INTEGRATION OF DIGESTER AND THERMO-CHEMICAL DIGESTATE TREATMENT EQUIPMENT WITH HEAT RECOVERY Field of the invention The present invention relates to the area of biogas production using an anaerobic digester and more specifically handling of feedstock for the anaerobic digester to increase the biogas production. Background of the invention Anaerobic digesters have been known for numerous years and the technology is constantly undergoing development to improve the production of the biogas. In the present transition towards a more sustainable energy supply to society the need for as well as the desire for the improvement of the technology has significantly increased. As the anaerobic digester due to their inherent limitation in converting certain parts of a typical biomass feedstock, there is a need for moving the present limits to enhance the capabilities of the anaerobic digestion process and further the utilization of the digestate as a residual product from the anaerobic digestion process. Objective of the invention The object of the present invention is therefore to provide for an improved method for production of biogas that will enhance the yields of biogas obtained, increase the speed of biogas production or both objectives at the same time and further make effective use of the digestate in a subsequent processing step for liquid hydrocarbon production. In addition to the desire for producing a sustainable biogas stream there is an already existing desire for providing the nutrient rich residual product for a circular environmental usage. Summary The invention relates to a method for combined gaseous and liquid hydrocarbon production, where a gaseous biogas fuel is produced from an anaerobic digestion process in an anaerobic digester and a liquid fuel is produced in a thermo-chemical process in a thermo-chemical process plant producing a liquid hydrocarbon, where the thermo-chemical process has an excess heat production from the thermo-chemical process, the method comprising supplying excess heat from the thermo-chemical process to the anaerobic digestion process. A significant advantage of the invention may be that the need for externally supplied energy may be reduced or even eliminated. By synergistically combining the anaerobic digestion with a subsequent thermo-chemical process and then apply excess heat from the thermo-chemical process back to the anaerobic digestion allows not only an efficient fuel production in the form of biogas fuel and liquid fuel, but also allows the production to run more efficiently by reducing or eliminating the need for externally supplied energy. One advantage of the invention may be that the combined anaerobic digestion process and thermo-chemical process may significantly increase the ability to take in abundant lignin-containing feedstock. As a result of combining the anaerobic digestion with the thermo-chemical process, a combined increase of fuels in the form of biogas and biooil may be obtained. The much more efficient utilization of the feedstock for fuel production may allow of a less intensive anaerobic digestion process due to the remaining energy potential of the feedstock being utilized for production of biooil. This facilitates an increased fuel production at in a more cost-efficient manner. A further advantage of the invention may be that the combined anaerobic digestion process and thermo-chemical process may decrease the retention time of the feedstock in the anaerobic digestion. A further advantage of the invention may be that a nutrient rich product, which is substantially free of pathogens, may be obtained from the process. By applying a combination of anaerobic digestion with application of thermo-chemical processing of the digestate a resulting nutrient rich product may be obtained that is substantially free of pathogens. A further advantage of the invention may be the nutrient rich product is substantially free of microplastics. By applying a combination of anaerobic digestion with application of thermo-chemical processing of the digestate a resulting nutrient rich product may be obtained that is substantially free of microplastics. A further advantage of the invention may be the nutrient rich product is substantially free of pharmaceutical traces. By applying a combination of anaerobic digestion with application of thermo-chemical processing of the digestate a resulting nutrient rich product may be obtained that is substantially free of pharmaceutical traces. In the present context it should be understood that the thermo-chemical process may also be referred to as a thermo-chemical step. In an advantageous embodiment of the invention, an excess heat is produced from burning gases. In an advantageous embodiment of the invention, the burning of gases may comprise methane, ethane, propane, butane, hydrogen, and any combination thereof. In an advantageous embodiment of the invention, the burning of gases involves gases produced by the anaerobic digestion and/or the thermo-chemical process. In an embodiment of the invention, the burning of gases involves gases produced by the anaerobic digestion. In an embodiment of the invention, the burning of gases involves gases produced by the thermo-chemical process. In an embodiment of the invention, the burning of gases involves gases produced by the anaerobic digestion and the thermo-chemical process. An advantage of the invention may be that the excess heat from the thermochemical process reduce the energy consumption from external sources, leading to an overall decrease in energy consumption for the combined anaerobic digestion and thermo- chemical process, making the combined anaerobic digestion and thermo-chemical process a more sustainable solution. In an advantageous embodiment of the invention the combined anaerobic digestion and thermo-chemical process has reduced energy consumption from external sources. In an advantageous embodiment of the invention, the combined anaerobic digestion process and thermo-chemical process will significantly increase the ability to take in abundant lignin-containing feedstock. In an advantageous embodiment of the invention, the anaerobic digestion process produces a digestate as a residual product and where the digestate is used as a feedstock for the thermo-chemical process. In an advantageous embodiment of the invention, the digestate is dewatered to a predetermined level before being used as a feedstock for the thermo-chemical process. In an advantageous embodiment of the invention, the thermo-chemical step may comprise a pyrolysis process such as a slow pyrolysis process or a catalytic pyrolysis process. In an advantageous embodiment of the invention, the concentrated digestate is further dried to a dry matter content of at least 85 % by weight such as at least 90 % by weight prior to entering the pyrolysis process. In an advantageous embodiment of the invention, the heat required for heating the feedstock for the anaerobic digestion is at least partly supplied by heat recovered from the pyrolysis process. In an advantageous embodiment of the invention, an evaporated moisture in a drying process is condensed, and wherein a recovered latent heat is used to heat the incoming feedstock to the anaerobic digestor. In an advantageous embodiment of the invention, the thermo-chemical step comprises a hydrothermal liquefaction process. In an advantageous embodiment of the invention the thermo-chemical step comprises a pyrolysis process. In an advantageous embodiment of the invention, the hydrothermal liquefaction process comprises preparing a pumpable feed mixture from the concentrated digestate. In an advantageous embodiment of the invention, the thermo-chemical step comprises a hydrothermal liquefaction process comprising pressurizing the feed mixture to a pressure in the range 100 to 400 bar, such as 120 bar to 380 bar, 160 bar to 340 bar, such as 200 bar to 300 bar, such as 240 bar to 260 bar. In an embodiment of the invention, the liquefaction process comprises pressurizing the feed mixture to a pressure in the range 100 to 400 bar, such as 120 bar to 380 bar, 160 bar to 340 bar, such as 200 bar to 300 bar, such as 240 bar to 260 bar. In an embodiment of the invention, the liquefaction process comprises pressurizing the feed mixture to a pressure below 100 bar, such as 1 bar to 80 bar, such as 10 bar to 70 bar, such as 20 bar to 60 bar, such as 30 bar to 50 bar. In an embodiment of the invention, the liquefaction process comprises pressurizing the feed mixture to a pressure above 400 bar, such as 401 bar to 800 bar, such as 450 bar to 750 bar, such as 500 bar to 700 bar, such as 550 bar to 650 bar. In an advantageous embodiment of the invention, the thermo-chemical step comprises a hydrothermal liquefaction process comprising heating the feed mixture to a conversion temperature in the range 250 to 410 °C, such as 280 to 400°C, such as 300 to 390°C, such as 330 to 380°C, such as 350 to 374°C, thereby producing a converted feed mixture. In an advantageous embodiment of the invention, the liquefaction process comprises heating the feed mixture to a conversion temperature in the range 80 °C to 240 °C, such as 100 to 235°C, such as 120 to 230 °C, such as 150 to 225°C, such as 170 to 220°C, such as 200 to 220°C. In an embodiment of the invention, the liquefaction process comprises heating the feed mixture to a conversion temperature in the range 400°C to 600 °C such as 420 to 580°C, such as 440 to 560°C, such as 460 to 540°C, such as 480 to 520°C, thereby producing a converted feed mixture. In an embodiment of the invention, the thermo-chemical step comprises a hydrothermal liquefaction process comprising cooling the converted feed mixture to a temperature in the range 50 to 250 °C, such as 75 to 225°C, such as 100 to 200 °C, such as 125 to 175°C. In an embodiment of the invention, the cooling of the converted feed mixture is set to a temperature in the range 0 to 50 °C such as 10 to 40°C, such as 20 to 30 °C. In an embodiment of the invention, the cooling of the converted feed mixture is set to a temperature in the range 250 to 400 °C, such as 275 to 375°C, such as 300 to 350 °C. In an embodiment of the invention, the hydrothermal liquefaction process comprises depressurizing the converted feed mixture to a pressure in the range 1 to 70 bar such as 10 to 60 bar, such as 20 to 50 bar, such as 30 to 40 bar. In an embodiment of the invention, the hydrothermal liquefaction process comprises depressurizing the converted feed mixture to a pressure in the range 0.1 to 1 bar such as 0.2 to 0.9 bar, such as 0.3 to 0.8 bar, such as 0.5 to 0.6 bar. In an embodiment of the invention, the hydrothermal liquefaction process comprises depressurizing the converted feed mixture to a pressure in the range 70 to 200 bar such as 100 to 180 bar, such as 120 to 160 bar. In an advantageous embodiment of the invention, the thermo-chemical step comprises a hydrothermal liquefaction process comprising separating the converted feed mixture into an oil phase, a gas phase, an aqueous phase, and a solid phase. In an advantageous embodiment of the invention, the thermo-chemical step comprises a hydrothermal liquefaction process characterized by a. Preparing a pumpable feed mixture from the concentrated digestate; b. pressurizing the feed mixture to a pressure in the range 100 to 400 bar; c. heating the feed mixture to a conversion temperature in the range 250 to 410 °C thereby producing a converted feed mixture; d. cooling the converted feed mixture to a temperature in the range 50 to 250 °C; e. depressurizing the converted feed mixture to a pressure in the range 1 to 70 bar; f. separating the converted feed mixture into an oil phase, a gas phase, an aqueous phase, and a solid phase. In an advantageous embodiment of the invention, the retention time in the anaerobic digestion step (ii) is less than 100 days, such as less than 80 days, such as less than 60 days, such as less than 40 days, such as less than 30 days, such as less than 25 days, such as less than 20 days, such as less than 15 days. In an advantageous embodiment of the invention, the retention time of the anaerobic digestion step (ii) is at least 12 hours, such as at least 1 day, such as at least 5 days, such as at least 10 days. In an embodiment of the invention, the retention time in the anaerobic digestion step (a) is 12 hours to 100 days, such as 12 hours to 80 days, such as 1 to 60 days, such as 5 to 40 days, such as 10 to 40 days. In an embodiment of the invention, the retention time in the anaerobic digestion step (ii) is 12 hours to 40 days, such as 12 hours to 30 days, such as 1 to 25 days, such as 5 to 20 days, such as 10 to 15 days. In an advantageous embodiment of the invention, the anaerobic digestion step comprises a continuous anaerobic digestion process. In embodiment of the invention, the anaerobic digestion step is a batch process. In an advantageous embodiment of the invention, the temperature of the anaerobic digester is 45 to 70 °C, such as 48 to 60 °C, such as 45 to 70 °C, such as 49 to 59 °C, such as 50 to 55 °C. In an advantageous embodiment of the invention, the pH value of the anaerobic digester is 6.0 to 9.0, such as 6.0 to 8.5, such as 6.5 to 8.5, such as 7.0 to 8.5. The invention further relates to a solid product obtainable by the method according to the invention or any of its embodiments, where the product comprises phosphorous in a concentration of at least 0.1 wt % such as at least 1.0 wt %. According to one aspect of the present invention the objective of the invention is achieved through a method for combined gaseous and liquid hydrocarbon production, where a gaseous biogas fuel is produced from an anaerobic digestion process in an anaerobic digester and a liquid fuel is produced in a thermo-chemical process in a thermo-chemical process plant producing a liquid hydrocarbon, where the thermo- chemical process has an excess heat production from the thermo-chemical process, the method comprising supplying excess heat from the thermo-chemical process to the anaerobic digestion process. Advantageously the anaerobic digestion process produces a digestate as a residual product and where the digestate is used as a feedstock for the thermo-chemical process. Preferably the digestate is dewatered to a predetermined level before being used as a feedstock for the thermo-chemical process.

Brief description of the drawings The invention will be described in more detail in the following detailed description, with reference to embodiments shown in the drawings, where: FIG. 1 shows a schematic overview of a combined biogas and biooil production facility. FIG.2 shows a schematic overview of a further embodiment of a combined biogas and biooil production facility. FIG.3 shows a schematic overview of a further embodiment of a combined biogas and biooil production facility.

Detailed embodiment In the figures the following numbering is allocated to the individual processes: 1: Pre-treatment step/pre-treatment equipment 2: Anaerobic digestion step/anaerobic digestion equipment 3: Digestate concentration step/digestate concentration equipment 4: Thermochemical process step/thermochemical process equipment 5: Residue upgrading step/residue upgrading equipment 6: Methanation step FIG. 1 shows an embodiment of a process/method for producing gaseous and liquid fuels and/or other chemicals from organic matter such as biomass and/or waste comprising i. A pretreatment step; ii. An anerobic digestion step converting the organic matter to a biogas stream and a digestate stream; iii. A digestate concentration step concentrating the dry matter content of the digestate thereby producing an aqueous stream and a concentrated digestate stream enriched in dry matter content; iv. A thermo-chemical step converting the concentrated digestate stream to liquid fuels/bio-oil and/or other chemicals, where the thermo-chemical step is a hydrothermal liquefaction step or pyrolysis step. v. An upgrading step for nutrient rich residuals The process may in the thermo-chemical step also comprise producing a nutrient rich product that can be utilized directly or after separation and/or mixing with other materials as a fertilizer product in agriculture. ANAEROBIC DIGESTER (2) The retention time in the anaerobic digestion step (ii) is typically less than 40 days such as less than 30 days; preferably the retention time in the anaerobic digestion step (ii) is less than 25 days; even more preferably the retention time in the anaerobic digestion step is less than 20 days such as less than 15 days. The retention time of the anaerobic digestion step (ii) is typically at least 12 hours such as a retention time of at least 1 day; preferably the retention time of the anaerobic digestion step is at least 5 days such as at least 10 days. Preferred the anaerobic digestion step comprises a continuous anaerobic digestion process. However, the process may also be a batch process. Advantageously the anaerobic digestion step (ii) comprises a thermophilic digestion step. The temperature of the anaerobic digester is typically in the range 45 to 70 °C such as in the range 48 to 60 °C; preferably the temperature of the anaerobic digester is in the range 45 to 70 °C such as in the range 49 to 59 °C; even more preferably the temperature of the anaerobic digester is in the range 50 to 55 °C. The pH value of the digester is typically in the range 6.0-9.0 such as a pH value in the range 6.0-8.5; preferably the pH value of the digester is in the range 6.5-8.5 such as a pH value in the range 6.5 -8.0. The feedstock to the anaerobic digester typically comprises animal manures including animal beddings such as manure from dairy production such a manure from livestock production, cattle manure, pig manure, horse manure, deep litter or a combination thereof. In addition to the animal manures the feedstock to the anaerobic digester may also comprise food waste such as kitchen waste, restaurant wastes including oil and greases, separated organic fraction from municipal solid waste, industrial food and non-food waste such as slaughterhouse waste, fats, oils and grease from restaurants, organic household waste, glycerine or a combination thereof. These feedstocks may also be used alone. The feedstock may further comprise one or more lignocellulosic feedstock such as agricultural residues like straw, grasses, husks, corn stover, green house waste, bagasse from sugar production, yard waste, woody biomass such as branches, demolition wood etc., seaweed, lake weed, energy crops, rice crop residue. The lignin content of the feedstock to the anaerobic digester is typically in the range 0.1 to 50 % by weight such as a lignin content of 1 to 30 wt % by weight; preferably the lignin content of the feedstock to the anaerobic digester is in the range 5 to 20 % by weight such as a lignin content of 5 to 15 wt % by weight. Lignin is normally not immediately digestible and therefore an indirect measure of feedstock flexibility i.e., feedstock that will normally not be converted and hence result in lower carbon efficiency for the anaerobic digestion process as such. Although pretreatment may give some improvements in this the digestate typically will have a relatively high content of lignin, obviously dependent on the feedstock. Typical wheat straw has 15-20% lignin content. The combined anaerobic digestion process and thermo-chemical process will significantly increase the ability to take in abundant lignin-containing feedstock. The nitrogen content of the feedstock to the anaerobic digestion step (ii) is typically in the range 0.1 to 10 % by weight such as a nitrogen content of the feedstock to the anaerobic digestion step (ii) in the range to 1.0 to 5.0 % by weight; preferably the nitrogen content of the feedstock to the anaerobic digestion step (ii) is in the range 1 to 3 % by weight. Introduction of the feedstock to the anaerobic digester comprises preparing a pumpable/movable feedstock slurry prior to the anaerobic digestion step (ii) wherein the dry matter content the feedstock slurry is of up to 25 % by weight such as up to 20 % by weight; preferably the feedstock slurry is of up to 15 % by weight such as up to 10 % by weight; even more preferably the dry matter content of the slurry is up to 5 % by weight such as up to 2.5 % by weight. Dependent on the type of feedstock the feedstock slurry preparation step may include reducing the particle size of the feedstock to less than 50 mm such a size reduction of the feedstock to a particle size of less than 40 mm; preferably the particle size of the feedstock is reduced to less than 30 mm prior to the anaerobic digestion step (ii) such as a particle size of less than 20 mm. The feedstock dry matter content may be controlled by mixing with a recirculated stream of digestate from the anaerobic digestion or adding diluted one or more water streams from the digestate concentration step (iii) and/or the thermo-reductive step. The feedstock preparation may further comprise adding bio oil produced in the thermo- reductive step (iv) to the slurry in the feedstock slurry preparation step. To reduce total energy consumption heat from the thermo-reductive step may be used to heat the feedstock slurry prior to entering the anaerobic digestion step (ii). In an embodiment of the invention, the methane content in the biogas is at least 50 % by volume such as a methane content of the biogas of at least 60 % by volume; preferably at least the methane content in the biogas is at least 65 % by volume such as at least 70 % by volume. The biogas from the anaerobic digestion stage is further upgraded by contact with hydrogen in a fixed bed biomethanation reactor comprising anaerobic microorganisms. The biogas upgrading in the biomethanation reaction comprises biological conversion of the carbon dioxide (CO ₂ ) and hydrogen into methane and water. The biomethanation reactor is filled with granular support structures upon which a biofilm is developed through occasional sprinkling of the biomethanation reactor with liquid digestate comprising hydrogenotrophic methanogens from an anaerobic digester. The hydrogenotrophic methanogens are multiplied as a result of feeding the reactor with CO ₂ and hydrogen, rendering a biofilm suited for CO ₂ upgrading. The sprinkling of digestate over the biomethanation reactor ensures sufficient buffer capacity in the reactor to control the pH and provides the necessary macro- and micronutrients. The use of digestate microbacterial cultures ensures resistance towards potential inhibitors such as for example hydrogen sulfide. Hereby the temperature of the fixed bed bioreactor for biogas upgrading is in the range 10 to 70 °C such as a temperature in the range 25 to 65 °C; preferably the temperature of the fixed bed bioreactor for biogas upgrading is in the range 35 to 65 °C such as a temperature in the range 50 to 60 °C. The hydrogen required for the biogas upgrading step is preferably produced by electrolysis using renewable electricity. The stoichiometric relationship between CO ₂ and hydrogen is 1:4 according to the reaction: ^^ _ଶ ^ ^^ _ଶ ՜ ^^ _ସ ^ ʹ^^ _ଶ ^^ The CO ₂ may preferably be added in small excess to ensure full utilization of the hydrogen. The biogas from the anaerobic digestion step (ii) may be heated by heat exchange with a stream from the thermo-chemical step (iv). - Pretreatment by leaching - Gas production per dry matter content in feedstock averages 254 m3 methane per ton dry matter feedstock, which is a considered a high yield of production again significantly contributing to a circularity. - The scale is significant as gas production per day in a modern anaerobic digestion facility is around 20.000.000 m3 methane per year. - The anaerobic digestion takes place in three overall stages. The first stage is hydrolysis, where large structures, i.e. polymers (proteins, carbohydrates and fats) are broken down to monomers (amino acids, sugars and fatty acids) by acidogenic hydrolytic bacteria. The second stage is fermentation, where these monomers are degraded further into smaller molecules such as volatile fatty acids by acidogenic fermentative bacteria. The third stage is methanogenesis, where acetogenic bacteria further degrade the molecules to acetate or hydrogen and CO ₂ . The acetate can then be converted into methane and CO ₂ by aceticlastic methanogenic bacteria and the hydrogenotrophic methanogenic bacteria finally converts the hydrogen and CO ₂ into methane and water. NUTRIENT RICH PRODUCT (5) The nutrient rich product produced in the thermo-chemical process comprises phosphorous in a concentration of at least 0.1 wt % such as at least 1.0 wt %; preferably in a concentration of at least 2.0 wt %; even more preferably the nutrient rich product comprises phosphorous in a concentration of at least 3.0 wt % such as a phosphorous content of at least 4.0 wt %. Due to process conditions in the thermo-chemical process the nutrient rich product produced by the process are substantially free of pathogens. By substantially free of pathogens is meant that the content is reduced below detection. Further, and again due to the process conditions in the thermo-chemical process, the nutrient rich product is substantially free of microplastics. By substantially free of microplastics is meant that the content is reduced to below 0.006 wt%. Further, and again due to the process conditions in the thermo-chemical process, the nutrient rich product is substantially free of pharmaceutical traces. By substantially free of pharmaceutical traces is meant that the content is reduced to below detection limits. The nutrient rich solid product from the thermo-chemical step may be mixed with a part of the concentrated digestate from the concentration step (iii) for use as a fertilizer product. The nutrient rich solid product and/or a solid product from the thermo-chemical step may be dried using heat recovered from the thermo-chemical step. If the thermo-reductive step is a slow pyrolysis, the carbon content in the nutrient rich solid product may be above 50 wt%. If the thermo-reductive step is fast pyrolysis, the carbon content in the nutrient rich solid product may be below 50 wt%. CONCENTRATION OF DIGESTATE (3) The dry matter content of digestate from the anaerobic digestion step (ii) is preferably concentrated to at least 25 % by weight in the digestate concentration step (iii) prior to the thermo reductive step (iv) such as at least 30 % by weight; preferably the dry matter content of the digestate from the anaerobic digestion step (ii) is concentrated to at least 35 % by weight such as at least 40 % by weight prior to the thermo reductive step (iv). The digestate concentration step (iii) comprises for example use of a filter press and/or a decanter centrifuge and/or a screw press and/or a double screw press. PYROLYSIS (4) The thermo reductive step (iv) may comprise a pyrolysis process such as a slow pyrolysis process or a catalytic pyrolysis process. The concentrated digestate is further dried to a dry matter content of at least 85 % by weight such as at least 90 % by weight prior to entering the pyrolysis process. The heat required for drying the digestate is at least partly supplied by heat recovered from the pyrolysis process, for example the heat may be generated from combustion of the pyrolysis gas and/or oil. The evaporated moisture in the drying process is condensed, and wherein the recovered latent heat is used to heat the incoming feedstock to the anaerobic digestor. - Temperature range for slow pyrolysis process (above 350 °) - Products from slow pyrolysis process (biochar (around 50% of feedstock C), bio-oil (around 25% of feedstock C), pyrolysis gas (CO, CO2, H2, other; around 25% of feedstock C) - Catalytic pyrolysis process will typically be carried out at 450-600 °C, and the residence time will typically be between x and y seconds. The process requires an inert atmosphere (no oxygen), for maximizing bio oil yield. HYDROTHERMAL LIQUEFACTION (4) Alternatively, the thermo reductive step (iv) may comprise a hydrothermal liquefaction process characterized by a. Preparing a pumpable feed mixture from the concentrated digestate; b. pressurizing the feed mixture to a pressure in the range 100 to 400 bar; c. heating the feed mixture to a conversion temperature in the range 250 to 410 °C thereby producing a converted feed mixture; d. cooling the converted feed mixture to a temperature in the range 50 to 250 °C; e. depressurizing the converted feed mixture to a pressure in the range 1 to 70 bar; f. separating the converted feed mixture into an oil phase, a gas phase, and an aqueous phase, and a solid phase. The hydrothermal liquefaction process may comprise heating and converting the feed mixture at a temperature up to 400 °C such as heating and converting the feed mixture at a temperature of up to 390 °C; preferably heating and converting the feed mixture at a temperature of up to 380 °C such as heating and converting the feed mixture at a temperature of up to 374 °C. The hydrothermal liquefaction process may comprise heating and converting the feed mixture to a temperature of above 280°C such as heating and converting the feed mixture at a temperature of above to 300 °C; preferably heating and converting the feed mixture at a temperature of above to 330 °C such as heating and converting the feed mixture at a temperature above 350 °C. In order to optimize the hydrothermal liquefaction process, the pumpable feed mixture may be preheated to at least 80 °C prior to entering the pressurization step such as preheating the feed mixture to at least 100 °C prior to entering the preheating step; preferably the feed mixture is preheated to a temperature of at least 120 °C such as a temperature of at least 150 °C prior to entering the pressurization step; even more preferably the feed mixture is heated to at least 170 °C such as at least 200 °C prior to entering the pressurization step. The hydrothermal liquefaction process may include that the feed mixture is pre- pressurized to a pressure of up to 50 bars prior to the preheating step such as a pre- pressurization of the feed mixture of up to 40 bars prior to the preheating step; preferably the feed mixture is pre-pressurized to a pressure of up to 30 bars prior to the preheating step such as pre-pressurizing the feed mixture to a pressure of up to 20 bars prior to the preheating step. Advantageously the feed mixture is pressurized to at least 50 bars in the pressurization step prior to heating the feed mixture to the conversion temperature in the heating step (c) such as pressurizing the feed mixture to a pressure of at least 80 bars in the pressurization step; preferable the feed mixture is pressurized to a pressure of at least 150 bars prior to heating the feed mixture to the conversion temperature such as a pressurizing the feed mixture to a pressure of at least 180 bar prior to heating the feed mixture to the conversion temperature. The density of the feed mixture during the conversion at the conversion temperature is maintained in the range 100 to 800 kg/m ³ such as in the range 300 to 700 kg/m ³ ; preferably the density of the feed mixture at the conversion temperature is maintained in the range 350 to 650 kg/m ³ such as in the range 400 to 600 kg/m ³ . Preferably the pH of the conversion process is maintained so that the pH value of the aqueous phase separated from the converted feed mixture is alkaline. Preferably the pH of the conversion process is controlled so that the pH value of the aqueous phase separated from the converted feed mixture is alkaline. Preferably the pH of the conversion process is maintained so that the pH value of the aqueous phase separated from the converted feed mixture is above 8 such as a pH value of aqueous phase separated from the converted feed mixture of at least 8.5; preferably the pH value of the aqueous phase separated from the converted feed mixture is in the range 8 to 10 such as a pH of the aqueous phase separated from the converted feed mixture in the range 8.5-9.5. Preferably the pH of the aqueous phase separated from the converted feed mixture is controlled by adding a base to the feed mixture in the feed mixture preparation step. Preferably the base is selected among potassium carbonate, potassium hydroxide, potassium formate, potassium acetate, sodium carbonate, sodium hydroxide, sodium formate and/or sodium acetate, ammonia or a combination thereof. The control of the pH may at least partly be performed by at least partly recycling the separated aqueous phase from the separation to the feed mixture preparation step. The bio-oil produced is at least partly recycled to the feed mixture preparation step (i). A solid phase is separated from the converted feed mixture prior to cooling the converted feed mixture. To obtain individual parts of the solid phase residue as separate streams the solid phase is separated in a hydro cyclone and/or one or more filters. To avoid high ash and high nitrogen content in the bio-oil, the concentrated digestate fraction may advantageously be washed with water prior to the thermo-chemical step. The water may preferably be a recycled, water stream from the thermo-chemical process step or the drying step in case of a hydrothermal liquefaction process or a pyrolysis process, respectively. The wash water may be mixed with the liquid digestate fraction from the separation step b). In Fig. 2 the recycling streams are shown including further options for reusing water and residual heat, hereby increasing the energy efficiency of the gas and bio-oil production further. The fact that some of the streams shown in Fig. 1 or 3 are left out does not exclude the combination of these. In Fig. 3 the recycling streams are shown including further options for reusing water and residual heat, hereby increasing the energy efficiency of the gas and bio-oil production further. The fact that some of the streams shown in Fig. 1 or 2 are left out does not exclude the combination of these.