  We investigate the scenario in which primordial black holes (PBHs) with
masses Mpbh < 10^9 g undergo Hawking evaporation, around the Big-Bang
nucleosynthesis (BBN) epoch. The evaporation process modifies the Universe's
expansion rate and the baryon-to-photon ratio, leading to an alteration of the
primordial abundance of light nuclei. We present numerical solutions for the
set of equations describing this physics, considering different values of PBH
masses and abundances at their formation, showing how their evaporation impacts
the abundances of light nuclei, obtained by incorporating the non-standard
Hubble rate and baryon-to-photon ratio into the BBN code PArthENoPE. The
results are then used to place upper bounds for the PBH relative abundance at
formation in the range 10^8 g < Mpbh < 10^9 g, providing the strongest
constraints existing to-date in this mass range.
