Repowering is the option of replacing existing equipment with new technology. The United States has roughly 1400 operating coal-fired generating units producing almost 2 billion MWh of electricity per year [1]. By 2015, more than 90% of those units will be over 30 years old. Furthermore, in addition to producing almost 50% of the United States’ electric power, these older units produce almost 35% of the total CO2 emissions in the United States and up to 40% of the ground level air pollutants such as SO2 and NOX [15,16]. As these systems age, steam production efficiency declines and the units struggle to meet emission compliance. An alternative to shutting down many of these facilities could be to “repower”.

Repowering can involve partial or total replacement of existing infrastructure. The extent of repowering depends on many factors including: (1) environmental discharge limits, (2) permitting requirements, (3) increased demand or generating load, (4) fuel cost, and (5) transmission requirements. For example, converting a coal burning facility to a biomass burning facility requires boiler modifications, addition of a gasifier, and addition of biomass handling facilities. These changes are essential because biomass has a lower heating value and more material will be required to produce the same amount of energy. Repowering, however, increases environmental performance, as the conversion from coal to biomass can reduce NOX emissions by 60%, SO2 by 80% and particulate matter by 80%. The down side is that biomass prices tend to fluctuate and competition for biomass is steadily increasing. High biomass feedstock prices will seriously impact the economics of repowered systems [3].