Renewable Energy - biogas

Are there any incentives

There are many federal and state funding sources to help finance the cost of a digester. 

Producers also can contact their State Rural Development Office Energy Coordinator for assistance in identifying and applying for grants and loans.

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Can I obtain financing

Beyond traditional banks, there are several other mechanisms to finance on-farm biogas recovery systems.  Some companies and utilities offer power purchase agreements, in which the digester is financed and owned by a non-farm entity, and the famer is paid a price per kilowatt hour for providing manure for electricity generation.  These financing arrangements vary, but a general rule is the party who pays the most to finance the project retains the most from the long-term revenues.  The U.S. EPA AgSTAR Program directory of professionals specializes in digester design and financing.

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How much will it cost

While the upfront cost of a digester can be significant, under the right conditions, one can pay for itself in three to seven years.  Additionally, anaerobic digestion systems are cost competitive with conventional waste management systems, as many use the same technology. One benefit of a digester is that it can generate revenues through energy production over its lifetime. The installed cost of a covered, heated digester system can range from $200 - $450 per cow, plus annual operating and maintenance costs.  Conventional waste storage and treatment systems cost between $200 - $400 per cow. The U.S. EPA detailed cost equations for digesters can help in planning.

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What is a biodigester

Anaerobic digesters, or biodigesters, are systems that break down manure in oxygen-free conditions. Biogas, a mixture of methane, carbon dioxide, and other gases, is a natural product of anaerobic digestion, and can be captured for use in energy generation. Biogas recovery systems on digesters can reduce energy costs, odor, and the environmental impact of dairy operations.

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What is the benefit

The benefits of anaerobic digesters are multifold.  First, digesters provide a waste management system for dairy operations, which help reduce odor and protect water quality.  Second, when biogas is flared or used for energy production, it destroys methane, a very potent greenhouse gas.  Finally, if designed properly, digesters can provide a significant cost savings and revenue stream, through gas and electricity sales, charging tipping fees for waste disposal from other operations, and by generating bedding for dairy operations.

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What kind of digester do I need

There are three main types of digester, each of which is suited to different conditions.

  • Covered Lagoon – The covered lagoon is the most basic type of digester.  It comprises a large lined or earthen lagoon, outfitted with a gas-tight cover.  These systems typically receive liquid manure (less than 2 percent solids) from flush management systems.  Covered lagoon digesters work best in warmer climates, such as the southern United States, as these conditions allow for greater biogas production.  In colder temperatures, covered lagoons may not produce sufficient gas for use in a generator, but can still be flared to reduce greenhouse gas emissions and odor.

  • Plug Flow Digester – Plug flow digesters use covered, insulated tanks that are heated to generate biogas.  Plug flow systems can handle thicker manure (11-14 percent solids), and because they are heated, are well suited to any climate.  Excess biogas can be used to run a generator and digested solids can be separated and reused as bedding.

  • Complete Mix Digesters – Complete mix digesters use covered, insulated tanks that heat and mix manure to generate biogas.  Complete mix digesters are best suited for manure with 3-10 percent solids and require heating coils and a motor-driven mixer to circulate the contents.  Excess biogas can be used to run a generator and digested solids can be separated and reused as bedding.

 

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Where can I find more information

If you would like a detailed preliminary assessment of your farm's potential for a digester, call DFA Energy at  816-801-6146.

The U.S. EPA AgSTAR Program provides detailed information on all aspects of digester development at the following links:

Industry directory
State incentives for renewable energy
Best practices guide: Every savings opportunity for dairy

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