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Investing in improved air quality

Thomas Hill Energy Center on a sunny summer day.
Thomas Hill Energy Center
Visit one of Associated Electric Cooperative’s coal plants on a nice day, and it’s likely you won’t notice emissions from the stacks, even with all the units generating electricity. On a cold day, you may see puffs of water vapor due to condensation. These very low emissions result from more than $1 billion spent since 1994 to improve air quality.

We’ve been proactive in meeting our environmental responsibilities, and our members are proud of our achievements.

  • Members’ investments have reduced emissions significantly, including 65 percent to 90 percent reductions in sulfur dioxide, nitrogen oxides and mercury emissions.
  • Associated Electric was one of the first to convert all its coal units to 100 percent low-sulfur coal, reducing sulfur dioxide emissions more than 90 percent in 1994.
  • We’ve built on that conversion to low-sulfur coal, which is lower in mercury too. We were one of the first to install environmental controls called selective catalytic reduction equipment, designed to reduce nitrogen oxides emissions by more than 90 percent from our coal units. Associated Electric helped pioneer research, and has voluntarily reduced mercury years ahead of 2016 regulations.
  • We’ve researched other technologies – like dry sorbent injection – to further improve air quality, and we've invested in continuous emissions monitoring equipment. We’re committed to fulfilling our environmental responsibilities and compliance with environmental regulations.

Associated Electric’s proactive investment in environmental controls and our research into lower-cost alternatives have positioned us to fulfill our environmental responsibilities and comply with existing and pending regulations.

Charts above: Associated Electric has achieved tremendous reductions in emissions with significant investments and innovative research while keeping members' electricity reliable and affordable. Just as it has reduced sulfur dioxide and nitrogen oxides emissions, it also has reduced mercury since 2010 -- years before limits under EPA's long-awaited Mercury and Air Toxics Standards (MATS) rule went into effect in April 2016.

Associated uses low-sulfur coal, which is naturally lower in mercury. In 2011, Associated reduced mercury emissions further with use of refined coal.

In 2015, the cooperative installed activated carbon injection systems to further reduce mercury emissions and meet the Mercury Air Toxics Standards effective in 2016.

Overall, Associated has reduced mercury 85 percent since 2010 – well below mercury compliance standards.  Work in 2018 focused on fine-tuning those activated carbon systems, achieving very efficient mercury compliance testing at all five coal units. Staff also worked tirelessly to renew air permits for the simple- and combined- cycle gas plants as required, as well as report data to state and federal agencies.

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