Document ID: EPA-HQ-OAR-2005-0161-3050
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-03-26T04:00Z

CARIBBEAN BASIN ETHANOL DEHYDRATION

                                     ENERGY USUAGE AND CO2 EMISSIONS

Hydrous ethanol is imported from Brazil to dehydration plants in the
Caribbean Basin where it is processed through molecular sieve technology
into anhydrous ethanol.  The dehydration process requires steam energy
to heat and cool ethanol.  The energy used to create steam is generated
by burning fossil fuels which range from natural gas in Trinidad to
heavy fuel oil at the plants in the other countries.

Industry experts have calculated that approximately 4000 BTU’s of fuel
and .05kwh of electricity are used in the conversion of one gallon of
hydrous to anhydrous ethanol.1  All this fossil fuel energy usage
represents less than 5 gCO2MJ when calculated using the GREET model. 

Additional CO2 emissions are generated from the transportation of the
ethanol from Brazil to the Caribbean Basin and then onward to the United
States.  These emissions are no greater than from the transportation of
ethanol directly from Brazil to the United States.  

Also, pathways for Brazilian cane-based ethanol through CB ethanol
dehydration facilities are more economically viable than the pathway for
ethanol shipped via a direct route for anhydrous ethanol from Brazil to
California.  As noted by EPA in their proposed RFS2 rules, “the most
likely route(for Brazilian cane-based ethanol is) through the Caribbean
Basin Initiative”” because the ethanol would not be subject to the
54 cent per gallon and 2.5% ad valorem tariffs.  Indeed, since a duty
drawback loophole ended in September 2008, direct Brazil to U.S. ethanol
shipments have practically ceased.

In analyzing the differences in the direct Brazil to U.S. pathway and
the CB dehydration pathway to determine the lifecycle emissions, it is
necessary for a fair comparison to look at such factors as the fugitive
emissions from the pipelines carrying the hydrous or anhydrous ethanol
as well the natural gas.  Dehydration plants in the Caribbean Basin are
at or near the ports so the distances traveled- and  the accompanying
fugitive emissions -in pipelines are negligible.  This is not the case
in Brazil.  Fossil fuels such as natural gas may be shipped hundreds of
miles and even imported from Bolivia in pipelines of various age and
states of repair.

Since the same technology is used in Brazil and in CB countries to
dehydrate ethanol, the same amount of energy should be generally
required to power the dehydration process in Brazil and the Caribbean
Basin.  The dehydration plants in the Caribbean Basin are 

1. Source:  Swain, R.L. Bibb, “Molecular Sieve Dehdyrators.  How they
became the industry standard and how they work”, Chapter 19 in the
Alcohol Textbook, p. 292

newer than those in Brazil and because of age and technology are more
efficient.  These factors as well as the greater emissions from  the
cyclohexane and benzene used in the azeotropic distillation of some of
the dehydration plants in Brazil needs to be considered in comparing the
dehydration pathways in the Caribbean Basin and Brazil.  

We encourage EPA to use these factors as credits and lower the life
cycle carbon footprint of Caribbean Basin dehydration.

The energy usage differs from plant to plant in the Caribbean Basin. 
The table below indicates the range.

                         CO2 EMISSIONS FROM CB ETHANOL DEHYDRATION

                                                       

  ENERGY USAGE                            Per Gallon of Anhydrous
Produced

    Gallons of fuel oil                                             
.031   to .044

    BTU of natural gas                                            5,000

    KWH of electricity                                            .0458
to .0617

                                          CO2 EMISSIONS CALCULATIONS

                                                                        
           Natural Gas   Fuel Oil    Electricity

 CO2 emissions per gallon of 

       anhydrous ethanol produced (lbs)                         0.47    
          0.65

CO2 emissions (gCO2/MJ)                                            2.64 
             3.67

CO 2 emissions(gCO2/MJ) per gallon 

         of anhydrous ethanol produced                                  
                                   1.31

TOTAL CO2 EMISSIONS FROM 

          ENERGY USAGE                                               
3.95               4.98

Caribbean Basin ethanol dehydration emits less than 5 g of CO2/MJ from
fossil fuels used to produce anhydrous ethanol.  Credits from factors
indicated above should be applied to reduce this number.  Nevertheless,
this number should be within the life cycle threshold to classify CB
ethanol as an advanced biofuel.