What is Anaerobic Digestion and How is it Used?
Anaerobic digestion has been used for a long time and across all corners of the globe. As concerns about the environment and climate change continue to increase, the demand to generate renewable energy is growing. This is pushing many agricultural and industrial businesses to turn to waste-to-energy technologies.
Anaerobic digestion systems have been used commercially for over 30 years to reduce methane emissions, help decrease water pollution, improve organic waste disposal methods, control odors, and create renewable energy.
What is anaerobic digestion?
Anaerobic digestion is a treatment process that is used on organic materials, such as food waste, manure, or sewage sludge. Microorganisms naturally break down these materials in a tank that lacks oxygen to create an energy-rich biogas.
How does anaerobic digestion work?
The incoming waste is put into an airtight chamber that is held at a temperature between 95 to 140 degrees, typically for 3-4 weeks. Naturally occurring microorganisms and bacteria break down the organic solids and emit a biogas that is comprised primarily of methane and carbon dioxide.
What are the benefits of anaerobic digestion?
There are many benefits that come from utilizing anaerobic digestion to effectively manage organic waste. The biogas produced can be used as electricity, provide combined heat and power, or be turned into clean biomethane. Biomethane is another name for renewable natural gas (RNG) made from organic waste. RNG is the lowest-carbon fuel available and can be net carbon-negative over its lifecycle.
Anaerobic digestion also creates a nutrient-rich byproduct that is packed with organic matter and can be used directly as fertilizer. This creates a closed-loop, circular system that transforms biosolids and food waste into valued resources.
Another plus: when utilizing anaerobic digestion, the amount of waste that would typically be sent to the landfill is reduced. In turn, harmful green house gas emissions are lowered, as organic matter that decomposes at a landfill emits large amounts of methane and lowers our air quality!
When and where did it originate?
For several centuries, it has been known that combustible gas is generated when organic waste decomposes. For example, during the 17th century, Jan Baptist van Helmont of Belgium first discovered that decaying organic matter could result in flammable gas. In 1808, Sir Humphrey Davy determined that methane was present in the gases produced by cattle manure.
For decades, India, China and Western European countries have been employing anaerobic digester technology. India is credited for having created the first-ever anaerobic digester in 1859. The digester was built at a leper colony in Bombay, and utilized human waste to generate gas to meet lighting needs.
Today the United States has over 2,100 anaerobic digester sites producing biogas with 247 located at a farm, 1,241 located at a wastewater treatment site, 38 standalone sites and 645 landfill gas projects.