NOVELTY - Integrated process for producing diesel fuel from biological material, comprises: providing a first hydrocarbon stream comprising 5-100C hydrocarbons by catalytic cracking/isomerization of Fischer-Tropsch paraffins of biological origin; providing a second hydrocarbon stream comprising predominantly 15-18C hydrocarbons by catalytic hydrodeoxygenation of biological hydrocarbons; mixing the first and second hydrocarbon streams; fractionating the resulting mixed hydrocarbon stream; and recovering a middle distillate fraction.    USE - The process is useful for producing diesel fuel from biological material. The lignocellulosic material is useful for producing diesel fuel from purely biorenewable sources, where the lignocellulosic material is waste and/or by-products of the wood-processing industry. The biological middle distillate fraction is useful as an additive for improving the cetane value, cloud point and/or pour point of a fuel produced by other means (all claimed).    ADVANTAGE - The process: provides high quality middle distillate fraction; avoids high cost of transportation and storage due to the use of industrial waste materials; provides high grade diesel fuel; has ability to produce autonomous hydrogen; and provides diesel fuel, which is superior in quality compared to both crude fossil based diesel fuel and fatty acid methyl ester biodiesels, and has excellent ignition properties and a uniform combustion.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) the use of lignocellulosic material for producing diesel fuel from purely biorenewable sources, where biomass comprising lignocellulosic material is gasified and used to provide a Fischer-Tropsch paraffin stream, which is then cracked under isomerizing conditions, biological hydrocarbons are hydrodeoxygenated to provide a predominantly 15-18C normal-paraffin (n-paraffin) stream, which is optionally isomerized under non-cracking conditions, the two streams are combined and fractionated, and a middle distillate fraction is recovered;    (2) a method for narrowing the chain length distribution of a Fischer-Tropsch derived diesel fuel, comprising combining 5-95% of a Fischer-Tropsch derived hydrocarbon stream of 5-100C hydrocarbons with 5-95% of a predominantly 15-18C hydrocarbon stream obtained by hydrodeoxygenation of biological hydrocarbons, fractionating the combined hydrocarbon stream and recovering a fraction of 11-20C hydrocarbons;    (3) a biological middle distillate fraction obtainable by the process, comprising Fischer-Tropsch derived hydrocarbons (5-95%) having 11-20 carbon atoms, where 5-95% of the hydrocarbons have predominantly 15-18 carbon atoms; and    (4) an equipment for producing fuel from biological material, comprising hydrodeoxygenation reactor (3) for hydrodeoxygenating a feed of biological hydrocarbons, cracking/isomerization reactor (11) for catalytically cracking and isomerizing a feed of Fischer-Tropsch paraffins of biological origin, a separation unit (12) for distilling a combined feed of hydrocarbons provided from the reactors and for the recovery of a middle distillate boiling at 150-400 degrees C and the separation of a top fraction boiling at a lower temperature, a hydrogen separation unit for the separation of hydrogen from the top fraction and means for feeding the hydrogen to the reactors, and means (13, 15, 8) for providing of additional hydrogen for the reactors from the non-hydrogen portion of the top fraction.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic flow diagram of an integrated process for producing diesel fuel.    Hydrodeoxygenation reactor (3)    Fischer-Tropsch reactor (4)    Pressure swing adsorption unit (8)    Cracking/isomerization reactor (11)    Separation unit. (12)