Cofiring of biomass in coal-fired boilers has been tested and demonstrated in a number of utility installations including Alien, Kingston and Colbert Fossil Plants of TVA; Shawville Generating Station of Penelec/GPU; Steam Plant #2 of Tacoma Public Utilities; King Station of Northern States Power; Greenidge Station of New York State Electric and Gas; Plants Hammond, Mitchell, and Yates of Georgia Power; Plant Kraft of Savannah Electric; Jeffries Station of Santee Cooper; and several other installations. All types of combustion technologies have been used to cofire biofuels with coal including cyclone boilers, wall-fired and tangentially-fired pulverized coal boilers, fluidized-bed boilers, and stoker-fired boilers. Capacities used in cofiring tests and commercial applications have ranged from 50 MW to > 500 MW. Supporting these tests and demonstrations have been fundamental studies and experiments on biofuel safety issues, blended biofuel/coal storage and transport, pulverizer issues, fuel chemistries associated with blending, and related concerns. This activity in cofiring has resulted from utility interest in customer service and customer support in a deregulated utility environment, the potential for niche situations where blending of biofuel achieves fuel cost savings, and the potential for environmental benefrt (e.g., NOx SO2 and fossil CO2 reductions). The cofiring programs have resolved some issues, and have demonstrated that biofuel use, with coal, in large utility boilers can be beneficial for both the utility and its customers. Further, the cofiring programs have led to the development of a significant database concerning biofuel properties, boiler performance when cofiring biofuels, and combustion mechanisms when cofiring biofuels with coal. This database has been coupled with computer programs to evaluate certain issues associated with blending, such as ash behavior related to slagging or fouling. The cofiring programs have also defined certain issues that remain unresolved, at least in part. These issues include (I) the influence of cofiring on ash properties and flyash sales; (2) the influence of cofiring on boiler slagging and fouling problems; (3) the influence of fuel blending on pulverizer performance; (4) the maximum percentage of cofiring as a function of materials handling and combustion technologies; and (5) the required characteristics of biofuel particles to achieve defined project-specific goals such as avoiding derate, achieving dispatch, achieving NOx control, producing a coproduct from oversized particles, and otherwise meeting customer-service, environmental and economic goals.