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In order to understand the benefits and performance of alternative energy sources, comparison must be made to the current technology.  Petroleum is a fossil fuel that is the number one transportation fuel used in the world.  The following links provide information about how petroleum is obtained, used, processed, and issues surrounding petroleum energy technologies.

Home  -  Production & Usage - Oil Drilling & Refinement - Energy Analysis - Petroleum Consumption Issues - Gas Prices

Petroleum is an unprocessed fossil fuel which was formed over millions of years from naturally decaying biomass.[1,2]  Deceased plant and animal matter was covered by layers of mud, silt, and sand, which were compressed into sedimentary rock over millions of years.  Over time, geologic heat and pressure exerted on the biomass by the rock layer formed the carbon-rich crude oil, which is now found in porous rock.  Additionally, non-liquid sands and shale exist in locations without sufficient conditions to liquefy the hydrocarbon matter.[2]  Figure 1 shows the well-to-tank lifecycle of petroleum products.

Figure 1: Well-to-tank lifecycle of petroleum products.[1]


Crude oil is comprised of a variety of elements and compounds including carbon and hydrogen (in the form of hydrocarbons), sulfur and trace amounts of oxygen, nitrogen, metals and salts.[1]  Six major classes of hydrocarbons are derived from crude oil, as is described in Table 1.

Table 1: Hydrocarbon classes.[1]





CnH2n+2 general formula
Straight or branched chain molecules
Gas or liquid at ambient conditions

Methane, ethane, propane, butane


C6H5-R, where R is a longer chain molecule
Ringed structure, alternating double bonds
Typically liquid

Benzene, napthalene

Napthenes/ Cycloalkanes

CnH2n general formula
Ringed structure, exclusively single bonds

Cyclohexane, methyl cyclopentane


CnH2n general formula
Linear or branched chain, one double bond
Liquid or gas

Ethylene, butene, isobutene

Dienes/ Alkynes

CnH2n-2 general formula
Linear or branched chains
Two carbon-carbon double bonds
Liquid or gas

Acetylene, butadiene

Crude oil is retrieved from porous rock reservoirs by natural or artificial lift methods (Energy Information Administration, 2008).  In natural lift extraction, the underground pressure of the reservoir can be used to force crude oil into wells drilled from the surface to the reservoir. Natural pressure eventually diminishes such that mechanical pumps are required to generate an artificial lift. Oil can also be extracted by the waterflood or other working fluid injection methods intended to raise the reservoir pressure (Energy Information Administration, 2008).  Methods to extract crude oil from sands and shale involve mining and heating, and technological improvements are required.

Post extraction, crude oil is refined to separate the useful components listed in Table 1.  Fractional distillation, which operates on boiling point differences, is the unit operation used in oil refineries (flash demonstration).  A plethora of useful chemicals is obtained by fractional distillation, including well-known gasoline, kerosene, and lubricating oils (i.e. used to produce motor oil) (Freudenrich, 2001). Post fractionalization, chemical processing is used to break long carbon chains and obtain useful chemical entities. Chemical processing involves cracking or breaking long chains, unification or combining small pieces, and alteration or rearrangement of various sized pieces (Freudenrich, 2001).

The United States is the number one global consumer of petroleum products, as is shown by the Petroleum Consumption chart below.  This raises concerns of national security, due to the high level of petroleum imports to the US.  Reducing US dependence on foreign oil is necessary to enhance national security, and the solution to the problem will involve lowering demand, especially in the transportation sector.  Alternative and renewable transportation fuels can help to offset petroleum consumptio, however the chemical process industry stands to suffer a great loss if production of chemical feedstocks by petroleum refineries is reduced.  The development of feasible biorenewable chemical feedstock refining methodologies is a corequisite to an economy powered by alternative fuels.

Questions to be addressed:

1. How much fuel do we use directly for transportation?

2. What fraction currently is provided by each fuel type, e.g. gasoline, diesel fuel, jet fuel, other?


Freudenrich, C. (2001, January 4). How Oil Refining Works. Retrieved March 8, 2009, from HowStuffWorks:

Energy Information Administration. (2009, February). Petroleum Basic Statistics. Retrieved March 9, 2009, from :

Energy Information Administration. (2008, January). _Crude Oil Production._Retrieved March 9, 2009, from :

Energy Information Adminstration. (2007). Annual Energy Review. Retrieved April 5, 2009, from:

Kohl, Keith. (2007). The Peak Oil Crisis. Retrieved April 6, 2009, from Energy & Capital:

Home  -  Production & Usage - Oil Drilling & Refinement - Energy Analysis - Petroleum Consumption Issues - Gas Prices

This page was designed and compiled by Alex Poss, Karen Haman, and Scott Nielsen as part of the Spring 2009 course offering of Engineering Analysis of Alternative Energy Systems (52:133) at The University of Iowa College of Engineering.  Questions regarding page content should be directed to Prof. Gary Aurand.

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