Biomass is an attractive renewable fuel to supplement coal combustion in utility boilers. Coal cofiring was successful with up to a 20% biomass mix. Results of extensive applications have shown that cofiring of biomass with coal have accomplished the following: (1) increased boiler efficiency, (2) reduced fuel costs and (3) reduced emissions of NOx and fossil CO2. Every ton of biomass cofired directly reduces fossil CO2 emissions by over 1 ton. Woody biomass contains virtually no sulfur, so SO2 emissions are reduced in direct proportion to the coal replacement. Biomass is a regenerable biofuel. When a fossil fuel is replaced by a biofuel, there is a net reduction in CO2 emissions. Biomass can contain considerable alkali and alkaline earth elements and chlorine, which, when mixed with other gas components derived from coal such as sulfur compounds, promotes a different array of vapor and fine particulate deposition in coal fired boilers. (C) 2002 Elsevier Science Ltd. All rights reserved.