NOVELTY - Lean gas plant comprises (a) a lean gas source (1) for supplying a lean gas, (b) a lean gas power generation device, through which the lean gas is supplied, (c) a lean gas separation device (3), through which the lean gas is separated into an exhaust gas and a fuel gas, (d) a power transfer means (4) for supplying power produced from the lean gas power generation device into a power grid (5), (e) a gas delivery means for feeding the heating gas into a gas system, (f) an actuator (8) for optionally acting upon the lean gas power generation device.    USE - The lean gas plant is useful for providing a negative controlling power range (claimed).    DETAILED DESCRIPTION - Lean gas plant comprises (a) a lean gas source (1) for supplying a lean gas, (b) a lean gas power generation device, through which the lean gas is supplied, (c) a lean gas separation device (3), through which the lean gas is separated into an exhaust gas and a fuel gas, (d) a power transfer means (4) for supplying power produced from the lean gas power generation device into a power grid (5), (e) a gas delivery means for feeding heating gas obtained from the lean gas separation device into a gas system, (f) an actuator (8) for optionally acting upon the lean gas power generation device and/or the lean gas separation device having lean gas supplied from the lean gas source, and (g) a control system, by which at least the actuator is controllable in dependence on the power requirement of the power grid, where (h) the Lean gas separation device is electrically operated. An INDEPENDENT CLAIM is also included for the recovery of lean gas comprising converting lean gas into power and/or supplying the lean gas to the fuel gas processed in the gas system, where the power demand of the power system is recorded for providing control power for a power system and during the positive power demand, lean gas is introduced in the power supply system, and during negative power demand electricity is retrieved from the power supply system and is used for the treatment of lean gas into fuel gas.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of the lean gas system for providing the negative control performance.    Lean gas source (1)    Lean gas separation device (3)    Power transfer means (4)    Power grid (5)    Actuator (8)