  Incorporating a realistic model for accretion of ultra-relativistic particles
by primordial blackholes (PBHs), we study the evolution of an Einstein-de
Sitter universe consisting of PBHs embedded in a thermal bath from the epoch
$\sim 10^{-33}$ sec to $\sim 5\times 10^{-9}$ sec. In this paper we use Barrow
et al's ansatz to model blackhole evaporation in which the modified Hawking
temperature goes to zero in the limit of the blackhole attaining a relic state
with mass $\sim m_{pl}$. Both single mass PBH case as well as the case in which
blackhole masses are distributed in the range $8\times 10^2 - 3\times 10^5$ gm
have been considered in our analysis. Blackholes with mass larger than $\sim
10^5$ gm appear to survive beyond the electroweak phase transition and,
therefore, successfully manage to create baryon excess via $X-\bar X$
emissions, averting the baryon number wash-out due to sphalerons. In this
scenario, we find that the contribution to the baryon-to-entropy ratio by PBHs
of initial mass $m$ is given by $\sim \epsilon \zeta (m/1 {gm})^{-1}$, where
$\epsilon$ and $\zeta$ are the CP-violating parameter and the initial mass
fraction of the PBHs, respectively. For $\epsilon $ larger than $\sim 10^{-4}$,
the observed matter-antimatter asymmetry in the universe can be attributed to
the evaporation of PBHs.
