  Step Chemical Reaction Networks (step CRNs) are an augmentation of the
Chemical Reaction Network (CRN) model where additional species may be
introduced to the system in a sequence of ``steps.'' We study step CRN systems
using a weak subset of reaction rules, \emph{void} rules, in which molecular
species can only be deleted. We demonstrate that step CRNs with only void rules
of size (2,0) can simulate threshold formulas (TFs) under linear resources.
These limited systems can also simulate threshold \emph{circuits} (TCs) by
modifying the volume of the system to be exponential. We then prove a matching
exponential lower bound on the required volume for simulating threshold
circuits in a step CRN with (2,0)-size rules under a restricted
\emph{gate-wise} simulation, thus showing our construction is optimal for
simulating circuits in this way.
