  Most stars form in binaries and the evolution of their discs remains poorly
understood. To shed light on this subject, we carry out 3D ideal MHD
simulations with the AMR code FLASH of binary star formation for separations of
$10-20\,\mathrm{AU}$. We run a simulation with no initial turbulence (NT), and
two with turbulent Mach numbers of $\mathcal{M} = \sigma_v/c_s = 0.1$ and $0.2$
(T1 and T2) for $5000\,\mathrm{yr}$ after protostar formation. By the end of
the simulations the circumbinary discs in NT and T1, if any, have radii of
$\lesssim20\,\mathrm{AU}$ with masses $\lesssim0.02\,\mathrm{M}_\odot$, while
T2 hosts a circumbinary disc with radius $\sim70-80\,\mathrm{AU}$ and mass
$\sim0.12\,\mathrm{M}_\odot$. These circumbinary discs formed from the
disruption of circumstellar discs and harden the binary orbit. Our simulated
binaries launch large single outflows. We find that NT drives the most massive
outflows, and also removes large quantities of linear and angular momentum. T2
produces the least efficient outflows concerning mass, momentum and angular
momentum ($\sim$61 per cent, $\sim$71 per cent, $\sim$68 per cent of the
respective quantities in NT). We conclude that while turbulence helps to build
circumbinary discs which organise magnetic fields for efficient outflow
launching, too much turbulence may also disrupt the ordered magnetic field
structure required for magneto-centrifugal launching of jets and outflows. We
also see evidence for episodic accretion during the binary star evolution. We
conclude that the role of turbulence in building large circumbinary discs may
explain some observed very old ($>10\,\mathrm{Myr}$) circumbinary discs. The
longer lifetime of circumbinary discs may increase the likelihood of planet
formation.
