  The well-established effective action and effective potential framework from
the quantum field theory domain is adapted and successfully applied to
classical field theories of the Doi and Peliti type for diffusion controlled
reactions. Through a number of benchmark examples, we show that the direct
calculation of the effective potential in fixed space dimension $d=2$ to
one-loop order reduces to a small set of simple elementary functions,
irrespective of the microscopic details of the specific model. Thus the
technique, which allows one to obtain with little additional effort, the
potentials for a wide variety of different models, represents an important
alternative to the standard model dependent diagram-based calculations. The
renormalized effective potential, effective equations of motion and the
associated renormalization group equations are computed in $d=2$ spatial
dimensions for a number of single species field theories of increasing
complexity.
