  Infrared renormalons and $1/Q^2$ power corrections in deep-inelastic sum
rules are studied. The renormalization of operators with power divergence are
discussed. The higher-twist terms in the operator product expansion are shown
to account for the residual soft contributions survived from the
Kinoshita-Lee-Nauenberg type of cancellation in Feynman diagrams. The presence
of some degree of arbitrariness in the twist separation allows one to define
the most convenient higher-twist operators suitable for a particular
non-perturbative method. The discussion is focused on the Bjorken sum rule, for
which the $1/Q^2$ corrections are considered on a lattice.
