  Neutrino emissivity from the electron $\nu\bar\nu$ bremsstrahlung in the
liquid layers of the neutron star crusts is studied. Nuclear composition of
matter in neutron star crusts is considered for various scenarios of neutron
star evolution. For the deep layers of the crust, the compositions of cold
catalyzed matter, accreted matter and hot matter ($T \ga 5 \times 10^9$~K) are
shown to be very different, and this implies differences in the neutrino
emissivity at given density and temperature. Neutrino-pair bremsstrahlung, due
to collisions of relativistic degenerate electrons in a Coulomb liquid of
atomic nuclei, is considered. The neutrino energy loss rate is expressed in a
simple form through a Coulomb logarithm $L$ -- a slowly varying function of
density, temperature, and nuclear composition. Non-Born corrections, thermal
width of electron Fermi sphere, and finite sizes of nuclei are taken into
account. Implications for cooling of neutron stars are discussed.
