TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The biological origin of the first hydrocarbon stream comprises: biomass, which is virgin or waste materials of plant, animal and/or fish origin, where the biological hydrocarbons are based on oils, fats and/or waxes of plant, animal and/or fish origin; or waste or by-product(s) of the wood-processing industry and the biological hydrocarbons of the second hydrocarbon stream comprise tall oil or tall oil fatty acids. The biomass is municipal waste, industrial waste or by-products, agricultural waste or by-products, waste or by-products of the wood-processing industry, waste or by-products of the food industry and/or marine plants.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The equipment further comprises a hydroisomerization reactor (10) downstream of the hydrodeoxygenation reactor and a Fischer-Tropsch reactor (4) upstream of the cracking/isomerization reactor. The means for providing additional hydrogen include at least one unit of an autothermal reformer (13), a water gas shift reactor (15) or the pressure swing adsorption unit. The equipment comprises: lines for feeding off-gases from any one of the reactors comprising deoxygenation reactor, cracking/isomerization reactor, Fischer-Tropsch reactor or hydroisomerization reactor to the hydrogen separation unit and lines for feeding recovered and/or reformed hydrogen to any one of the reactors; means for feeding water produced in the reactor(s) to a waste water treatment unit (22) of a pulp and paper mill and/or means for feeding energy produced in the Fischer-Tropsch reactor to a drying process of the pulp and paper mill; and means for feeding wood based waste from the pulp and paper mill to a reactor for producing synthetic gas for the Fischer-Tropsch reactor and/or means for feeding tall oil and/or tall oil fatty acid from the pulp and paper mill to the hydrodeoxygenation reactor.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The first hydrocarbon stream is provided by: gasification of biomass feedstock to provide synthesis gas; Fischer-Tropsch reaction of the synthesis gas to provide 1-100C paraffins; and cracking/isomerization of the resulting 5-100C paraffins to increase the proportion of diesel hydrocarbon 11-20C paraffins in the resulting first hydrocarbon stream. The second hydrocarbon stream is provided by hydrodeoxygenation of the biological hydrocarbon feedstock to provide a stream of saturated predominantly 15-18C n-paraffins and non-cracking hydroisomerization of the n-paraffins to increase the proportion of iso-paraffins in the resulting second hydrocarbon stream. In the process: a top fraction boiling at a temperature lower than the middle distillate fraction is used in the integrated process for providing hydrogen for the catalytic reaction(s) which provide(s) the first and/or the second hydrocarbon stream(s); and 5-95% of each first and second hydrocarbon streams are combined in a separator, in which the resulting mixed stream is fractionated into a middle distillate comprising 11-20C hydrocarbons and a light fraction comprising hydrogen and 1-4C hydrocarbons, and the middle distillate is recovered for use as diesel fuel. The light fraction is directed to a hydrogen separation unit to separate hydrogen for recirculation to the cracking/isomerization step, hydrodeoxygenation step and/or hydroisomerization step. The light fraction and/or off-gas of the Fischer-Tropsch paraffins comprise hydrogen, carbon monoxide and/or 1-4C hydrocarbons, which are also directed to the hydrogen separation unit. The hydrogen separation unit comprises a hydrogen permeable membrane and 1-4C hydrocarbons and carbon monoxide from the membrane are directed to an autothermal reforming unit to produce a gas comprising hydrogen, carbon monoxide, carbon dioxide, nitrogen and water. The gas or its part is supplied to a water gas shift unit to produce more hydrogen from carbon monoxide and water. The hydrogen is separated in a pressure swing adsorption unit (8) for recirculation in the integrated process to the hydrodeoxygenation step, hydroisomerization step and/or cracking/isomerization step. The additional hydrogen required in the process is produced by feeding methanol, preferably biomethanol to the autothermal reforming unit. In the process, a heavy fraction comprising 21-100C hydrocarbons and a naphtha fraction comprising 5-10C hydrocarbons are also recovered, where at least a part of the heavy fraction is recirculated to the cracking/isomerization step to be cracked and hydroisomerized to increase the amount of 11-20C hydrocarbons in the first hydrocarbon stream. The fractionation is set to provide a distillate fraction consisting 15-18C hydrocarbons. The process is operated in connection with a wood-processing industry and the biological feeds to the integrated process originate in or as by-products or waste of the wood-processing industry, which comprises a kraft mill producing crude tall oil and/or tall oil fatty acids. The water produced in the integrated fuel process is supplied to the wood-processing industry for purification and sulfur freed in the fuel process is fed to the sulfur circulation of the wood-processing industry. The integrated fuel process is further integrated with a pulp and paper mill and lignocellulosic material is utilized as raw materials for the fuel process and the wastes and energy from the fuel process are handled and/or utilized in unit operations of the pulp and paper mill. Preferred Components: The recovered fraction or middle distillate fraction comprises at least 25%, preferably 40-80% or more of 15-18C hydrocarbons. EXAMPLE - A feed of biological hydrocarbons comprising crude tall oil from the kraft mill was optionally thermally refined and was passed to catalytic hydrodeoxygenation (HDO) reactor charged with a standard hydrodeoxygenation/desulfurization catalyst based on cobalt-molybdenum/aluminum oxide. The saturated normal-paraffins from the HDO reactor had a chain length within the desired diesel or middle distillate range of 11-20C and, in the case of tall oil, the fatty acids were predominantly 15-18C and, and the chain length was almost purely 18C. A feed of purified (tar and sulfur free) synthesis gas was produced by gasification of wood bark and wood slash, which was a waste product of the kraft mill. The obtained synthesis gas having a hydrogen/carbon monoxide-volume ratio of 2 was fed to Fischer-Tropsch (FT) reactor. The reactor was charged with cobalt on alumina FT catalyst. The hydrocarbons created in the FT reactor comprised of very long 1-100C hydrocarbons. After removal of the off-gases consisting of unconverted synthesis gas, methane and light hydrocarbons up to 4C, a wax stream comprising a mixture of paraffinic hydrocarbons (5-100C) was obtained, which was solid at ambient temperature. The FT wax was not as such a suitable component for liquid fuels and was cracked to chain lengths more suitable for liquid fuels. This was performed in cracking/isomerization reactor, which was charged with a platinum/ZSM-23 catalyst. Both the HDO and FT reactions produced water as an undesired by-product in addition to the hydrocarbon streams. The water streams were merged and purified in the existing waste water facility of the closely located kraft mill. Light off-gases (carbon monoxide, hydrogen, carbon dioxide and gas containing 1-4C) of the top fraction of the separation unit and light fractions form the process units were collected and fed via appropriate lines to a hydrogen permeable membrane unit for hydrogen recovery. The non-permeable mixture of hydrocarbons and other gases from the membrane unit was directed to an autothermal reformer to be processed to a mixture of hydrogen, carbon monoxide, carbon dioxide, nitrogen, and water. The product gas mixture from reformer acted as a supply for the subsequent water gas shift reactor that produced more hydrogen by the reaction between carbon monoxide and water. Hydrogen was separated in the following pressure swing adsorption unit and was fed into a hydrogen recirculation line for feeding the various processes. Extra hydrogen, when available, was fed into the synthesis gas pool to align the hydrogen/carbon monoxide ratio. The complete outlets, both gas and liquid phases of hydroisomerization and cracking/hydroisomerization in the proportion of FT (40-60%) and HDO (60-40%) hydrocarbons were directed to the separation unit, where unreacted gases and any gaseous hydrocarbons (1-4C) formed by cracking were separated as a top fraction and directed to membrane separation and to the subsequent reforming. The mixed hydrocarbon stream was distilled and the fractions according to selected boiling point ranges were recovered. A naphtha fraction consisting of 5-10C hydrocarbons with boiling point at below 150 degrees C was collected and a middle distillate fraction consisting of 11-20C hydrocarbons boiling at 150-350 degrees C to give a diesel fuel.