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OVERVIEW OF THE LIFECYCLE EMISSIONS MODEL ( LEM)
Mark A. Delucchi
Institute of Transportation Studies
University of California
One Shields Avenue
Davis, California 95616
madelucchi@ ucdavis. edu
August 2002
Introduction
The task of developing and evaluating strategies to reduce emissions of urban air
pollutants and greenhouse gases is complicated. There are many ways to produce and
use energy, many sources of emissions in an energy lifecycle, and several kinds of
pollutants ( or greenhouse gases) emitted at each source. An evaluation of strategies to
reduce emissions of greenhouse gases must be broad, detailed, and systematic. It must
encompass the full “ lifecycle” of a particular technology or policy, and include all of the
relevant pollutants and their effects. Towards this end, I have developed a detailed,
comprehensive model of lifecycle emissions of urban air pollutants and greenhouse
gases from the use of variety of transportation modes.
The Lifecycle Emissions Model ( LEM) estimates energy use, criteria pollutant
emissions, and CO2- equivalent greenhouse- gas emissions from a variety of
transportation and energy lifecycles. It includes a wide range of modes of passenger
and freight transport, electricity generation, heating and cooking, and more. For
transport modes, it represents the lifecycle of fuels, vehicles, materials, and
infrastructure. It energy use and all regulated air pollutants plus so- called greenhouse
gases. It includes input data for up to 20 countries, for the years 1970 to 2050, and is
fully specified for the U. S. The remainder of this section provides a further overview of
the LEM.
Transportation modes in the LEM
The LEM calculates lifecycle emissions for the following passenger
transportation modes:
• light- duty passenger cars ( internal- combustion engine vehicles [ ICEVs]
operating on a range of fuel types [ see below]; battery- powered
electric vehicles [ BPEVs]; and fuel- cell electric vehicles, with or without
an auxiliary peak- power unit [ FCVs];
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• full- size buses ( ICEVs and FCVs)
• mini- buses ( albeit modeled crudely)
• mini- cars ( ICEVs and BPEVs)
• motor scooters ( ICEVs and BPEVs)
• bicycles
• heavy- rail transit ( e. g., subways)
• light- rail transit ( e. g., trolleys)
and the following freight transport modes:
• medium and heavy- duty trucks
• diesel trains
• tankers, cargo ships, and barges
• pipelines
Fuel and feedstock combinations for motor vehicles
For motor vehicles, the LEM calculates lifecycle emissions for a variety of
combinations of end- use fuel ( e. g., methanol), fuel feedstocks ( e. g., coal), and vehicle
types ( e. g., fuel- cell vehicle). For light- duty vehicles, the fuel and feedstock
combinations included in the LEM are:
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Fuel --
>
↓ Feedstock
Gasoline Diesel Methanol Ethanol Methane
( CNG, LNG)
Propane
( LPG)
Hydrogen Electric
Petroleum ICEV,
FCV
ICEV ICEV BPEV
Coal ICEV ICEV ICEV,
FCV
BPEV
Natural gas ICEV ICEV,
FCV
ICEV ICEV ICEV,
FCV
BPEV
Wood or grass ICEV,
FCV
ICEV,
FCV
ICEV BPEV
Soybeans ICEV
Corn ICEV
Solar power ICEV,
FCV
BPEV
Nuclear power ICEV,
FCV
BPEV
The LEM has similar but fewer combinations for heavy- duty vehicles HDVs,
mini- cars, and motor scooters.
Fuel, material, vehicle, and infrastructure lifecycles in the LEM
The LEM estimates the use of energy, and emissions of greenhouse gases and
urban air pollutants, for the complete lifecycle of fuels, materials, vehicles, and
infrastructure for the transportation modes listed above. These lifecycles are
constructed as follows:
Lifecycle of fuels and electricity:
• end use: the use of a finished fuel product, such as gasoline, electricity,
or heating oil, by consumers;
• dispensing of fuels: pumping of liquid fuels, and compression or
liquefaction of gaseous transportation fuels
• fuel distribution and storage: the transport of a finished fuel product to
end users; for example, the shipment of gasoline by truck to a service
station. Includes operation of bulk- service facilities;
• fuel production: the transformation of a primary resource, such as
crude oil or coal, to a finished fuel product or energy carrier, such as
gasoline or electricity. Includes a detailed model of emissions and
energy use at petroleum refineries;
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• feedstock transport: the transport of a primary resource to a fuel
production facility; for example, the transport of crude oil from the
wellhead to a petroleum refinery. Includes a complete country- by-country
accounting of imports of crude oil and petroleum products by
country;
• feedstock production: the production of a primary resource, such as
crude oil, coal, or biomass. Based on primary survey data at energy-mining
and recovery operations, or survey or estimated data for
agricultural operations.
Lifecycle of materials:
• crude- ore recovery and finished- material manufacture: the recovery
and transport of crude ores used to make finished materials, and the
manufacture of finished materials from raw materials ( includes
separate characterization of non- energy- related process- area
emissions);
• the transport of finished materials to end users.
Lifecycle of vehicles:
• materials use: see the “ lifecycle of materials”;
• vehicle assembly: assembly and transport of vehicles, trains, etc.;
• operation and maintenance: energy use and emissions associated with
motor- vehicle service stations and parts shops, transit stations, and so
on;
• secondary fuelcycle for transport modes: building, servicing, and
providing administrative support for transport and distribution modes
such as large crude- carrying tankers or unit coal trains.
Lifecycle of infrastructure:
• energy use and materials production: the manufacture and transport of
raw and finished materials used in the construction of highways,
railways, and so on; energy use and emissions associated with the
actual construction of the transportation infrastructure. ( Presently these
are represented crudely; future versions of the LEM will have a more
detailed treatment of the infrastructure lifecycle.)
Sources of emissions in lifecycles
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The LEM characterizes greenhouse gases and criteria pollutants from a variety of
emission sources:
• from the combustion of fuels that provide process energy ( for example,
the burning of bunker fuel in the boiler of a super- tanker, or the
combustion of refinery gas in a petroleum refinery);
• as a result of the evaporation or leakage of energy feedstocks and
finished fuels ( for example, from the evaporation of hydrocarbons from
gasoline storage terminals);
• from the venting, leaking, or flaring of gas mixtures that contain
greenhouse gases ( for example, the venting of coalbed gas from coal
mines);
• as a result of chemical transformations that are not associated with
burning process fuels ( for example, the curing of cement, which
produces CO2, or the denitrification of nitrogenous fertilizers, which
produces N2O, or the scrubbing of sulfur oxides ( SOx) from the flue
gas of coal- fired power plants, which can produce CO2);
• as a result of changes in the carbon content of soils or biomass, or
emissions of non- CO2 greenhouse from soils, due to changes in land
use.
Pollutant tracked in the LEM
The LEM estimates emissions of the following pollutants:
• carbon dioxide ( CO2); • sulfur dioxide ( SO2J);
• methane ( CH4); • total particulate matter
• nitrous oxide ( N2O); • particulate matter less than 10
microns diameter ( PM10);
• carbon monoxide ( CO); • chlorofluorocarbons ( CFC- 12);
• nitrogen oxides ( NOx); • hydrofluorocarbons ( HFC- 134a);
• nonmethane organic compounds
( NMOCs), weighted by their ozone-forming
potential;
• the CO2- equivalent of all of the
pollutants above
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Ozone ( O3) is not included in this list because it is not emitted directly from any
source in a fuelcycle, but rather is formed as a result of a complex series of chemical
reactions involving CO, NOx, and NMOCs.
The LEM estimates emissions of each pollutant individually, and also converts
all of the pollutant into CO2- equivalent greenhouse- gas emissions. To calculate total
CO2- equivalent emissions, the model uses CO2- equivalency factors ( CEFs) that convert
mass emissions of all of the non- CO2 gases into the mass amount of CO2 with an
equivalent effect on global climate. These CEFs are similar to but not necessarily the
same as the “ Global Warming Potentials” ( GWPs) used by the Intergovernmental Panel
on Climate Change ( IPCC). The CEFs are discussed in a separate section of the model
documentation.
Material commodities in the LEM
Finally, the LEM includes the following materials:
• plain carbon steel • zinc die castings
• high strength steel • powdered metal components
• stainless steel • other materials ( lead)
• recycled steel • sodium
• iron • sulfur
• advanced composites • titanium
• other plastics • sulfuric acid
• fluids and lubricants • potassium hydroxide
• rubber • nickel and compounds
• virgin aluminum • lithium
• recycled aluminum • cement
• glass • concrete
• copper • limestone
Note that recycled steel and recycled aluminum are treated as separate materials
from virgin steel and virgin aluminum. In this way, the full lifecycle of materials
including recyling is explicitly represented.
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Input: projections of energy use and emissions
As part of a major revision to the LEM, I have added projections of energy use
and emissions, or changes in energy use and emissions, for the period 1970 to 2050. The
user now specifies any target year between 1970 and 2050, and the model looks up or
calculates energy- use intensities, emission factors, or other data for the specified year.
There are several different kinds of projections in the LEM: look- up tables
( usually based on energy- use or emissions projections from the EIA), constant
percentage changes per year, logistic functions with upper or lower limits, and logistic
functions with upper and lower limits. These projections are discussed in more detail in
a separate section of the model documentation.
Major outputs of the LEM
The LEM produces the following tables of results ( discussed in more detail in a
separate section of the model documentation):
• emissions per mile from motor vehicles: CO2- equivalent emissions ( in
g/ mi) by stage of fuelcycle and for vehicle manufacture, for the
feedstock/ fuel/ vehicle combinations shown above;
• emissions from electricity use: CO2- equivalent emissions ( in g/ kWh-delivered)
for different sources of electricity generation;
• emissions from use of heating fuels: CO2- equivalent emissions ( in g/ 106-
BTU- heat- delivered) for natural gas, LPG, electricity, and fuel oil;
• summary of % change in lifecycle g/ mi emissions from alternative- fuel
vehicles, relative to conventional gasoline LDVs or diesel HDVs;
• BTUs of process and end- use energy per mile of travel by stage of
lifecycle, for different feedstock/ fuel/ vehicle combinations;
• breakdown of energy use by type of energy ( e. g., diesel fuel, natural gas,
propane), stage of lifecycle, and feedstock/ fuel combination;
• vehicle characteristics: input data and results regarding vehicle weight
and energy use;
• emissions from EVs, by region: a macro runs the model for regional data
for EV recharging and prints the g/ mi results for up to six different
regions;
• emissions by IPCC sector: The g/ mi results for vehicles are mapped into
the IPCC sectors used in GHG accounting ( e. g., “ energy/ road
transport,” “ energy/ industry,” “ land- use/ forestry”);
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• emissions by geographic sector: The g/ mi results for vehicles are
mapped into a geographic framework that distinguishes in- country
from outside- of- country emissions;
• emissions by individual pollutant: one set of tables reports emissions of
each individual pollutant ( not weighted by CO2- equivalency factors)
for each stage of the upstream fuelcycle for each feedstock/ fuel;
another table does the same for vehicle manufacture and assembly;
• CO2- equivalent emissions by pollutant: a new table summarizes the
contribution of each pollutant to upstream fuelcycle CO2- equivalent
emissions;
• emissions from complete transportation scenarios: a new table of results
shows g/ passenger- mi emissions from a user- specified mix of travel by
conventional motor vehicles, alternative- fuel vehicles ( including
electric vehicles), mini- cars, scooters, buses, trolleys, subways, bicycles,
and walking;
• print macros: the LEM has macros that run the model for up to 40
different target years and then prints a pre- selected group of results
tables in publication- ready format;
• emissions from other countries: the LEM can be programmed to
calculate all results for the characteristics of any of up to 20 different
countries. Separate data files exist within the LEM for each of the
countries.
Overview of revisions to the LEM ( since 1993 version)
The structure and input data of the LEM have been completely overhauled. For
example, the inputs and model structure for vehicle emissions, vehicle fuel economy,
feedstock recovery, transportation of feedstocks, fuel production, and distribution of
fuels have been redone to be more detailed, flexible, consistent, and realistic. Many data
on energy use, fuel characteristics, and emissions are estimated or projected from 1970
to 2050.
The output has been cleaned up and presented in considerably more detail.
Estimates of g/ 106 BTU emissions are presented for each GHG ( without the CEF
weighting), for each stage of all of the fuelcycles. Fuelcycle GHG emissions for electric
vehicles are calculated for the U. S. and each of six regions. A macro runs the LEM for
up any target year and prints all of the main results in publication- ready tables.
Many major new components have been added, most notably:
• projections of energy use, emissions, emission control, and other parameters
through the year 2050
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• updated energy use parameters and emission factors, on the basis of EPA’s
standard emission- factor handbook, AP- 42, the IPCC’s Revised 1996 IPCC Guidelines for
National GHG Emission Inventories, and other sources
• models and default data to represent emissions for other countries ( e. g.,
Canada) ( Appendix B)
• detailed original calculations of CO2- equivalency factors for all gases,
including a complete ( albeit preliminary) representation of the nitrogen cycle
• several modes added: mini- cars, motor scooters, mini buses, heavy- rail transit,
light- rail transit, and bicycling
• PM and SO2 added as greenhouse gases and urban air pollutants;
• NMOCs weighted by their ozone- forming potential
• a mobile- source emission factor model, akin to a highly simplified version of
the EPA’s MOBILE model
• update and revision of the representation and data for the modeling of the
lifecycle of materials ( Appendix H)
• more detailed treatment of motor- vehicle energy use, on the basis of weight,
thermal efficiency, and aerodynamic drag
• new estimation of the relationship between vehicle weight, materials
composition, and fuel economy
• fuel economy estimated as a function of number ( weight) of passengers in cars,
buses, mini- buses, mini- cars, and scooters
• fuel economy and hence GHG emissions estimated as a function of vehicle
payload, including number of passengers in cars or buses
• light- duty fuel cell vehicles using gasoline, methanol, ethanol, or hydrogen,
with or without an auxiliary peak- power unit
• a new model of refinery emissions, based on emissions from individual process
areas
• a more detailed calculation of emissions from the use of oxygenates
• a much more detailed treatment emissions from corn/ ethanol and wood bio-fuel
cycles
• perennial grasses as a feedstock for the production of ethanol
• soybeans to biodiesel fuelcycle ( Appendix A)
• natural gas to diesel fuel via the Fischer- Tropsch ( F- T) process
• F- T diesel of methanol made from associated natural gas that otherwise would
be vented or flared
• natural gas to hydrogen via reforming
• coal to synthetic crude oil
• diesel fuel in LDVs, and gasoline in HDVs
• lifecycle emissions from the use of forklifts
• lifecycle emissions from the use of motor scooters
• an option to specify HDVs as buses rather than trucks
• a distinction between large- scale centralized liquefaction and small- scale
liquefaction at service stations, for LNG and LH2
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• a detailed analysis of energy used to manufacture agricultural chemicals
• a model of changes in carbon sequestration in biomass and soil due to changes
in land use ( including changes associated with fossil- fuel production)
• more detailed representation of emissions of nitrogen species from soils, due to
cultivation, and fertilizer use ( Appendix C)
• representation of feedstock production and fuel production in physical
input/ output terms
• detailed tracking of imports of crude oil, and venting and flaring emissions and
refining emissions in individual exporting countries or regions
• tracking of imports and coal, and venting of coalbed methane in individual
exporting countries or regions
• tracking of source of enrichment of uranium, with different energy intensities
for different enriching countries
• a detailed representation of natural gas transmission and distribution
• added explicit representation of international transport of coal
• a more consistent and detailed representation of feedstock and fuel transport
• emissions from energy use by service stations and marketing facilities
• fuelcycle emissions from the use of NG, LPG, fuel oil, and electricity for space
heating and water heating
• rudimentary treatment of the extent to which alternative- fuel production
displaces existing production or stimulates new demand
• a new treatment of “ own use” of fuel
• explicit representation of geographic sources and shipping of materials and
motor vehicles
Overall, the present model is more powerful, and quite a bit easier to use, than
the previous model. In general, the the overall affect of the revisions is to make
alternative fuels more attractive.
Documentation of the model
The 1997 version of the model is documented in several reports, shown below.
Complete up- to- date working documentation is available from the author.
M. A. DeLuchi, Emissions of Greenhouse Gases from the Use of Transportation Fuels and
Electricity, ANL/ ESD/ TM- 22, Volume 1, Center for Transportation Research, Argonne
National Laboratory, Argonne, Illinois, November ( 1991). 142 pp.
M. A. DeLuchi, Emissions of Greenhouse Gases from the Use of Transportation Fuels and
Electricity, ANL/ ESD/ TM- 22, Volume 2, Appendices A- S, Center for Transportation
Research, Argonne National Laboratory, Argonne, Illinois, November ( 1993). 524 pp.
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M. A. Delucchi, Emissions of Criteria Pollutants, Toxic Air Pollutants, and Greenhouse Gases,
from the Use of Alternative Transportation Modes and Fuels, UCD- ITS- RR- 96- 12, Institute of
Transportation Studies, University of California, Davis, January ( 1996). 150 pp.
M. A. Delucchi and T. E. Lipman, Emissions of Non- CO2 Greenhouse Gases from the
Production and Use of Transportation Fuels and Electricity, UCD- ITS- RR- 97- 5, Institute of
Transportation Studies, University of California, Davis, February ( 1997). 150 pp.
M. A. Delucchi, A Revised Model of Emissions of Greenhouse Gases from the Use of
Transprtation Fuels and Electricity, UCD- ITS- RR- 97- 22, Institute of Transportation
Studies, University of California, Davis, November ( 1997). 210 pp.
Results are published in two articles in the peer reviewed literature:
M. A. DeLuchi, “ Greenhouse- Gas Emissions from the Use of Transportation Fuels and
Electricity,” Transportation Research- A 27A: 187- 191 ( 1993).
M. A. Delucchi, “ A Lifecycle Emissions Analysis: Urban Air Pollutants and
Greenhouse- Gases from Petroleum, Natural Gas, LPG, and Other Fuels for Highway
Vehicles, Forklifts, and Household Heating in The U. S.,” World Resources Review 13 ( 1):
25- 51 ( 2001).