Propane: An underrated fuel of the future

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While EVs bask in the spotlight of an energy transition, they cast a shadow on other fuels that can help offset conventional diesel and gasoline usage. Propane, a staple in many American households, is one of these underdog fuels. Propane, or liquified petroleum gas (LPG), is an energy-dense gas produced as a byproduct of natural gas processing and crude oil refining. It is typically stored as a liquid under pressure in tanks, powering appliances like grills, furnaces, and water boilers [1]. However, as will soon be revealed, its abilities extend far beyond smoking burgers on a Sunday afternoon. Affordable costs, abundant supply, and performance benefits suggest that propane, much like electrification, can help modernize America’s transportation sector.

The transportation sector is undergoing a shift from conventional gasoline and diesel to alternative fuels, most notably electricity, but also fuels like CNG, biodiesel, and propane. Last summer, I had the pleasure of interning with the New Jersey Clean Cities Coalition, a nonprofit dedicated to promoting the use of alternative fuels in the state’s transportation sector. My primary project was a fleet evaluation, where I analyzed the economic, energy security, and environmental impacts of alternative fuels on a gasoline and diesel work truck fleet. This involved research into fueling infrastructure, vehicle performance limitations, and costs and emissions modeling. Propane revealed itself to have attractive attributes that make it a compelling fuel for the future. In the following sections, I will evaluate the impacts of propane usage across several core competencies: financial viability (economics), environmental and energy security impacts, and performance viability. The first two sections concern the question: What benefits and drawbacks does propane use offer to individual fleets, the nation, and local/greater environmental health? The third section, on performance viability, concerns whether or not propane use is viable for a fleet, regardless of its potential benefits. After all, even if the numbers add up on paper, propane vehicles must be able to meet the sometimes intense demands of fleets, especially those performing emergency operations.

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Economics of Propane Fleet Implementation

Propane often has a lower cost per gallon than gasoline at primary fueling stations (those dedicated to vehicle fueling). For instance, Alliance Autogas, a fleet conversion organization with a large propane fueling network, reported average propane prices for the week of September 1, 2023 between $1.39 and $1.71 per gallon, depending on the US region [2]. During the same week, gasoline prices in the United States averaged $3.82 per gallon [3]. Thus, per-gallon costs can be more than halved by propane conversion. It should be noted that propane has roughly 27% less energy per gallon than gasoline [1]. However, the cost per gallon averaging less than half that of gasoline still makes it a more economical choice per unit of energy. Furthermore, propane is a higher octane fuel than gasoline, reducing maintenance needs and extending engine lifetime [1]. Taken together, reduced fuel and maintenance costs can often result in a net payback for fleets that implement propane vehicles.

Infrastructure complexity and costs are also minimal with propane implementation. Traditionally, propane vehicle fueling stations simply consist of an above ground tank and dispensing equipment. Total infrastructure costs can be as low as $65,000, and suppliers will often cover equipment costs in exchange for a fuel contract [1].

Environmental and Energy Security Impact of Propane Fleet Implementation

The emissions case for propane is favorable compared to its conventional counterparts. The Argonne National Lab GREET model estimates that conventional propane use reduces a vehicle’s lifetime greenhouse gas emissions by nearly 13% compared to a gasoline counterpart [1]. The use of renewable propane, sourced from feedstocks like fat, vegetable oil, and waste grease, can significantly increase this reduction. According to the AFDC, the carbon intensity of renewable propane can be four times less than conventional propane [1]. Thus, propane, especially when sourced renewably, can help fleets reduce their carbon footprint. Additionally, compared to diesel, propane use can cut nitrogen oxide emissions by roughly 95% in applications like school busing [4]. This is important considering the harmful effects of local air pollutants like nitrogen oxides, especially around vulnerable populations like children.

Since 2000, US propane production has more than tripled, with recent production near 2.6 million barrels per day (mbpd) [5]. Exports make up over half of this, at 1.5 mbpd, while imports are only 80,000 bpd, meaning that the fuel is largely sourced domestically [6]. It is thus an energy-secure fuel for use in the United States.

Furthermore, propane is sourced from crude oil refining and natural gas processing. When derived as a byproduct of natural gas production, according to the AFDC, it almost completely eliminates a fleet’s lifetime petroleum consumption [1]. While the US has recently become a net petroleum exporter, foreign imports still average over 8 million barrels per day, near 40% of consumption [7]. Natural gas is domestically abundant, with imports less than 10% of domestic consumption and exports rapidly rising [8]. Thus, by relying on a fuel that is not solely oil-based, like gasoline or diesel, fleets promote domestic energy security and reduce foreign oil reliance. Renewable propane, being sourced from domestic renewable feedstocks, has a similar energy security benefit.

Performance and Operational Viability of Propane Fleet Implementation

Propane Autogas already has a solid market size, being the third most common transportation fuel, behind only gasoline and diesel. This is not surprising considering its performance characteristics. Propane vehicles can match or exceed the performance (power, acceleration) of conventional counterparts, even for heavy duty vehicles [1]. For example, propane-fueled school buses provide a range up to 400 miles. Compare this to electric bus options which can get 75-210 miles on a single charge [9]. Keep in mind that charging is a much more time consuming process than refueling with liquid propane. Additionally, the cost of a propane vehicle is roughly a third the price of an electric bus, allowing propane to replace conventional diesel fleets three times as fast as e-buses [9]. Thus, even for heavy duty applications, propane is a functional choice for vehicle fleets.

Furthermore, propane’s higher octane rating and lower contamination characteristics can reduce engine wear and extend lifetime, making it an even more attractive option. New dedicated propane or bi-fuel (gasoline and propane) vehicles are widely available and can be purchased straight from manufacturers. Existing vehicles can be converted to run on propane as well [1].

To conclude, the transition of the transportation sector requires all options on the table to be considered. Propane, with its domestic abundance, operational viability, affordability, and relatively simple fueling infrastructure, makes quite the case for economic, energy security, and environmental gains. Although electric vehicles dominate the passenger vehicle industry, and will likely continue to, propane is worth exploring for decarbonization efforts in other sectors of transportation- like heavy duty trucking operations.


References

  1. AFDC. (n.d.). Alternative Fuels Data Center: Propane. Retrieved October 22, 2023, from https://afdc.energy.gov/fuels/propane_basics.html
  2. Alliance AutoGas. (n.d.). Alternative Fuel Powered by Propane. Alliance AutoGas. Retrieved October 22, 2023, from https://allianceautogas.com/
  3. EIA. (n.d.). Gasoline and Diesel Fuel Update. Retrieved October 22, 2023, from https://www.eia.gov/petroleum/gasdiesel/index.php 
  4. Lillian, B. (2019, August 19). Propane vs. Diesel School Buses: Study Shows Clear Winner When it Comes to Emissions. NGT News. https://ngtnews.com/propane-vs-diesel-school-buses-study-shows-clear-winner-when-it-comes-to-nox-emissions
  5. EIA. (n.d.). U.S. Field Production of Propane (Thousand Barrels). Retrieved October 22, 2023, from https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=M_EPLLPA_FPF_NUS_MBBL&f=M
  6. EIA. (n.d.). U.S. Imports & Exports. Retrieved October 22, 2023, from https://www.eia.gov/dnav/pet/pet_move_wkly_dc_NUS-Z00_mbblpd_4.htm
  7. EIA. (n.d.). Oil imports and exports—U.S. Energy Information Administration (EIA). Retrieved October 22, 2023, from https://www.eia.gov/energyexplained/oil-and-petroleum-products/imports-and-exports.php
  8. EIA. (n.d.). Natural gas imports and exports—U.S. Energy Information Administration (EIA). Retrieved October 22, 2023, from https://www.eia.gov/energyexplained/natural-gas/imports-and-exports.php
  9. STN. (2022, October 1). Propane School Buses: Let’s Clear the Air. School Transportation News. https://stnonline.com/partner-updates/propane-school-buses-lets-clear-the-air/

By Cameron Farid

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Cam Farid is a sophomore mechanical engineering student at Princeton University. He is the director of the Energy Journal team of the Princeton University Energy Association and is fascinated by the intersection of technology, geopolitics, and the global energy system.

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