Carbon & Air Emissions
At the onset of the Paris Agreement, the United States set a target of a 28% reduction from 2005 GHG emission levels by 2025. APS met this GHG reduction goal nine years ahead of schedule. Since 2005, APS’s annual GHG emissions have been reduced by almost 5 million metric tons, which represents a 28% reduction.
As Arizona’s population grows, APS plans to provide the increased energy required to support this growth as efficiently as possible relative to carbon emissions. We set long-term carbon emission goals based on our carbon intensity, as measured by the pounds of carbon emission per MWh of energy. By 2032, we expect our carbon-emission rate to decrease to less than 600 lb/MWh, which is a 48% reduction from our 2005 baseline year.
In 2018, the total APS carbon dioxide emissions were 13,137,903 tons. This represents an increase of 11.1% over total carbon dioxide emissions in 2017. The 2018 increase is attributable to greater utilization of coal-fired generation, especially the Four Corners units. The increased utilization of the coal-fired units was due primarily to two reasons. First, in 2018 the Four Corners units returned to service after major unit outages in which the units were retrofitted with selective catalytic reduction (SCR) technology—a technology that dramatically reduces nitrogen oxide emissions. As a result, the operation of these units increased in 2018. The other contributing factor was an increase in natural gas prices. The average natural gas price in 2018 was 16% higher than the previous three-year average.
However, when viewed with a longer-perspective lens, the trend is still towards reduced carbon emissions. Compared to just three years ago, the total company carbon dioxide emissions have decreased by 12.2%, and the percentage of total carbon dioxide emissions from coal-fired units has decreased almost 10%. While we expect year-over-year carbon emissions to vacillate, the long-term trend for carbon dioxide emissions continues to be on a downward trajectory.
In addition to carbon reductions, we on the pathway to reduce nitrogen oxide (NOx) and sulfur dioxide (SO2) intensity by 93% and 89%, respectively. Since 2005, we have had an intensity reduction of 77% for NOx and 86% for SO2. This resulted from our commitments to reduce emissions and institute operational efficiency enhancements.
APS reduces its environmental impact by closing older, less-efficient coal units and upgrading environmental controls on newer units. SCR technology currently is employed at six of our power plants. As noted above, installation of two new SCRs at the Four Corners Power Plant in 2018 resulted in an 88% NOx reduction at that facility.
Learn more about our air emissions trends.
We believe it is important to disclose our carbon management strategies and GHG emissions to customers, investors and other stakeholders. APS voluntarily reports annually to the CDP (formerly the Carbon Disclosure Project), a global nonprofit organization that collects and analyzes environmental data for investors to use in financial decisions. This organization’s network of investors represents more than $100 trillion in assets. CDP reporting provides a benchmark to evaluate how well we manage our carbon emissions, climate change risk, and to identify opportunities for improvement.
We have participated in CDP since 2006. In 2018, our CDP reporting for climate change received a “Management” score (letter grade “B”), which puts APS in the top quartile for U.S. utilities for the action and approaches in managing climate change. This score is also higher than the electric utility average of C, and higher that the North American regional average of C. Our Scope 1, 2 and some of scope 3 GHG emissions reported to CDP are third-party verified.
In addition, we submit a comprehensive annual report of our GHG emissions to the Environmental Protection Agency (EPA) as required by federal law.
Learn more about our CDP responses and documents.
To measure our overall carbon reduction—not just decreasing emissions from generation but also throughout our company operations—we use a carbon-avoidance metric. This reflects actions taken company-wide, including retiring coal units, installing renewable generation and energy efficiency, increasing our building and operating efficiencies, and pursuing fleet electrification.
In 2018, we avoided 4.5 million metric tons of carbon. Since 2015, APS has avoided 18.1 million metric tons of carbon dioxide emissions that otherwise would have been emitted had we not taken actions to reduce the emissions. That is equivalent to removing almost 4 million automobiles from the road.