A Well-to-Wheels Lifecycle Assessment of Used Vegetable
Oil Biodiesel Produced On MIT Campus
Alexander Pak
Biodiesel@MIT
Summer 2007
8/17/07
1
Executive Summary ..............................................................................................3
Methodology and Assumptions .............................................................................4
2.1 Scope of the Lifecycle Analysis ...................................................................4
2.1.1 Process Scope......................................................................................4
2.1.2 Geographic Scope ................................................................................5
2.2 Petroleum Diesel Model ..............................................................................6
2.2.1 Crude Oil Extraction..............................................................................6
2.2.2 Crude Oil Transportation.......................................................................7
2.2.3 Crude Oil Refining ................................................................................7
2.2.4 Diesel Fuel Transportation....................................................................9
2.2.5 Diesel Fuel Use/Combustion ................................................................9
2.3 UVO-Biodiesel Model ................................................................................10
2.3.1 UVO Collection/Transportation ...........................................................10
2.3.2 UVO Transesterification......................................................................12
2.3.3 Biodiesel Transportation/Fueling ........................................................14
2.3.4 Biodiesel Use/Combustion..................................................................14
Data and Analysis ...............................................................................................16
3.1 Petroleum Diesel Results ..........................................................................16
3.1.1 Energy Lifecycle .................................................................................16
3.1.2 Emissions Lifecycle ............................................................................17
3.2 Biodiesel Results.......................................................................................18
3.2.1 Energy Lifecycle .................................................................................18
3.2.2 Emissions Lifecycle ............................................................................18
3.3 Comparison of Petro-Diesel and Biodiesel ................................................19
Conclusions ........................................................................................................22
Appendix 1: Crude Oil Extraction ........................................................................23
Conventional Onshore Extraction....................................................................23
Conventional Offshore Extraction....................................................................23
Advanced Steam Injection...............................................................................24
Advanced CO2 Injection ..................................................................................25
Crude Oil Extraction Lifecycle Inventory..........................................................26
Appendix 2: Transportation Models for Petro-Diesel and Biodiesel ....................27
Crude Oil Transportation .................................................................................27
Diesel Fuel Transportation ..............................................................................29
UVO Collection/Transportation........................................................................30
Biodiesel Fuel Transportation..........................................................................34
Appendix 3: Crude Oil Refinery...........................................................................36
Appendix 4: Transesterification Reactor .............................................................37
Appendix 5: Engine Combustion of Petro-Diesel and Biodiesel..........................38
Diesel Fuel Combustion ..................................................................................38
Biodiesel Fuel Combustion..............................................................................38
References .........................................................................................................40
2
Executive Summary
Biodiesel@MIT, a student group at MIT, has been working to install on campus a
batch reactor that recycles used vegetable oil (UVO) from dining halls and
converts it into biodiesel fuel. The group has determined that MIT has the
potential to produce 3000 gallons of biodiesel every year, enough to run the MIT
Fleet on B20 (20% biodiesel, 80% petroleum diesel blend) fuel.
Biodiesel is theoretically a cleaner alternative energy source as it comes from an
agricultural feedstock and thus, requires less fossil fuel in order to produce it.
However, many other energy and material inputs are required to produce
biodiesel instead of petroleum diesel. Besides the actual production of biodiesel,
MIT also has to store, collect, and filter UVO and then distribute the biodiesel.
The purpose of this study is to do a comprehensive audit of the energy input and
emissions of two possible scenarios: MIT’s continued use of petroleum diesel or
a switch to a biodiesel blend fuel source.
In the first scenario, the comprehensive audit considered all of the material and
energy inputs/outputs involved in petroleum diesel use, from oil extraction to enduse combustion. This assessment is known as a well-to-wheels analysis, a type
of lifecycle analysis (LCA). An extensive lifecycle analysis incorporates factors
such as the construction and decommissioning of the equipment used. Those
factors, however, were not included within the scope of this study.
In the second scenario, both petroleum diesel and biodiesel blend together in the
end product. The audit, then, must also consider the material and energy
inputs/outputs involved in the production of UVO-based biodiesel, from the
gathering of UVO to end-use combustion. To this end, this study integrates
different lifecycle studies that have been done on both petroleum diesel and
biodiesel with varying assumptions. Following their methodologies, this study has
developed a model that simulates the energy and emissions flows in petroleum
and biodiesel use specific to MIT Campus.
Based on the study’s proposed model, biodiesel is a cleaner, environmentally
friendlier alternative to petroleum diesel. Lifecycle energy use, carbon dioxide
emissions and other air emissions such as NOx are all reduced in biodiesel use.
The following table summarizes the benefits of biodiesel.
Type
Energy Use
Fossil CO2
NOx
SOx
CO
PM10
All HC
% Reduction in B100
81.3
91.7
0.4
38.2
44.2
79.6
66.7
3
% Reduction in B20
16.3
18.3
0.1
7.7
8.8
15.9
13.3
Methodology and Assumptions
The purpose of this study is to document and determine the environmental
feasibility of introducing a UVO-based biodiesel blend into MIT’s Fleet.
Furthermore, this study also aims to provide a detailed lifecycle analysis
methodology for future studies to use and improve in their own LCA’s.
The well-to-wheels assessment of petroleum diesel mainly follows the
methodology of the 1998 report by the National Renewable Energy Laboratory
entitled “Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an
Urban Bus.” The assessment of biodiesel is based on a custom model this study
developed as well as a model developed by Argonne National Laboratory,
“Greenhouse Gases, Regulated Emissions, Energy Used in Transportation”
(GREET). The study emulates the life cycle inventory (LCI) method done in the
NREL report. The LCI quantifies and compares the energy and material flows
involved over the entire lifecycle of both petroleum diesel and biodiesel. The
report, and this study, then compares the two fuels on the basis of a brakehorsepower-hour (bhp-h). This comparison is necessary as fuel chemistry affects
engine performance.
2.1 Scope of the Lifecycle Analysis
2.1.1 Process Scope
The two scenarios this study is comparing are the usage of petroleum diesel
versus the usage of UVO-biodiesel blend in MIT’s fleet. In the LCA, the study
considers all of the processes involved in the production and use of petroleum
diesel. These processes are as follows:
•
•
•
•
•
Extraction of crude oil
Transportation of crude oil to oil refineries
Refining of crude oil into diesel fuel
Transportation of diesel fuel to site
Engine use of diesel fuel
For each of these steps, an LCI was done to compare the overall energy inputs
and emissions with those of the second scenario. However, rather than
considering the entire lifecycle of the biodiesel fuel, the scope of the study was
limited to only the processes that would change with the installation of the
biodiesel reactor. For the purposes of this study, the models will follow the
energy inputs and emissions for B100. However, when the study compares the
petroleum diesel to the biodiesel blend, this study’s results will be converted to
reflect those of B20. These processes are as follows:
•
Collection and transportation of the used vegetable oil to the reactor
4
•
•
•
Conversion of UVO to biodiesel
Transportation and fueling of the fleet with B100
Engine use of B100
The second scenario disregards the feedstock agriculture, transportation and
conversion to oil of the biodiesel as both scenarios include the usage of
vegetable oil on campus dining halls.
2.1.2 Geographic Scope
Most of the existing literature in biodiesel LCA’s focus their analyses on a
national average. This study, however, tries to specifically base its analysis on
the location of MIT’s campus. Most of the crude oil in Massachusetts comes from
foreign sources. Therefore, the study includes international data in its
assessment. Using Petroleum Administration for Defense District (PADD) data
and Massachusetts’ Energy Profile, the LCA shapes the transportation models to
reflect Massachusetts’ specific means of receiving and refining both crude oil and
diesel fuel. Unfortunately, not enough information could be found to study crude
oil extraction and refining on a geographic specific level. Instead, this study uses
the 1998 NREL report’s data based on international and national averages
respectively. The following two tables summarize the geographic scope of this
study.
Table 1 – Geographic Scope of Petroleum Diesel Processes
Process
Crude Oil Extraction
Scope
International averages based on MA’s
crude oil sources
PADD 1 averages
National averages
Massachusetts averages
National averages
Crude Oil Transportation
Crude Oil Refining
Diesel Fuel Transportation
Diesel Fuel Combustion
Table 2 – Geographic Scope of Biodiesel Processes
Process
UVO Collection/Transportation
UVO Conversion to Biodiesel
Biodiesel Fueling/Transportation
Biodiesel Fuel Combustion
Scope
MIT campus averages
Reactor specific
MIT campus averages
National averages
5
2.2 Petroleum Diesel Model
2.2.1 Crude Oil Extraction
To model petroleum diesel, the study created a LCI based on the LCI’s used in
the 1998 NREL report’s model of both domestic and foreign crude oil extraction.
Three main processes were used to encompass the entirety of crude oil
extraction- onshore production, offshore production, and enhanced recovery.
Enhanced recovery describes the process of injecting steam or CO2 into the
ground to recover crude oil. The following table describes the domestic and
foreign allotment of each process in the 1998 NREL report:
Table 3 – Domestic and Foreign Crude Oil Extraction by Process
Process Type
Conventional Onshore
Conventional Offshore
Steam Injection
CO2 Injection
Domestic Allotment (%)
69
20
6.93
4.07
Foreign Allotment (%)
77
20
1.89
1.11
The report also provides LCI’s for domestic crude oil extraction and foreign crude
oil extraction. These LCI’s measure raw material inputs, energy inputs, and air
emissions in a kilogram of petroleum diesel. The 1998 NREL report, however,
allocates 50% of all crude oil in the US to domestic production, while the other
50% is due to foreign imports. This study only recognized crude oil profiles in
Massachusetts’ district, PADD 1. This district receives 99% of its crude oil from
foreign sources1:
Table 4 – PADD 1 Crude Oil Profile (Thousand Barrels) YR2005
Source
Domestic Crude Oil
Foreign Crude Oil
Barrels Received
8299
1316138
% of Total Barrels
0.63
99.37
In order to calculate the energy required and emissions for diesel fuel from crude
oil extraction, this study assigned relative contributions of the energy and
emissions from domestic and foreign extraction. The 1998 NREL study uses
mass % allocation to determine how much of the LCA is attributed to diesel fuel
once the crude oil is refined. Therefore, we only need to employ one addition
formula, equation (1), to calculate the relative contributions:
Relative Contribution of Crude Oil Extraction = ηNREL * %Source / 100
1
“Petroleum Navigator.” EIA
6
(1)
The variable ηNREL refers to the numbers in the 1998 NREL report’s LCI while the
variable %Source refers to the percentages in Table 4. For an extensive description
of the crude oil extraction model, see Appendix 1.
2.2.2 Crude Oil Transportation
The crude oil transportation model in the 1998 NREL report again categorized
crude oil by source, mode of transportation, and PADD. The modes of
transportation considered were by pipeline, tanker, barge, railcar, and truck.
Using average contributions of each mode of transportation over all 5 PADDs,
the NREL report composed LCI’s for a kilogram of domestic and foreign crude oil
transportation. In this study, the LCI was changed to meet the assumptions
pertaining to MIT, particularly the change to PADD 1. The following table shows
the composition of crude oil transportation in PADD 1 based on mode:
Table 5 – Domestic and Foreign Crude Oil Transportation by Mode for PADD 1 YR2005
Mode
Pipeline
Tanker
Barge
Railcar
Truck
Domestic Barrels
(Thousands)
2481
0
3171
1260
3334
% of Dom.
Total
24.21
0
30.95
12.30
32.54
Foreign Barrels
(Thousands)
23816
478191
82539
0
0
% of Foreign
Total
4.07
81.81
14.12
0
0
Table 5 depicts the total number of barrels transported by a specific mode of
transportation to and within PADD 1. Using these numbers, it’s possible to
calculate the relative contributions of each mode of transportation with regards to
energy use and emissions by using equation (2):
R.C. of Transportation by Mode = ηNREL / (%NREL / 100) * (%2005-Trans / 100) (2)
The variable ηNREL refers to the numbers in the NREL report’s LCI, while %NREL
refers to the percentage breakdown of transportation modes assumed in the
report (found in Appendix 2) and %2005-Trans refers to the numbers in Table 5.
Equation (3) then calculates the relative contribution of domestic and foreign
crude oil to the entirety of crude oil transportation:
R.C. of Crude Oil Transportation = (R.C. of Trans. by Mode) * %Source / 100 (3)
For more information, see Appendix 2.
2.2.3 Crude Oil Refining
Due to the lack of data, the crude oil refining model discards the geographic
PADD separation and instead basis its analysis on a national average of data
7
available from US refineries. Figure 1 describes the model used by the 1998
NREL report.
A mass allocation by % was used to determine the energy use and emissions
specific to the production of diesel fuel. When the NREL study was conducted,
crude oil refineries in the US produced 13.4 weight % of the mass of their total
products in diesel fuel with less than 0.05% sulfur content. Therefore, 13.4% of
total energy use and emissions were allocated to the production of diesel fuel in
that report.
Since 1998, refinery technologies have developed and improved the efficiency of
their systems. Energy use and emissions are decreased for every kilogram of
processed crude oil. However, diesel fuel production has also increased to 18.1
weight % as of 20052. Considering that the diesel fuel this report is assessing,
diesel with 15ppm and under sulfur content, is 82 weight % of the total crude oil
processed as diesel fuel with less than 0.05% sulfur content3, crude oil refineries
have increased efficiency and increased production of diesel fuel, the study
determined that the LCI of the 1998 report would best reflect a net estimate of
the refineries’ energy use and emissions today.
Figure 1 – The Crude Oil Refinery Model used by the 1998 NREL report
For more information, see Appendix 3.
2
3
“Petroleum Navigator.” EIA
“Petroleum Navigator.” EIA
8
2.2.4 Diesel Fuel Transportation
In the 1998 NREL report, the diesel fuel transportation model follows two routes:
transportation via pipeline to truck and local transportation via truck. Using data
from the Association of Oil Pipelines, their model determined that the average
pipeline ships diesel fuel 595 miles while trucks travel an average of 100 miles.
The model used in this study incorporates the LCI done by the NREL report and
modifies it to meet the diesel fuel transportation profile for Massachusetts.
Diesel fuel is assumed to be transported via three main modes: pipeline, truck
and barge. Massachusetts receives most of its land-shipped diesel fuel from two
diesel storage facilities. These facilities are located in New Haven, CT and
Providence, RI. Diesel is transported via pipeline from these sites to Springfield,
MA. The diesel fuel is then shipped by truck to its local surroundings, including
MIT. Diesel fuel is also transported by barge from NYC’s harbors to Boston’s
harbors. The following table describes the different modes of transportation:
Table 6 – Diesel Fuel Transportation by Mode YR2005
From
New Haven, CT
Providence, RI
Springfield, MA
NYC Harbor
To
Springfield, MA
Springfield, MA
MIT
Boston Harbor
Mileage
65
86
90
334
Mode
Pipeline
Pipeline
Truck
Barge
The LCI for diesel fuel transportation in the NREL report only includes pipeline
and truck transportation. However, since transportation of crude oil and
transportation of diesel fuel are relatively similar, it’s possible to use the LCI for
the transportation by barge of crude oil. In the 1998 NREL report, it assumes that
domestic barges travel an average of 200 km. The study then calculated the
relative contributions of each mode to transport a kilogram of diesel fuel by using
equation (4):
Relative Contribution by Mode = ηNREL / (DNREL / 100) * (D2005-Trans / 100)
(4)
The variable ηNREL refers to the LCI numbers in the 1998 NREL report. The
variable DNREL refers to the distances assumed in the NREL report while D2005Trans refers to the distances in the current model.
For more information, see Appendix 2.
2.2.5 Diesel Fuel Use/Combustion
The combustion of diesel fuel in the engine is when the energy content of the fuel
is converted into work and tail-pipe emissions are released. This study assumes
9
that the average fuel economy of the trucks used is 7250 Btu/bhp-h. Since the
lower heating value for diesel is 43.5 MJ/kg, 0.172 kg of fuel delivers 1 bhp-h. It
is important to convert the energy inputs and emissions from the previous LCI’s
into MJ/bhp-h and g/bhp-h respectively as that will be the standard this study
compares petroleum diesel to biodiesel.
End-use combustion of the diesel is when the most emissions are released.
Many studies have been performed to measure engine emissions using diesel
fuel. This study bases engine emissions of total hydrocarbons excluding CH4
(THC), nitrous oxides (NOx), carbon monoxide (CO) and particulate matter less
than 10 microns in diameter (PM) on Society of Automotive Engineers (SAE)
studies4. Carbon dioxide emissions were taken from the 1998 NREL report. CH4
emissions are based on a study done by the Aerodyne Mobile Laboratory
conducted in 2004.
Sulfur dioxide emissions are estimated based on the sulfur content of the fuel.
During combustion, all of the sulfur is converted into sulfur dioxide. Therefore,
sulfur dioxide emissions for a kilogram of diesel fuel can be calculated with the
following equation:
Sulfur Dioxide Emissions = wt% of sulfur * conversion factor of sulfur to SO2 (5)
The conversion factor is given by the molar mass ratio of SO2 to S. For more
information, see Appendix 5.
2.3 UVO-Biodiesel Model
2.3.1 UVO Collection/Transportation
MIT’s campus dining facility currently disposes UVO through Baker Commodities,
a company that collects and then disposes of the waste oil. In this study’s
proposed scenario, collection and transportation of the UVO would be transferred
to MIT Facilities. This study uses Baker Commodities collection protocol in order
to model the energy use and emissions of UVO collection and transportation.
The proposal suggests that UVO be collected from seven dining locations. Using
the ruler function in Google Earth, the study measured the estimated mileage a
truck would travel to pick up UVO from each location and transport it to W92, the
proposed reactor location. Table 7 describes the UVO collection/transportation
model based on information from Ward Ganger, Head of MIT’s Campus Dining:
4
“Comparison of Chassis Dynamometer In-Use Emissions with Engine Dynamometer FTP
Emissions in Three Heavy Duty Diesel Vehicles” and “Transient Emissions from #2 Diesel and
Biodiesel Blends in a DDC Series 60 Engine.”
10
Table 7 – UVO Collection/Transportation Model
Site
Faculty Club
Lobdell
Baker
McCormick
Next House
Simmons
Hotel@MIT
W92 to Garage
Miles
per Trip
2.35
1.21
1.22
1.22
1.22
0.87
0.87
0.84
UVO per
Trip (gal)
55
110
55
55
55
55
55
-
Trips per
Year
3
12
3
2
2
4
10
36
UVO per
Year (gal)
165
1320
165
110
110
220
550
-
Miles per
Year
7.05
14.52
3.66
2.44
2.44
3.48
8.70
30.24
Using this model, the study calculated the energy required and emissions for the
transportation of UVO. The energy required is based on the energy content of
petroleum diesel, 146.4 MJ/gal, and an estimate of its fuel economy. The study
adopts an estimate of 4 MPG for a heavy duty truck5. Using equation (6), the
study then calculated the total energy required to transport UVO in a year:
Energy to Transport UVO = DMPY / F.E.Diesel * E.C.Diesel
(6)
The variable DMPY refers to the total mileage trucks must travel in a year to collect
UVO. The variable F.E.Diesel refers to the fuel economy of diesel and E.C.Diesel
refers to the energy content of diesel. Next, the study found the amount (in kg) of
biodiesel MIT could produce in a year. Based on results in MIT’s laboratories, 80
weight % of the UVO is converted into biodiesel. Using equation (7), the study
calculated the amount of biodiesel produced yearly from UVO:
Biodiesel Produced Yearly = VGPY * ρUVO * % Conversion to Biodiesel
(7)
The variable VGPY refers to the total gallons of UVO collected in a year, while
ρUVO refers to the density of UVO, 3.33 kg/gal. Finally, the study calculated the
average energy used to transport a kilogram of biodiesel:
Energy per kg Biodiesel: Energy to Transport Yearly / Biodiesel Yearly
(8)
Emissions data is based on The Greenhouse Gases, Regulated Emissions, and
Energy Use in Transportation Model (GREET) created by Argonne National
Laboratory. The GREET model has an extensive database of energy use and
emissions of different vehicle types with various fuels. This study uses the
emissions values for CIDI (compression-ignition, direct-injection) diesel engine
vehicles in order to calculate total emissions per kilogram of biodiesel with the
following equation:
Emissions by Transportation = ηGREET * DMPY / Biodiesel Produced Yearly (9)
5
1998 NREL report.
11
The variable ηGREET refers to the emissions numbers from the GREET model. For
more information, see Appendix 2.
2.3.2 UVO Transesterification
Biodiesel@MIT plans to install a batch reactor from MBP, Bioenergy, LLC to
convert collected UVO into biodiesel. The reactor has its own patented
technology and doesn’t require steam. Therefore, the three main sources of
energy use and emissions are the electricity to run the reactor, methanol (MeOH)
production and potassium hydroxide (KOH) production. In this study, the energy
use and emissions were calculated separately for each source.
The energy required to power the reactor were estimated based on conservative
estimates of the pumps and heating of the UVO. Based on these calculations,
the study estimates 52.6 kWh / tonne of UVO6. Emissions produced from
electricity usage were calculated using Tiffany Groode’s methodology for
assessing MIT’s greenhouse gas inventory.
Electricity is generated from various sources. Table 8 describes Massachusetts’
electricity profile based on source:
Table 8 – Average Breakdown of Massachusetts Electricity by Source YR2005-2007
Source
Coal
Natural Gas
Petroleum
Hydroelectric
Nuclear
Other Renewables
% of Massachusetts Electricity
27.5
44.6
11.7
2.2
10.8
3.7
Assuming an average of 8% energy loss through distribution and transmission
losses in the Massachusetts grid, the study then calculated the energy delivered
from the utilities by source for a kilogram of biodiesel:
Energy from Util. by Source = Ereactor / (1-%loss/100) * %Source/100 * %Conv/100 (10)
The variable Ereactor refers to the electricity required per kilogram of UVO. The
variable %Source refers to the energy profile of Massachusetts electricity by source
and %Conv refers to the percent weight conversion of UVO to biodiesel. Each
source of electricity has its own efficiency. Table 9 describes the efficiencies of
each of the sources:
6
“Comparative Life Cycle Analysis of Diesel, Commercial Diesel and Biodiesel produced from
WVO.” Joseph Roy-Mayhew.
12
Table 9 – Efficiency of Sources of Electricity
Source
Coal
Natural Gas
Petroleum
Hydroelectric
Nuclear
Other Renewables
% Efficiency
34
41.2
34.2
35
34
35
Using these values, equation (10) calculates the total energy generated at the
utilities by source for a kilogram of biodiesel:
Total Energy by Source = Energy from Util. by Source / (%eff / 100)
(10)
Once the total energy used had been calculated, the study found the emissions
associated with that energy separated by source. Using the conversion factors
found in Table 10, the following equation was used to calculate carbon, NOx and
CH4 emissions per kilogram of biodiesel:
Emissions by Source = Tot. Energy by Source (MMBtu) * Conv. Factor / 100 (11)
Table 10 – Emissions Factors for Energy Sources
Source
Coal
Natural Gas
Petroleum
Hydroelectric
Nuclear
Other Renewables
C Emissions
(tonne C/MMBtu)
0.027
0.01633
0.0225
0
0
0
NOx Emissions
(g/MMBtu)
0.75
1.1
0.91
0
0
0
CH4 Emissions
(g/MMBtu)
0.298
1.1
0.36
0
0
0
Finally, to calculate CO2 emissions, the study assumes 99% combustion
efficiency and converts the carbon content into CO2 using the following equation:
CO2 = C Emissions * %combust/100 * Conversion Factor of C to CO2
(12)
The conversion factor is equal to the molar mass ratio of CO2 to C. Other types of
air emissions are excluded since emissions from MeOH will contribute over 98%
of the total emissions for those types.
Similarly, the energy input and emissions can be calculated for KOH production.
To do this, the study assigns an electricity-equivalent energy content for the KOH
(MJ/kg). Since 1 wt% of the UVO is the required amount of KOH, the study can
calculate the electricity needed for the KOH necessary for a kilogram of UVO.
Again, using the same methodology previously mentioned, the study can
13
calculate the total energy input and emissions for KOH production (see Appendix
4).
Energy use and emissions for methanol production are based on the LCI for the
Soybean Oil Conversion process in the 1998 NREL study. In the MBP reactor, an
excess 6:1 molar ratio of MeOH is needed to maximize conversion to biodiesel.
Therefore, 0.22 kg of MeOH is needed for every kilogram of UVO in the reactor.
In the NREL report, an average of 0.08628 kg of MeOH is used for every
kilogram of vegetable oil. By the following equation, the study calculated the
energy use and emissions from MeOH production for every kilogram of biodiesel:
Methanol LCI = ηNREL * %Conv * mMeOH / mNREL
(13)
The variable ηNREL refers to the LCI numbers for MeOH production from the
NREL study. The variable mMeOH refers to the mass of MeOH needed in MIT’s
reactor for a kilogram of UVO while mNREL refers to the mass of MeOH used to
convert a kilogram of vegetable oil.
For further information, see Appendix 4.
2.3.3 Biodiesel Transportation/Fueling
The transportation model for the newly converted biodiesel closely follows the
transportation model used for UVO collection and transportation. Essentially,
trucks will drive to W92 to fill their tanks (25 gallons) with the new biodiesel blend
and then drive back to the parking garage, NW62.
The model differs from the UVO collection/transportation in that the gallons
collected now refer to gallons of biodiesel filled. For the purpose of comparing
pure biodiesel to petroleum diesel, the study assumes that the tank will be filled
with B100. The study will account for the B20 blend when it compares the
petroleum diesel scenario to the B20 scenario; mixing the B20 blend requires no
additional energy and releases zero emissions. The same methodology to
calculate energy use and emissions in the UVO collection/transportation step can
be used in this step as well. However, there is no need to include the percent
conversion to biodiesel as it has already been converted.
For more information, see Appendix 2.
2.3.4 Biodiesel Use/Combustion
End-use combustion of biodiesel is where most of the emissions in the LCA are
produced. Just as the study did for end-use combustion of petroleum diesel, the
study compiled data from various tests done on B100 emissions and B20
14
emissions. As a means of comparison, emissions data is given per bhp-h. For
biodiesel, 0.203 kg of B100 is needed to produce 1 bhp-h7.
The engine use of biodiesel is the step in which this study incorporates the CO2
released from biomass. Biodiesel is derived from a feedstock which is grown
through agriculture. During agriculture, the feedstock uptakes CO2 as the plants
undergo photosynthesis. Therefore, a percentage of the total carbon content of
the biodiesel is actually recycled biomass carbon and should not be considered
in the net emissions of CO2. On average, pure biodiesel is 77.2% carbon. In the
biodiesel, the carbon contained in the fatty acids reacted with methanol is
considered non-biomass carbon while the carbon in the fatty acid portion of the
methyl ester is considered biomass carbon. Of the total carbon content, 73.2% of
it is attributed to biomass carbon8.
It is also assumed that biodiesel contains zero sulfur content. As a result,
biodiesel has zero SOx emissions from end-use combustion.
Emissions data for THC including CH4, CO, NOx and PM10 were taken from
various research papers9 that have tested the emissions of biodiesel blends
including B100 and B20. CO2 emissions were taken from the 1998 NREL report.
For more information, see Appendix 5.
7
1998 NREL study.
1998 NREL study.
9
“Biodiesel Comprehensive Handbook” and “Transient Emissions of #2 Diesel and Biodiesel
Blends in DDC Series 60 Engines.”
8
15
Data and Analysis
In this study, LCI’s are presented for pure biodiesel, petroleum diesel and B20
blends. These LCI’s are useful for comparing energy inputs and air emissions of
the different fuel types. However, the two fuel types should not be compared by
mass as they will burn differently in an engine. Instead, the total energy use and
emissions of the two fuels should be compared based on the work they deliver
on the engine. In the study’s final analysis, the two fuels will be compared on
their lifecycle energy use and emissions in delivering 1 bhp-h in a standard diesel
engine.
It should be noted that this lifecycle analysis does not incorporate cold flow
properties of biodiesel. In cold ambient temperature, biodiesel may drastically
decrease in efficiency. Other studies are currently being done to determine the
best way to offset these temperature changes.
3.1 Petroleum Diesel Results
In a standard diesel engine, 0.172 kg of petroleum diesel is required for 1 bhph10.
3.1.1 Energy Lifecycle
The energy inputs for each step of petroleum diesel’s lifecycle are summarized in
the following figure:
Figure 2 – Lifecycle Energy Audit of Petroleum Diesel
10
1998 NREL report.
16
Crude oil extraction is the most energy intensive of the steps involved in
petroleum diesel production. Of the total energy input, crude oil extraction makes
up 89.7% of it. Foreign crude oil extraction makes up 99.3% of the total energy
required for extraction since almost all oil in Massachusetts comes from foreign
sources. Reducing dependence on foreign oil will greatly reduce energy use.
After crude oil extraction, crude oil refining is the second most energy intensive,
making up 5.7% of the total energy input.
3.1.2 Emissions Lifecycle
The CO2 emissions for each step in petroleum diesel’s lifecycle are summarized
in the following figure:
Figure 3 – Lifecycle CO2 Emissions Audit of Petroleum Diesel
Tailpipe emissions of CO2 contribute 85.5% of the total emissions of CO2.
Following engine emissions, crude oil refining is the second most CO2 emissions
intensive, contributing 9.8% of the total CO2 emissions.
The following table shows the lifecycle air emissions of other greenhouse gases
over the lifecycle of petroleum diesel:
Table 11 – Lifecycle Air Emissions of Petroleum Diesel (g / bhp-h)
Process
NOx
SOx
CO
Crude Oil Extraction
0.03
0.16
0.02
Crude Oil Transportation
0.02
0.19
0.00
Crude Oil Refining
0.13
0.44
0.04
Diesel Fuel Transportation
0.02
0.00
0.01
Diesel Fuel Combustion
5.01
0.05
2.52
Total
5.21
0.84
2.60
PM10
0.03
0.01
0.08
0.00
0.18
0.30
All HC
0.21
0.13
0.00
0.01
0.21
0.56
Again, combustion is where most emissions are released into the environment.
17
3.2 Biodiesel Results
In a standard diesel engine, 0.203 kg of pure biodiesel is required for 1 bhp-h11.
3.2.1 Energy Lifecycle
The energy inputs for each step in biodiesel’s lifecycle are summarized in the
following figure:
Figure 4 – Lifecycle Energy Audit of Biodiesel
The batch reactor is the most energy intensive of all the steps in UVO-biodiesel
production. The reactor process requires 94.9% of the total energy input. Of the
reactor process, methanol production takes up 92.3% of the total energy required
to convert UVO into biodiesel.
3.2.2 Emissions Lifecycle
The CO2 emissions for each step in biodiesel’s lifecycle are summarized in
Figure 5. Just as it was with the petroleum diesel, the greatest amount of CO2 is
released during the combustion of biodiesel. Combustion emissions contribute
57.5% of the total emissions of CO2. The reactor process is the second greatest
contributor of CO2. The process emits 39.0% of the total emissions of CO2.
11
1998 NREL report.
18
Figure 5 – Lifecycle CO2 Emissions Audit of UVO Biodiesel
3.3 Comparison of Petro-Diesel and Biodiesel
The total energy inputs over the lifecycle of petroleum diesel, pure UVO-biodiesel
and B20 are summarized in the following figure:
Figure 6 – Comparison of Lifecycle Energy Input of Petro-Diesel, B100 and B20
Pure UVO-biodiesel produced on MIT campus requires 81.3% less energy in its
lifecycle that petroleum diesel. In the proposed scenario, however, petroleum
diesel will be replaced with B20. Petroleum diesel and B100 can be mixed in
three ways: splash blending, in-tank blending and layered blending. To splash
blend, petro-diesel is put into the vehicle’s tank followed by biodiesel. The mixing
19
from turning, going over bumps and changing elevations is enough to blend the
fuels. In-tank blending is where petro-diesel and B100 are pumped into the tanks
at the same time. Finally, layered blending is a passive form of blending in which
biodiesel is layered over petroleum diesel. The B100 will sink and blend with the
petro-diesel since it is denser.
Therefore, no additional energy inputs are required to produce the end result B20
blend. The study calculated the total energy input required for B20 by using the
following equation:
B20 LCA Energy = 0.80 * EPD + 0.20 * EBD
(14)
The variable EPD refers to the lifecycle energy input of petro-diesel while the
variable EBD refers to the lifecycle energy input of biodiesel. Based on these
calculations, this study has found that B20 reduces energy use by 16.3%.
The total CO2 emissions over the lifecycle of petroleum diesel, pure UVObiodiesel and B20 are summarized in the following figure:
Figure 7- Comparison of Lifecycle CO2 Emissions of Petro-Diesel, B100 and B20
The B100 blend reduces CO2 emissions by 91.7%. Using the same methodology
stated above, the study also calculated the CO2 emissions of the B20 blend.
Based on these calculations, the study found that B20 reduced CO2 emissions by
18.3%.
The lifecycle results of other air emissions for the B20 blend are summarized in
the following table:
20
Table 12 – Lifecycle Air Emissions for B20
Air Emission
NOx
SOx
CO
PM10
All HC
B20 Emissions (g / bhp-h)
5.21
0.78
2.37
0.26
0.49
Based on these results, the study calculated that B20 reduced all emissions,
including NOx. Although biodiesel emits greater amounts of NOx during engineuse combustion, its total NOx emissions over its lifecycle still amount to fewer
emissions from the lifecycle of petroleum diesel. This is mainly due to the fact
that if MIT produces biodiesel, it will be recycling the already used vegetable oil
instead of disposing of it. Therefore, NOx emissions from processes before UVO
collection are excluded from the LCA. Table 13 summarizes the results for these
air emissions:
Table 13 – Comparison of Lifecycle Air Emission Reduction for B100 and B20
GHG Type
NOx
SOx
CO
PM10
All HC
% Reduction in B100
0.4
38.2
44.2
79.6
66.7
% Reduction in B20
0.1
7.7
8.8
15.9
13.3
It should be noted that all SOx emissions in B100’s lifecycle come from its
upstream processes rather than from combustion.
21
Conclusions
Biodiesel@MIT’s proposal to implement a UVO-biodiesel production program
promises to reduce MIT Fleet’s energy use and emissions by a significant
amount. The lifecycle energy used to supply the diesel currently fueling MIT’s
fleet can be reduced by 16.3% with the usage of B20. CO2 emissions can also be
reduced by 18.3% and other GHG emissions can be reduced by as much as
15.9%.
However, other factors still need to be considered such as the temperature
during the winter time. Certain technologies may have to be implemented to
ensure effective use of B20 during the winter. As such, these additions will affect
the LCA of biodiesel.
Unfortunately, the scope of this study did not include a sensitivity analysis of the
data and results. Future LCA studies of MIT produced biodiesel should look into
how different assumptions affect the change in results. One example of such
factor is the model of the UVO collection/transportation. Collection trucks may
change paths or make trips more frequently or less frequently. Future studies
should also incorporate more data sets in order to accurately represent the
lifecycle energy use and emissions of both petroleum diesel and biodiesel as a
range of possible numbers. One example of a data set this study lacked was
information on crude oil refinery and extraction technologies in PADD 1.
22
Appendix 1: Crude Oil Extraction
Conventional Onshore Extraction
The following figure depicts the system boundaries and flows considered in the
onshore extraction model in the 1998 NREL study:
Figure 8 – Conventional Onshore Crude Oil Extraction
In this study, however, solid waste, water effluents and VOC emissions were not
considered within its scope. Energy used to construct and decommission
equipment used in extraction was excluded in both studies. The only raw
materials considered were crude oil and natural gas. Energy requirements were
based on the electricity used for pumping and the natural gas used for oil
recovery. Due to lack of information, these assumptions were used for both
domestic and foreign oil extraction. Mass allocation was used to determine how
much of the energy use and emissions were due to the crude oil product versus
the natural gas product.
Please see Life Cycle Inventory of Petroleum Diesel and Biodiesel for Use in an
Urban Bus, the 1998 NREL report, for a complete description of the model.
Conventional Offshore Extraction
Figure 9 depicts the system boundaries and flows considered in the offshore
extraction model in the 1998 NREL report.
23
Solid waste, water effluents and VOC emissions as well as energy used for
equipment production/destruction were excluded from this study’s model. The
only raw materials considered were natural gas and crude oil. Energy
requirements were based on natural gas as offshore rigs use natural gas for
pumping, recovery and electricity production. These assumptions apply to both
domestic and foreign oil extraction. Mass allocation was used to determine
emissions for the crude oil product.
Figure 9 – Conventional Offshore Crude Oil Extraction
Please see Life Cycle Inventory of Petroleum Diesel and Biodiesel for Use in an
Urban Bus, the 1998 NREL report, for a complete description of the model.
Advanced Steam Injection
Figure 10 depicts the system boundaries and flows considered in the 1998 NREL
report for advanced steam injection. In this study, however, solid waste and VOC
emissions are not considered. The raw materials considered were crude oil,
natural gas, and water for steam generation. Energy requirements were based
on electricity for pumping and natural gas for recovery and steam generation. It is
assumed that all of the natural gas was burned for steam generation so all
emissions and energy use are allocated to the crude oil product.
24
Figure 10 – Advanced Onshore (Steam Injection) Crude Oil Extraction
Please see Life Cycle Inventory of Petroleum Diesel and Biodiesel for Use in an
Urban Bus, the 1998 NREL report, for a complete description of the model.
Advanced CO2 Injection
The following figure depicts the system boundaries and flows considered in the
1998 NREL report on advanced CO2 injection:
Figure 11 – Advanced Onshore (CO2 Injection) Crude Oil Extraction
In this study, solid waste and VOC emissions were not considered within its
scope. Energy used to construct and decommission equipment used in extraction
25
was excluded in both studies. The only raw materials considered were crude oil
and CO2. Energy requirements were based on the electricity used for pumping
and preparation of the CO2.
Please see Life Cycle Inventory of Petroleum Diesel and Biodiesel for Use in an
Urban Bus, the 1998 NREL report, for a complete description of the model.
Crude Oil Extraction Lifecycle Inventory
The following figures depicts the modified LCI used in this study:
Figure 12 – Domestic Crude Oil Extraction LCI
Figure 13 – Foreign Crude Oil Extraction LCI
26
Appendix 2: Transportation Models for Petro-Diesel and
Biodiesel
Crude Oil Transportation
The following figure depicts the breakdown of transportation modes used in the
1999 NREL study:
Figure 14 – Crude Oil Transportation Breakdown by Mode
The numbers in Figure 14 are used in the equations stated in the methodology
for crude oil transportation. The following figure depicts the model used for
loading and unloading:
27
Figure 15 – Crude Oil Transportation Loading/Unloading
28
The following figures depict the LCI for crude oil transportation used in this study:
Figure 16 – Foreign Crude Oil Transportation LCI
Figure 17 – Domestic Crude Oil Transportation LCI
Please see Life Cycle Inventory of Petroleum Diesel and Biodiesel for Use in an
Urban Bus, the 1998 NREL report, for a complete description of the model.
Diesel Fuel Transportation
The 1998 NREL report uses the system boundaries depicted in Figure 18 to
model diesel fuel transportation. Loading is modeled as it is for crude oil
transportation.
29
Figure 18 – Diesel Fuel Transportation
Figure 19 shows the LCI used for diesel fuel transportation in this study.
Figure 19 – Diesel Fuel Transportation LCI
Please see Life Cycle Inventory of Petroleum Diesel and Biodiesel for Use in an
Urban Bus, the 1998 NREL report, for a complete description of the model.
UVO Collection/Transportation
The following figures depict the paths this study assumed trucks would take to
collect UVO from all of the sites on campus:
30
Figure 20 – The assumed path the transportation truck would take
to transport UVO from the Faculty Club to W92.
Figure 21 – The assumed path the transportation truck would take
to transport UVO from Lobdell to W92.
31
Figure 22 – The assumed path the transportation truck would take
to transport UVO from McCormick, Baker and Next House to W92.
Figure 23 – The assumed path the transportation truck would take
to transport UVO from Simmons to W92.
32
Figure 24 – The assumed path the transportation truck would take
to transport UVO from Hotel@MIT to W92.
Figure 25 – The assumed path the transportation truck would take
to get back to the garage facility from W92.
The following figures depict the LCI model for UVO transportation based on the
GREET model:
33
Figure 26 – UVO Transportation LCI Emissions Based on GREET
Figure 27 – UVO Transportation LCI Energy
Biodiesel Fuel Transportation
The following depict the LCI of biodiesel fuel transportation based on the GREET
model:
Figure 28 – Biodiesel Transportation LCI Emissions Based on GREET
34
Figure 29 – Biodiesel Transportation LCI Energy
35
Appendix 3: Crude Oil Refinery
The following figure depicts the LCI model used in this study for crude oil refining
based on the 1998 NREL report:
Figure 30 – Crude Oil Refining LCI
Please see Life Cycle Inventory of Petroleum Diesel and Biodiesel for Use in an
Urban Bus, the 1998 NREL report, for a complete description of the model.
36
Appendix 4: Transesterification Reactor
The methodology for calculating energy and emissions of KOH production follow
the same methodology for doing the same with electricity usage in the reactor.
The following table summarizes the data pertaining to KOH that this study used:
Table 14 – Electricity Equivalent Energy Required for KOH
Electricity Equiv. Energy Content
KOH’s Required Wt% of UVO
Equivalent Elec. Needed for KOH
1.87
1
0.0052
MJ / kg KOH
%
kWh / kg UVO
The following figures represent the LCI’s used in this study for the batch reactor:
Figure 31 – Methanol Production LCI
Figure 32 – UVO Conversion to Biodiesel LCI
37
Appendix 5: Engine Combustion of Petro-Diesel and
Biodiesel
Diesel Fuel Combustion
The following figures represent emissions data used in this study:
Figure 33 – Average Emissions in SAE Papers on Diesel Engine Emissions
Figure 34 – Emissions Data for Diesel (SOx and CH4)
Biodiesel Fuel Combustion
The following figures represent emissions data used in this study for B100:
Figure 35 – Average Emissions Data for B100 Combustion
38
Figure 36 – Average Emissions Data for B20 Combustion
39
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