NOVELTY - System for adsorptive bulk separation of a gas stream, comprises: a displacement purge adsorptive separator (I) operably coupled to a feed gas source to adsorb at least a portion of the diluent component from the feed gas (102) to produce a product, where (I) comprises an adsorbent bed (124, 126), a purge gas source for displacement purge regeneration of adsorbent bed and a product gas conduit (110) for supplying the product; and a second fluid processing device (III) fluidly coupled to (I) and/or the feed gas source, where (III) is an adsorptive fluid separator and/or an engine.    USE - The system is useful for adsorptive bulk separation of a gas stream. The method is useful for producing an upgraded methane fuel gas product for combustion fuel, which is useful in natural gas reciprocating engines to generate electrical power in generation installations at landfill gas collection sites. The method is useful for producing an upgraded methane fuel component of a digester gas produced as a product of a biomass digester produced at substantially ambient pressure. The method is useful for providing upgraded tailgas, comprises providing an adsorptive purification system for receiving a tailgas exhaust feed stream, providing a downstream bulk displacement purge adsorptive separation system and supplying tailgas exhaust feed stream from the adsorptive purification system to the downstream bulk displacement purge adsorptive separation system to produce upgraded tailgas.    ADVANTAGE - The energy efficiency of the system is increased by more than 20% compared to a system not utilizing an adsorptive bulk separator. The fuel gas recovery efficiency is greater than 70% in a product stream as compared to the feed. The diluent gas recovery efficiency is greater than 85% in a product stream as compared to the feed. The substantial pure fuel gas purge stream is recovered greater than 95% in the product stream. The system operates at pressure higher than ambient pressure but substantially lower than a corresponding pressure swing adsorption feed pressure (all claimed). The process is cost effective.    DETAILED DESCRIPTION - System for adsorptive bulk separation of a gas stream having a first component and a diluent component, comprises: a displacement purge adsorptive separator (I) operably coupled to a feed gas source to adsorb at least a portion of the diluent component from the feed gas (102) to produce a product, where (I) comprises an adsorbent bed (124, 126), a purge gas source for displacement purge regeneration of adsorbent bed and a product gas conduit (110) for supplying the product; and a second fluid processing device (III) fluidly coupled to (I) and/or the feed gas source, where (III) is an adsorptive fluid separator and/or an engine. INDEPENDENT CLAIMS are included for:    (1) a displacement purge adsorptive bulk separation fuel gas upgrading system for hydrogen recovery/carbon dioxide transfer from an anode exhaust of an molten carbonate fuel cell containing low quality hydrogen, comprising a displacement purge adsorptive bulk separator having an air side and a hydrogen feed side, and a fuel cell having an anode and a cathode, the anode is fluidly coupled to a feed inlet for the hydrogen feed side of displacement purge adsorptive bulk separator, the anode providing low quality hydrogen at a relatively low pressure to the displacement purge adsorptive bulk separator, which provides an upgraded hydrogen feed from the displacement purge adsorptive bulk separator to the anode feed, the cathode being fluidly coupled to the air side of the displacement purge adsorptive bulk separator to receive a fluid stream comprising carbon dioxide;    (2) a method for providing a product, comprising providing a system containing a bulk displacement purge adsorption separator fluidly coupled to at least one additional fluid stream processing device of an adsorptive fluid separator and/or an engine, and supplying a feed gas stream to the system to produce an upgraded product gas; and    (3) a method for upgrading hydrogen recovery/carbon dioxide transfer from an anode exhaust of an molten carbonate fuel cell containing low quality hydrogen, comprising providing a displacement purge adsorptive bulk separator, providing a fuel cell having an anode and a cathode, where the anode is fluidly coupled to a feed inlet for the displacement purge adsorptive bulk separator, the anode provides low quality hydrogen at a relatively low pressure to the displacement purge adsorptive bulk separator, and using the displacement purge adsorptive bulk separator to provide an upgraded hydrogen feed to the anode, where the cathode is fluidly coupled to an air side of the displacement purge adsorptive bulk separator to receive a fluid stream.    DESCRIPTION OF DRAWING(S) - The figure is a schematic process flow diagram comprising a displacement purge adsorptive bulk separation gas upgrading system comprising:    Feed gas; (102)    Adsorbent bed; (124, 126)    Product gas conduit; (110)    Purge gas stream; (114)    Purge gas source. (132)