Non-radiative (NR) carrier recombination limits the efficiency of photovoltaic energy conversion. Minority carrier lifetimes in Si exhibit a variety of dependences on optical injection levels, depending on the types of defects present. To date, models of non-radiative recombination in silicon were proposed for point defects (e.g., Fe interstitials) and extended defects (e.g., dislocations). Direct measurement of local carrier concentration near recombination centers is technically difficult, therefore, computational modeling may be helpful to understand various carrier recombination pathways in materials such as mc-Si. In this paper, modeling is used to compare intensity-dependent NR recombination lifetimes in Si. The usefulness of the model goes beyond mc-Si photovoltaics.