The petroleum-based transportation fuel system is complex and highly developed, in contrast to the nascent low-petroleum, low-carbon alternative fuel system. This report examines how expansion of the low-carbon transportation fuel infrastructure could contribute to deep reductions in petroleum use and greenhouse gas (GHG) emissions across the U.S. transportation sector. Three low-carbon scenarios, each using a different combination of low-carbon fuels, were developed to explore infrastructure expansion trends consistent with a study goal of reducing transportation sector GHG emissions to 80% less than 2005 levels by 2050.1 This goal was for analytic purposes only. These scenarios were compared to a business-as-usual (BAU) scenario and were evaluated with respect to four criteria: fuel cost estimates, resource availability, fuel production capacity expansion, and retail infrastructure expansion.
Initial evaluations of these four criteria enable consideration of screening-level questions about fuel infrastructure in the low-petroleum, low-carbon scenarios:
1. How do alternative fuel costs compare to conventional fuel costs?
2. Are low-carbon resources sufficient?
3. How does expansion of alternative fuel production capacity compare to conventional production capacity replacements, upgrades, and expansion?
4. How do costs of providing alternative fuel retail infrastructure compare to conventional retail infrastructure?
Although definitive comparisons are not possible in this screening study, results suggest that expansion of the retail infrastructure for alternative fuels may pose greater issues than fuel costs, resources, or production capacity. The study does not address market barriers and transition costs associated with the development of new advanced vehicle and low-carbon fuel markets, so fuel cost estimates do not reflect investment risks or projected fuel prices. However, an evaluation of each scenario suggests that the goal of a reduction of 80% in GHGs can be reached while maintaining total fuel costs that are ultimately lower than BAU fuel cost projections without imposing excessive demands on energy resources such as biomass, natural gas, or renewable electricity systems.
The amount of new fuel production capacity required [e.g., billions of gallons of gasoline equivalent energy (BGGE) per year] in the low-carbon scenarios is comparable to those for conventional fuels in the BAU scenario, despite the transition to different fuels, because fuel demand in the low-carbon scenarios is lower. Expansion of retail infrastructure, on the other hand, may prove challenging in terms of spatial coverage and sustainable business models for retail outlets. Suggestions in the study for further analysis call for improved cost estimates, an improved understanding of the influence of refueling infrastructure on consumer vehicle purchase decisions, exploration of the potential role of public-private partnerships in infrastructure planning and expansion, and spatial and temporal market and infrastructure expansion trends.

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