CACHE / AIChE Modules on Energy in the Curriculum
Module Title: Energy Emissions Analysis
Module Author: Jason Keith
Author Affiliation: Michigan Technological University
Concepts: Energy Emissions
Problem Motivation: The availability of energy has become an important part of our society. In
this and related problems, we will discuss issues of energy consumption, energy reserves, and
energy related emissions. Furthermore, we will analyze conventional and alternative energy
systems. A particular emphasis will be placed on the generation of hydrogen for use in fuel cells
for transportation and/or stationary applications.
Problem Information
Example Problem Statement: The heat of combustion of gasoline is about 125,000 Btu / gallon.
Assuming gasoline is isooctane (C8H18) and perform the following calculations. The density of
gasoline is 44.9 lb/ft3.
a. Write the stoichiometric equation for isooctane combustion with oxygen.
b. Determine the emissions in lb CO2 / lb C8H18
c. Determine the emissions in lb CO2 / MM Btu
Example Problem Solution:
a) The stoichiometric equation is:
C8H18 + 25/2 O2 → 8 CO2 + 9 H2O
b) Determine the emissions in lb CO2 / lb C8H18
For convenience we will use English units to solve this problem. The stoichiometric equation
shows that for every lbmol of isooctane, there are 8 lbmol of carbon dioxide emissions.
Thus,
 8lbmol CO2   44lb CO2   lbmol C8 H18 
lb CO2


  3.1

lb C8H18
 1lbmol C8H18   lbmol CO2   114lb C8H18 
c) Finally, the heat of combustion can be used to determine the emissions per unit of
energy.
 3.1 lb CO2  
  44.9lb C8H18   ft 3  106 Btu 
lb CO2
gal




  149


3
ft
MM Btu
  7.48gal  MM Btu 
 lb C8H18   125,000 Btu  
Home Problem Statement: The heat of combustion of ethanol (C2H5OH) is about 76,000 Btu /
gallon. Perform the following calculations. The density of ethanol is 49.2 lb/ft3.
a. Write the stoichiometric equation for ethanol combustion with oxygen.
b. Determine the emissions in lb CO2 / lb C2H5OH and compare with gasoline.
c. Determine the emissions in lb CO2 / MM Btu and compare with gasoline.