According to the EIA’s January electricity update, more than $30 billion of flue gas desulfurization (FGD) systems, also known as scrubbers, were installed at over 110 coal-fired power plants across 34 states in 2007 to 2011.

“Scrubbers remove most sulfur dioxide (SO2), a precursor to the formation of acid rain and fine particulate matter, which is associated with premature mortality,” the report stated.

The amount of scrubbed generating capacity rose almost 66%, to just over 191 GW from 115 GW, in that time period.

This 191 GW represents almost 60% of the total coal-fired, steam electric generation capacity in the country.

The increase in the installation of scrubbers was partially due to the implementation of government initiatives such as the Environmental Protection Authority’s Clean Air Interstate Rule in 2005, according to the EIA.

Other than scrubber investments, burning less coal and switching to lower sulfur coal by many power plants also played a significant part in reducing emissions.

The EIA report confirms the effectiveness of scrubbers in reducing SO2 emissions with emissions declining significantly as the use of scrubbers grew.

Nationally, power plant SO2 emissions in 2011 were 68% lower than the 1990 level and 46% lower than the 2007 level.

Five states accounted for 43% of the total $30 billion investment, with Ohio topping the list with an investment of $3.6 billion during the period.