Published on EGEE 401: Energy in a Changing World (https://www.e-education.psu.edu/egee401)

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Ethanol

Reading Assignment

Visit the Department of Energy, Energy Explained [1]. Read the page, "Biofuels: Ethanol & Biodiesel" then read "Ethanol" and all subpages.

Visit fueleconomy.com, and read Ethanol [2](full page)

Return to the Fuel Economy Guide Model Year 2017 [3] and read the section on page 41, "Ethanol Flexible Fuel Vehicles."

How Ethanol is Made

As the name implies, the process of producing ethanol is fermentation. Most commercial ethanol production is done using the dry-mill method. The basic steps are as follows (source: Ethanol-Blended Fuels presentation [4], Chapter 2: Ethanol Science & Technology, from the Nebraska Ethanol Board):

  • Milling. The corn (or other grain) passes through a hammer mill. It comes out as a powder.
  • Liquification. A mixture made of this grain powder, water, and an enzyme enters a high-heat cooker, where it's liquefied. The enzyme helps to break down the grain compound to aide in the liquefaction process.
  • Saccharification. The liquefied mash is cooled, and another enzyme is added to the mix. This enzyme converts the starch into fermentable sugars (dextrose).
  • Fermentation. Yeast is added to the sugar mixture to begin the fermentation process. The sugars break down to ethanol (a form of alcohol) and carbon dioxide.
  • Distillation. The fermented mixture is distilled. The ethanol separates from the solids.
  • Dehydration. A dehydration process removes water from the separated ethanol.
  • Denaturing. A small amount of gasoline is added to the ethanol in order to make it undrinkable. All ethanol used as a fuel must be made nonpotable.

Byproducts of this process, including distiller's grain and carbon dioxide, are useful in the farming and ranching industries and may be sold by the ethanol-manufacturing plant for various purposes. But according to many experts in agriculture, making ethanol a major player in the fuel industry has serious drawbacks.

Controversy

Ethanol is made by fermenting corn or grain, products which are also food. Growing the crops requires a lot of land and a lot of energy for planting, fertilizing, harvesting, transportation, and so forth. There is considerable debate about ethanol as an alternative fuel source on several fronts. First, the diversion of large amounts of crop land that could be producing food. Secondly, according to some calculations, it takes more energy to produce ethanol than is available in the ethanol itself. (Source: "Ethanol – Is it worth It?," Chemical & Engineering News [5])

And there is a third question, when one takes into account all of the greenhouse gas emissions from the entire process of producing the ethanol, does ethanol actually result in less or more emissions than gasoline?

Emissions

The Energy Independence and Security Act of 2007 (EISA) [6] gives this definition for how greenhouse gas emissions from renewable fuels are calculated:

"The term lifecycle greenhouse gas emissions means the aggregate quantity of greenhouse gas emissions (including direct emissions and significant indirect emissions such as significant emissions from land use changes), as determined by the Administrator, related to the full fuel lifecycle, including all stages of fuel and feedstock production and distribution, from feedstock generation or extraction through the distribution and delivery and use of the finished fuel to the ultimate consumer, where the mass values for all greenhouse gases are adjusted to account for their relative global warming potential."

The Renewable Fuel Standard program is a national policy that originated with the Energy Policy Act of 2005 (amending the Clean Air Act) and was expanded by EISA of 2007. Implemented by the Environmental Protection Agency, the RFS program "requires a certain volume of renewable fuel to replace or reduce the quantity of petroleum-based transportation fuel, heating oil or jet fuel." The EPA's lifecycle analysis of green house gas emissions under the RFS includes emissions related to feedstock production and transportation, fuel production and distribution and use of the finished fuel. (Not required, but for more detail see Lifecycle Analysis of Greenhouse Gas Emissions under the Renewable Fuel Standard.) [7]

As fair as this may seem, however, the devil is in the details. Controversy continues regarding which measures are used and how these calculations are made, to fairly and objectively reflect the environmental impact of alternative fuels so that they may be evenly compared.

Reading Assignment

Read Biofuels Might Hold Back Progress Combating Climate Change [8]

Optional Reading

Ethanol Emissions: Higher or Lower? [9] from factcheck.org, presents an excellent review and discussion of research findings related to ethanol's envrionmental impact.

 


Source URL: https://www.e-education.psu.edu/egee401/content/p9_p3.html

Links
[1] http://tonto.eia.doe.gov/energyexplained/index.cfm?page=biofuel_biodiesel_home
[2] http://www.fueleconomy.gov/feg/ethanol.shtml
[3] http://www.fueleconomy.gov/feg/FEG2000.htm
[4] http://ethanol.nebraska.gov/wordpress/resources/school-presentations/
[5] http://pubs.acs.org/email/cen/html/010207085554.html
[6] http://nepis.epa.gov/Exe/ZyNET.exe/P100B3F8.txt?ZyActionD=ZyDocument&Client=EPA&Index=2006%20Thru%202010&Docs=&Query=%28the%20term%20%27lifecycle%29%20OR%20FNAME%3D%22P100B3F8.txt%22%20AND%20FNAME%3D%22P100B3F8.txt%22&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&UseQField=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3A\ZYFILES\INDEX%20DATA\06THRU10\TXT\00000027\P100B3F8.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h|-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=p|f&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=2
[7] https://www.epa.gov/renewable-fuel-standard-program/lifecycle-analysis-greenhouse-gas-emissions-under-renewable-fuel
[8] http://www.scientificamerican.com/article/biofuels-might-hold-back-progress-combating-climate-change/
[9] http://www.factcheck.org/2015/11/ethanol-higher-emissions-or-lower/