While reducing carbon emissions is important, it is not the only emissions we care about. SMMPA has made significant progress on reducing a wide range of different emissions – all of which improve air quality.


Acid Rain Program
The Acid Rain Program (ARP) and Cross State Air Pollution Rule (CSAPR) were designed to be a market driven approach to the reduction of emissions where each utility was required to hold and retire sulfur dioxide emission allowances for each ton of sulfur dioxide emitted. SMMPA’s Sherco 3 burns sub-bituminous western coal with a sulfur content that is less than 1 percent. Sherco 3 is also equipped with a state-of-the-art dry scrubber system which has enabled this generating unit to successfully meet both the ARP and CSAPR regulations on sulfur dioxide. SMMPA does not sell any of its surplus allowances.


Cross State Air Pollution Rule
As mentioned above, the CSAPR was a market driven approach to control sulfur dioxide. The CSAPR was also designed to reduce nitrogen oxides (NOx) via a similar market driven approach. To comply with the NOx provisions of the CSAPR, Xcel and SMMPA studied the alternatives and invested in new low-NOx burners that were installed in Sherco 3 in 2008. This has resulted in a decrease in nitrogen oxidesemissions of approximately 70%. 


Regional Haze
Reducing regional haze will improve the visibility in the nation’s national parks and wilderness areas. In 1999 the EPA published the regional haze regulations, the first phase of which required certain plants to install Best Available Retrofit Technology (BART). That phase did not impact Sherco 3. The Minnesota Pollution Control Agency (MPCA) must submit its plans for phase 2 to the EPA in 2021. SMMPA will continue to monitor the development of the MPCA’s phase 2 plan and take the necessary potential action steps required at Sherco 3 to comply. 


Mercury and Air Toxics Standards
SMMPA supports reasonable reductions in mercury emissions. As the federal Mercury and Air Toxics Standards (MATS) are being finalized, the State of Minnesota has sought to create clear guidance and certainty related to mercury reduction via a new law, the Minnesota Mercury Emissions Reduction Act (MMERA). Xcel Energy and Minnesota Power are required to reduce mercury emissions at their largest generating facilities by 90 percent by the year 2010 for dry scrubber units and 2014 for wet scrubber units, which effectively accelerated the then existing federal program by up to eight years and increased required removal rates from 70% to 9%. Though not specifically covered under the law, SMMPA is similarly impacted due to its joint ownership of Sherco 3. The MPCA has not yet set a final mercury emission level for Sherco 3.


MACT 40, CFR 63 for Reciprocating Engines

The EPA has established new standards for stationary reciprocating internal combustion engines (RICE). SMMPA took action to upgrade SMMPA and member-owned facilities to meet these new standards.


There are three primary components in the upgrades to meet the new standards. First, install oxidation catalysts on each engine which removes in excess of 70% of carbon monoxide emissions. Because these oxidation catalysts are generally integral to the engine’s exhaust silencer, adding this new catalyst also required replacing the silencer and exhaust stacks. 


Second, add crankcase ventilation systems to all units which filters and returns any oil fumes back into the engines rather than venting to atmosphere. 


Third, implement formal operating and maintenance procedures designed to optimize the operation of the engines thereby minimizing any emissions – a practice that SMMPA had already implemented years earlier. 

SMMPA will continue to work with state, local and national stakeholders on the development and implementation of reasonable, cost-effective emissions reduction legislation and regulations as it operates its plants in an environmentally responsible manner.