Greenhouse Gas Inventory

Sonoma County is committed to measuring, tracking, and reporting our greenhouse gas (GHG) emissions to communicate progress and focus our actions.

While our ambitious GHG reduction goals take into account the critical role both regional and state entities play, our GHG inventory reflects the sectors and emissions sources that can be reduced through the actions of local governments and regional entities.

The Sonoma County Regional Climate Protection Authority (RCPA) established a baseline communitywide GHG inventory for calendar year 2010 and a backcast inventory for 1990 as part of the Climate Action 2020 and Beyond (CA2020) development process. The RCPA has since completed inventory updates for 2015, 2018, and 2020 to help track progress towards achieving the short and long-term emissions reduction goals established in CA2020 and in the Sonoma Climate Mobilization Strategy.

2020 GHG Inventory Update

The Sonoma County Regional Climate Protection Authority (RCPA) has just completed its 2020 Greenhouse Gas Inventory Update. Additional details from the inventory will be posted in the near future, but the links below provide access to our initial results:


RCPA has recently published its fourth inventory of communitywide greenhouse gas (GHG) emissions, bringing the report up to date through 2020 with thirty years of local inventory data. This article explores the details of the current inventory and provides RCPA’s initial analysis of emission reduction trends and future mobilization opportunities. In short, Sonoma County greenhouse gas emissions in 2020 stand at 3.04 MTCO2e (metric tons of carbon dioxide equivalent) and have decreased 22.9 percent from 1990. This reduction is just over 2% short of the Climate Action 2020 goal of reducing emissions by 25 percent below 1990 levels by 2020. While Sonoma County did not fully meet these ambitious 2020 climate goals, this level of GHG reduction is still an incredible accomplishment. It shows long-term dedication to climate protection efforts across all of RCPA’s member jurisdictions, agency partners, and local community-based organizations.


In 2016,  RCPA led the Climate Action 2020 initiative and created the county’s first community GHG inventory using 2010 data. This effort also created a historical backcast using 1990 data to provide a benchmark from which to track the impacts of local climate protection campaigns. As part of Climate Action 2020, an ambitious set of goals was adopted by the RCPA Board, including the target of reducing GHG emissions to 25% below 1990 levels by 2020.
Following the initial inventory in 2016, RCPA completed updates in 2018 using 2015 data, in 2020 using 2018 data, and now in 2022 with 2020 data. All of these inventories follow the U.S. Community Protocol for Accounting and Reporting of Greenhouse Gas Emissions produced by ICLEI and last updated in July 2019.
Finally, as part of the Sonoma Climate Mobilization Strategy adopted by the RCPA Board in March 2021, the countywide GHG goals have been further strengthened. The updated goals call for Sonoma County to become carbon neutral by 2030, working toward even deeper emissions reductions of 80% below 1990 levels by 2030. RCPA is also working with agency partners to expand local carbon sequestration efforts to balance the remaining emissions and ensure carbon neutrality.

2020 Inventory Overview

The results from RCPA’s inventory show that countywide emissions for 2020 were just over 3 million metric tons of carbon dioxide equivalent. Building Energy emissions stand at just over 2/3 of a million metric tons, or 23% of countywide emissions. Transportation emissions are the largest sector at 1.7 million tons and account for 58% of the total. Water, solid waste, and agriculture show much smaller emissions totals and lower percentages of the whole. As with past inventories, major opportunities still exist in lowering emissions from both the building and transportation sectors. RCPA will also look further into the solid waste and agricultural sectors for additional opportunities to make its 80% reduction goal.

When one looks at emission totals from 1990 to 2010, a time span of 30 years, a sharp downward trend is apparent, beginning at 3.94 million metric tons in 1990 to 3.0 million tons in 2020. As mentioned above, RCPA’s 2020 total is a 23% reduction from 1990 levels and falls just over 2% short of the countywide Climate Action 2020 goal. Although this indicates that the ambitious 2020 target was not met, this is still an incredible accomplishment and RCPA offers a whole-hearted thank you to anyone and everyone working on climate-related issues in Sonoma County for making this happen.

After reviewing the data used to calculate emission levels, RCPA estimates that the COVID-19 pandemic did impact Sonoma County’s emissions in 2020. Due to the “stay at home” orders and the subsequent slowing of the economy in 2020, vehicle miles traveled were dramatically lowered for a number of months in 2020 and 2021. This resulted in lowered greenhouse gas emissions in the on-road transportation sector that began to rise again as restrictions were lifted.
Although these short-term COVID-19 impacts on GHG emissions are evident, the long-term impacts are still uncertain. RCPA expects that emissions will continue to rise at a lower rate than vehicle miles traveled due to improvements in fuel efficiency and a shift from fossil fuel vehicles to hybrid and electric vehicles. The State of California’s recently announced requirement for 100 percent zero-emission vehicle sales by 2035 is another major step in this direction.

2020 Inventory Results by Sector

Building Energy
In the Building Energy sector, GHG emissions have been reduced nearly 50% as compared to the 1990 baseline. In general, energy efficiency programs continue to reduce the amount of raw energy consumed by local homeowners. Secondly, and more importantly, the formation of Sonoma Clean Power in 2014 has led to a dramatic reduction in GHG emissions as they have invested in new sources of 100% renewable power. Looking forward, efforts in the upcoming years will need to focus on replacing heating, cooling, and cooking that use natural gas. Instead, a dedicated effort will be needed to switch instead to heat pump and induction technologies that are more efficient and produce significantly fewer GHG emissions.

The Transportation sector continued to be the largest contributor to emissions, with on-road emissions at 58% of total emissions. RCPA’s current analysis shows only a 1% reduction in emission since 1990, albeit with a 16% reduction from 2018. As mentioned prior, RCPA believes that this short-term reduction is due to the COVID-19 pandemic and Sonoma County will need to work hard to keep these gains. Given that the transportation sector makes the majority of the entire inventory, RCPA efforts will continue to place great focus here. Specifically, RCPA is working closely with colleagues at Sonoma County Transportation Authority on two fronts. First, staff are continuing to implement “fuel-shift” strategies that increase the number of electric vehicles owned by local residents and businesses. Additionally, expanded focus also needs to be placed on “mode-shift strategies” that encourage the use of public transportation, bikes, scooters, or other forms of active transportation.

Emissions from the water sector make up only 1% of the inventory and there has been negligible change between 2018 and 2020. Compared to 1990 emissions, there has been a 68% reduction in emissions, with this coming almost entirely from the water conveyance sub-sector. This dramatic decrease from 1990 levels is another Sonoma County success story featuring Sonoma Water and their Carbon Free Water campaign. Since 2015, Sonoma Water has had contracts in place to procure 100% of its electricity needs through renewables and carbon-free resources. This has been one of the leading factors in the dramatic 68% decrease in emissions related to water pumping and treatment systems.

Solid Waste
Emissions from solid waste currently make up only 6% of RCPA’s most recent inventory, but can be seen as another local success story. Jurisdictional efforts to comply with new state waste reduction laws over the past few years have contributed to this decrease in emissions. AB 1826 (Chesbro, 2014) requires businesses that generate a specified amount of organic waste per week to arrange for recycling services for that waste and for jurisdictions to implement a recycling program to divert organic waste from businesses subject to the law. Additionally, SB 1383 (Lara, 2016) sets requirements for jurisdictions to coordinate efforts between city and county planners, waste haulers, waste processing facilities, recyclers, commercial businesses, residents, and edible food recovery organizations to reduce organic waste disposal by 75 percent by 2025 and to rescue at least 20 percent of currently disposed surplus food by 2025 for people to eat instead of being throw away. Between these two efforts, almost all businesses in the county producing over four cubic yards of waste per week have access to a blue and green bin for recycling and composting. Given these statewide changes, and the local efforts of the countywide waste management authority, Zero Waste Sonoma, emissions from solid waste are down 50% from 1990 levels.

Finally, the agriculture sector makes up 13% of the countywide total and has shown very little change from 1990 to 2018 to 2020. Given that the majority of these emissions are due to manure management, future efforts could focus here to evaluate additional reduction opportunities.


In conclusion, here are the key findings from the most recent 2020 GHG inventory:

  • Overall emissions have decreased 22.9% from 1990 levels, just short of RCPA’s 25% reduction goal.
  • Building energy emissions and emissions from solid waste have both decreased approximately 50% during this time.
  • Transportation continues to be the largest source of emissions and the largest opportunity area for future reductions.
  • Short-term impacts from COVID-19 are evident in the data, but long-term impacts are still uncertain.
  • And finally, to meet RCPA’s carbon neutrality goals for 2030, dramatic decreases in emissions and large-scale increases in sequestration are both needed.