Method for producing bio-oil

Abstract

A process for the production of crude bio-oil comprising the steps of a) providing organic waste comprising a digestate, b) introducing algae to the waste, c) cultivating the algae, d) performing hydr

Description

FIELD OF THE INVENTION The present invention is concerned with processes for the production of bio-oil from algae and organic waste, bio-oil and further sustainable fuels produced from the processes, and systems for producing bio-oil. BACKGROUND Liquid hydrocarbon fuels used in aviation and other transport fuels are currently supplied from fossil fuel otherwise known as petroleum or crude oil. Due to global climate change, there is an urgent need to move away from the use of fossil fuels. The development of sustainable energy solutions that reduce global carbon emissions, while maintaining high living standards, is a major challenge facing society. Transportation which is critical to economic development, globalization, and the advancement of society requires, for the main part, liquid hydrocarbon fuel. Although some ground vehicles and small aircraft are beginning a slow transition toward electric propulsion with energy sourced from solar radiation or wind, the extreme power requirements of jet aircraft require a more concentrated source of energy which currently can only be supplied by a concentrated liquid hydrocarbon fuel. There remains a demand for liquid hydrocarbon fuel for the aviation industry and some other transportation industries. As the world transitions away from reliance on petroleum for fuel and other products, alternative sources of liquid fuel are needed. An option for liquid fuel sources which do not originate from fossil fuels are biofuels, which may be derived from biomass via a variety of thermal, chemical and biochemical methods. For instance, hydrothermal liquefaction (HTL) uses heat and pressure to liquefy the organic matter in biomass / waste feedstocks to produce crude bio-oil. Such processes can therefore be used to convert waste organic matter into biocrude which can be further processed to provide sustainable fuels. One potential source of biomass for conversion to liquid fuel is from algae such as microalgae and cyanobacteria. Many such algae have high lipid content, making them extremely suitable for conversion to bio-oil. The conversion of microalgae to a crude oil can be achieved using techniques such as those described above, e.g. hydrothermal liquefaction (HTL). HTL can covert the organic carbon from algae into liquid hydrocarbons making it suitable for industries such as the aviation industry and thus creating a sustainable aviation fuel (SAF). Microalgae are typically microscopic plant-like organisms that inhabit a wide range of aquatic environments. There are tens of thousands of different species living in a wide range of habitats from fresh and salt water from high salinity to low and high temperature and they form the basis of all aquatic food chains. Like land plants including trees, they use photosynthesis to convert CO2 into a range of organic molecules. Similarly, cyanobacteria “blue-green algae” are capable of performing photosynthesis to obtain biological energy and convert CO2 to organic molecules. An advantage of algal cultivation over cultivation of land plants is their high growth rates and the ability to maintain continuous cultivation unlike crops which typically have one or two harvests a year. Cultivation of algae will typically require a source of nutrients, a source of water and potentially some control of parameters such as temperature and light. Suitable growth conditions for cultivating any given algae would be known to the skilled person. Various industries produce organic waste material, for instance food waste from domestic or industrial food production / consumption and waste products such as digestate from anaerobic digestion plants. Such waste material can be costly to dispose of and may in some instances contribute to landfill. Conversion of such waste organic material may potentially be converted into biofuels via the processes described above. However, it is a less preferable source of biomass for such processes than algae. Conversion of such waste organic material alone to bio-oil may provide low yields and lower quality bio-crude. There is an unmet need for sustainably sourced liquid hydrocarbon fuels such as SAF. SUMMARY OF INVENTION The present invention is concerned with processes for the production of crude biooil comprising the steps of: providing organic waste material; introducing algae into said waste material to form a culture; cultivating said algae in the culture; and performing hydrothermal liquefaction on at least a portion of the resultant biomass to produce crude bio-oil. This process has the advantage that the waste organic material may provide a source of nutrients such as nitrogen, phosphorus and organic molecules for the algae, facilitating growth and avoiding the need to provide alternative feed to the algae which may be expensive and / or environmentally damaging. The growth of the algae during cultivation absorbs carbon dioxide (CO2) from the atmosphere, further reducing the overall carbon footprint of the process. Thus, it may be possible to provide biofuel which is carbon neutral, or even carbon negative. The processes of the present invention also provide an efficient use of organic waste material such as digestate from anaerobic digestion and / or food waste, which may otherwise be costly to dispose of, and may in some instances be consigned to landfill. After cultivation of the algae, the remaining organic waste material, together with the algal biomass, forms part of the biomass which is converted to crude bio-oil via HTL. Thus, the biomass used for HTL may comprise both algal biomass and residual organic waste material. Conversion of such waste organic material, e.g. digestate and food waste, alone to bio-oil may provide low yields and lower quality bio-crude. By combining this biomass with algae, which have a high lipid content, a higher quality and yield of bio-oil can be obtained. A further advantage of the invention is that hydrothermal liquefaction can be performed on wet biomass. Moreover, HTL can convert a variety of organic components, e.g. proteins carbohydrates and lipids, into bio-oil. Thus, the processes of the present invention avoid the need for extensive initial drying and processing of the biomass prior to conversion to bio-oil. Such steps may be energy and labour intensive. As both the organic waste material and the algal biomass are subjected to hydrothermal liquefaction, it is not necessary to separate these components before HTL is performed. Thus, biomass comprising both algae and waste organic material may be extracted from the culture and subjected to HTL without the need for difficult and costly separation steps. The processes of the present invention may comprise further steps to “upgrade” the crude bio-oil in order to provide a biofuel such as gasoline, diesel or aviation fuel. These upgraded biofuels may be suitable for use for heating, energy production, or transportation. The biofuels may be used (e.g. as fuel for vehicles) alone, or else may be mixed with fuels from other sources such as fossil fuel derived fuels. In a preferred embodiment, the bio-oil is upgraded to be suitable for use as aviation fuel, e.g. jet fuel. Thus, the present invention may advantageously provide a source of sustainable aviation fuel (SAF). The present invention provides a process for production of crude bio-oil comprising the steps of: (a) providing organic waste material comprising at least one of digestate and food waste; (b) introducing algae to said organic waste material to form a culture; (c) cultivating the algae within said culture to obtain biomass comprising algae and organic waste material; and (d) performing hydrothermal liquefaction on at least a portion of the biomass to form crude bio-oil. The algae may comprise or consist of one or more algae selected from the groups: Botryococcus, Monoraphidium, Rhodophyta, Chlorophyta, Chrysophyta, Cryptophyta, diatoms, Dinophyta, Tribophyta, Tribonema, Tetraselmis, Glaucophyta, Spirulina, Nannochloropsis, Chlorella, cyanobacteria, Euglena, Microcystis, Anabaena, Dictyosphaerium, Nodularia, Oscillatoria, Spirogyra, Hydrodictyon, Nitella, Oedognium, Phormidium and filamentous algae. In some embodiments the algae may comprise or consist of one or more selected from the groups: Arthrospira, Chlorella, Scenedesmus, Nannochloropsis, Monoraphidium, Euglena, Phaeodactylum, Tetraselmis, Tetradesmus, and Botryococcus. In some embodiments the algae may comprise or consist of one or more selected from Scenedesmus obliquus, Nannochloropsis oculata, Spirulina (Arthrospira platensis) and Monoraphidium minutum. In some embodiments the organic waste material is digestate. In some embodiments the algal culture of step (c) further comprises wastewater. Said wastewater may be from an anaerobic digestion plant or food waste sources. In some embodiments step (b) comprises adding a first algal culture having an algal density of at least 0.5 Kg / m3, preferably at least 1.0 Kg / m3, in terms of dry weight of algae to a mixture comprising the organic waste material. The first algal culture may be added in an amount of 10% or more by volume compared to the total volume of the resultant culture. In some embodiments the algae comprises a cyanobacterium such as Spirulina (Arthrospira platensis), and the first algal culture is added in an amount of 40% or more, preferably 50% or more, by volume compared to the total volume of the resultant culture. In some embodiments the processes further comprise step of scaling up an algae culture prior to its introduction to the waste organic material in step (b). The scale up may comprise one or more inoculation and growth steps. The scale-up steps may be performed inside a building wherein the cultures are maintained within a predetermined temperature range and supplied with artificial light at a predetermined intensity. In some embodiments the culture step (c) is performed in one of more of a production raceway and / or an open pond system. In some embodiments, the culture step (c) is performed in one or more open ponds. In some embodiments a portion of the algal biomass is harvested during step (c). The harvested algal biomass may be dried to provide a bulk dry algal biomass. In some embodiments one or more of the following may extracted from the harvested algal biomass: triacylglycerides (TAG), glyco-lipids, phospho-lipids, waxes, sterols, soluble proteins, insoluble proteins, monosaccharaides, oligosaccharides, starch, cellulose, chlorophyll, carotenoids, phycobilins, and w-3 fatty acids. In some embodiments the process is performed as a batch process, a continuous process or a semi-continuous process. In some embodiments the aqueous phase obtained from hydrothermal liquefaction in step (d) is reintroduced to the culture of step (c). In some embodiments the process may comprise the further step (e) of processing the crude bio-oil to obtain at least one biofuel selected from naptha, kerosene and diesel. The processing step (e) may comprise one of more one of the following processes: filtration, emulsification, transesterification, hydro cracking, catalytic cracking, zeolite cracking, catalytic hydrotreating and fractionation. In some embodiments the step (e) may comprises catalytic hydrotreating, preferably followed by fractionation. In some embodiments the processes of the present invention may further comprise mixing the biofuel with one or more fossil fuel derived fuels to form a blended fuel. The present invention further provides a system for production of crude bio-oil comprising: (i) means for supplying and containing organic waste material, wherein said organic waste material comprises digestate and / or food waste; (ii) means for introducing algae to said organic waste to form a culture; (iii) means for cultivating the algae within said culture to obtain biomass comprising algae and organic waste; (iv) means for performing hydrothermal liquefaction on at least a portion of the biomass to form crude bio-oil. The present invention further provides a biorefinery plant comprising the above described system. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 shows a simplified outline scheme for integrating algal cultivation with HTL. Fig. 2 shows a flow diagram describing integrated algal cultivation with HTL followed by upgrading to biofuels. Fig. 3 shows a schematic view of a process of algae culture scale-up and processing to provide bulk dry microalgae biomass and / or sustainable aviation fuel. Fig. 4 shows a schematic view of a process of algae culture scale-up. DETAILED DESCRIPTION The present invention provides a process for production of crude bio-oil comprising the steps of: (a) providing organic waste material comprising at least one of digestate and food waste; (b) introducing algae to said organic waste material to form a culture; (c) cultivating the algae within said culture to obtain biomass comprising algae and organic waste material; and (d) performing hydrothermal liquefaction on at least a portion of the biomass to form crude bio-oil. Crude bio-oil or bio-crude refers to the organic liquid obtained from the hydrothermal liquefaction of biomass. It comprises primarily organic components, and is separable from the aqueous phase from HTL. As used herein, the term “algae” includes both microalgae, i.e. microscopic single celled algal species which may be found in fresh and salt water, as well as cyanobacteria “blue-green algae”. Examples of algae which may be used according to the present invention include algae selected from the following groups: Botryococcus, Monoraphidium, Rhodophyta, Chlorophyta, Chrysophyta, Cryptophyta, diatoms, Dinophyta, Tribophyta, Tribonema, Tetraselmis, Glaucophyta, Spirulina, Nannochloropsis, Chlorella, cyanobacteria, Euglena, Microcystis, Anabaena, Dictyosphaerium, Nodularia, Oscillatoria, Spirogyra, Hydrodictyon, Nitella, Oedognium, Phormidium and filamentous algae. As discussed above, algae have the potential to provide an excellent source of biomass for conversion to biofuel, as they may accumulate lipids to a high degree, and can have elemental compositions high in carbon and hydrogen. Thus, algae species having high lipid content may be particularly useful in the present invention. However, other organic components including lipids, carbohydrates and proteins may be converted into biooil during hydrothermal liquefaction. Therefore, the lipid content is not critical. Other properties of the algae which make them particularly suitable for use in the present invention include the ability to grow on land not required for other uses, being well adapted to being cultivated on waste streams e.g. municipal or industrial wastewater, high ability to capture carbon from waste streams, high resilience to environmental fluctuations and resistance to contaminations from external bacterial, fungal or protozoan infections. Particularly advantageous algae having the above properties include algae selected from the groups: Arthrospira, Chlorella, Scenedesmus, Nannochloropsis, Monoraphidium, Euglena, Phaeodactylum, Tetraselmis, Tetradesmus, and Botryococcus. Most preferably the algae used in the present invention comprise or consists of one or more selected from Scenedesmus obliquus, Nannochloropsis oculata, Spirulina (Arthrospira platensis) and Monoraphidium minutum. These algae have been shown to provide advantageous combinations of properties, in terms of growth rate, lipid accumulation, resistance to environmental fluctuations and contamination, and adaptability to growing in culture medium of the present invention, e.g. wastewater streams. Other algae species which may potentially be useful in the present invention include Tribonema minus and Botryococcus braunii. As used herein, the term digestate refers to the material remaining after the anaerobic digestion (decomposition under low oxygen conditions) of a biodegradable feedstock. Digestate may be produced by acidogenesis and methanogenesis. Suitable digestate for use in the present invention may originate from an anaerobic digestion plant which may utilise one or more of the following feedstocks: sewage sludges, such as liquid sludge, untreated sewage sludge, composted sludge, and lime treated sludge; animal waste, such as animal fats, animal blood, food remains, stomach contents, rumen contents, animal carcasses, and poultry, fish and livestock manure; energy crops such as corn, maize, millet and clover, including either the whole crops or waste from harvesting said crops such as stems and stalks; municipal wastes such as food waste, coffee filters and grounds, tea, organic leftovers, bakery waste, and kitchen waste; agricultural wastes such as fruits, molasses, stems, plant straw, and bagasse (residue after crushing sugarcane or sorghum stalks); and industrial waste such as food / beverage processing waste, dairy wastes, starch / sugar industry wastes, slaughterhouse wastes, and brewery wastes. In some embodiments, the digestate used may be digestate complying with the British Standard Institution’s Publicly Available Specification (BSI PAS 110 (2014)). As used herein, the term food waste may include domestic or commercial food waste, as well as industrial waste from food / drink production. Food waste may include animal products, such as meat, animal fats, animal blood, stomach contents, rumen contents, animal carcasses, dairy and eggs; plantbased food waste such as fruit or vegetable matter, coffee filters or grounds, tea, bakery waste; kitchen waste; and industrial waste such as food / beverage processing waste, dairy wastes, starch / sugar industry wastes, slaughterhouse wastes, and brewery wastes. In the processes of the present invention algae is grown in a culture comprising organic waste material comprising digestate and / or food waste. The culture will also comprise water. Saltwater and freshwater may be used to cultivate algae. In some embodiments of the processes of the present invention, freshwater is preferred. Thus, the cultures according to step (b) / (c) of the present invention preferably comprise freshwater. More preferably the culture of step (b) / (c) comprises wastewater, e.g. from an anaerobic digestion plant or food waste source. This has the advantage of supplying further nutrients to the culture and avoiding waste. Such wastewater may also advantageously retain waste heat from the anaerobic digestion plant / food production or processing plant from which it originates, thereby saving energy which may be needed in order to retain the culture at the correct temperature. When wastewater from an anaerobic digestion plant or food waste source is supplied to the culture, this may be provided separately from the waste organic material comprising digestate and / or food waste, or mixed together with said waste organic material. Thus, the culture medium in which the algae is grown in step (c) of the present invention will comprise organic waste material and water, The step (b) of the processes of the present invention may typically comprise adding a first algae culture “inoculation culture” to a mixture comprising the waste organic material. The first algal culture will comprise the algae of interest (typically at a high concentration) suspended in growth medium, e.g. freshwater, salt water or wastewater comprising nutrients for algal growth. The first algae culture may result from an algal scale-up process. In some embodiments the processes of the present invention may comprise a step of scaling up an algae culture prior to its introduction to the waste organic material in step (b). This scaling up will typically comprise a series of inoculation and growth steps, wherein algal cultures are transferred to a container containing growth medium and then allowed to grow until they reach a specific algal density, before repeating said inoculation and growth steps in progressively larger volumes of growth medium. The culture scale-up process is an important step for algae production facilities which occurs prior to introduction of the algae to the organic waste material. In preferred embodiments the algae may be scaled up in a controlled environment. For instance, this could be inside of a temperature controlled structure such as a portable cabin or building. Such a structure is preferably situated adjacent to the site for cultivating the algae with the organic waste mixture (step (c)), e.g. a production raceway or an open pond system. Thus, the scaled-up algae may be easily transferred to the culture comprising organic waste material once scaled up without needing to be transported from an external site. The scale up of the algae may be performed according to any suitable process known in the art for scaling up algae cultures. For instance, the scale up may be performed according to the process described in Fig. 4. In preferred embodiments, the scale up may be performed beginning with axenic or non-axenic cultures of the target algae species, using seawater, freshwater, wastewater, or commercial growth media, preferably sterilized, for instance with an autoclave. Examples of suitable commercially available algal growth media which may be used for the scale up include F / 2 commercial media. The culture may then be scaled up in progressively increasingly sized containers, such as flasks, carboys, bags, or combinations thereof. For instance, the culture may be scaled up from a 250 ml container to a 1L conical flask, then 5L flasks, then 20L carboys, and finally 80L bags (inside polytunnel). Optionally, one or more stages of the scale up process may take place inside a polytunnel rather than inside a building. Water or media used for algal cultures according to the present invention, especially cultures of 20L or more during scale up or later, may preferably be pre-treated, for instance via chlorination followed by neutralization. In preferred embodiments, the abiotic parameters may be selected to match the conditions of the outside environment. For instance, the temperature of the cultures during scale up may be maintained in the range of 15 C to 30 C, preferably 18 C to 25 C, more preferably 19 C to 21 C. The cultures may be aerated with filtered (0.2 pm) ambient air. The air may have a CO2 content of approximately 0.039%. The aeration may be at a rate of 0.6 L (v / v), for instance using a capillary tube (e.g. 1mm capillary glass tube) inside the containers such as flasks / carboys to bubble the air-CO2 mixture inside the cultures. The scale up cultures may be supplied with artificial light (for instance in steps performed indoors, e.g. in a temperature controlled structure, without natural light). Suitable sources of illumination include Light Emitting Diode (LED) lights, or fluorescent lamps. An average irradiation of 50 - 250 pmol photons per m2 per second (pmol / m2 / s) may be used, preferably 100 - 200 pmol / m2 / s, yet more preferably 140-160 pmol / m2 / s, most preferably 150 pmol / m2 / s. A photoperiod to match outside conditions may preferably be used. For instance, the light dark cycle may be approximately 18:6. Once the final scale up culture reaches a suitable density such as 0.5 Kg / m3 in terms of dry weight of algae (i.e. the weight of dry algal biomass per volume of the culture including algae and culture medium), preferably 1 Kg / m3, it may be introduced to the organic waste material to form a culture (step (b)) according to the processes of the present invention. In order to provide efficient inoculation, once an algal culture reaches the desired density during scale up, it should preferably be introduced to the new culture medium (e.g. culture medium comprising organic waste material according to steps (b) / (c) of the present invention) in an amount of at least 10% by volume of the resultant volume of the new culture. The new culture may be in the form of an open pond or a production raceway comprising water and waste organic material. Thus, for example, if a small production raceway having a volume of 2 m3 were used for the new culture, an inoculation volume of 200 L or more of scaled up algae culture having the desired density should preferably be used to inoculate the new culture. In preferred embodiments, the algal culture used for inoculation (first algal culture, which may result from previous scale up steps) having a density of at least 0.5 Kg / m3 in terms of dry weight, preferably at least 1 Kg / m3 in terms of dry weight, is introduced to the culture media in an amount of 10 to 60% by volume of the final (resultant) culture volume, preferably 10 to 50%. For microalgae such as Scenedesmus obliquus, Nannochloropsis oculata, and Monoraphidium minutum, the preferred inoculation amount is at least 10% by volume of the final culture volume, such as 10 to 20%. For cyanobacteria such as Spirulina (Arthrospira platensis), the preferred inoculation amount is at least 40% by volume of the final culture volume, such as at least 50% by volume of the final culture volume. For cyanobacteria, example inoculation amounts include 40 to 60%, preferably 45 to 55% by volume of the final volume. These inoculation amounts may also apply to each step of the scale up process. The cultivation step (step (c)) of the present invention may occur in any suitable container. For instance, the cultivation of the algae in waste organic material may take place in a production raceway, or an open pond. In preferred embodiments the cultivation step (c) takes place in an open pond, or multiple of open ponds. The use of a production raceway or open pond system have the advantage that sunlight can be used for photosynthesis, reducing / eliminating the need for artificial light to provide energy for the algal growth. The term “culture” is used herein to refer to algae suspended within a culture medium, such as water (e.g. freshwater, salt water, or waste water) comprising nutrients necessary for algal growth. The temperature of the algal culture during cultivation step (c) may be determined by ambient temperature at the site of the culture, if kept outside. In some embodiments, the ponds may be thermoregulated to keep them within acceptable temperature ranges, for instance in the range 5 C to 35 C, preferably 10 C to 30 C, more preferably 15 C to 30 C, most preferably 15 C to 25 C. Alternatively any suitable photobioreactor may be used, having a natural or artificial light source. In some embodiments, a portion of the algal biomass may be harvested after the cultivation step (c) and before hydrothermal liquefaction step (d). Thus, some of the algae may be separated from the remainder of the culture for other purposes that HTL, or else for extraction of useful products prior to recombination with the remainder of the biomass for HTL. In some embodiments, the harvested algal biomass may be dried to provide bulk algal biomass for sale or other purposes. Any suitable drying techniques may be used, such as centrifuging and / or evaporation. Useful products may be extracted from the algal biomass. Examples of such products include one or more selected from: lipids, proteins, carbohydrates, pigments, ash and minerals. Particularly preferred products which may be extracted from the algal biomass include one or more selected from: triacylglycerides (TAG), glyco-lipids, phospho-lipids, waxes, sterols, soluble proteins, insoluble proteins, monosaccharaides, oligosaccharides, starch, cellulose, chlorophyll, carotenoids, phycobilins, and w-3 fatty acids. Thus, in some embodiments, the processes of the present invention include the step of extracting one or more of the above products from the harvested algal biomass. After extraction of the product, the remaining algal biomass may optionally be used for conversion to bio-oil, e.g. via HTL. Thus, after extraction of the products the algal biomass may be recombined with the remaining biomass of step (c), and subjected to HTL, or else directly subjected to HTL without recombination with the biomass of step (c). The processes of the present invention may be performed as batch processes, continuous processes, or semi-continuous processes. In some embodiments individual batches of biomass comprising algae and organic waste may be produced for conversion to crude bio-oil via HTL by performing steps (a) to (c) sequentially and then performing HTL on the resultant biomass (for example all of the resultant biomass). Alternatively, the culture of step (c) may be continuously supplied with additional organic waste material, and optionally other components such as wastewater and additional nutrients, and portions of the biomass comprising algae and organic waste may be continuously, or periodically removed for HTL. Such a continuous process would therefore allow the culture to retain an algae population and therefore avoid / reduce the need for repeated scale-up of new algal cultures for inoculation of the organic waste material culture of step (c). Harvesting of the biomass for HTL treatment may occur at a suitable point, such as at a specified time interval, or else when the algae reaches a specific density such as 0.5 Kg / m3 or 1 Kg / m3 in terms of dry weight of algae (i.e. the weight of dry algal biomass per volume of the culture including algae and culture medium). Hydrothermal liquefaction refers to a thermochemical depolymerisation, decomposition and recombination process which typically occurs in an enclosed reactor to convert wet biomass into biocrude oil and other chemicals. In the context of the present invention, hydrothermal liquefaction involves subjecting organic biomass to elevated temperature and pressure until at least a portion of the biomass is converted to crude bio-oil. In some embodiments, the biomass may be treated prior to HTL (step (d)), for instance by concentration and / or drying and / or purification of the biomass. Hydrothermal liquefaction according to the present invention may be performed using a reactor temperature in the range 200 C to 550 C (degrees Celsius), preferably 200 C to 400 C. The HTL may typically be performed at a pressure in the range 5 MPa to 30 MPa, preferably 10 MPa to 25 MPa. HTL may be performed with or without a catalyst according to need. Suitable catalysts include water-soluble inorganic compounds and salts, such as KOH, NaOH and Na2CO3, as well as transition metal catalysts comprising at least one of selected from nickel, palladium, platinum and ruthenium, which metals are supported on carbon, silica or alumina. In some embodiments additional organic solvents may be used during HTL to modify the composition of the bio-crude, and / or increase yield. Examples of suitable organic solvents include alcohols, such as methanol, ethanol, isopropanol and glycerol. The HTL may be performed using conditions and processes known in the art such as those described in Biddy, M., Davis, R., Jones, S., &Zhu, Y., National Renewable Energy Laboratory, 2013, PNNL-22314, Whole Algae Hydrothermal Liquefaction Technology Pathwaym, https: / / www.nrel.gov / docs / fy13osti / 58051 .pdf (Biddy et al.). An advantage of HTL is that water may be used as the solvent, which avoids the need to significantly dry the biomass which can be time and energy intensive. Further, multiple organic components, including carbohydrates and proteins can be converted to bio-oil, and not solely lipids. In addition to crude bio-oil, HTL may produce solids, e.g. biochar, CO2 and an aqueous phase. In preferred embodiments, one or more of the aqueous phase, solids (e.g. biochar), and CO2 may be recycled for use in the algal cultivation step(s). This has the advantages of providing additional nutrients, and / or reducing the CO2 emissions of the overall process. The aqueous phase, e.g. wastewater, may be treated via hydrothermal gasification to convert any organics to CO2 and CH4. The CH4 may be combusted to provide heat for the HTL, or else for heating an algae culture during step (c) or during scale up of the algae. Treated wastewater may be returned to the algal cultures to provide a source of nutrients such as nitrogen. In order to provide higher quality biofuels, the biocrude obtained from HTL may be further upgraded, e.g. to provide low carbon (C6-C14) alkane products. The upgrading will typically remove impurities, decreasing the concentration of O, N, S, and the viscosity. These steps are advantageous as the presence of the oxygenated compounds in the biocrude can make them reactive at room temperature by forming gum overtime. Further, the storage and transportation of direct biocrude (compared with refined biofuels) in containers is more difficult due to its acidity and presence of higher nitrogen (e.g. 10-20%), oxygen, and sulphur amounts. Compounds containing nitrogen and sulphur in the biocrude could also form storage instability by forming NOx or SOx during combustion. Thus, it is advantageous to perform further processing steps on the bio-crude obtained. In some embodiments of the processes of the present invention, after HTL the crude bio-oil may be subjected to further processing steps, i.e. “upgrading” to provide refined biofuels, e.g. “bio” gasoline, diesel and jet fuel. Such further processing steps may include one of more of filtration, emulsification, hydro cracking, catalytic cracking, zeolite cracking, catalytic hydrotreating and fractionation. In some embodiments, the crude bio-oil may be upgraded by subjecting it to catalytic hydrotreating. The treatment may remove oxygen, e.g. by conversion to CO? and water, and nitrogen, e.g. by conversion to ammonia which may be retained in an aqueous phase. Sulfur may be converted to hydrogen sulfide. In preferred embodiments the oxygen content may be reduced to less than 2 wt.%, preferably less than 1 wt.%, and the nitrogen may be reduced to less than 0.6 wt.%, preferably less than 0.3 wt.% of the upgraded biocrude. Suitable catalysts which may be used for catalytic hydrotreating are known in the art, and include nickel based catalysts. In some embodiments the crude bio-oil, optionally after catalytic hydrotreating, may be fractionated into separate fractions. For instance, the (optionally catalytically hydrotreated) bio-oil may be fractioned into fractions comprising one or more of a naptha range, a kerosene range, a diesel range, and a heavy oil range material. Heavy oil obtained from the bio-oil, e.g. via fractionation, may be further treated by cracking, e.g. catalytic cracking, to obtain additional shorter chain fuels such as naptha, kerosene, or diesel range biofuel components. In some embodiments, the upgraded biofuel such as kerosene may be suitable for use as an aviation fuel, i.e. sustainable aviation fuel (SAF). Suitable upgrading techniques which may be used in processes of the present invention include those known in the art, such as those described in Biddy et al. In some embodiments, the refined biofuels produced by the processes of the present invention, e.g. bio-diesel, bio-naptha, and bio-kerosene, may be blended with one or more fuels derived from fossil fuels, e.g. liquid hydrocarbon fuels such as naptha, kerosene, diesel and gasoline derived from fossil fuel sources. Such blending can result in fuels which are more environmentally friendly (having a lower carbon footprint) than entirely fossil fuel derived fuels, whilst also providing desired properties for a given use, e.g. in transportation for automobiles, aviation and shipping. The steps of the processes of the present invention, may take place at a single site, e.g. a biorefinery plant, or else be split across multiple sites. In a preferred embodiment, the inoculation of the organic waste with algae (step (b)), cultivation of algae (step (c)), and hydrothermal liquefaction (step (d)) all take place at a single location (i.e. at a biorefinery plant). An advantage of such a process is that waste materials, heat and biproducts such as biogas, CO2 and wastewater may advantageously be recycled or used in other process steps without the need for expensive transportation of materials. More preferably, such a biorefinery plant may be situated adjacent to a plant producing waste organic material, e.g. an anaerobic digestion plant which produces digestate or a food production / processing plant which produces food waste. The biorefinery plant may be integrated with such an aerobic digestion plant or food processing / production plant, such that organic waste material may be directly transferred to the biorefinery plant for use in an algal culture according to the present invention. Thus, in a preferred embodiment, all steps of the processes of the present invention occur at a single site, e.g. a biorefinery plant. In an embodiment, the present invention therefore provides a system for production of crude bio-oil comprising: • means for supplying and containing organic waste material, wherein said organic waste material comprises digestate and / or food waste; • means for introducing algae to said organic waste to form a culture; • means for cultivating the algae within said culture to obtain biomass comprising algae and organic waste; • means for performing hydrothermal liquefaction on at least a portion of the biomass to form crude bio-oil. The means for supplying and containing organic waste material is typically a container suitable to hold organic waste material, such as an open pond system, or a production raceway. The means for supplying organic waste material may be, for instance a pipe configured to receive waste organic material and pump it into the container. Alternatively, the container may contain a suitable opening, to allow delivery of organic waste material. For instance, in the case of open ponds, the organic waste delivery may be delivered directly into the top of said ponds. The means for introducing algae may similarly be a pipe configured to receive algae and deliver / pump it into the container for the organic waste material, or else an opening in the container suitable for introduction of algae. The means for cultivating the algae within said culture to obtain biomass comprising algae and organic waste may refer to the container such as an open pond or production raceway which is suitable for supporting algal growth, i.e. configured to provide sufficient growth conditions such as light, either from sunlight if outdoors, or via artificial light if the container is situated indoors or is otherwise covered. The means for performing hydrothermal liquefaction will typically be a reactor configured to receive biomass, and to provide the necessary temperature and pressure conditions needed to convert said biomass to crude bio-oil. The reactor may be situated adjacent to the algal culture such that biomass may be easily transferred to the reactor for HTL. The system described above may be contained in a plant e.g. a biorefinery plant. Fig. 1 shows a simplified outline scheme for integrating algal cultivation with HTL. Sunlight (118) and CO2 are absorbed by algae (116) cultures which may be in any suitable configuration, such as an open pond system, flat-panel photobioreactor (PBR) (112), an airlift PBR (106), a tubular PBR (108), a bubble column (110), or a raceway (114). In the present invention, the algae are preferably initially cultivated in an exogenous reactor, and then subsequently transferred to a new container such as an open pond system supplied with organic waste material and water. The water may preferably be wastewater from an aerobic digestion plant and / or food production. The cultivated algae are used as an input for HTL, where they are subjected to heat and pressure in a reactor (130) and converted to biocrude (122), CO2 (124), Biochar (126) and an Aqueous Phase (128). The Aqueous Phase and CO2 may optionally by recycled for use in the algal cultivation. The bio-crude is then further processed to provide biofuels (104) according to need. Fig. 2 shows a flow diagram describing integrated algal cultivation with HTL followed by upgrading to biofuels. Components such as water, nutrients and flue gas are used as input for algal growth. The algal biomass may then be concentrated / dewatered via suitable methods such as settling, dissolving, air floatation or centrifuging prior to HTL. In some embodiments, one or more of these concentration / dewatering methods may be performed on the biomass of the present invention, comprising algae and organic waste prior to HTL. HTL may then be performed on the biomass resulting in components including crude biooil, off gas and an aqueous phase. Further upgrading processes such as catalytic hydrotreating and product fractionation may then be performed to produce a refined biofuel such as gasoline, diesel and jet fuel. The processes may be integrated with a hydrogenation plant, such that H2 produced from the hydrogen plant is used in processes such as catalytic hydrogenation. Fig. 3 shows a schematic view of a process of algae culture scaling and processing to provide bulk dry microalgae biomass and / or sustainable aviation fuel. The process starts with water inlet, water pre-treatment, culture step (not included the scale up of the culture), downstream processing, and product packaging. In some embodiments of the processes of the present invention, the biomass may undergo an ultrafiltration step prior to hydrothermal liquefaction. In Fig. 3, the following labels are used: P: Pumps; F: Filters; T: Tanks; C: Centrifuge; UF: Ultrafiltration; FD: Freeze Dryer; HTL: Hydrothermal Liquefaction; SAF: Sustainable Aviation Fuel. Fig. 4 shows an example scale-up process for an algal culture. The master culture, is used to inoculate 250 ml flasks, which are then used to inoculate 1L flasks, followed by inoculation and scale up in 5L flasks, followed by 20L carboys. These steps may typically be performed in a temperature controlled, air conditioned environment. The 20L carboys are then used to inoculate 80L bags, followed by small raceways / reactors, followed by seeding raceways, which raceways / reactors may typically be kept in a polytunnel. The seeding raceways may then be used to provide the culture to inoculate the production raceways, or ponds, which are used for the final cultivation step before harvesting / HTL. The final production raceways or ponds may typically be located outdoors. Standard F / 2 commercial media may be used as the culture media. From 20L up, the water pre-treatment method are typically those uses in higher scale cultures (chlorination followed by neutralization). The abiotic parameters in the controlled temperate room (for the 250 ml flasks to 20L carboys) typically match the temperature in outdoor conditions. For instance the temperature may be in the range 19 - 21 °C, and the cultures may be aerated with filtered (0.2 pm) ambient air (0.039% CO2) at a rate of 0.6 L (v / v) using a 1 mm capillary glass tube inside the flasks / carboys to bubble the air-CO2 mixture inside the cultures. The suggested illumination may be provided using either LED or fluorescent lamps and an average irradiation of 150 pmol photons per m2 per second may be used. The photoperiod (light:dark cycle) used may be 18:6. As used herein, “means plus function” features may be expressed alternatively in terms of their corresponding structure. 5 It will be understood that the present invention is described herein purely by way of example, and modifications of detail can be made within the scope of the invention. All documents cited herein are incorporated by reference.

Claims

1. A process for production of crude bio-oil comprising the steps of:(a) providing organic waste material comprising digestate;(b) introducing algae to said organic waste material to form a culture;5 (c) cultivating the algae within said culture to obtain biomass comprisingalgae and organic waste material; and(d) performing hydrothermal liquefaction on at least a portion of the biomass to form crude bio-oil;wherein the algae comprises one or more selected from Scenedesmus obliquus, 10 Nannochloropsis oculata, Spirulina (Arthrospira platensis) and Monoraphidium minutum.

2. The process of claim 1, wherein the algal culture of step (c) further comprises wastewater from an anaerobic digestion plant or food waste sources.

3. The process of claim 1 or claim 2, wherein step (b) comprises adding a 15 first algal culture having an algal density of at least 0.5 Kg / m3, preferably at least1.0 Kg / m3, in terms of dry weight of algae to a mixture comprising the organic waste material.

4. The process of claim 3, wherein the first algal culture is added in an amount of 10% or more by volume compared to the total volume of the resultant 20 culture.

5. The process of claim 3, wherein the algae comprises a cyanobacterium such as Spirulina (Arthrospira platensis), and wherein the first algal culture is added in an amount of 40% or more, preferably 50% or more, by volume compared to the total volume of the resultant culture.26 06 256. The process of any preceding claim, further comprising the step of scaling up an algae culture prior to its introduction to the waste organic material in step (b).

7. The process according to claim 6, wherein the scale up comprises one or 5 more inoculation and growth steps.

8. The process of claim 6 or 7, wherein the scale-up steps are performed inside a building wherein the cultures are maintained within a predetermined temperature range and supplied with artificial light at a predetermined intensity.

9. The process of any preceding claim, wherein the culture step (c) is10 performed in one of more of a production raceway and / or an open pond system.

10. The process of any preceding claim, wherein a portion of the algalbiomass is harvested during step (c).

11. The process of claim 10, wherein the harvested algal biomass is dried to provide a bulk dry algal biomass.15 12. The process of claim 10 or 11, wherein one or more of the following isextracted from the harvested algal biomass: triacylglycerides (TAG), glyco-lipids, phospho-lipids, waxes, sterols, soluble proteins, insoluble proteins, monosaccharaides, oligosaccharides, starch, cellulose, chlorophyll, carotenoids, phycobilins, and co-3 fatty acids.20 13. The process of any preceding claim, which is performed as a batchprocess, a continuous process ora semi-continuous process.

14. The process of any preceding claim, wherein the aqueous phase obtainedfrom hydrothermal liquefaction in step (d) is reintroduced to the culture of step (c).

15. The process of any preceding claim, comprising the further step (e) of 25 processing the crude bio-oil to obtain at least one biofuel selected from naptha, kerosene and diesel.

16. The process of claim 16, wherein the processing step (e) comprises one of more one of the following processes: filtration, emulsification, transesterification, hydro cracking, catalytic cracking, zeolite cracking, catalytic hydrotreating and fractionation.5 17. The process of claim 15, wherein step (e) comprises catalytichydrotreating, preferably followed by fractionation.

18. The process of any one of claims 15 to 17, further comprising mixing the biofuel with one or more fossil fuel derived fuels to form a blended fuel.26 06 25

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