  Baryon number is an accidental symmetry of the Standard Model (SM) Lagrangian
that so far has been measured to be exactly preserved, although it is expected
to be violated at higher energies. In this work we compute order-of-magnitude
estimates for the matching contributions of generic ultraviolet models to
effective operators that generate nucleon decay processes. This is done in a
systematic and automated way using operators constructed from SM fields up to
dimension nine and working in a framework that has proved useful in the study
of lepton-number violation. For each of the operators we derive estimates for
the rates of different nucleon-decay channels. These allow us to establish
model-independent lower bounds on the underlying new-physics scale and identify
potential correlations between the various decay modes. The results are most
relevant for genuine models that do not generate nucleon decay at a lower
order. This analysis is especially timely given the expected future
sensitivities in numerous experiments such as Hyper-K, DUNE, JUNO and THEIA.
