NOVELTY - The process comprises passing the biogas through a liquid petroleum fraction at 100-250 degrees C and pressure of 1-2 atmospheres, while contacting the biogas and the liquid petroleum fraction with transition metals in metallic form to produce a gaseous effluent, and condensing the effluent to liquid form. The transition metal has an atomic number of 24-74. The liquid petroleum fraction is mineral oil, diesel oil, naphtha, kerosene, gas oil, and gasoline. The biogas is passed to a reaction vessel (11) partially filled with the liquid petroleum fraction to a first externally controlled liquid level.    USE - The process is useful for producing liquid fuel from a biogas such as natural gas (claimed), hydrogen, carbon monoxide, methane, benign gases such as nitrogen and carbon dioxide and gaseous petroleum-based products such as ethane and ethylene, where the liquid fuel is useful in a diesel engine and a gasoline engine.    ADVANTAGE - The process is capable of economically and continuously producing liquid fuel from a biogas for a prolonged period of time without adding additional quantities of liquid petroleum fraction to the reaction vessel and particulate emissions and odor.    DETAILED DESCRIPTION - The process comprises passing the biogas through a liquid petroleum fraction at 100-250 degrees C and pressure of 1-2 atmospheres, while contacting the biogas and the liquid petroleum fraction with transition metals in metallic form to produce a gaseous effluent, and condensing the effluent to liquid form. The transition metal has an atomic number of 24-74. The liquid petroleum fraction is mineral oil, diesel oil, naphtha, kerosene, gas oil, and gasoline. The biogas is passed to a reaction vessel (11) partially filled with the liquid petroleum fraction to a first externally controlled liquid level to cause the biogas to bubble through the liquid petroleum fraction and through a metallic grid of the transition metal immersed in the liquid. The effluent is condensed by continuously and simultaneously: passing the biogas; drawing the effluent from a head space (14) in the reaction vessel above the liquid level through a condenser (33) to convert the gaseous reaction product mixture to liquid condensate and uncondensed gas; passing the liquid condensate and uncondensed gas into a product vessel (12) having a second externally controlled liquid level to separate the liquid condensate from the uncondensed gas; and drawing the liquid condensate separated from the product vessel as a liquid fuel, while recycling the uncondensed gas from the product vessel to the reaction vessel by directing the uncondensed gas below the first liquid level and through the first metallic grid. The metallic grid in the reaction vessel is defined as a first metallic grid. The process further comprises passing the gaseous reaction product mixture through a second metallic grid of the transition metal and passing the uncondensed gas through a fixed bed of inert packing material to recover entrained liquid before recycling the uncondensed gas to the reaction vessel. The second metallic grid is external to the reaction vessel and the product vessel. The catalytic transition metal comprises the first and second metallic grids. The reaction vessel is equipped with a first liquid level control means to define minimum and maximum liquid levels, means for heating liquid, an inlet gas distributor, the metallic grid of the transition metal, and a vaporized product outlet port. The inlet gas distributor and the first metallic grid are positioned below the minimum liquid level. The vaporized product outlet port is positioned above the maximum liquid level. The condenser is arranged to receive the vaporized product emerging from the vaporized product outlet port. The product vessel is equipped with a second liquid level control means to define minimum and maximum liquid levels.    DESCRIPTION OF DRAWING(S) - The figure shows a flow diagram of a process for producing liquid fuel.    Reaction vessel (11)    Product vessel (12)    Gaseous head space (14)    Level control (15)    Condenser. (33)