FYI: Benefits of Combined Heat and Power in Corn Ethanol Plants

To date, CHP and ethanol industry stakeholders have recognized that the efficiencies of CHP could further improve energy use patterns of dry mill ethanol plants, but the levels of impact have been unclear.

This paper by the U.S. Environmental Protection Agency Combined Heat and Power Partnership summarizes an analysis of state-of-the-art natural gas-, coal-, and biomass-fueled dry mill ethanol plants—comparing energy consumption and CO2 emissions of the ethanol production process with and without CHP systems.  . . .

The analysis shows that the use of CHP can result in reductions in total energy use of almost 55 percent over state-of-the-art dry mill ethanol plants that purchase central station power rather than use CHP. With certain CHP configurations, CO2 emission reductions from using CHP to displace central station power even exceed the CO2 emissions from the CHP system and ethanol plant, resulting in negative net CO2 emissions for the plant compared with base case conditions. . . . more

I had thought that plants employing CHP were more common than indicated in this report.  . . . No wonder power consumption is such a big concern.  Of course lower power comes at the price of higher capital costs, but after all these plants are part of the energy industry that should be aware of these costs.  And when are these plants going to start using part of their product to generate their power requirements?  Get with the program!

Comments

[brian hans]

'Of course lower power comes at the price of higher capital costs, but after all these plants are part of the energy industry that should be aware of these costs. And when are these plants going to start using part of their product to generate their power requirements? Get with the program!'

Coal = $35/t delivered. Corn = $130/t delivered. Which would your CPA tell you to use?

The way to get business off of coal is to make it cost competitive with other forms of energy. This means a CO2 tax of ~$25/t emissions or some other way to get it to $120/t.

[ty cambell]

To supplement or eliminate fossil fuel consumption, biofuel plants are being run on waste products such as adjacent manure producing biogas, or baled local biomass crops, or local biomass waste. A new process uses corn distillation waste sludge, and another uses surplus distillers grains to provide production power. Wood chips, baled miscanthus grass, peach pits, walnut shells, citrus peals or surplus distillers grains – whatever is on hand – These are the things that ethanol producers are using to offset or eliminate fossil fuels. Ethanol plants integrated with adjacent or nearby sources of manure biogas are the trend. They are totally self-powered, burning no fossil fuels. 14 new ethanol plants are being built in Texas. A number of them are self-powered by manure-biogas, and most of them will rely more on water-frugal sorghum feedstock rather than corn. Different feedstocks are handled different ways. For example, there are three types or sorghum: (1) grain sorghum; (2) sweet sorghum; (3) and biomass sorghum. Sweet sorghum is handled like sugar cane. The juice is squeezed and fermented, and the fiber can be burned or digested into production power. Until cellulose biofuel is commercialized, 20 ton per acre biomass sorghum could be baled locally to power an ethanol refinery. Sorghum matures early, and grows back after you cut it. In Texas, farmers are getting 2 to 3 cuttings from one planting, with little or no irrigation. Arid Oklahoma is also going sorghum. Arizona has the best example of a totally self-powered biofuel refinery - integrated with a dairy farm - in Vicksburg. This is a 10 to 1 return, because the distillers grains byproduct is fed directly to onsite cows, and their onsite manure powers the whole operation. The feedstock is corn, which is fractionated, and processed into ethanol (starch), biodiesel (corn germ oil), and distillers grains (protein). Integration is what is making biofuel production highly profitable. If you were to do a case by case study, today’s efficiency ratio is well above outdated reports. First generation ethanol continues to evolve.

[Invisible Green Hand]

I posted some additional perspectives on the study here, if you're interested in exploring/debating the issue further:
http://invisiblegreenhand.blogspot.com/2007/12/making-ethanol-production-cheaper-and.html

[Kit P]

TY thanks for the update.

Anaerobic digestion (AD) of manure has a number of benefits:

1.Reduce ghg by capturing CH2 and N2O
2.Reduce odor
3.Reduce air and water pollution
4.More efficient capture of nutrients (N,P,K) in manure
5.More efficient use of nutrients fro growing crops
6.Reduce ghg associated with producing ammonia
7.Reduce environment impact of strip mining and process potassium and phosphorous
8.Reduce safety hazards associated with manure handling
9.Reduce ghg associated with offsetting fossil fuels.
10.Reduce wind and water erosion by producing organic fertilizer

Decaying biomass produces CH2 and N2O with a ghg potential of about 21 and 310. By processing waste using anaerobic digestion (AD), ghg is captured and converted to energy. Nitrogen, potassium, phosphorous and micro nutrients are converted organic fertilizer which bind soil together to prevent erosion.