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Combined Heat and Power Partnership

Dry Mill Ethanol

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An Innovative Solution

An innovative partnership between an ethanol plant and rural electric utility is located near the city of Macon, Missouri, where a CHP system was built in 2003. A partnership was forged between the Macon Municipal Utilities (which purchased a natural gas-fired 10 MW combustion turbine) and Northeast Missouri Grain, LLC (which built the CHP system's housing and control building).

Each organization pays for half of the cost of the natural gas that powers the turbine. The project supplies 10 MW of electricity to the utility at 50 percent lower natural gas costs than traditional generation capacity. The project provides nearly 60 percent of the plant's steam needs for ethanol production, while reducing its natural gas costs by 20 percent per year.

The CHP project requires approximately 25 percent less fuel than the typical system of onsite boilers and purchased electricity, and based on this comparison, reduces CO2 emissions by an estimated 30,200 tons per year. EPA recognized the energy and environmental benefits of this project by presenting Macon Municipal Utilities with a 2007 ENERGY STAR® CHP Award.

Analysis by the EPA's Combined Heat and Power (CHP) Partnership shows a strong technical fit for CHP in ethanol facilities and a potential reduction of approximately 15 percent in the energy intensity of dry mill ethanol production. Given the massive construction activity in this sector, the time is right to integrate CHP into new and expanding dry mill ethanol facilities and to ensure that CHP is part of the base design for future cellulosic ethanol biorefineries.

CHP can be a compelling application for ethanol production facilities because:

  • Energy is the second highest cost of production.
  • Electric and steam demands are large and coincident. For a 15 to 50 million gallon per year (MGY) facility:
    • Typical power demand is 2 to 6 megawatts (MW).
    • Typical steam use is 40,000 to 150,000 pounds per hour (lb/hr).
  • Electric and steam profiles are relatively flat.
  • Facilities usually run 24 hours per day, seven days per week.

As of May 2008, more than 145 dry mill ethanol plants are operational in the United States, with a total capacity of approximately 8,500 MGY, and an additional 61 plants are under construction or are undergoing an expansion, with a collective capacity of approximately 5,000 MGY. EPA has been providing outreach and technical assistance to the ethanol industry for the past five years to raise awareness and assist ethanol developers in implementing CHP. Seventeen dry mill ethanol plants now use CHP to generate steam and electricity reliably and efficiently on site; another seven are under construction.

A variety of CHP system configurations are available for dry mill ethanol facilities:

  • Boiler/Steam Turbine CHP: Proven technology fired by solid fuel, including coal, biomass, or cofiring. Sized for thermal loads, may limit electrical production. If coal-fired, may pose permitting challenges.
  • Gas Turbine CHP: Requires supplemental steam when the turbine is sized to meet the facility's electric load. By adding supplemental firing to the system, it can be sized to meet electric and thermal loads.
  • Biomass CHP With Gasification: Least expensive fuel, but the technology is capital-intensive and still being commercialized. Considered "green" electricity if sold; tax credits could be available.
  • Integrated Volatile Organic Compound (VOC) Destruction: Produces power with steam from thermal oxidizer or incorporates VOC destruction in turbine or boiler systems; can minimize compliance costs.
  • Ethanol/Utility Partnerships: Public power companies and rural electric cooperatives are engaging in joint CHP ownership arrangements with ethanol facilities as thermal hosts in states including North Dakota, Missouri, and Kansas. For details on these win-win projects, see the CHP Partnership's article in District Energy Magazine (PDF), (8 pp, 118K).

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Additional Resources

Case Studies

The Partnership works closely with The Midwest CHP Application Center to promote CHP in ethanol plants. The Midwest CHP Application Center has developed a number of case studies Exit EPA for CHP at ethanol plants.

Presentations

The CHP Partnership has presented at numerous workshops and conferences to promote CHP at ethanol plants.

  • 2006 Fuel Ethanol Workshop & Expo, June 2006 (PDF) (14 pp, 171K) describes the voluntary CHP Partnership, depicts typical CHP efficiency for ethanol plants, and outlines a business case for incorporating CHP into the ethanol industry. Includes calculations describing potential fuel savings for natural gas-fired ethanol plants.
  • Governors' Ethanol Coalition, February 2006 (PDF) (16 pp, 692K) describes CHP for the ethanol industry; outlines CHP basics and the technology's efficiency and environmental benefits; and features the Russell, Kansas, ethanol plant and its partnership with a local municipal utility.
  • Sixth International Decentralized Energy and Cogeneration Conference and Exhibition, October 2005 (PDF) (40 pp, 1.3 MB) outlines the growth in the ethanol industry, including the effect the Renewable Fuels Standard will have on the industry, and how CHP can generate significant cost savings for ethanol production plants. CHP technology and system options are also described.
  • Governors' Ethanol Coalition, March 2005 (PDF), (26 pp, 521K) supplies information on the ethanol industry and how CHP is an excellent fit for ethanol businesses. Also includes diagrams and descriptions of CHP technology options appropriate for installation at ethanol plants. Briefly describes some of the policies that states can adopt to improve adoption of CHP by the ethanol industry.

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