County of San Diego 2005/2006 Greenhouse Gas Emissions Inventory

4.2.3 Transportation Sector
As with many other local governments, transportation within the jurisdictional boundaries of unincorporated San
Diego County constitutes the greatest percentage (69 percent) of community wide greenhouse gas emissions –
2,909,342 metric tons CO 2 e.
Table 4.5: 2005 On-road Transportation Emissions
by Type
Greenhouse Gas
Emissions
(metric tons CO 2 e)
Share of Total
Transportation
Emissions
Source
Local Roads 846,671 31%
State Highways 1,919,023 69%
TOTAL 2,765,694 100.0%
Ninety-five percent of transportation sector emissions came from on-road travel, with the remaining five percent
originating from off-road mobile sources. As shown above in Table 4.5, travel on local city roads constituted 31
percent of on-road emissions, and 69 percent came from travel on state highways within unincorporated areas. An
estimated 85 percent of transportation emissions were due to gasoline consumption with the remaining
approximately 15 percent coming from diesel use and less than one percent from compressed natural gas.
Please see Appendix D for more detail on methods and emissions factors used in calculating emissions from the
Transportation Sector.
4.2.4 Solid Waste Sector
The solid waste sector constituted three percent of total emissions for the unincorporated San Diego County
community in 2005. Emissions from the solid waste sector are an estimate of future methane generation from the
decomposition of municipal solid waste (MSW) and alternative daily cover (ADC) sent to landfill in the base year.
These emissions are considered Scope 3 because they are not generated in the base year, but will result from the
decomposition of 2005 waste over the full 100+ year cycle of its decomposition.
The solid waste sector also includes Scope 1 base year emissions from landfills in the jurisdiction, known as
“landfill waste-in-place.” As stated in the Government Inventory section, about 75 percent 18 of landfill methane
emissions are captured through landfill gas collection systems, but the remaining 25 percent escape into the
atmosphere as a significant contributor to global warming. Please see Table 4.6 below for a summary of emissions
per major waste type. 19
18 US EPA AP 42.
19 Waste characterization figures were provided by the 2004 California Waste Characterization Study,
http://www.ciwmb.ca.gov/Publications/default.asp?pubid=1097
2005/2006 San Diego County Greenhouse Gas Emissions Inventory 36