Brazil has favorable edaphoclimatic conditions for the cultivation of biomass for energy. On the other hand, the country plans to expand its thermal power park using fossil fuels, including coal. This paper estimates the potential of co-firing biomass from energy forests in power plants based on Brazilian coal (low rank coal) from the main deposits in the south of Brazil. The technical limits of adding woody biomass to a boiler with a fluidized bed running on Brazilian coal is evaluated along with the availability of this biomass in the south of Brazil. Findings indicate that the main technical limit for boilers operating with different mixtures of biomass and coal is the alteration in the volume of exhaust gas, which varies depending on the percentages of biomass in the co-firing. The limits for biomass availability were based on environmental sustainability and the economic viability of transport. Results indicate that biomass should be available within a radius of around 120 km, which is equivalent to approximately 4,500,000 ha. Only 0.4% of this area would be required to feed a thermal plant of 600 MWe with 30% biomass. (c) 2012 Elsevier Ltd. All rights reserved.