This study quantifies and compares the environmental impacts of production systems of biomass and roundwood from different wood species—maritime pine, eucalyptus, and cryptomeria. The results showed that roundwood and biomass from eucalyptus had the highest environmental impacts in most of the environmental categories. In contrast, cryptomeria products had the lowest impacts. For biomass, the impacts were higher for the forest production scenario when less biomass was produced (eucalyptus). The literature review showed that one of the main topics under study in the quantification of the environmental impacts of biomass is the allocation methodology. Thus, this study compared the environmental impacts of the various scenarios considering different methods of allocation: sub-division of processes, volume, mass, economy, and energy. The results showed that, for most scenarios, the biomass environmental impacts calculated by subdivision of processes had the highest values. In contrast, the environmental impacts of biomass calculated by economic allocation had the lowest environmental impact in most scenarios. The impacts of mass and energy allocation were similar for both products in all scenarios. Furthermore, this study showed that the system boundaries in biomass production have a strong influence on the environmental impacts and require further research.