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August 17, 2007

Nuclear reactor steam can lower the cost of ethanol

Steam from nuclear plants could find a significant market by using it for ethanol production

Researchers and engineers at Oak Ridge National Laboratory and the US Department of Energy are suggesting using the steam from existing nuclear power plants in the Corn Belt to reduce the costs of producing ethanol from corn and other biomass

There is one economic limitation, however. The cost of the corn delivered to a fuel ethanol plant is strongly dependent upon the cost of transporting the corn from the farm. The only nuclear reactors that can economically provide steam for this application are in the Corn Belt, along the Mississippi River or other waterways where cheap barge transportation is available, or where there is a demand for the by-products of ethanol production.

For a large ethanol plant producing 100 million gallons of fuel ethanol per year, about 80 MWt of steam is required, which represents a potential market for 150-psi (about 180 °C) steam from existing light-water nuclear power plants. This low-temperature steam is of lower value for electricity production, but it could significantly improve ethanol economics, create an expanded market for nuclear energy, reduce greenhouse gas emissions, and reduce foreign oil imports.

For about a decade, steam produced by the Bruce nuclear power station in Ontario was used for ethanol production. Plants in Switzerland and Russia produce both electricity and district heat.

The steam from nuclear reactors has been used for district heating (45 reactors), desalination (10 reactors), and industrial uses (25 reactors). Coproduced steam, however, has never been a major product of nuclear reactors for two reasons: (1) There are few customers near rural nuclear plant sites, and (2) most of the markets for steam are so small as to not be worth the complications of coproducing steam and electricity. The production of fuel ethanol from corn today, and the future production of fuel ethanol from other forms of biomass, change this. The need is for large quantities of steam in rural areas—the same areas in which nuclear power plants are located.

Based on the price of electricity, the cost of low temperature steam from a nuclear power plant is about half the cost of steam from natural gas. Last, ethanol plants traditionally operate at constant production but have the potential to shift some of the steam demand to nighttime. The largest use of energy in the ethanol production process is for distillation, which must operate at steady state. However, the energy demand for drying the animal feed by-products could potentially be shifted to nighttime.

A goal of the U.S. government is to displace 30 percent of the nation’s gasoline
use by 2030, initially by using corn, and then cellulose, for the production of
ethanol. That is an extraordinary challenge that requires increasing ethanol production by more than an order of magnitude. For this scale of operation, the total steam demand at a few hundred plants would be tens of gigawatts.

3 comments:

Snake Oil Baron said...

From what I understand, the whole idea of ethanol from corn is a cross between wishful thinking from the corn growers and a hoped for transitional step for ethanol enthusiasts - few of whom think corn and other food crops will be used in the final industry. The source of ethanol will need to be plants that can be grown on land that is too salty or otherwise unsuitable for wilderness and crops. A recent news story mentioned that the byproduct of biodiesel production can now be converted via bacterial fermentation to ethanol giving two fuels from one source. I also understand that new filtering technology could eliminate the ethanol distillation step altogether.

Perhaps the spare heat could be used for a less efficient but less energy intensive form of desalinization by heating sea water at coasts, letting the water laden air rise up insulated pipes over mountain ranges where it would normally cool to rain, and then enter non insulated pipes going down the other side of the mountain condensing to water where the denser air and liquid water would contribute to a down draft, sucking more warm wet air up the mountain.

bw said...

I recognize that ethanol production especially corn ethanol production is very inefficient. But if we are using this as a means to give aid for corn farmers for political reasons then it might as well be more efficient.

We can also use the nuclear reactor steam for other biofuel processes ideally ones that are more efficient.

DV8 2XL said...

Process heat from nuclear reactors could also be used to produce liquid fuels from coal feedstock as well.