The present invention relates to an ultra-low emission stored exhaust gas-assisted internal combustion powerplant. The powerplant comprises a variable torque drive turbine connected to a piston compressor through a gearbox. The gearbox comprises a planetary or epicyclic gear to selectively direct power from the drive turbine to the compressor and at least one output shaft. The compressed air is mixed with fuel in a staged combustor, the hot exhaust gasses are used to drive the variable torque drive turbine or cooled and stored in a exhaust gasses storage system.