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Dome of a sewage sludge digester fermenter facility

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

Methane Digesters

Reduce SourcesElectricityShift Production
Reduce SourcesIndustryUse Waste
6.18–9.83
Gigatons
CO2 Equivalent
Reduced / Sequestered
(2020–2050)
$173.4–284.78
Billion $US
Net First Cost
(To Implement Solution)
$-2.83–-1.63
Billion $US
Lifetime Net
Operational Savings
Industrial-scale anaerobic digesters control decomposition of organic waste, and convert methane emissions into biogas, an alternative fuel, and digestate, a nutrient-rich fertilizer.

Solution Summary*

Methane Digesters (Large)

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.

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Methane Digesters (Small)

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.

Anaerobic digestion is used in backyards and farmyards around the world, and that use is on the rise. Small-scale digesters dominate in Asia. More than 100 million people in rural China have access to digester gas, which is used for cooking, lighting, and heating. In fact, during his years in ancient China, Marco Polo encountered covered sewage tanks that produced cooking fuel.

Biogas can reduce demand for wood, charcoal, and dung as fuel sources and therefore their noxious fumes, which impact both planetary and human health. Digestate enriches home gardens and small agricultural plots.

* excerpted from the book, Drawdown
Impact:

We project that large methane digesters can grow from current estimated values of 0.7% of global electricity generation (around 100TWh) to 487-761 TWh by 2050. The cumulative results would range from 6.2-9.8 gigatons of greenhouse gases emissions avoided at marginal first costs of $173-285 billion.