Northern Indiana Public Service Company (NIPSCO) has developed a long-term demonstration firing biomass and petroleum coke with coal at its Bailly Generating Station boiler #7, a 160 MW, (net) cyclone boiler. This demonstration, funded by the US Department of Energy (USDOE) Office of Energy Efficiency and Renewable Energy (EERE) and the USDOE National Energy Technology Laboratory (NETL), has been developed as part of the Electric Power Research Institute (EPRI) biomass cofiring demonstration program. The NIPSCO demonstration program - the triburn program - has involved designing and constructing a fuel preparation and blending facility. It then involved extensive testing of firing clean urban wood waste - biomass -with coal firing petroleum coke with coal, and firing various blends of urban wood waste and petroleum coke with coal. Results of the extensive testing program have shown that the triburn blends of biomass and petroleum coke with coal have accomplished the following: (1) increased boiler efficiency, (2) reduced fuel costs; and (3) reduced emissions of oxides of nitrogen (NOx), mercury, and fossil carbon dioxide (CO2). At the same time, the triburn program has not increased other emissions, This paper summarizes the results of testing at Bailly Generating Station, discusses the impacts of petroleum coke and wood waste, discusses the synergies between these two opportunity fuels, and considers the implications of the demonstration. (C) 2000 Elsevier Science Ltd. All rights reserved.