We establish a quantitative factorization theorem for the identity operator on $c_0$ via non-compact operators $T: C_0(K) \to X$, where $K$ is a scattered, locally compact Hausdorff space and $X$ is any Banach space not containing a copy of $\ell^1$ or with weak$^*$ sequentially compact dual unit ball. We show the connection between these factorizations and the essential norm of the adjoint operator. As a consequence of our results, we conclude that the essential norm is minimal for the Calkin algebra of these spaces.