  The infrared asymptotics of probability of radiation of twisted photons in an
arbitrary scattering process of quantum electrodynamics (QED) in a vacuum is
investigated. This asymptotics is universal and corresponds to the radiation
produced by a classical current. Such a radiation is known as the edge
radiation. We represent it in terms of the twisted photons: the exact
analytical formulas for the average number of radiated twisted photons are
derived. We find the average projection of the total angular momentum of the
edge radiation and the angular momentum per photon. It is shown that the edge
radiation can be used as a source of twisted photons with large angular
momentum. Moreover, this radiation can be employed as a superradiant coherent
source of twisted photons in the infrared domain, in particular, in the THz
part of the electromagnetic spectrum. Several general selection rules for the
radiation and absorbtion of twisted photons are proved. These selection rules
allow one, in particular, to modulate the one-particle radiation probability by
means of scattering of charged particles on symmetrically arranged crystals.
