Skip to Content | Accessibility Assistance | Resize Text: decrease font size increase font size reset

Tracking Sonoma County's Greenhouse Gas Emissions

On this page

One of RCPA's main goals is to employ a tracking system to capture greenhouse gas (GHG) emission data and assess progress in Sonoma County’s emission reduction goal of reducing emissions by 25% below 1990 levels by 2015. RCPA is working with interested stakeholders including city planning departments, PG&E, and the Climate Protection Campaign to track emissions data and provide transparent methodologies following accepted local government protocols.

Sonoma County Carbon Budget and Economic Impact for 2010

At the May 26, 2011 Climate Protection Everybody Profits conference held in Petaluma, RCPA staff presented the following handout, detailing aggregate communitywide emissions from transportation, electricity, and natural gas in 2010, comparing the total to the 2015 “carbon budget,” and translating the fossil fuel use into dollars leaving the County.

Sonoma County Carbon Budget and Economic Impact for 2010


2009 Countywide GHG Emissions Inventory

Sonoma County’s GHG emissions in 1990: 3.6 million metric tons carbon dioxide (CO2)
Goal of 25% below the 1990 level: 2.7 million metric tons carbon dioxide (CO2)
Sonoma County’s GHG emissions in 2009: 4.28 million metric tons carbon dioxide (CO2)

Sonoma County Total Emissions 1990 - 2009

Bar graph representing the annual combined carbon dioxide emissions in millions of tons for Solid Waste, Electricity, Natural Gas, and Transportation from 1990 through 2009. Transportation accounts for approximately 2.5 million tons, with Electricity and Natural Gas each accounting for approximately 0.5-0.7 million tons, and Solid Waste with approximately 0.1 million tons of carbon dioxide emissions during the stated period. The combined totals range from a 1990 baseline low of approximately 3.7 million tons to a 2008 high of approximately 4.4 million tons. It also depicts the projected decreasing total combined emissions needed to reach the Sonoma County 2015 Target of 2.7 million tons and the State of California 2050 Target of 0.7 million tons.
The dip in emissions in 2005 and 2006 corresponds with an increase in the proportion of electricity from hydropower.
Data source: 2009 Greenhouse Gas Emission Assessment, Dave Erickson and Ann Hancock, Climate Protection Campaign

Emissions Countywide by Sector for 2009

Sonoma County Total Emissions - 2009
4,282,269 tons

Sonoma County Total Emissions - 2009, refer to table below for alternate text description

Sector Tons of GHGs Percentage of
Transportation 2,648,402 62%
Residential Electricity 363,057 9%
Commercial Electricity 313,989 7%
Industrial Electricity 80,140 2%
Agriculture & Water Pumping Electricity 34,465 1%
Residential Natural Gas 449,101 11%
Commercial Natural Gas 207,381 5%
Industrial Natural Gas 47,443 1%
Agriculture & Water Pumping Natural Gas 5,380 0.13%
Solid Waste 96,537 2%

Data source: 2009 Greenhouse Gas Emission Assessment, Dave Erickson and Ann Hancock, Climate Protection Campaign

Climate Protection Campaign Annual Report Card (PDF)

Following the ICLEI-Local Governments for Sustainability approach, the four main sectors for calculating aggregate GHG emissions are Electricity, Natural Gas and Transportation, Solid Waste, and Agriculture.

Transportation represented 62% of countywide emissions in 2009, making it the single largest source of emissions. Electricity and natural gas represent 36% of emissions for Sonoma County. Emissions from agriculture, forestry and other biomass, while important, were not included in the Climate Protection Campaign’s 2010 update on greenhouse gas emissions due to the lack of an accepted, cost effective protocol for accounting for GHG emissions in this sector.

What do these numbers mean?

The monthly electricity use of almost seven homes in the PG&E service territory is about 1 metric ton (or 1 home for almost 7 months). On average, one car emits 6.5 metric tons of CO2 in a year. The average Californian emits 10.4 metric tons CO2 in a year and the average American emits 14.8 metric tons. (Sources: California Air Resources Board’s EMFAC model and PG&E GHG Emission Rates)

Many factors play a major role in Sonoma County’s GHG emission levels. GHG emissions may fluctuate each year depending on:

Annual rainfall: PG&E’s electricity procurement includes a large portion of low-GHG hydroelectric power from the Pacific Northwest. During years of high rainfall, PG&E’s emission factors decrease (the electricity used in Sonoma County is cleaner).

Population: Transportation related emissions increase as the population increases.

Economy: In booming economic times, GHG emissions increase. In a recession with higher unemployment or more vacant buildings, GHG emissions decrease.

For example, according to the 2005 countywide GHG emissions inventory, between 1990 and 2000 GHGs increased by 28%. Key factors during that decade included an increase in VMT of 42.5% and an increase in population of 18%. Although total greenhouse gases emitted by Sonoma County in 2009 decreased from 2008, according to the Climate Protection Campaign, the economic downturn is the probable main cause of this decrease.

Back to Top of Page

Links to Calculate Your Carbon Footprint

Back to Top of Page

Detailed Data Information

Coefficients and Methodology for Countywide Aggregate GHG Data Reporting

The following information about methodology and coefficients for tracking emissions is taken from the Climate Protection Campaign’s (CPC’s) Greenhouse Gas Emissions Update, September 2010: ICLEI-Local Governments for Sustainability is developing a communitywide data protocol for tracking GHG emissions. ICLEI’s protocols have been the recognized standard for emissions inventories for Sonoma County.


Electricity Use in Buildings (million kWh)
Residential  1,302
Commercial 1,126
Industrial  287
Agricultural (not in buildings)  124
Total 2,840

Natural Gas in Buildings (million therms)
Residential  76.8
Commercial  35.4
Industrial  8.1
Agricultural  0.9
Total  745,679

Electricity Emission Factors: Emission factors are the coefficient for converting kilowatts of electricity consumed into pounds of carbon dioxide emitted. The electricity emission factor that has been used in annual Sonoma County inventories has been the utility-specific factor available through Climate Action Registry reports. Most of Sonoma County is served by Pacific Gas and Electric Company, except for Healdsburg, which is served by the publicly owned City of Healdsburg Electric.

PG&E emission factors:

Electric for 2009: 0.558 lbs CO2 per kWh (average of 2003-2008 emission factors)
Electric for 2010 (provisional): 0.559 lbs per CO2 per kWh (average of 2004-2009 emission factors)
Natural Gas: 11.7 lbs CO2 per therm

Note: Emission factors vary every day and every year. PG&E’s emission factor in 1990 was 0.56, and in 2008 it was 0.641 lbs/kWh (Source)

City of Healdsburg emission factor:

Electric: 0.46 lbs CO2 per kWh (Source PDF)

Total energy use:

Electricity Use in Millions of kWh

County Sector 2006 2007 2008 2009 Total Usage
Sonoma Total 2841 2937 2970 2853 11603


Natural Gas Use in Millions of Therms

County Sector 2008 Total Usage
Sonoma Non-Residential 38.123100 38.123100
Sonoma Residential 79.022067 79.022067
Sonoma Total 117.145167 117.145167

Back to Top of Page

Mobile Sources (Transportation Sector)

Emissions from Transportation countywide for 2009

AVMT 4120.7
Tons eCO2 2,648,402

Mobile source emissions are difficult to quantify. ICLEI recommends using vehicle miles traveled (VMT) estimates from local or regional authorities in conjunction with the EMFAC model to generate fuel use numbers, and then normalizing the fuel use numbers generated with actual fuel use numbers from the state Board of Equalization. This method is based on an estimate of VMT, which is only distantly related to the physical reality of automobile use. Actual local fuel distribution numbers would be a superior proxy to estimate fuel used in the county. While fuel distributed in the county is not necessarily used in the county, trips that originate outside the county but terminate inside the county “net out” against trips that originate within the county, but terminate outside. There are two other data points that can be used as a cross-check to verify emissions calculations based on fuel sales. CPC also cites two other sources of data that can be used for cross-checking emissions – number of vehicles registered in the county and trends in vehicle counts obtained from CalTrans. These indicators track actual conditions that directly reflect vehicle use in the county.

2008 Gasoline Sales by County

Sonoma: 215.82 Million Gallons

2008 California Retail Diesel Sales by County

Sonoma: 22.83 Million Gallons

Board of Equalization: Motor Vehicle Fuel Monthly Motor Vehicle Fuel Distributions Report

DMV vehicle registration by county (PDF)

2009 Sonoma County
Autos: 306,307
Trucks: 109,243
Total vehicles: 487,042

CalTrans: California Motor Vehicle Stock Travel, and Fuel Forecast (MVSTAFF)

Back to Top of Page

Solid Waste

Emissions from Solid Waste countywide for FY 2008/2009

Tons solid waste 263,087
Tons eCO2 96,537

The landfill gas collection system on the Central Landfill in Sonoma County can be used to estimate fugitive emissions from landfills. Fugitive emissions should be added to the ongoing emissions estimates from landfills inside and outside the County receiving the County’s solid waste. Changes in where Sonoma County landfills its solid waste should be reflected in its quantification of emissions.

Water Delivery, Wastewater Treatment and Septic Systems

The provision of water, end use heating of water, and resulting wastewater treatment are major contributors to energy use in the County. Report on emissions from the water sector in Sonoma County (PDF)

Non-utility delivered fuels

In Sonoma County and other counties with a rural population, non-utility delivered fuel sources may represent a significant source of emissions. Liquid propane gas falls into this category.

Agriculture and Forestry

The County has approximately 480,000 acres of forestland, and roughly 230,000 acres that are currently functioning as timberland. The Community Climate Action Plan estimates that 375,000 acres of land in the County is capable of growing timber. This sector can be both a source of emissions through timber conversion and deforestation, and a sink for sequestering carbon in biomass as new trees absorb CO2.

The Community Climate Action Plan:

Back to Top of Page

Other data sources:

Other relevant reports:

Finally, there are some other good indicator programs already out there to consider:

Coefficients and Methodology for Local Government Operations GHG Data Reporting

The California Air Resources Board, in partnership with the Climate Action Registry, ICLEI - Local Governments for Sustainability, and others, has released a Local Government Operations Protocol.

Local governments in Sonoma County work within the framework of ICLEI - Local Governments for Sustainability’s Cities for Climate Protection ™ (CCP) Program.

RCPA seeks to become a data repository for local government GHG emissions inventories. City and County staff can contact Mike Sandler, RCPA Program Manager at (707) 565-5379 or for more information.

Back to Top of Page