Summary & Cost Estimation for Ethanol Production Using Low-Cost Steam from Nuclear Power Plants 

Charles W. Forsberg  - Oak Ridge National Laboratory
Samuel Rosenbloom  - U.S. Department of Energy
Richard Black - U.S. Department of Energy 

(1/20) After corn, energy is the second largest cost in the production of fuel ethanol. Most of the energy demand is in the form of steam for the distillation columns and for drying the byproducts. Steam from existing nuclear power plants in the Corn Belt and along the Mississippi River can potentially be supplied at lower costs than steam from fossil fuels. The idea of using nuclear power plants to coproduce electricity and heat is not new.  Canadian nuclear power plants have been used to produce electricity and steam, with the steam used for various industrial applications ─ including the use of steam for about a decade from the Bruce Nuclear Power Station in Canada for production of ethanol.  Plants in Switzerland and Russia produce both electricity and steam for district heat. The existing technologies can assure that the steam from the nuclear plant has no radioactivity associated with it. 

Historically, steam from nuclear reactors in the United States has been used only for electricity production because (1) the prices for fossil fuels have been low and (2) there have not been markets for large quantities of steam in the rural locations where nuclear power plants are located. The development of fuel-ethanol production from corn is now creating a new potential market for large quantities of steam from existing commercial nuclear reactors.  The size of corn-ethanol plants is rapidly increasing, as is the corresponding steam demand per plant. The scale of ethanol production is now sufficiently large to consider using steam from nuclear power plants. 

The price of nuclear plant steam can be estimated from the price of electricity. A nuclear power plant produces steam that can be sold or used to produce electricity. The utility will demand at least the same revenue from the sale of steam as the sale of electricity. A rough estimate of the price of steam can be calculated from the wholesale price of electricity. An example can clarify this. The price of electricity varies across the country, thus this example will use the recent average market price for wholesale electricity in Minnesota of $53.89/MWhr(e). Minnesota is a major producer of fuel ethanol and has nuclear reactors at Monticello and Prairie Island. The efficiency of nuclear power plants is ~33%; that is, if one less BTU of electricity is produced, three BTUs of steam become available. However, nuclear reactors produce high-temperature steam whereas ethanol plants require only relatively low-temperature steam. In converting high-temperature steam to electricity, 40% of the electricity is obtained by the time the steam pressure is 150 psi (suitable for ethanol production) with the remaining 60% of the electricity produced in the low pressure turbines. Using this information, a rough estimate can be made of the corresponding price of steam from a nuclear plant given the price of electricity. 

$53.89/MWhr(electricity) x 0.33 x 0.6 =   $10.67/MWhr(steam)  = $3.13 per million BTU. 

The price of electricity is lower at night than during the day. If some of the steam demand (such as for byproduct drying) can be shifted to the night time, steam costs may be a half or third as much. There are constraints. Obviously, the ethanol plant must be built next to the nuclear plant. Only about half of the nuclear power plants (50 plants) in the United States are candidates for supplying steam to ethanol plants given the logistics of transporting corn. There are other challenges that must be addressed. The historical experience, the challenges, the business risks, and the potential gains in using steam from existing nuclear power plants are described.

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