  We present a new theoretical and practical strategy to renormalize
non-perturbatively the energy-momentum tensor in lattice QCD based on the
framework of shifted boundary conditions. As a preparatory step for the fully
non-perturbative calculation, we apply the strategy at 1-loop order in
perturbation theory determining the renormalization constants of both the
gluonic and the fermionic components of the energy-momentum tensor. Using
shifted boundary conditions, the entropy density of QCD is directly related to
the expectation value of the space-time components of the renormalized
energy-momentum tensor. We then discuss its practical implementation by
numerical simulations of QCD with 3 flavours of Wilson quarks for temperatures
between 2.5 GeV and 80 GeV.
