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Using Natural Gas for : Comparing Three Technologies

In the , natural gas is can also serve as the source in centrally-fueled fleets that use used primarily for genera- for plug-in electric or large quantities of ), but will not tion and residential, commercial, electric vehicles. This fact be covered in this fact sheet. and industrial applications, but it sheet compares some efficiency and is also used as a fuel for on-road environmental metrics for three This comparison of pathways in vehicles, especially in medium- or possible options for using natural light-duty vehicles is based on a heavy-duty vehicles in centrally- gas in light-duty cars. detailed analysis (Wang and fueled fleets. Elgowainy 2015), which uses the The analysis presented here com­ GREET model (Greenhouse Gases, It has been proposed for greater pares these pathways. It is not­ Regulated Emissions, and Energy use as a fuel for on-road vehicles, intended to recommend for or use in Transportation). Scientists particularly in light-duty vehicles. against increased use of natural at Argonne National Laboratory This can mean burning natural gas gas in light-duty vehicles. Related developed GREET to estimate in an internal ongoing analysis considers use energy use and emissions across the like those used in most natural gas, ofnatural gas with these three entire fuel life cycle from extraction , diesel-powered vehicles on technology pathways in medium- to end use in transportation. the road today. However, natural gas or heavy-duty vehicles (for example,

Natural Gas On-Road Fuel: Three Technology Options

Internal combustion Fuel cell electric Plug-in electric engine vehicle vehicle vehicle 1 2 3

BURNING REFORMING GENERATION

COMPRESSED NATURAL GAS TO ELECTRICITY FROM NATURAL GAS HYDROGEN NATURAL GAS

Figure 1. , natural gas to hydrogen, and electricity from natural gas 2 POLICY AND ANALYSIS

Considering Life Cycle Efficiency Each of the three pathways for using natural gas has strengths and weaknesses that determine where efficiency losses and emissions occur across the entire life cycle. Vehicle efficiency determines only part of the story. Figure 2, which is based on GREET results, gives a look at the fuel life cycle for the three types of natural gas cars, showing how energy conversion efficiency at each major step leads to the ultimate system efficiency for each pathway. The percentages (light blue circles) show natural gas conversion efficiencies along steps of the life cycle. Below each pathway, the changes in the height of the light blue bar show how much of the energy92%* in one mmBtu of 99% 98% 16%** natural gas is used during each step. Natural gas internal combustion engine vehicles running on compressed natural gas (CNGV) have the greatest losses during combustion at the vehicle propulsion stage. Fuel cell 92%electric* vehicles (FCEVs) have the greatest99% losses 98% 16%** during via reforming andDrilling, during Processing, and Transportation from hydrogen in the vehicle. NG Distribution NG Compression CNGV 175 92%* 99% 98% 16%** In addition, plug-in electric vehicles (PEVs) have the greatest losses during electricity generation. miles per 1 mmBtu mmBtu Drilling, Processing, and Transportation NG Distribution NG Compression CNGV 175 natural gas 92%* 99% 98% 16%** miles per Drilling,CNGV Processing, and Transportation1 mmBtu NG Distribution NG Compression CNGV 175 93% mmBtu ** 72% 97% miles per 92% 35% 1 mmBtu natural gas mmBtu Drilling, Processing, and Transportation NG Distribution NG Compression CNGV 175 natural gas City Gate City miles per ** 1 mmBtu 93% 72% mmBtu97% 92% 35% Drilling, Processing, and Transportation naturalNG gasSMR** Plant H **Compression H T&D H Fueling FCEV 93% 72% 97% 92% 35%2 | 2 | 2 255 FCEV 93% 72% 97% Gate City 92% 35%** miles per 1 mmBtu mmBtu Drilling, Processing, Gate City and Transportation NG SMR** Plant H2 Compression H2 T&D H2 Fueling FCEV City Gate City | | 255 natural gas Drilling,Drilling, Processing, Processing, and and Transportation Transportation NG SMR** Plant NGH CompressionSMR** Plant H T&DH CompressionH Fueling FCEV H T&D H Fueling FCEV miles per 1 mmBtu 2 | 2 2| 2 | 2 | 2 255 255 mmBtu miles per 1 mmBtu miles per ** 1 mmBtu 93% mmBtu 50% 94% 85% natural gas 67% (including natural gas mmBtu charging losses) natural gas PEV ** 93% 50% 93%94% 85% 67%50%** (including 94% 85% 67% (including charging losses) charging losses) 93% 50% 94% 85% 67%** (including Drilling, Processing, and Transportation NG Power Plants*** Electricitycharging T&Dlosses) Charging PEV 325 Drilling, Processing, and Transportation NG Power Plants*** Electricity T&D Charging PEV | | 325 miles per miles per 1 mmBtu Drilling, Processing,1 andmmBtu Transportation NG Power Plants*** Electricity T&D Charging PEV mmBtu | 325 mmBtu natural gas miles per natural gas Drilling, Processing, and Transportation1 mmBtu NG Power Plants*** Electricity T&D Charging PEV | 325 mmBtu Eciency miles per 1 mmBtu natural gas Key Loss Steps Eciency mmBtu Figure 2. Fuel life cycle efficiency natural gas Remaining Energy Eciency Key Loss Steps

Energy conversion efficiency Key loss steps Remaining energy  Eciency Key Loss Steps Remaining Energy Key Loss Steps Remaining Energy * Efficiency of drilling, processing, and transportation varies slightly between pathways due to expected differences in pipeline distanceRemaining to use, as Energy shown in Wang and Elgowainy (2015). ** Actual end-use efficiency will depend on drive cycle and other factors. Efficiency values here are representative based on an estimate of 17% average efficiency of gasoline for typical drive cycles and the relative MPGGE of each vehicle. Drive cycle simulations adjusted for on-road performance were used to estimate miles/mmBtu. *** Primarily from natural gas combined cycle plants.

Reference: Wang, Michael and Amgad Elgowainy (2015). “Well-to- GHG Emissions of Natural Gas Use in Transportation: CNGVs, LNGVs, EVs, and FCVs. Presented October 10, 2014. Argonne National Laboratory. https://greet.es.anl.gov/publication-EERE-LCA-NG. POLICY AND ANALYSIS 3

Understanding Life Cycle Emissions An accounting of involves more than vehicle fuel economy and life cycle system efficiency. With natural gas, a variable and uncertain portion of greenhouse gas emission occurs due to leakage of methane throughout the life cycle. Using GREET, greenhouse gas emissions can be compared across pathways with very different distributions205 miles per mmBtu of emissions across the fuel life cycle. natural gas

In Figure 3, the grey bars show how greenhouse gas emissions (in dioxide equivalents) are distributed across Drilling, Processing,different steps and of Transportation the life cycle for each pathway.NG DistributionThe figure also shows howNG the Compressiondifferent fuel economies in the lightCNGV blue 200 miles per mmBtu circles contribute to the final grams of emissions per mile shown in figures 3 and 4. ang(W and Elgowainy 2015). natural gas390 g/mi WTW CO e miles per mmBtu 2 * Drilling, Processing, and Transportation NG Distribution NG Compression205 natural gas CNGV emissions 14 kg CO2/mmBtu of NG 16 kg of CO2/mmBtu 19 kg CO2/mmBtu 80 kg CO2/mmBtu of NG of CNG of CNG

Drilling, Processing, and Transportation NG Distribution NG Compression CNGV * 14 kg CO2/mmBtu of NG 16 kg of CO2/mmBtu 19 kg CO2/mmBtu 39080 kg CO2/mmBtu WTW CO2e of NG of CNG g/mi of CNG emissions: 390 g/mi WTW CO e miles per 2460 * emissions mmBtu H2 14 kg CO2/mmBtu of NG 16 kg of CO2/mmBtu 19 kg CO2/mmBtu 80 kg CO2/mmBtu of NG of CNG of CNG 452 miles per mmBtu H2

Drilling, Processing, and Transportation NG SMR Plant Gate City H Compression H T&D H Fueling miles per FCEV 2 | 2 | 2 460 mmBtu H2 260 Drilling, Processing, and Transportation NG SMR Plant H Compression H T&D H Fueling FCEV g/mi 2 | 2 | 2 WTW CO2e Drilling, Processing, and Transportation NG SMR Plant H Compression H T&D H Fueling FCEV emissions 2 | 2 | 2 260 9 kg CO2/mmBtu of NG 97 kg CO2/mmBtu 103 kg CO2/mmBtu 120 kg CO2/mmBtu 120 kg CO2/mmBtu g/mi of H2 of H2 of H2 WTWof CO H2e 9 kg CO2/mmBtu of NG 97 kg CO2/mmBtu 103 kg CO2/mmBtu 120 kg CO2/mmBtu 1202 kg CO2/mmBtu WTW CO2e emissions emissions: 255 g/mi of H2 of H2 of H2 of H2 9 kg CO2/mmBtu of NG 97 kg CO2/mmBtu 103 kg CO2/mmBtu 120 kg CO2/mmBtu 120 kg CO2/mmBtu of H2 of H2 of H2 of H2 miles per mmBtu 880 electricitymiles (including per mmBtu miles per mmBtu 861 electricity (including 880 electricity (including chargingcharging losses) losses) charging losses)

Drilling, Processing, and TransportationDrilling, Processing, and TransportationNG Power Plants** NG Power Electricity Plants** T&D Electricity Charging T&D Charging PEV BEV Drilling, Processing, and Transportation NG Power Plants** Electricity T&D | Charging | PEV | 200 200 g/mi g/mi WTW CO2e emissions WTW CO2e 11 kg CO2/mmBtu of NG 140 kg CO /mmBtu 150 kg CO /mmBtu 175 kg CO /mmBtu 175 kg CO /mmBtu 11 kg CO2/mmBtu of NG 2 1402 kg CO /mmBtu 2 150 kg CO /mmBtu2 175 kg CO /mmBtu 175 kg CO /mmBtu WTWemissions CO2e of electricity of electricity 2 of electricity 2 of electricity 2 2 200 g/mi 11 kg CO2/mmBtu of NG 140 kg CO2/mmBtu 150of electricity kg CO2/mmBtu of electricity175 kg CO2/mmBtuof electricity 175 kg CO2/mmBtuof electricity emissions: Figure 3. Fuel life cycle greenhouse gas emissionsof electricity of electricity of electricity of electricity Eciency * Steam methane reforming Eciency * Steam methane reforming **Primarily from natural gas combined cycle plants CO2e Emissions (cumulative, including upstream steps) **Primarily from natural gas combined cycle plants VehicleEciency fuelCO economye emissions are due to both energy CO CO2 euse2e emissions andEmissions methane (cumulative, leakage (cumulative, including including upstream upstream steps) steps)* Steam methane reforming  2 (not WTW) CO e emissions are due to both energy use and methane leakage CO22e emissions are due to both energy use and methane leakage **Primarily from natural gas combined cycle plants CO2e Emissions (cumulative, including upstream steps) CO e emissions are due to both energy use and methane leakage * Efficiency2 of drilling, processing, and transportation varies slightly between pathways due to expected differences in pipeline distance to use. ** Primarily from natural gas combined cycle plants.

Acronyms and Abbreviations g/mi grams per mile NG natural gas Btu British thermal unit GHG greenhouse gas PEV plug-in

CNG compressed natural gas H2 hydrogen SMR steam methane reforming CNGV compressed kg kilogram T&D and distribution

CO2e equivalent MPGGE miles per gallon gasoline equivalent WTW to wheel FCEV fuel cell electric vehicle mmBtu million Btu 4 POLICY AND ANALYSIS

Summary: How Far Can Natural Gas Take a ? It depends on how we use it. Figure 4 compares system efficiencies, showing how far differently powered cars can go on one mmBtu of natural gas, which is equivalent to about nine gallons of gasoline. Gasoline vehicles can travel 200 miles on this much energy. On this same amount of energy from natural gas, fuel cell vehicles can go about 255 miles, electric vehicles can travel 325 miles—with battery size determining the number of charging events needed—and internal combustion engine natural gas vehicles can go 175 miles. The key difference among these technology pathways, as detailed above, is the efficiency with which they convert natural gas to other forms of energy. Combustion of natural gas in engines on board a vehicle tends to be much less efficient than natural gas use in a modern combined cycle electric generation plant or through reforming to hydrogen and use in a fuel cell.

Comparing Technology Options When natural gas is inexpensive relative to other for on-road vehicles, it could benefit consumers and the economy. However, all three natural gas pathways provide energy security by helping reduce reliance on -based fuels in the transportation sector. Environmental performance, including life cycle greenhouse gas emissions, is also a key metric to compare technological alternatives. Considering the options for using natural gas for transportation—and their energy and environmental consequences—can help ensure that we get the most possible value from this new era of natural gas. How far can a car Howgo on far can a car go on 1 million Btu of Natural Gas? How far can a car go on1 1million million Btu Btu of of Natural Natural Gas? Gas? Gasoline Vehicle Gasoline Vehicle (on 1 million Btu* of gasoline) Gasoline(on 1 million Vehicle Btu* of gasoline) 430 (on 1 million Btu* of gasoline) 430 miles 430 miles 200 gCO2e/mi 200 gCO2e/mi miles 200 gCO2e/mi Natural Gas Internal Natural Gas Internal Combustion Engine Combustion Engine Natural Gas Internal 390 390 Combustion Engine 175miles 175miles 390 gCO2e/mi gCO2e/mi 175miles gCO2e/mi on Cell Vehicle on Hydrogen from Natural Gas from Natural Gas Fuel Cell Vehicle on Hydrogen 255 255 from Natural Gas 255miles gCO2e/mi 255miles 255 gCO2e/mi miles 2Electric55 Vehicle on Electricity gCO2e/mi from Natural Gas Electric Vehicle on Electricity from Natural Gas 200 Electric Vehicle on Electricity 200 from32 Natural5miles Gas gCO2e/mi miles 325 200 gCO2e/mi miles Figure325 4. How far can a car go on 1 million Btu of natural gas? gCO2e/mi Miles traveled per million Btu of natural gas One million British thermal units (Btu) is the energy contained in Miles traveled per million Btu of natural gas One million British thermal units (Btu) is the energy contained in Well-to-wheel Emissions (area proportional to emissions) approximately 9 gallons of gasoline. Miles traveled perper millionmillion Btu of natural gasWell-to-wheelWell-to-wheel emissionsEmissionsOne (area million proportional British to thermal emissions) units (Btu)approximately is the energy 9 gallons contained of gasoline. in  Btu of natural gas (area proportional to emissions) Well-to-wheel Emissions (area proportional to emissions) approximately 9 gallons of gasoline.

* One million Btu is the energy contained in approximately nine gallons of gasoline.

Cover images from left: Chevy Impala CNG vehicle For information on the GREET Model from Corportation; Keith Wipke, see greet.es.anl.gov NREL 18281; Fit EV For more information, visit: www.energy.gov/eere/ about-us/policy-and-analysis-team DOE/GO-102015-4685 • December 2015