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Anaerobic Digester: Pros & Cons

Consistent Power - As the amount of waste is produced continually, such as with a dairy farm, there is a constant stream of inputs into the digester creating a stable source of electricity generation. Each dairy cow can produce 2kWh to 3kWh of electricity per day, which can be used to power the farm and/or be sent to the grid.

GHG Reduction - Dairy and swine manure make up the majority of the of livestock emissions that contribute 7% to GHG emissions. Adding digesters at the technically feasible farms could reduce methane release by 66%. These reductions in Greenhouse Gas emissions can earn carbon credits which can be sold to generate an additional source of revenue.

Improved Water Quality - By going through the digester the waste streams remove phosphorous and metals that could otherwise end up contaminating water supplies.

Renewable - Animal or human waste is a continual source of input material that does not use any natural resources.

Odor Reduction - Placing waste streams in digesters, rather than leaving them exposed to the environment, can reduce odors at farms, landfills and municipal waste plants.

Valuable By-Products - The digestate (compost and fertilizer) can be used or sold for farm use, creating an additional revenue stream of up to $150/cow.

Expensive - Installation costs on average $500 per cow, which on a 500 cow farm would cost $250,000. In addition, operating expenses range from $11,000 to $51,000 annually. Despite the cost savings/revenue potential, it may be difficult for farmers to obtain financing for these systems.

Large Farms Only - Anaerobic digesters are economically feasible for larger farms. The EPA suggests farms should have at least 300 cows before installing a system, making it difficult for smaller farmers to capture additional revenue through this process.

Time Consuming - System operation and maintenance is estimated to take 30 to 60 minutes per day to ensure efficient operation.

High Land Use - The larger the farm, the greater the land use will be for the manure tank, as well as the digestate once the manure has completed the digester cycle.

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