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In a paper posted on the arXiv a few weeks ago Berti, Brito and Cardoso\cite{Berti+14} suggest that ultra-high-energy particles can emerge fromcollisions in a black hole's ergosphere. This can happen if the processinvolves a particle on an outgoing trajectory very close to the black hole.Clearly such a particle cannot emerge from the black hole. It is argued\cite{Berti+14} that this particle can arise in another collision. Thus theprocess involves two collisions: one in which an outgoing particle is producedextremely close to the horizon, and a second one in which energy is gained. Thereal efficiency of this process should take into account, therefore, the energyneeded to produce the first particle. We show here that while this process iskinematically possible, it requires a deposition of energy that is divergentlylarge compared with the energy of the escaping particle. Thus, in contradictionto claims of infinitely high efficiencies, the efficiency of the combinedprocess is in fact extremely small, approaching zero for very high outputenergies. Even under more general conditions than those considered in\cite{Berti+14} the total energy gain never diverges, and is larger only by afactor of a few than the energy gain of the original collisional Penroseprocess that takes place between two infalling particles\cite{Piran+75,PiranShaham77,Bejger+12}

Super-Penrose collisions are inefficient - a Comment on: Black hole fireworks: ultra-high-energy debris from super-Penrose collisions