Combined Heat and Power can cut total net energy use by 55% in dry-mill ethanol plants. - US EPA

[JohnWxy]

Report: Combined Heat and Power can Significantly Alter Energy Consumption and Carbon Emissions for Corn Ethanol Production
20 December 2007

The adoption of combined heat and power (CHP) in dry mill ethanol plants can reduce total energy use by up to almost 55% over state-of-the-art dry mill ethanol plants that purchase central station power and can result in negative net CO2 emissions depending upon the fuel type used and CHP configuration, according to an updated report by the US Environmental Protection Agency’s (EPA) CHP Partnership.

The analysis only considers the energy consumed in the plant itself; it does not consider the energy consumed in growing, harvesting, and transporting the feedstock corn, or in transporting the ethanol product.
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In all cases, fuel consumption at the plant increases with the use of CHP. However, total net fuel consumption is reduced, as electricity generated by the CHP systems displaces less efficient central station power. In the two natural gas CHP cases with excess power available for export (Cases 2 and 3), the displaced central station fuel represents a significant credit against increased fuel use at the plant. The total fuel savings for Cases 2 and 3 are 44 percent and 55 percent, respectively, over the natural gas base case.

Total CO2 emissions are reduced for all CHP cases compared to their respective base case plants. Total net CO2 emissions in Case 2 represent an 87% reduction compared to the natural gas base case. Total plant CO2 emissions for Case 3 are actually less than the displaced central station emissions, resulting in a negative (-0.71 pounds per gallon) net CO2 emissions rate compared to the base case.
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cutting total net energy consumption by half results in doubling the net gain on energy inputs for the processing of the feed-stock into ethanol (this does not include the farm costs which is about one fourth the total energy inputs to make ethanol). So this would reduce your total process energy about 38% - 39%.


a link to this report was posted as a response to a thread some time ago by Fledermaus, but knowing how disinclined some are to reading a long report I thought this article had it's value as a summary.

link to full report

[DCKit]

1. I hope they're not talking about using the waste corn from the ethanol process...

because that's an excellent source of processed animal fodder - it's already halfway broken down by fermentation.

[JohnWxy]

2. I know you can use corn stover and of course the really good bio-fuel is cattle poop using an

anaerobic digester. this can almost entirely eliminate the use of any fossil fuel. THis also eliminates the farmers need to deal with the cattle poop as waste which costs money and uses land.