The use of forest biomass residues to generate electricity can contribute to the sustainability of the energy matrix, circularity in forest production chains and resource conservation. The challenge for biomass power plants is to generate as much energy as possible considering the resources available. This article aims to analyze the eco-efficiency of an electrical energy cogeneration unit from the burning of forest biomass residues, considering the historical evolution of indicators in the period between 2010 and 2019. The results indicate that the plant became more eco-efficient in the period evaluated, producing more energy in relation to the use of biomass (from 0.30 MWh t −1 in 2010 to 0.48 MWh t −1 in 2019), associated with a 55.5% reduction in ash generation for each ton of biomass used. Eco-efficiency also increased when considering the consumption of diesel oil, electricity and water. The main factor responsible for the advance of eco-efficiency indicators was the improvement in the quality of biomass consumed by the plant. An adequate understanding of the efficiency of electricity generation from forest biomass residues is important for reducing costs and environmental impacts, especially in the context of the circular economy.