The sustainable use of forest resources is an intensively debated topic, raising environmental, socio-cultural and economic concerns. The debate culminates around forest bioenergy. The bioenergy debate has been characterized by a strong polarisation between different perspectives on environmental impacts. In particular, the claims about carbon sequestration have been contrasted with other ecological impacts. This article focuses on the debate over the use of tree stumps as a relatively novel source of forest bioenergy. To shed light on the constellation of the different arguments and actors in the debate on the sustainability of forest bioenergy, we conducted an empirical qualitative analysis of Finnish argumentation on tree stump removal, using media and interview data and relating the emerging sustainability arguments to the dimensions debated in the EU biofuel sustainability policy. The analysis shows the variation of views across Finnish expert stakeholders and the fora where the arguments are made. Climate impacts dominate the media discussion, while other sustainability dimensions are covered in expert discussion. Our findings have implications for the interpretation and use of scientific arguments in energy debates, in particular regarding environmental sustainability.