Greenhouse Gas Inventory –
Frequently Asked Questions

A selection of questions and answers related to the 2020 Greenhouse Gas Inventory.
Last updated 2022-11-19

Inventory Protocol

What protocol does RCPA use for the Sonoma County Greenhouse Gas Inventory?

  • RCPA follows the U.S. Community Protocol for Accounting and Reporting of Greenhouse Gas Emissions published by the International Council for Local Environmental Initiatives (ICLEI) for the five Basic Emission Generating Activities:
    • 1) Use of electricity by the community,
    • 2) Use of fuel in residential and commercial stationary combustion equipment,
    • 3) On-road passenger and freight motor vehicle travel,
    • 4) Use of energy in potable water and wastewater treatment and distribution, and
    • 5) Generation of solid waste by the community.
  • The current version 1.2 of the protocol was released in July 2019 ( and includes the main protocol document as well as several appendices which RCPA uses as reference in our calculation of the five basic emission generating activities. While the protocol does contain guidance on calculating air travel emissions and on developing consumption-based inventories, RCPA’s inventory has and remains focused on the five basic activity sectors. Please see below for specific information on these two optional areas.

Jurisdictional Alignment

Are all jurisdictions in the county using comparable greenhouse gas inventory protocols?

  • RCPA conducts a “community” level inventory and currently uses the S. Community Protocol for Accounting and Reporting of Greenhouse Gas Emissions v1.2. Several jurisdictions also conduct their own “municipal” inventory of emissions using the Local Government Operations (LGO) Protocol also developed and distributed by ICLEI. The LGO protocol focuses on government-operated buildings, vehicles, and other internal operations. Although the methodologies used in the two protocols are similar, results are not necessarily directly comparable due to the differing scopes of the efforts. RCPA staff is currently evaluating options to provide comprehensive reporting of both jurisdictional LGO emission inventories and the communitywide inventory that RCPA produces. Such an integrated tool would be useful for both local government staff and community members alike for future emission reduction planning.

Inventory Updates

How often is the RCPA Communitywide Greenhouse Gas Inventory updated?

  • RCPA’s current workplan calls for updating the inventory every two years, although we can see clear value in compiling an updated inventory each year as we get closer to our 2030 carbon neutrality goals. RCPA staff will evaluate making upgrades to our inventory tracking system to allow for more easily updating inventory data on an annual basis. As part of this process, we are exploring options of completing two inventory years each time or compiling a scaled-down inventory every other year to allow for better trend analysis of key emissions data as we get closer to our 2030 carbon neutrality goals. Additional indicators that track local transportation improvements and/or housing density will also be looked at for potential integration into our existing greenhouse gas inventory methodology and reporting procedures.

Wildfire Emissions

Does the inventory include the loss of acreage due to wildfire?

  • RCPA does not include greenhouse gas emissions in our community inventory directly attributable to wildfires. Given that the majority of carbon released during wildfires is “biogenic” (recently formed by biological processes), these emissions are excluded from our inventory following ICLEI protocol guidance. Within the Solid Waste sector, the total tons of solid waste disposed in Sonoma County increased significantly following the 2017 wildfires due to the large volume of fire debris. The resulting debris was largely ash, and by the time it was delivered to the landfill there were minimal gases left to escape and emissions from the debris were negligible.
  • Additionally, the California Air Resources Board (CARB) estimates annual greenhouse gas emissions from wildfires. CARB also works with other State agencies to develop an ecosystem carbon inventory for natural and working lands to quantify the carbon stored in the State’s forests, soils, and other natural lands. (

Consumption-Based Emissions

Are consumption-based emissions included in the RCPA Community Greenhouse Gas Inventory?

  • RCPA does not currently include consumption-based emissions in the Sonoma County Greenhouse Gas Inventory. Consumption-based inventories attempt to include all human activities in Sonoma County that drive an increase or decrease in atmospheric GHG emissions. Rather than trying to account for every source of emissions, RCPA’s approach focuses on monitoring progress on the largest emissions sources that can most directly be influenced by local government actions. The consumption-based emissions categories that were excluded from this inventory update include the consumption of goods and services imported into Sonoma County and air travel.
  • As an alternative, RCPA has previously included results from a 2015 study ( released by the Cool Climate Network, a University-Government-Business-NGO Partnership at the University of California, Berkeley. Based on this study, Sonoma County’s total consumption-based emissions in 2015 were 7.2 million MT CO2e, significantly higher than the approximately 3.4 million MT CO2e activity-based emissions reported in the 2015 and 2018 inventory updates. In general, consumption-based inventory techniques complement the RCPA inventory and can help our community identify additional actions that we can all take to reduce emissions from our consumption of goods and services. RCPA will continue to include any updated results that are released by the Cool Climate Network, but does not plan to conduct a Sonoma County-specific consumption-based inventory due to budget limitations.

Energy Data

Does the inventory allow for a break-out of energy use differences between single family and multifamily housing, or for the ability to look at utility usage data broken out by income level?

  • The electricity and natural gas data inputs to the RCPA inventory are segregated by residential vs. non-residential and do not allow RCPA to disaggregate single family housing energy use from multifamily housing. Alternatively, there are several other sources of jurisdiction-specific building energy data that may be useful for these purposes. These include the Cost-Effectiveness Explorer developed by the California Statewide Codes & Standards Program ( jurisdiction/sonoma-county/summary), as well as the Bay Area Energy Atlas developed by UCLA’s California Center for Sustainable Communities, in partnership with and funded by the Bay Area Regional Energy Network ( The Bay Area Energy Atlas specifically allows a user to break out utility data by income levels for each jurisdiction.

Natural Gas Leakage

Do natural gas calculations include any direct contribution for expected leakage?

  • Our calculations do not build in an escalator for natural gas leakages equivalent to the transmission and distribution line loss factor that is added to electricity usage. The ICLEI protocol does not recommend this approach or provide a calculation methodology. A process for calculating these “fugitive emissions” is included in the Global Protocol for Community-Scale Greenhouse Gas Inventories (GPC), Ver. 1.1 ( which references the IPCC Guidelines for National Greenhouse Gas Inventories published in 2006 and updated in 2019. ( RCPA staff will evaluate these approaches for potential inclusion in future inventory reports.

COVID-19 Impacts

Did COVID-19 impact our Transportation emissions in 2020 as to show only a temporary reduction from 1990 levels?

  • The dramatic short-term reduction we see in transportation emissions was most likely caused by the onset of the COVID-19 pandemic in March 2020 and the subsequent shelter-in-place orders that were enacted. Our on-road transportation calculations are derived from vehicle miles travelled (VMT), and it can be surmised that 2020 transportation emissions would not have shown any decrease from 1990 levels if not for the impacts of COVID-19 on local VMT counts. As the pandemic subsides and travel patterns return to more recognizable pre-pandemic levels, we expect that emissions will rise, but at a lower rate than the direct vehicle miles traveled due to additional improvements in fuel efficiency and a shift from fossil fuel vehicles to hybrid and electric vehicles.

SMART Rail Emissions

Can SMART ridership be further analyzed from a per-capita basis to better compare against other transportation modes?

  • Our analysis of greenhouse gas emissions from the SMART rail system is based on annual systemwide diesel usage and the percentage of operating track in Sonoma County. While additional analysis of SMART ridership patterns would be helpful from a forecasting and planning perspective, it is currently not possible using the data compiled for the inventory. RCPA staff will work with our SCTA counterparts and with SMART directly to better understand what additional resources may be available for this further analysis of ridership trends.

Air Travel Emissions

Are air travel emissions included in the RCPA Community Greenhouse Gas Inventory?

  • Emissions resulting from air travel are not included in the RCPA inventory because of the challenges in determining the origin and/or destination of flights and because Sonoma County communities do not have control over aircraft sources. Although emissions directly produced by aircraft are not included in the inventory, airport building energy use is captured in the building energy sector, and emissions from aircraft ground-support equipment (GSE) are captured in the off-road transportation sub-sector.
  • The appendices of the U.S. Community Protocol for Accounting and Reporting of Greenhouse Gas Emissions do offer a simplified methodology (Appendix D, TR. 6) for calculating emissions from air travel based on the amount of jet fuel and aviation gasoline that is dispensed at the airport. Alternatively, the Global Protocol for Community-Scale Greenhouse Gas Inventories (GPC) also offers a similar methodology (Section 7.6.1) for calculating air-travel emissions. RCPA will continue to evaluate using these methods to provide an adjunct report to our main activity-based inventory.

Solid Waste Emissions

How is the transportation of solid waste into/out of Sonoma County handled in the data that is received from Zero Waste Sonoma?

  • The solid waste disposal values used in the inventory contain all jurisdiction waste that was disposed in California landfills, transformation facilities, engineered municipal solid waste conversion facilities, and/or exported out-of-state, except for declared disaster debris disposal and disposal in Class II facilities, as those two types of tonnage are no longer tracked by jurisdiction of origin. Zero Waste Sonoma compiled the data from waste hauler reports and transfer station self-haul tonnages based upon where the solid waste originated.

Supervisor Districts

Can the data be broken out by Supervisor Districts for electricity use, Sonoma Clean Power service level, and/or transportation mode-split percentages?

  • All of the data inputs used in the RCPA Greenhouse Gas Inventory are either collected at the jurisdictional level or are county-level datasets that are apportioned out to jurisdictions by population. It would prove to be very difficult–if not impossible–to translate these multiple inputs into a format that would provide reliable results through both a jurisdictional lens and through a County supervisorial district lens. Alternatively, final emission results could potentially be allocated back to individual districts by raw population counts, but this method would only mirror population levels and could also lead to discrepancies between jurisdictional and supervisorial emission level reporting.

Sequestration Potential

Can sequestration potential forecasts be conducted in conjunction with the Sonoma County Agricultural Preservation and Open Space District to determine future opportunities, as well as any loss of acreage/type per fire event?

  • RCPA will be consulting with the Sonoma County Agricultural Preservation and Open Space District (SCAPOSD) and the County of Sonoma’s Climate Action and Resiliency Division (CARD) as they develop a countywide Carbon Inventory and Sequestration Potential Study. This effort is expected to include both a quantitative estimate of the existing ecosystem carbon stored in the county’s land base, as well as projections and estimates of the carbon sequestration potential of the county based on carbon impacts from vegetation change, wild and prescribed fires, agricultural processes, and other land use activities.

Local Boundaries

Was the analysis completed using specific “city limits” or the larger set of Zip Codes that encompass and surround incorporated cities?

  • RCPA attempts to segment all data used in the inventory by jurisdictional boundaries not zip codes, but it is impossible for us to verify the exact boundaries used for each data set. As an example, the data that is provided by PG&E, Sonoma Clean Power, and Zero Waste Sonoma are pre-filtered by jurisdiction (including an “unincorporated” category) and RCPA accepts the data as labelled. Additionally, some calculations are based upon county or state averages that are apportioned to specific jurisdictions based on population or employment counts derived from the most recent census data. Again, for these RCPA is not able to verify the exact boundaries used and accepts the data as released publicly.

Housing Unit Density

Can RCPA track single-family and multifamily housing unit density per acre by jurisdiction as an indicator metric?

  • RCPA is planning to incorporate a series of climate indicators and resilience metrics into future Greenhouse Gas Inventory reports. These metrics will be linked to housing, transportation, land use, social equity, and environmental conditions that are related to, but may not directly link to, greenhouse gas emissions and climate change. Tracking single-family and multifamily housing unit density for each jurisdiction will be included in the scoping for this work to provide additional context for our greenhouse gas inventory trends.

Transportation Mode Shift

What is the percentage of mode shift countywide that is needed to meet our 2030 goals?

  • While RCPA’s greenhouse gas inventory looks backward in time to determine our past emissions profile, the Comprehensive Transportation Plan (CTP) produced by our SCTA colleagues looks forward in time to determine needed actions. RCPA and SCTA staff will work together to integrate the results from the greenhouse gas inventory with guidance from the CTP to guide our future actions and report this progress each time the inventory is released.

Breakout by Water Sources

Is there an ability to break out water users by municipal water versus well users to view the per capita impact? Can the emissions intensity of water sources be investigated further for well users versus municipal water as a side study to inform groundwater sustainability agencies?

  • These are all important questions, but outside of the current scope of the greenhouse gas inventory. RCPA can work with Sonoma Water to compile existing information related to the countywide water sourcing and distribution system to answer some of these questions. While this information would not be directly tied to the calculations in the inventory, the results could be presented as an adjunct report for additional context and insight.

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