King County Emissions Inventory


The Emissions Inventory is like the carbon footprint of the entire County; it details how much greenhouse gases were emitted 2019-2020, with historical data from previous Emissions Inventories to put it in perspective. The report is put together by the County, with help from an outside contractor with expertise. It is done every two years, and the latest report, although released in Sept 2022, covers emissions in 2019 and 2020.

The emissions inventory comes in two parts: a geographic inventory, and a consumption-based inventory. The geographic inventory covers GHG emissions from fossil fuels that were emitted inside the County's geographical borders. The consuption-based inventory covers GHG emissions anywhere in the world that were caused as a result of activities of county residents. The geographic inventory includes emissions from things made inside the County that are shipped elsewhere for delivery. The consumption-based inventory includes emissions from things made outside the county that are shipped to county residents. The geographical inventory covers vehicles miles driven in the county, while the consumption-based inventory includes emissions from trips by county residents that could be entirely outside the county (e.g., driving from New York to Chicago). 

So how are we doing at reducing our emissions? This is one of the key questions that the Emission Inventory is designed to answer. The Report uses 2019 as a reference year, because 2020 was the first year of the pandemic and is not representative. Overall, from 2008 to 2019, our emissions increased by 10%. Our population grew by 18%, and our per capita emissions decreased by 7%. The per capita decrease is a positive sign, but but the reduction rate is not nearly enough to make a 50% reduction by 2030.

The factors that drove emissions up in 2019 are population growth, more carbon-intensive electricity from PSE, increased air travel, and growth in employment & industry. The main drivers of emissions reductions since 2015 are improved vehicle efficiency, decreased commercial energy use per job, and decreased residential energy use per home. Energy efficiency, not clean energy or changes in behavior have been key for the reductions we've seen up to 2019.

What impact did the pandemic have? Total emissions in 2020 were down 15% compared to 2019. Aviation fuel use was down by 40%. Commercial natural gas usage was down by 13%; most of this was due to less usage in commercial buildings, but even residential buildings used less, probably because 2020 was a warmer year. Industrial operations, and the emissions that go with them, also dropped significantly. One other change in 2020, which may or may not be pandemic related, PSE reduced the carbon intensity of their electricity by 25%. These large reductions were driven by changes in behavior.

Geographic Emissions Sources in 2019

The chart below shows sources of GHG emissions for the geographic emissions inventory.

Plan for Reducing Emissions 

The County has emissions reductions goals to meet, and they are 50% by 2030, 75% by 2040, and 95% by 2050, compared to a baseline of 2007. The wedge analysis chart below shows the path to get there, and the role each policy plays. Policies in solid colors are Federal, State, and County policies that are already in place, or in the implementation phase (i.e., they are current enacted law). Policies in dotted colors are policies that the County is projecting could be enacted, and, if they were, the GHG reductions that would result. This is the emissions gap –A the difference between the path we are on now, and the path we need to be on. As part of the Emissions Inventory, there is an Excel spreadsheet that allows you to play with the assumptions and modeling that go into these projections, and as you change them you can see the difference it makes too the emissions reductions. For instance, you can change projected rate of EV adoption, and see what difference that would make, or change the rate at which people update their heating systems to use heat pumps.

Consumption-based emissions sources

This is like a carbon footprint of everyone in the County. It shows higher overall emissions, mostly because we are a relatively rich community who import some of our emissions, and these imports aren't reflected in the geographical emissions.

These emissions are worldwide, and cannot be measured directly. Therefore, there is reliance on modeling. Modeling is based on six key factors: household size, household income, vehicle ownership, home size, educational attainment, and home ownership.

The differences in emissions from the consumption-based inventory can be tracked down to the neighborhood level, as shown in the map below:

As you can see, the amount of emissions vary widely between neighborhoods. There are various factors behind the differences:

The report sums it as follows:

historical land use plans and the resulting built environment today are major drivers of consumption-based emissions, but also where people of different incomes are able to live. Because of historic discrimination and inequities, nonwhite Americans - particularly Black, Hispanic/Latino, and Native Americans - are less likely to be able to afford to buy a suburban single-family home. As a result, America's - and King County's - highest emission neighborhoods are also among the whitest and wealthiest.