids side, digestate supplants fossil fuel-based fertilizers while improving soil health.

Germany leads the way among established economies with nearly eight thousand methane digesters as of 2014—almost 4,000 megawatts of installed capacity in total. Adoption is increasing in the United States, including use at the waste water treatment plant for the nation’s capital.

Technical summaries for each solution will be available May 1, 2017.

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