After diesel is produced in a refinery, it is stored in bulk tanks and distributed to fueling stations in tank trucks. Emissions resulting from the storage of petroleum and petroleum fuels consist of two main types: fugitive and spillage emissions. Fugitive emissions are hydrocarbon emissions that escape from storage tanks, pipes, values, and other sources of leaks. These emissions are generally greater for gasoline than diesel due to its higher vapor pressure.
The low vapor pressure of diesel has generally resulted in limited requirements on vapor recovery from storage and fueling equipment. The vapor pressure from diesel is so much lower than that of gasoline, that the uncontrolled diesel vapor losses are less than 10 percent of gasoline emissions with 95 percent emission control (see Section 4.9).
Vapor losses primarily occur when tank trucks are filled at the bulk terminal, unloaded at the fueling station, and during vehicle fueling. Spillage during vehicle fueling is also a significant source of emissions.
3.4.5 LPG Storage and Distribution
The fuel-cycle steps for LPG parallel those for diesel. LPG is stored and distributed in pressurized tanks as shown in Table 3-8.
Table 3-8: LPG Production and Distribution Phases
Heaters, pumps, fugitive
Pipeline (pumps), ships (engines)
Refining process emissions
Transport to bulk storage
Transport to local station
Tanker trucks (engines & fugitive)
Local station distribution
Above ground tanks
3.5 LPG from Natural Gas
LPG is produced when liquids are extracted from natural gas. Marginal emissions in the SoCAB are zero since processing of LPG occurs in Canada or the Southwest states.
Fugitive emissions from gas production are discussed in Section 4.3.
The emissions rate for fugitive losses was determined from the annual emissions divided by annual production. Based on this data, fugitive losses in the United States represent 0.8 percent of total throughput. Fugitive losses were allocated to natural gas and LPG. The allocation to LPG was 3 percent, which is proportionate to the LPG content in natural