What is a carbon footprint and how is it measured?
A carbon footprint is the total CO2 and other greenhouse gases produced by a home, business or government agency. To measure its carbon footprint, SLVWD joined the California Climate Action Registry (CCAR) in 2007 and the national Climate Action Registry in 2008.
Using established protocols, SLVWD has assessed and reported its greenhouse gas emissions (GHG) for the years:
Reports for all six years have been certified by CCAR and CAR, with SLVWD consistently recognized as a "Climate Action Leader."
What are SLVWD's sources of greenhouse gas emissions?
The four primary sources of the District's GHG emissions over the years 2006-2011are listed below:
Mobile combustion (District vehicle fleet)
Stationary combustion (generators and natural gas)
Purchased electricity (water pumping and building use)
Commuting (combustion from employee vehicles).
Comparing SLVWD's Greenhouse Gas Emissions from 2006 - 2011
As the chart below shows, the District's largest overall source of GHG emissions is
electricity, which is used mostly to operate its deep-water wells. The District purchases its electricity from PG & E, which includes both fossil-fuel and alternative energy sources in its mix. Clearly, electricity used for booster pumps and well-pumping is the District's largest source of GHG emissions.
The District's emissions from stationary combustion are generated by natural gas and other fossil fuels to run generators. Stationary combustion emissions increased from 10 mt CO2e in 2006 to 40 mt CO2e in 2011. The increase reflects increasing accuracy in tracking stationary combustion emissions, as well as a significant increase in power outages in 2011, which required more generator time.
The large majority of the District's electricity powers groundwater pumping and booster bumps. In wet years groundwater pumping starts relatively late in the season and demand for water is generally lower. In dry years, groundwater pumping starts earlier in the season, and demand for water is generally higher. Figure 2 shows that kilowatt hours (kwh) of electricity used remained the same from 2007 to 2008, even though GHG emissions increased in 2008. What factor might explain this increase?
As the chart below shows, the District's GHG emissions from purchased electricity generally increases with the number of kwh used in every year, but it also depends on PG & E's mix of fuel sources. Compared to 2007, in 2008 PG & E's energy portfolio was more fossil fuel intensive. (One of the alternative fuel sources that PG & E reduced in 2008 was hydropower, due to the statewide drought.) In 2009, even though the District's kwh increased slightly, its GHG emissions dropped somewhat, which reflects a subsequent change in PG & E's mix of fuel sources.
The District was required to estimate the number of kwh hours used by the Felton water system for the entire calendar year 2008, even though the District acquired the system in September 2008 (PG & E records for this account were not available from January - August 2008.) So the estimates could have been high for 2008. From 2009 to 2010, the decrease in kwh shown in Figure 2 was likely due to 2010 being a relatively wet year. From 2010 to 2011, the decrease in kwh was due to several factors. 2011 was a wetter year, PG & E had more alternative fuels in its energy portfolio, and, perhaps most significantly, the solar panel installation at Lyon and Felton treatments plants began producing electricity in July 2011.
The District is not required to report GHG emissions from employee commuting, but it has done so every year. As Figure 1 shows, emissions have remained near 35 mt CO2e from 2006 through 2011.
With each successive year of reporting, the District has gained valuable new information to assist it in assessing levels and identifying sources of its GHG emissions. Because the District cannot control droughts or influence the choice of energy sources by PG & E, the District increased its own use of alternative and renewable sources of electricity. In 2011, the District invested in a substantial solar project, which contributed to a significant reduction that year in both kwh of purchased electricity and GHG emissions.