TO: Napa Countywide Climate Action Committee
FROM: Brian D. Bordona, Director of Planning, Building, and Environmental Services
REPORT BY: David Morrison, Special Projects Director
SUBJECT: Final Napa County Regional 2019 Greenhouse Gas Short-Lived Climate Pollutant Inventory Memorandum - August 2024 Update
RECOMMENDATION
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DISCUSSION & PRESENTATION: Staff will present the Final Napa County Regional 2019 Greenhouse Gas Short-Lived Climate Pollutant Inventory Memorandum. Staff requests the CAC receive the presentation, discuss, and provide any direction to staff regarding the memo.
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BACKGROUND
As requested by the CAC in developing the scope of work for the regional greenhouse gas (GHG) inventory last year, Ascent has completed its Final Napa County Regional 2019 Greenhouse Gas Short-Lived Climate Pollutant (SLCPs) Inventory Memorandum (see Attachment 1).
SLCPs include methane (CH4), black carbon (BC), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfuryl hexafluoride (SF6). Many of these SLCPs have high global warming potential (GWP) values, especially in the short term (within 20 years), that can be up to thousands of times more potent than carbon dioxide (CO2).
The Napa Regional SLCP Inventory is subject to the limitations of the certainty of the data and the availability of accurate methods. Research on more accurate methods of estimating SLCPs is ongoing. The more sophisticated methods used for the national and State inventories do not apply at the county level. The methods used in this inventory are based on the best available data and the most applicable methods at the time of writing.
The SLCP Inventory revises the estimates previously provided in the Regional GHG inventory. The values are primarily different with the removal of Black Carbon (BC) emissions due to non-anthropogenic wildfires (see discussion of BC below) and the recalculation of Fugitive Methane due to the absence of oil & gas production in Napa County. BC emissions from wildfires in 2019 were calculated separately but were not included in the inventory. Wildfire emissions are provided for informational purposes, to show the scale of these emissions relative to total BC emissions in the region. Wildfire BC emissions accounted for 81,771 MTCO2e, using the 20-year GWP factor, and 22,998 MTCO2e, using the 100-year GWP factor.
The inventory estimates that in 2019, the region’s SLCP emissions contributed a total of 1,113,680 metric tons of carbon dioxide equivalent (MTCO2e), using 20-year GWP factors, and 395,691 MTCO2e, using 100-year GWP factors. Most SLCP emissions in Napa County in 2019 were from non-fugitive methane (70 percent) (e.g., energy consumption, on- and off-road transportation, landfills, wastewater processes, and agriculture). The region’s per capita SLCP emissions are 50 percent higher than the Statewide per capita, likely due to the large share of landfill-related methane emissions.
Using the 20-year GWP, the primary components of the regional SLCP inventory are:
* Landfill methane 51.9%
* Commercial/Industrial HFC 12.7%
* Wastewater methane 12.0%
* Livestock methane 4.7%
* Residential HFC 4.4%
* Agricultural black carbon 4.0%
If black carbon emissions from wildfires were included in the 2019 SLCP Inventory, they would account for 7.0% of the total.
Black Carbon (BC)
Black carbon (BC), or soot, is a form of fine particulate matter that is also a short-lived climate pollutant (SLCP). BC was included in the Napa County Regional 2019 Greenhouse Gas SLCP Inventory and emissions are summarized in the Final SLCP Memo.
In recent months, there has been significant discussion by the public and by the CAC with regards to the issue of black carbon and the role it should play in the inventory of GHG emissions and reduction measures. The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report estimates that BC is the third most important individual contributor to warming after CO2 and methane.
BC emissions occur from both anthropogenic (human-caused) and non-anthropogenic (naturally occurring) sources. In Napa County, anthropogenic sources of BC emissions include incomplete burning of organic materials in various sectors, such as on-road and off-road transportation, buildings, and agriculture. The primary non-anthropogenic source of BC in the region is wildfires; and while an estimate was included in the SLCP memo for informational purposes, non-anthropogenic sources of BC are excluded from the County’s inventory of SLCP emissions to remain consistent with the California Air Resources Board’s (CARB) 2022 Scoping Plan.
The State strategy for achieving carbon neutrality by 2045, or sooner, was adopted by the California Air Resources Board (CARB) in 2022 and is detailed in the Scoping Plan for Achieving Carbon Neutrality (2022 Scoping Plan). This plan lays out a path to achieve targets for carbon neutrality and reduce anthropogenic greenhouse gas (GHG) emissions, as directed by Assembly Bill 1279. The 2022 Scoping Plan integrates the Short-Lived Climate Pollutant (SLCP) Reduction Strategy, adopted by CARB in 2017, which is California's plan for reducing emissions of high global-warming potential gases with short atmospheric lifetimes. Both the 2017 SLCP Strategy and the 2022 Scoping Plan distinguish between the anthropogenic and non-anthropogenic sources of BC emissions, and only include BC emissions from anthropogenic sources in the State’s BC inventory (which is a separate inventory from the main SLCP inventory).
CARB specifically excludes BC from the state’s main GHG inventory as it was not included in the State’s original 1990 inventory on which the State’s GHG reduction targets are based (established by Assembly Bill 32). Maintaining consistency with the State’s main GHG inventory and the 2022 Scoping Plan is critical to ensure that the RCAAP’s emissions analysis is based on substantial evidence and consistent with criteria defined in CEQA Guidelines 15183.5, as well as ensuring its legal defensibility should it be challenged in court.
The 2017 SLCP Strategy specifically discusses the issue of wildfires:
“Wildfire is the largest source of black carbon in California, harmfully impacting both public health and the climate. In general, wildfires are occurring at increasing rates and at increasing levels of severity. This trend raises concern over the long-term resilience of these forests and their ability to sequester carbon, mitigate climate change, and provide resource amenities. Since the legislative direction and intent of SB 1383 is to
include only anthropogenic, non-forest, sources of black carbon in the target, and in light of continued state research and policy development occurring in this area, a target for forest-derived black carbon emission reductions is not included in this SLCP Strategy. The Forest Carbon Plan, as well as the 2017 Scoping Plan Update, will continue to explore the interrelation of climate change and natural lands and lay out programmatic and scientific actions needed to increase carbon sequestration and decrease black carbon emissions from wildfire. Implementation of these plans is important to address emissions from California forest fires, and to address forest health generally, from both a public health and climate change perspective (page 7).”
GHG emissions reduction strategies, measures, and actions that focus on energy efficiency upgrades, building electrification, vehicle electrification, and strategies to reduce vehicle miles traveled (VMT) are examples of existing and proposed measures to reduce GHG emissions from fuel combustion in buildings and mobile sources. The reduction in GHG emissions from these measures will also have a co-beneficial reduction in BC emissions; however, as noted earlier, adding and quantifying BC emissions together with the primary GHG pollutants (CO2, CH4, and N2O) is challenging and inappropriate for several reasons:
• BC is a short-lived climate pollutant, which means it is typically measured with respect to its 20-year global warming potential (GWP) factor. This factor is incompatible with the 100-year GWP factors that are typically used for CO2, CH4, and N2O, and must be presented separately.
• Despite the increased wildfire risks with climate change, non-anthropogenic BC emissions are highly variable from year to year, and the prediction of these emissions is speculative. It could be caused by a variety of sources, even including direct ignition by humans, accidental or otherwise.
• BC from agricultural and residential wood burning is difficult to track. While some agricultural burns are permitted and reported to the Bay Area Air Quality Management District, some are not; and residential wood burning does not need to be reported.
Therefore, while BC emissions from anthropogenic sources are quantified in the SLCP inventory and reductions could be calculated separately, BC emissions reductions still cannot be effectively compared with other GHG emissions reductions, for the reasons stated above.
Staff will soon begin preparing a draft RCAAP document that identifies all the elements of the proposed plan. Quantified BC emissions in the SLCP inventory (along with other SLCPs) will be summarized and discussed in the RCAAP text, while BC reductions will be described qualitatively as co-benefits in applicable sector measures only for the reasons stated above. Qualitative BC reduction co-benefits may also be included in the criteria used to evaluate and prioritize both GHG and climate adaptation measures for implementation support, funding, or other considerations.
ENVIRONMENTAL IMPACT
ENVIRONMENTAL DETERMINATION: The proposed action is not a project as defined by 14 California Code of Regulations 15378 (State CEQA Guidelines) and therefore CEQA is not applicable.