State pollution control officials have taken 20 enforcement actions against ethanol plants in the past six years for air or water pollution, including six plants that were cited more than once. Here are the five largest penalties.PlantCityPenalty YearViolation

Minnesota EnergyBuffalo Lake$1,150,0002009Water

Corn Plus*Winnebago$1,041,0002009Air

Bushmills EthanolAtwater$ 800,000 2012Water/air

Corn Plus*Winnebago$ 760,0002011Water

Bushmills EthanolAtwater$ 425,0002009Water/air

* includes federal and state penalties. Source: Minnesota Pollution Control Agency, Star Tribune research