Strengthening the applicability of self-heating retorting process to oil shale via co-retorting

•Facile self-heating retorting of low energy input can well retort Longkou or Huadian oil shale to prepare oil.•Self-heating retorting of Fushun oil shale with lower oil content is unsatisfying.•Fushun oil shale can be well utilized by self-heating co-retorting with Longkou or Huadian oil shale.•Fushun oil shale can be well utilized by self-heating co-retorting with pine needles.•A new starting point for using renewable biomass to utilize low-grade oil shale is provided.