Sithe Energies, under a cooperative agreement with EPRI, the US Department of Energy, the Biomass interest Group (BIG) and the Upgraded Coal Interest Group (UCIG), has developed a demonstration of cofiring biomass with pulverized coal at the Seward Generating Station on Boiler #12. This demonstration, constructed and tested by Foster Wheeler Development Corporation (FWDC) included construction of a facility to receive, screen, store and transport sawdust into a front-fired pulverized coal boiler. This facility has several distinctive features including the sawdust receiving system, the silo storage for processed biomass, and the injection system using the centerpipe of the coal burners. The biomass is prepared separately and transported separately from the coal. The wood waste is then injected into the center of the coal flame and burned there for optimum biofuel performance. This demonstration, involving an extended period of cofiring testing, is based upon successful parametric tests conducted in December, 1996 and July, 1997. These tests documented the impact of cofiring, in the short term, on capacity, efficiency and emissions. Those results are now being evaluated over a long-term period. Additionally, operational and maintenance issues are being addressed with this demonstration and modifications have been made to improve the handling of the fuel. This paper describes the cofiring system, and reviews progress to date with the combustion tests. (C) 2000 Elsevier Science Ltd. All rights reserved.