County of San Diego 2005/2006 Greenhouse Gas Emissions Inventory

governments that operate wastewater treatment facilities, including wastewater pumps, treatment plants, septic
systems, collection lagoons, and other facilities, must therefore account for the emission of these gases in their
overall greenhouse gas emissions inventory. 11
Methane is generated under anaerobic conditions, which could occur at centralized facilities or septic tanks;
however, many centralized treatment facilities are utilize aerobic processes, and in these cases methane is not a
significant concern. Nitrous oxide is emitted at facilities that utilize nitrification and denitrification of wastewater.
In 2006, the County of San Diego operated eight wastewater treatment facilities, serving over 130,000 people,
including the residents and businesses located in Julian, Spring Valley, Lakeside, Alpine, and other areas in the
unincorporated region. Because these are aerobic facilities, nitrous oxide is the only greenhouse gas that must be
accounted for. The operation of San Diego County wastewater treatment facilities produced nearly 2,673 metric
tons of CO 2 e from nitrification/denitrification and from electricity consumed at the facilities.
Gas
N 2 0
Table 3.6: Wastewater Treatment Emissions by Type
Greenhouse Gas Emissions
Source
(metric tons CO 2 e)
Treated Effluent Released
to Environment 2,655
CO 2 , CH 4 , N 2 0 Electricity Consumption 18
TOTAL 2,673
3.4.5 Solid Waste Facilities
There are a variety of emissions associated with solid waste management services including the collection,
processing, and storage of solid waste generated from residents and businesses. 12 The most prominent source of
emissions from solid waste facilities is methane released by the decomposition of organic waste over time in
landfills. The scale of these emissions depends upon the size and type of the landfill and the presence of a landfill
gas collection system.
The County of San Diego had operational control of ten inactive landfills operated in 2006, and no active landfills.
Although inactive landfills are not accumulating additional waste, they continue to emit greenhouse gases. In 2006,
these landfills, which include San Marcos, Encinitas, Jamacha, and others, produced over 64,000 metric tons of
CO 2 e from the above sources (Table 3.8). Nearly 70 percent of these emissions came solely from the operation of
the San Marcos inactive landfill.
11 These emissions should not be confused with those described in Section 3.4.3, which refer to the transportation of water and wastewater.
This section refers exclusively to the decomposition and treatment of wastewater.
12 The County operates a recycling facility; however, emissions are not included here. While it is likely that recycling processes result in the
release of greenhouse gases, there are currently no accurate methods for estimating the amount of emissions from these activities. For this
reason, process and fugitive emissions from recycling and composting facilities are not included in LGOP.
2005/2006 San Diego County Greenhouse Gas Emissions Inventory 24