  The out of equilibrium nature of active systems can be exploited for the
design of information-based engines. We design two types of an active Szilard
engine that use a Maxwell daemon to extract work from an active bath composed
of non-interacting Active Brownian Particles (ABPs). The two engines exploit
either the quasi-static active pressure of ABPs or the long correlation time of
their velocities. For both engines the Landauer principle can be violated so
that larger work can be extracted compared to conventional Szilard engines
operating in quasi thermal equilibrium. For both of our engines,we identify the
optimal regimes at which the work extracted and the efficiency are maximized.
Finally, we we discuss them in the context of synthetic and biological active
systems.
