  The evaporation of molecules from dust grains is crucial to understand some
key aspects of the star- and the planet-formation processes. During the warm-up
phase the presence of young protostellar objects induces molecules to evaporate
from the dust surface into the gas phase, enhancing its chemical complexity.
Similarly, in circumstellar disks, the position of the so-called snow-lines is
determined by evaporation, with important consequences for the formation of
planets. The amount of molecules that are desorbed depends on the interaction
between the species and the grain surface, which is controlled by the binding
energy. Recent theoretical and experimental works point towards a distribution
of values for this parameter instead of the single value often employed in
astrochemical models.We present here a new "multi-binding energy" framework, to
assess the effects that a distribution of binding energies has on the amount of
species bound to the grains. We find that the efficiency of the surface
chemistry is significantly influenced by this process with crucial consequences
on the theoretical estimates of the desorbed species.
