Fuel-cycle emissions were evaluated in the context of marginal emissions associated with marginal alternative fuel consumption or gasoline displacement. A moderately small use of alternative fuels would displace gasoline that would be imported into the SoCAB or allow for additional exports from the SoCAB, while a more aggressive alternative fuels penetration may lead to a reduction in refinery output. Small increments of alternative fuel use would displace emissions from fuel hauling, vehicle fueling, and possible marine vessels used to import refinery blending components. On a small scale, other market conditions will influence refinery emissions more substantially than gasoline displacement due to alternative fuel use, leaving the refineries in the SoCAB operating at capacity. Many alternative fuels would be produced outside the SoCAB. Their marginal emissions correspond largely to fuel trucking or distribution and local vehicle fueling.
Electricity for EVs in use in the SoCAB is generated in the basin, the rest of California, and outside of California. Marginal emissions from power generated in the SoCAB are limited by several factors. Existing facilities in the SoCAB could not increase emissions beyond current permit levels and new facilities would need to buy offsets. Power plants in the SoCAB are subject to RECLAIM that provides a cap on power plant NOx emissions for each utility. If a utility is above its RECLAIM limit, it can install SCR on additional power plants or purchase NOx offsets. If a utility is already at its emission cap or in a position where it needs to purchase offsets with respect to SoCAB RECLAIM, any incremental power generation for EVs will result in no additional NOx emissions in the SoCAB. The CEC modeled the power generation requirements for baseline power and for EVs with several different power generation scenarios.
Based on CEC's analysis of the emissions of power plants with respect to their RECLAIM limits, marginal NMOG emissions from EVs, based on the CEC scenarios, are less than 0.01 g/mi.
Marginal emissions from diesel, and methanol distribution correspond to about 0.01 g/mi of NMOG. NMOG emissions from LPG distribution and fueling are currently very high due to vapor releases from fuel transfer operations. Vapor controls are assumed to be implemented for Scenario 3.
7.1 Emission Policy Considerations
The results of this study indicate that fuel spillage is a dominant source of fuel-cycle emissions if vehicle fueling vapor losses are eliminated. Once refueling vapor emissions are eliminated or are very low as in the case of diesel and methanol with ORVR, refueling spillage becomes the dominant source of NMOG. Spillage emissions in general tend to drop as fuel tank capacity is increased. For some vehicle technologies, fuel tank size will increase with lower fuel economy in order to maintain a constant range. While the consumer may not always utilize the full fuel tank capacity, the connection between marginal NMOG and fuel economy is weak.