The Bioenergy slider in En-ROADS simulates the use of trees, waste, and agricultural crops to create energy.
Bioenergy is separated out as distinct from renewables in En-ROADS, although some classify it as a type of renewable energy. Bioenergy has unique characteristics from wind, solar, and hydro. In particular, it releases carbon when burned, although this can be offset by the replanting or regrowth of other biomass. This regrowth takes a long time and is not guaranteed.
More information can be found in the En-ROADS User Guide section on Bioenergy here.