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In the present study, natural convection in a porous cavity in the presence of a non-isothermal biochemical heat source is investigated numerically. The porous cavity is assumed to be homogenous and the Darcy model is used for the momentum equation. The porous cavity includes two species namely biomass and substrate. The heat source generated in the cavity is equal to the rate of consumption of the substrate by the biomass. The bio-chemical source in the energy equation is proportional to the generation rate of solute concentration governed by a Monod model. Heat generation in the porous media, the rate of consumption of a substrate by a biomass, temperature distribution in the cavity, and the local Nusselt number are analyzed completely. The effect of porosity on the biochemical process is completely analyzed in this paper. Results showed that increasing the porosity leads to an increase in the bio-chemical heat generation in the cavity.