NOVELTY - An integrated fuel cell and additive gas supply system for a power generation system including a combustion engine (120), comprises: (a) a raw fuel storage and delivery subsystem (10) comprising a raw fuel source(s) capable of evolving a hydrogen-containing fluid stream; and (b) a power conditioning and buffering subsystem capable of receiving electric current from the electrochemical fuel cell.    USE - The integrated fuel cell (comprising proton exchange membrane) and additive gas supply system is for a power generation system including a combustion engine, which is an internal or external combustion engine used to energize a vehicle or a stationary device (claimed). It is for use in stationary power generation applications, particularly vehicular applications in which a combustion engine is the primary mobile power source.    ADVANTAGE - The diesel engine does not need to operate at a very inefficient point, while the vehicle is stopped. This increases engine lifetime, reduces emissions and reduces fuel consumption by ca. 5-30%. The integrated fuel cell and additive gas supply system permits immediate start-ups; and allows a smaller fuel processing and fuel cell system to be used and so reduces costs. It achieves increase power output by ca. 5-15%, and reduction of particulate matter and nitrogen oxide emissions by up to ca. 70%.    DETAILED DESCRIPTION - An integrated fuel cell and additive gas supply system for a power generation system including a combustion engine, comprises a raw fuel storage and delivery subsystem comprising a raw fuel source(s) capable of evolving a hydrogen-containing fluid stream, a storage vessel(s) for containing the raw fuel(s), and a conduit assembly for emitting a raw fuel stream(s) (14); a fuel processing and conditioning subsystem for producing a hydrogen-containing fluid stream from one of the raw fuel stream(s); an oxidant processing and conditioning subsystem (70) for producing an oxygen-containing fluid oxidant stream from a raw oxidant source; an actuatable fuel cell electric power generation subsystem (90) comprising an electrochemical fuel cell for generating electric current, heat and product water from the processed and conditioned fuel stream and the processed and conditioned oxidant stream; an actuatable engine subsystem (110) comprising a combustion engine for generating mechanical power, heat and an engine exhaust stream from a combustible fuel stream and a combustible oxidant stream; and a power conditioning and buffering subsystem capable of receiving electric current from the electrochemical fuel cell, and providing conditioned electric power upon demand to an electrical load(s), where a hydrogen-containing fluid stream is introduced into the combustible oxidant stream to form a combined stream, and the combined stream and combustible fuel stream are separately introduced into the engine and combusted.    DESCRIPTION OF DRAWING(S) - The flow diagram illustrates an integrated electric power and gas additive supply system for a combustion engine-propelled vehicle.    Raw fuel storage and delivery subsystem (10)    Raw fuel stream (14)    Oxidant processing and conditioning subsystem (70)    Fuel cell electric power generation subsystem (90)    Engine subsystem (110)    Combustion engine (120)