In 2012, 90 large sources in the state reported releasing a total of 19.2 million metric tons of carbon dioxide, methane and other greenhouse gases, about an 8 percent drop from the year before, the data shows.
The TransAlta coal-fired power plant in Centralia continued to be the single largest source of greenhouse gas emissions, releasing nearly 4.2 million metric tons of greenhouse gases, or about one-fifth of total emissions reported to the EPA. The facility, however, saw a 26 percent drop in emissions between 2011 and 2012.
BP's Cherry Point Refinery was the second-highest single source of emissions, followed by Shell Puget Sound Refinery in Anacortes, Tesoro Refinery in Anacortes, Alcoa Intalco Works in Ferndale, Phillips 66 refinery in Ferndale and Puget Sound Energy's Mint Farm natural-gas fired power plant in Longview, Wash.
Greenhouse gas emission released through power generation and other human activities contribute to climate change, and state officials say mandatory reporting of those emissions is a crucial first step in reducing pollution.
It helps the state "figure out what we need to go going forward," said Neil Caudill with the Department of Ecology.
The data may play an important role as state officials and other debate whether to put a price on carbon emissions through a carbon tax or cap and trade system. Gov. Jay Inslee has proposed capping carbon pollution as one way to meet the state's carbon-reducing goals.
A 2008 state law called for Washington to return to 1990 greenhouse gas emissions levels by 2020, and for greater reductions beyond that. In 2010, Washington state emitted 96 million metric tons of carbon dioxide, up from about 88.4 million a decade earlier.
Facilities that emit 25,000 metric tons or more per year of GHGs are required to submit annual reports to the EPA.
A Washington state law requires facilities that emit more than 10,000 metric tons of greenhouse gases per year to report their pollution. For the first time, those sources are reporting their 2012 emissions to the Department of Ecology.
Caudill said he estimates about 200 sources will be required to report under the state law. Ecology is currently processing and verifying those reports, which were due in November. The department plans to publish the data in coming months.
In 2012, the state's five refineries accounted for the largest amount of carbon pollution reported to the EPA by industrial sector, just slightly more than power plants.
TransAlta, a Canada-based company, has agreed to shut down one of its coal-burning units in Centralia by the end of 2020, and the final one by 2025.
The largest emitting industries include power plants, refineries, landfills and pulp and paper mills.