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Techno-economic assessment of low-carbon rail freight transportation - There have been many studies of how to decarbonize road transportation, but comparatively few on the best path for rail decarbonization in the United States. US railroads rely on diesel and have been resistant to electrification with catenary. Hydrogen, batteries, and biofuels are under consideration as options for decarbonization. The route from the Port of Los Angeles to Barstow (the Cajon Sub) is a good case study because of its high utilization and its uneven topography.
This analysis considered the net present cost over the lifetime of a locomotive of five technologies for traction along the Cajon Sub: Diesel, the current mainstay; biodiesel, a drop-in replacement with lower carbon intensity; hydrogen, a widely considered option for decarbonization of heavy freight; batteries, which are also widely used for transportation electrification; and catenary, a widely used but capital intensive way to decarbonize rail systems. It considered the net present value in three methods of calculation: private cost to a company without considering policies; the credit cost, meaning the private cost after considering the sale of credits under California’s low-carbon fuel standard and tax credits for hydrogen under the Inflation Reduction Act; and the social cost, considering the total cost to society of air pollution and greenhouse gas emissions. It conducted a Monte Carlo simulation which deployed wide ranges of values for inputs to produce a range of outputs for all fifteen NPV cost calculations. It also conducted analysis of the same route with only one train per day, to simulate options for lightly utilized railways.
The ranges for costs of all options at least partially overlapped, but clear trends were visible. The analysis found that for all three methods of calculation, on average, electrification with catenary is the lowest cost option, with battery electrification as a close second. The use of hydrogen fuel cells is the third lowest cost option, but with noticeably higher cost than the electric options. This is true even when ignoring externalities, and even more the case when considering them. When considering the full social cost of operation, diesel is the highest cost option, while when considering only the private cost, with or without tax credits and LCFS credits, biodiesel is the highest cost option while diesel is the second highest.
In the simulation with only one train per day, battery electric operation was the lowest cost option, for all three methods of calculation. Catenary was by far the highest cost option in this simulation, though if extremely low cost of catenary can be achieved, it could be competitive with other options. The choice between the other three depends on the method of calculation.
This study finds that over the lifespan of a typical locomotive, electrification through batteries or catenary is typically the most cost-effective option for rail operation, in most cases by a substantial margin. This holds true for both highly and lightly utilized rail corridors, and whether or not policies to reduce emissions are considered. It bolsters the case for electrification of land transportation.
