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8 Attachment C: Palo Alto 2024 Municipal Greenhouse Gas Emissions Inventory Overview of Methodology for Quantifying Greenhouse Gas Emissions The 2024 Municipal Greenhouse Gas (GHG) Emissions Inventory follows the calculation and reporting standards outlined in the International Council for Local Environmental Initiatives’ (ICLEI) Local Government Operation (LGO) Protocol1, which aligns with the Global Protocol for Community-Scale GHG Emissions Inventories (GPC) local government operations protocol.2 Under the LGO Protocol, GHG Emissions from Palo Alto’s municipal operations can be classified into four main sectors:
Buildings and other facilities (e.g., stationary combustion) Streetlights and Traffic Signals (e.g., electricity use) City vehicle and equipment fleet (e.g., mobile combustion) Wastewater facilities (e.g., wastewater treatment and discharge) Indirect emissions (e.g., employee commuting, landfilled solid waste generation) Activities taking place within a city can generate GHG emissions that occur inside the city boundary as well as outside the city boundary. To distinguish among them, the LGO Protocol groups emissions into three categories based on where they occur:
Scope 1 emissions: GHG emissions from sources located within the city boundary Scope 2 emissions: GHG emissions occurring as a consequence of the use of grid- supplied electricity, heat, steam and/or cooling within the city boundary Scope 3 emissions: All other GHG emissions that occur outside the city boundary as a result of activities taking places within the city boundary Palo Alto’s 2024 Municipal GHG Emissions
In 2024, the City emitted a total of 14,590 metric tons (MT) of carbon dioxide equivalent (CO2e) from municipal operations. As shown in Figure 1, GHG emissions from Palo Alto’s municipal operations are from five main sectors: Buildings and Other Facilities, Streetlights and Traffic Signals, City Vehicles and Equipment, Wastewater Facilities, and Indirect Emissions. Since the methodology has changed significantly for certain sectors since the first Municipal GHG Inventory was conducted in 2005, it is no longer possible to do an equivalent comparison with previous Municipal GHG inventories. However, the methodologies for Buildings and Other Facilities, Streetlights and Traffic Signals, and City Vehicles and Equipment are similar enough to make rough comparisons. For reference only, in 2005 the City emitted a total of 40,499 MT CO2e from municipal operations. By the end of 2024 the City reduced total municipal GHG emissions roughly 64% from the 2005 baseline.
1 LGO Protocol Rulebook; https://icleiusa.org/resources/local-government-operations-lgo-protocol/ 2 GPC Inventories for local government operations;
https://ghgprotocol.org/sites/default/files/standards/GPC_Full_MASTER_RW_v7.pdf
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8 Figure 1: 2024 Palo Alto Municipal Greenhouse Gas Emissions by Sector The majority of municipal GHG emissions, about 37%, are attributed to the Regional Water Quality Control Plant (RWQCP). Since the RWQCP is owned and operated by the City, 100% of GHG emissions are attributed to the City and are Scope 1. These GHG emissions include indirect nitrous oxide (N2O) emissions from wastewater effluent (about 95% of total wastewater GHG emissions), process nitrous oxide emissions from the treatment of wastewater without nitrification/denitrification (about 4% of total Wastewater Facilities sector GHG emissions), and natural gas combustion/leakage (about 1% of total Wastewater Facilities GHG emissions).
The second major contributor to GHG emissions is attributed to the Indirect Sources sector, or the City’s Scope 3 sources. These indirect sources account for about 33% of total GHG emissions and include GHG emissions resulting from employee commute mobile combustion (about 44% of the Indirect Emission Sources GHG emissions) and methane emissions resulting from landfilled solid waste (about 56% of the Indirect Emissions Sources GHG emissions). Landfilled solid waste methane emissions are a product of decomposing organic material generated and sent to the landfill by municipal operations. This subsector attributes methane emissions based on total landfilled solid waste generated in the inventory year and does not account for pre- existing landfilled solid waste methane emissions.
The third major contributor to GHG emissions includes GHG emissions from natural gas usage in Buildings and Other Facilities (excluding the RWQCP), considered a Scope 1 source. These GHG emissions accounted for 22% of total GHG emissions and are driven by natural gas combustion (about 97% of Buildings and Other Facilities GHG emissions), and natural gas leakage (about 3% of Buildings and Other Facilities GHG emissions).
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8 The final contributor to GHG emissions includes the City’s vehicle and equipment fleet sector, considered a Scope 1 source (except for the City’s electric vehicles, EVs, which are considered a Scope 2 source due to the energy source being purchased electricity). Together, these account for about 9% of total GHG emissions and are mainly driven by the City’s on-road vehicle fleet powered by gasoline, renewable diesel, and compressed natural gas (CNG) and off- vehicle/equipment fleet powered by gasoline and diesel. The City’s on-road vehicle fleet makes up about 97% of City Vehicle and Equipment Fleet GHG emissions, while off-road vehicles and equipment make up the remaining 3%.
Since electricity in the City is carbon-neutral, there are no GHG emissions from electricity consumption in City-owned buildings and facilities, streetlight and traffic signals, EVs, or City water-energy consumption.
A comparison of 2005 and 2022 through 2024 Palo Alto Municipal GHG emissions is shown in Figure 2 and Table 1. Overall GHG emissions declined slightly, with about a 5% reduction from 2022 to 2023, about a 1% reduction from 2023 to 2024, and about a total decrease of 6% over the three-year period.
Figure 2: Palo Alto Municipal GHG Emissions, 2005 and 2022-2024 As previously discussed, the methodology has changed significantly for certain sectors since the first Municipal GHG Inventory was conducted in 2005, so it is no longer possible to make an equivalent comparison with previous Municipal GHG inventories. However, the methodologies for Buildings and Other Facilities, Streetlights and Traffic Signals, and City Vehicles and Equipment are similar enough to make rough comparisons.
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8 Table 1: Palo Alto Municipal GHG Emissions (MT CO2e)
Sector and Subsector Scope 2005 2022 2023 2024
% Change
in 2024
from
2005*
Buildings and Other Facilities 10,698 3,398 2,844 3,154 - 70.5% - Electricity Use Scope 2 0 0 0
- Natural Gas Combustion Scope 1 3,291 2,755 3,055
- Natural Gas Leakage Scope 1 107 89 99
- Water-Energy Consumption Scope 2 0 0 0
Streetlights & Traffic Signals 748 0 0 0 - 100%
City Vehicles and Equipment Fleet 2,835 1,676 1,352 1,308 - 53.9% - On-road Renewable Diesel** Scope 1 499 182 182
- On-road Gasoline Scope 1 1,045 1,108 1,079
- On-road CNG Scope 1 6 20 7
- On-road Electric Scope 2 0 0 0
- Off-road Renewable Diesel** Scope 1 124 40 37
- Off-road Gasoline Scope 1 3 2 3
Wastewater Facilities (Regional
Water Quality Control Plant) 11,269* 5,715 5,722 5,354 - 52.5%* - Effluent Discharge Fugitive Scope 1 5,448 5,414 5,070 - Process N₂O Emissions Scope 1 200 206 207
- Electricity Use Scope 2 0 0 0
- Natural Gas Combustion Scope 1 65 99 75
- Natural Gas Leakage Scope 1 2 3 2
Indirect Emission Sources 5,567* 4,758 4,873 4,774 - 14.2%* - Employee Commute Scope 3 1,865 1,980 2,096
- Landfill Methane Scope 3 5,567 2,893 2,893 2,678
Power Generation Facilities 9,308 n/a n/a n/a n/a
Water Delivery Facilities 74 n/a n/a n/a n/a
Total MT CO2e 40,499* 15,546 14,792 14,590 - 64%*
Note: Percentages and MT CO2e may not add to the total due to rounding * Not an equivalent comparison due to different methodologies ** Diesel emissions factors were used in 2022
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8 Despite the overall downward trend, GHG emissions from natural gas combustion (Scope 1) in the Buildings and Other Facilities sector increased between 2023 and 2024 due to higher therms usage. These emissions had previously decreased by 16% from 2022 to 2023 but rose by 11% from 2023 to 2024. Nonetheless, total GHG emissions from natural gas combustion declined by 7% between 2022 and 2024.
Similarly, employee commute GHG emissions from the indirect emissions sources sector (Scope 3) increased by 6% between 2023 and 2024, as well as 6% between 2022 and 2023. This upward trend is attributed to a consistent rise in total daily commute miles due to increases in the number of City employees from filling position vacancies.
City Vehicle and Equipment Fleet emissions (Scope 1) experienced mixed changes. On-road gasoline emissions increased slightly - by 3% from 2022 to 2024 - while on-road CNG and off- road gasoline emissions remained relatively constant. On-road diesel and off-road diesel emissions dropped significantly - by 64% and 70%, respectively - between 2022 and 2024. These reductions are attributed to the City’s transition to renewable diesel for its municipal fleet beginning in 2023, which has a roughly 70% lower GHG emissions factor compared to conventional fossil diesel.5
A comparison of the on-road vehicle GHG emissions by City Department and vehicle fuel type (diesel, gasoline, and CNG) can be found in Table 2. Table 3 shows a historical comparison of on-road vehicle GHG emissions by City Department. Figures 3 and 4 show Palo Alto On-Road Vehicle GHG emissions by City Department. The fleet vehicles used by City Departments are used for the following purposes:
Administrative Services Department – purchasing and printing Community Services Department – administration, arts and culture, recreation, parks and golf
Fire Department – operations, support
Information Technology Department – information technology Planning and Development Department – inspection services Police Department – police, animal services
Public Works Department – engineering, facilities management, equipment management, operations, wastewater treatment operations, storm drainage, refuse, Palo Alto airport operations
Utilities Department – administrative services, electric operations, electric engineering, water / gas / wastewater engineering, water / gas / wastewater operations, resource management
5 CARB staff has reached out to several renewable diesel fuel producers and as of February 2023, is aware that renewable diesel produced by Neste meets the regulatory requirements and standards. Estimates in GHG emissions reduction based on emission factors provided by Neste accessed at: https://www.neste.com/en- us/products-and-innovation/neste-my-renewable-diesel/product-information
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8 Table 2: On-Road Vehicle GHG emissions by City Department & Vehicle Fuel Type (MT CO2e) City Department Diesel
Vehicles
Gasoline
Vehicles CNG Vehicles Total
(MT CO2e)
Administrative Services 2.4 0 0.2 2.6
Community Services 5.4 87.8 0 93.2
Fire 52.5 66 0.02 118.5
Information Technology 0 2.3 0 2.3
Planning and Development 0 18.6 0.03 18.7
Police 7 413.5 0 420.5
Public Works 56 214.3 4.5 274.9
Utilities 58.5 276.4 2.5 337.4
Total MT CO2e 181.9 1,078.8 7.3 1,268
Note: Totals and MT CO2e may not add to the total due to rounding Table 3: On-Road Vehicle GHG emissions by City Department (MT CO2e) City Department 2022 2023 2024 % of Total in
2024
Administrative Services 8.3 2.8 2.6 0.2%
Community Services 88.9 87.9 93.2 7.4%
Fire 228.9 118.7 118.5 9.3%
Information Technology 2.5 2.4 2.3 0.2%
Planning and Development 18.1 22.2 18.7 1.5%
Police 430 421.7 420.5 33.2%
Public Works 337.8 323.5 274.9 21.7%
Utilities 436 328.5 337.4 26.6%
Total MT CO2e 1550.2 1307.6 1268 100.0%
Note: Percentages and MT CO2e may not add to the total due to rounding
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8 Figure 3: Palo Alto On-Road Vehicle GHG Emissions by City Department Figure 4: 2024 On-Road Vehicle GHG Emissions by City Department