The most fair and effective counterclaim is: Healthy ecosystems are forever destroyed when forests are cut down, which must be done in order to produce biomass from wood.
This counterclaim addresses a significant environmental concern associated with biomass production, highlighting the potential negative consequences of sourcing biomass from forests. It draws attention to the broader ecological impact, rather than simply comparing biomass to fossil fuels or other renewable energy sources, making it a strong and nuanced counterpoint.