Study shows decrease in greenhouse gas emissions on BI

Published 1:30 am Tuesday, April 28, 2026

Andrea Martin and Hailey Weinberg from Cascadia Consulting Group gave a presentation to Bainbridge Island City Council April 21 on the most recent greenhouse gas emission data for the city.

The last completed report was in 2019, using 2018 data. For the 2026 study, 2023 inventory was used due to it being the most recent data, as a lag is often common with key sources.

Objectives of the study were to understand both where the City of Bainbridge Island is at right now with emissions and also how emissions are changing over time. The study was done through contribution analysis, a quantitative way to break down emission trends. Once there is a better understanding of emission sources and trends, data can be used to improve the city’s climate action plan, per documents.

Both community inventory and government inventory were taken into analysis in the study. Community inventory included building energy (electricity, fuel oil, propane), transportation (on-road vehicles, off-road equipment, public transit, ferries, air travel), solid waste (compost, landfill, septic), wastewater treatment, refrigerants, and agriculture.

Government inventory that was analyzed includes building and facilities energy (electricity, propane), transportation (fleet vehicles, off-road fleet equipment, employee commute), solid waste (landfill, compost, wastewater treatment process), and refrigerants.

Community emission findings

The largest source of emissions within community inventory was residential electricity, which made up one-third of emissions in 2023. Air travel, which was estimated with survey findings through SeaTac Airport, made up 20% of emissions for Bainbridge Island residents, and vehicles made up 14% of emissions. Aviation emissions increased 49% since 2014 due primarily to an increase in fuel consumption reported by SeaTac.

Since 2014, there has been a 14% decrease in emissions overall for community inventory on Bainbridge Island, with a 21% per-capita decrease in emissions. This is due to a transition to cleaner electricity sources between 2014 and 2023, shared Martin. This is largely due to an increase in Puget Sound Energy’s (PSE) Green Power Program participation numbers as well as renewables in PSE’s fuel mix. Other findings for community inventory consist of an 8% increase in residential electricity consumption since 2014.

Overall transportation emissions increased 13% since 2014 alongside a 6% increase in annual vehicle miles traveled by Bainbridge Island residents, largely due to population growth in the area. However, due to the rise of popularity of electric and fuel-efficient vehicles, on-road emissions have decreased by 6%. Solid waste findings included a 17% increase since 2014 as well.

Cascadia Consulting completed an analysis on what sources drive these overall emission trends. Quantified drivers of observed inventory trends include weather, energy grid, population growth, per-capita energy consumption, economic changes, and fuel switching.

Martin shared that Bainbridge Island is trending in the right direction, with an overall decrease in emissions over time. The largest seen changes for community inventory include a decrease in electricity consumption and an increase in air travel emissions.

COBI emission findings

Greenhouse gas emissions from government operations and buildings are a smaller proportion of the community, accounting for 0.3% of community-wide emissions. The City of Bainbridge Island has more direct control over these emissions, therefore it was included in the study as important to quantify.

Large emission sources for the city include off-road equipment, employee commute, on-road vehicles, and building electricity. Overall, government emissions have decreased 71% since 2014, which is attributed to the transition to cleaner electricity and fleet vehicle emissions.

In regard to government buildings and facilities, electricity consumption has increased, but emissions have actually decreased by 94% due to PSE’s Green Power Program, which is used for all buildings owned and managed by COBI.

For government transportation, there has been a reduction in fuel consumption and emissions, with data showing a 39% reduction in on-road fleet emissions, a 52% reduction in off-road vehicle and equipment emissions, and a 36% reduction in COBI employee commuting emissions. A decreasing trend was also seen in COBI’s landfilled waste emissions.

Overall, fleet vehicles contribute to a majority of emissions that are decreasing in the government inventory.