The US Department of Energy (DOE), Electric Power Research Institute (EPRI) and utilities are evaluating, testing and applying technology that can give a new, and potentially profitable, mission to existing coal-fired power plants. The oldest of all fuels, wood, and the old original fuel of the industrial revolution, coal, are key to this move to a new mission. Technical issues that can lead to doubt about, or outright rejection of, wood (or biomass) cofiring are, in fact, being reserved through testing and experience. DOE, EPRI and utilities have joined to cosponsor tests in full-sized boilers and design/cost/supply studies related to these tests. Economic calculations, based on the measured performance and on cost estimates confirmed in purchases for the tests, are presented in this paper. The technical feasibility is proved. The constraints are identified. So far, the profits are in the future. Policy changes that produce stronger economic incentives could make profit possible today, and enable this low-cost form of renewable power to be deployed. But, without the policy, or market, change, the economic barrier is a strong one, when biomass cofiring must compete with low-cost coal at low fuel cost and with low-capital-cost gas turbine combined cycle power plants. The economics would not be a barrier at all if biomass cofiring were in competition against moderate-velocity wind power or solar PV power. (C) 2000 Published by Elsevier Science Ltd.