EP4649130A2

EP4649130A2 - Apparatus and process for preparing feedstock

Info

Publication number: EP4649130A2
Application number: EP24710154.6A
Authority: EP
Inventors: Michael Howard PLATT; Wade Hastings MCROBERTS
Original assignee: Alps Ecoscience Uk Ltd
Current assignee: Alps Ecoscience Uk Ltd
Priority date: 2023-01-12
Filing date: 2024-01-11
Publication date: 2025-11-19
Also published as: GB202300485D0; WO2024150008A3; WO2024150008A2; GB2626312A

Abstract

A system for processing a feedstock comprising solids laden liquid, at least a portion of said solids being cellulosic material, the system comprising a stream of said feedstock (201), a cavitation apparatus (222) for processing the feedstock (201) by subjecting the feedstock to cavitation thereby reducing the size of at least a portion of said solids wherein an additive (200) is added to said stream of feedstock prior to being processed by the cavitation apparatus (222) to produce a stream of enhanced feedstock (205).

Description

APPARATUS AND PROCESS FOR PREPARING FEEDSTOCK BACKGROUND The present invention relates to an apparatus and process for preparing feedstock, particularly but not exclusively for onward processing by anaerobic digester. Processing waste products has become very important in view of environmental issues. It is now generally accepted that processing organic waste to produce biogas can be beneficial to society and have minimal impact on the environment. Waste products containing organic material may be left in slurry pits to break down slowly over time, typically more than six months, until the waste product turns into a product which can be used as liquid and solid fertilizers. These liquid and solid fertilizers are spread over crop fields in order to increase crop yields. However, the slurry pits often leak, leading to nitrate and nitrite run- off, which can contaminate local waterways. Furthermore, the process of breaking down the waste product produces various gases, such as carbon dioxide and methane, which are well known greenhouse gases, which simply rise into the atmosphere. It is well known that there are improvements which can be made to reduce the direct emission of these greenhouse gases, as well as speeding up the process of making fertilizers using Anaerobic Digesters (ADs). In its simplest form, an AD is a slurry pit with a lid and a pipe leading from the lid for conveying produced gases from the breakdown of the waste product. The waste product may be stirred in the AD and heat may be added to speed up the process. Biological additives may also be added to speed up the process. The produced gases are generally useful and are known as biogas. Biogas can be used to heat homes and used in electric power generation, as an alternative to natural gas. Most AD plants in the UK are fed with high energy crops and are located on farms. These high energy crops, such as maize and rye may be specifically grown for use in AD plants. High energy crops are fed as semi-solids into large AD tanks where they are digested for 30 to 60 days releasing available biogas, which is typically made up of 55% concentration of methane and 45% concentration of carbon dioxide. Other AD plants are fed with animal waste such as cattle dung and urine. Other AD plants are fed with a combination of high energy crops or waste organic material from crops. Other AD plants are fed with food waste collected via domestic recycling or commercial waste from restaurants and supermarkets. The municipal water treatment industry uses ADs to treat biosolids from sewage, releasing biogas to help offset the energy requirements from processing the sewage. OFMSW (Organic Fraction of Municipal Solid Waste) is organic material washed from processing black bin bag waste. Typically, the bin bag waste is washed, with the organic fraction rising a top of the water and floated off through a separate channel. In all cases, unreacted solids remain undigested and these tend to be fibrous with high lignocellulosic structures such as paper fibre, straw, plant stems and wood. The unreacted solid and liquid from AD is known as digestate. The digestate from known AD systems contains untapped biogas potential due to the structures essentially containing glucose and being difficult to breakdown in an industrial process, making the glucose hard to access. In all AD processes, digestate is produced which comprises a solid fibrous element and liquid. Digestates are applied to farmland as soil improvers and natural fertilisers. The exception is OFMSW, the digestate from which is not used as soil improvers and natural fertilisers and generally goes to landfill. The inventors have observed that more biogas can be extracted from cellulosic material which normally remains undigested in the AD process. A more complete breakdown would yield more useable biogas and less digestate. Furthermore, the inventors have observed that the normal 60-day cycle period it takes for feedstock to be processed through an AD can potentially be reduced. The inventors have also observed that there are potential improvements to be made to biogas production, quality and yield and potential for hydrogen production and reduced carbon dioxide emissions using dark fermentation. The inventors have also observed that it would be beneficial for digestate from OFMSW, to be processed to produce a digestate which could be used as soil improvers and natural fertilisers. SUMMARY AND STATEMENTS OF INVENTION In accordance with the present invention, there is provided a system for processing a feedstock comprising solids laden liquid, at least a portion of said solids being cellulosic material, the system comprising a stream of said feedstock, a cavitation apparatus for processing the feedstock by subjecting the feedstock to cavitation thereby reducing the size of at least a portion of said solids characterised in that an additive is added to said stream of feedstock prior to being processed by the cavitation apparatus to produce a stream of enhanced feedstock. The inventors have found that adding the additive to the stream of feedstock, which may be dosed by injection into a flowline through which the stream flows. The flowline may be a rigid pipe, flexible pipe, hose, open pipe or trough or other stream conveying means immediately before the micronisation stage may substantially improve the pretreatment of a feed stock before being further processed in an AD process and/or a dark fermentation process. The micronisation stage comprises a cavitation apparatus and may also comprise a maceration apparatus and may further comprise a progressive cavity pump for conveying macerated enhanced feedstock between the macerator and the cavitation apparatus. Optionally, the additive comprises a surfactant. Optionally, the additive comprises a bio-organic catalyst. Optionally, the additive comprises a protein-based surfactant synergist. Optionally, the additive comprises more than one surfactant. Optionally, one or more of the surfactants is an anionic surfactant. Optionally, the additive comprises a surfactant composition comprising a protein component having a concentration sufficient to substantially increase the surface activity of the one or more surfactants relative to the surface activity of the one or more surfactants in the absence of the protein component. Optionally, the anionic surfactant is selected from the group comprising: fatty acid alkylolamide sulfosuccinate, sodium lauryl sulphate, sodium lauryl ether sulphate, and alkyl benzene sulfonate. Optionally, the protein component is a mixture of multiple intracellular proteins, at least a portion of the mixture may include yeast polypeptides, which may be obtained from a yeast fermentation process and yeast heat shock proteins resulting from subjecting a mixture obtained from the yeast fermentation process to heat stress. Optionally, the size of solids is reduced to small particles by the cavitation apparatus, optionally so that at least 50% of the solids in the feedstock are reduced to below 100 microns. Optionally, the cavitation apparatus comprises a hydrodynamic cavitator. Optionally, the stream of feedstock flows through a feed pipe comprising a three-way valve, the additive added to the stream of feedstock through the three-way valve. Optionally, the stream of feedstock flows through a feed pipe comprising a mixing valve, the additive added to the stream of feedstock through the mixing valve. Optionally, the additive is pumped into the feed pipe. Optionally, a store of additive is held at a height to give sufficient head to the additive to flow into the feed pipe uniformly. Optionally, the stream of feedstock flows through a pipe, the additive injected into the pipe. Optionally, the system further comprises an inflow COD sensor for sensing the COD (Chemical Oxygen Demand) level in the feedstock and an outflow COD sensor for sensing the COD level in the enhanced feedstock. Optionally, the system further comprises a controller for receiving an inflow COD reading from the inflow COD sensor and receiving an outflow COD reading from the outflow COD sensor, the controller calculating a difference between the outflow COD reading and the inflow COD reading to obtain a COD difference reading. Optionally, the inflow COD sensor is arranged in a flowline in said stream of said feedstock. Optionally, the outflow COD sensor is arranged in a flowline conveying enhanced feedstock from said cavitation apparatus. Optionally, the system further comprises an additive dosing apparatus, the controller activating the dosing apparatus in response to the COD difference reading. Optionally, the cavitation apparatus rotates at a range of speed, wherein the controller adjusts the speed of rotation of the cavitation in response to the COD difference reading. Optionally, the system further comprises a macerator for macerating the solids in the stream of feedstock to produce a stream of macerated feedstock and feeding the macerated feedstock into the cavitation apparatus, the macerator apparatus having an inlet and an outlet and optionally, the additive is added to the stream of feedstock at the inlet of said macerator or optionally to the stream of macerated feedstock at the outlet of said macerator. Optionally, the system further comprises a pump for pumping the stream of feedstock into the cavitation apparatus, the pump having an inlet and an outlet and optionally, the additive is added to the stream of feedstock at the inlet of said pump or optionally at the outlet of said pump. Optionally, the cavitation apparatus comprises a cavitator unit, a motor and a control apparatus. Optionally, the cavitator unit comprises a shaft rotated by the motor, a housing defining a chamber, a fluid inlet conduit and a fluid outlet conduit in the housing and a rotor on the shaft and rotatably arranged within the chamber, optionally a cavitation zone optionally between distal ends of the rotor and an inner surface or recess of the housing. Optionally, the rotor may be shaped as a conical frustum and a peripheral surface shaped as a conical surface which extends in a tapered manner between said first and second side surfaces. Optionally, at least two arrays of bores or recesses may be formed in the peripheral surface, optionally the bores of each array of bores being arranged in a row extending around said peripheral surface, each bore extending radially into said rotor from said peripheral surface and may have a cavitation zone defined inside the bores. Optionally, the system further comprises an anaerobic digester, the stream of enhanced feedstock feeding the anaerobic digester. Optionally, the anaerobic digester comprises an inlet pipe for the stream of enhanced feedstock, an outlet pipe for facilitating removal of digestate and a gas outlet pipe for facilitating removal of biogas. The system may reduce tonnage of solid digestate produced by the anaerobic digester. Furthermore, viscosity of the feedstock in the digester may be reduced. The amount of carbon dioxide that is released in the process of the invention is negligible, the carbon being sequestered in the captured biomethane. Optionally, the anaerobic digester comprises a stirrer or gas agitator. As the viscosity of the feedstock in the anaerobic digester tank is lowered, less energy is required to stir or agitate the feedstock and less wear and tear on plant rotating machinery, such as the stirrer. Optionally, the system further comprises a dark fermentation apparatus, the stream of enhanced feedstock feeding the dark fermentation apparatus to produce a stream of fermented feedstock. Optionally, the stream of enhanced feedstock about to enter the dark fermentation tank and/or enhanced feedstock residing in the dark fermentation apparatus is inoculated. Optionally, the inoculation comprises at least one isolated bacteria culture. Optionally, the inoculation includes or comprises at least one of: Enterobacteriaceae; and Clostridium. Optionally, the Enterobacteriaceae comprises at least one of: Citrobacter freundii, Citrobacter freundii (KPC positive); Klebsiella oxytoca; and Morganella morganii. Optionally, the Clostridium comprises at least one of: Clostridium perfringens; and Paraclostridium bifermentans. Optionally, the inoculation comprises at least one of: Enterococcus durans; and Enterococcus faecium. Optionally, the fermented feedstock is feed to an anaerobic digester. Optionally, the dark fermentation apparatus comprises an enclosed tank, an inlet pipe for the stream of enhanced feedstock, an outlet pipe for facilitating removal of fermented feedstock and a gas outlet pipe for facilitating removal of fermentation gas. Optionally, at least a portion of the fermentation gas is fed into the anaerobic digester, optionally, through perforation, optionally fed into a bottom part of the anaerobic digester. Optionally, the fermentation tank comprises a heater and optionally, a stirrer. Optionally, hydrogen is removed from the fermentation gas and used in the hydrogen economy. Optionally, the dark fermentation apparatus further comprises a pH balancing system. Optionally, the dark fermentation apparatus further comprises a defoamer control system. Optionally, the dark fermentation apparatus further comprises a hydrogen sulphide control system. Optionally, the dark fermentation apparatus further comprises an Oxidation-Reduction Potential sensor and optionally an Electrical Conductivity sensor. Optionally, the system further comprises an ammonia stripper wherein the digestate flows through the ammonia stripper, optionally, the digestate comprises a liquid phase stream which flows through the ammonia stripper. Using a system of the present invention may obtain an excellent yield of biogas, with a 10-30% increase in biomethane production, a feedstock reduction of 10% and a liquid digestate reduction 10%. This may leave a digestate high in nitrogen. However, this nitrogen tends to be held as ammonia. The inventor proposes an ammonia stripper may be desired to produce a high quality ammonia sulphate for use as a fertilizer or the like. Optionally, the system further comprises a heat exchanger for raising the temperature of the digestate. Optionally, the system further comprises an ammonia scrubber for yielding ammonia sulphate. Optionally, the system of the invention is containerised: one container for the micronisation apparatus; and one for an additive dosing apparatus, which may comprise an additive storing container and apparatus of use in injecting the additive into the stream of feedstock. Optionally, the additive is added to the stream of feedstock using an additive dosing apparatus which may comprise at least two containers which may be bunded. Each container may comprise an isolation valve for allowing or disallowing flow of additive from each container into a flow line leading to a pump and/or a pressure sustaining valve. In use, at least one of the isolation valves is opened and the other may be closed. Pressure in the additive in the flowline may be dictated by the head of additive in the container, with a pump to optionally increase the pressure and a pressure sustaining non-return valve to ensure the pressure in the additive to be dosed into the stream of feed stock is at or above the pressure in the stream of feedstock at the point of dosing. The system may further comprise a pretreatment apparatus for pre-treating dry feedstocks, the system further comprising a dry feed hopper, a blending tank and a flowline for flowing residual digestate from the anaerobic digester to the blending tank, the blending tank optionally comprising a stirrer or agitator for blending a dry solids feed with the residual digestate to produce said feedstock and flowing through a flowline in said stream of said feedstock for onward processing by the micronisation apparatus. Optionally, the resultant feedstock comprises between 10% and 20% solids by weight and optionally 15% solids by weight, the residual being liquid phase. Optionally, the system further comprises a controller for receiving an inflow COD reading from the inflow COD sensor and receiving an outflow COD reading from the outflow COD sensor, the controller calculating a difference between the outflow COD reading and the inflow COD reading to obtain a COD difference reading. Optionally, the inflow COD sensor is arranged in a flowline in said stream of said feedstock. Optionally, the outflow COD sensor is arranged in a flowline conveying enhanced feedstock from said cavitation apparatus. Optionally, the system further comprises an additive dosing apparatus, the controller activating the dosing apparatus in response to the COD difference reading. Optionally, the cavitation apparatus rotates at a range of speed, wherein the controller adjusts the speed of rotation of the cavitation in response to the COD difference reading. The present invention also provides a system for processing a feedstock comprising solids laden liquid, at least a portion of said solids being cellulosic material, the system comprising a stream of said feedstock, a macerator apparatus for processing the feedstock by subjecting the feedstock to maceration thereby reducing the size of at least a portion of said solids characterised in that an additive is added to said stream of feedstock prior to being processed by the maceration apparatus to produce a stream of enhanced feedstock. The present invention also provides a system for processing a feedstock comprising solids laden liquid, at least a portion of said solids being cellulosic material, the system comprising a cavitation apparatus for processing the feedstock by subjecting the feedstock to cavitation thereby reducing the size of at least a portion of said solids characterised in that an additive is added to said feedstock prior to being processed by the cavitation apparatus to produce a stream of enhanced feedstock. The present invention also provides a system for processing a feedstock comprising solids laden liquid, at least a portion of said solids being cellulosic material, the system comprising a cavitation apparatus for processing the feedstock by subjecting the feedstock to cavitation thereby reducing the size of at least a portion of said solids characterised in that an additive is added to said feedstock immediately after being processed by the cavitation apparatus to produce a stream of enhanced feedstock. The enhanced feedstock may flow directly into an AD tank or into a dark fermentation tank. The present invention also provides a dark fermentation apparatus comprising a dark fermentation tank for containing an enhanced feedstock, the dark fermentation tank comprising a top enclosed portion to collect fermentation gas and a fermentation gas flowline leading from the top enclosed portion and a pressure regulating valve for selectively allowing fermentation gas to flow from the top enclosed portion through the fermentation gas flowline. Optionally, the pressure regulating valve comprises a motorised valve, a controller and a pressure sensor, the pressure sensor optionally arranged to measure the pressure of the gas held within the top enclosed portion of the dark fermentation tank. Optionally, the controller is set or programmed to activate the motorised valve to maintain the pressure of the fermentation gas held in the top enclosed portion of the dark fermentation tank at between 0.5 and 10 millibars and optionally between 1 and 5 millibars and optionally between 2 and 3 millibars above ambient atmospheric pressure. Optionally, the dark fermentation tank further comprises a feed pipe for flowing enhanced feedstock into the dark fermentation tank. The present invention also provides a control system for controlling and processing a feedstock comprising solids laden liquid, at least a portion of said solids being cellulosic material, the system comprising a stream of said feedstock, a cavitation apparatus for processing the feedstock by subjecting the feedstock to cavitation thereby reducing the size of at least a portion of said solids characterised in that an additive is added to said feedstock to produce an additive enriched feedstock prior to being processed by the cavitation apparatus, the output from the cavitation apparatus to produce a stream of enhanced feedstock, the system further comprising an inflow COD sensor for sensing the COD level in the feedstock and an outflow COD sensor for sensing the COD level in the enhanced feedstock. Optionally, the system further comprises a controller for receiving an inflow COD reading from the inflow COD sensor and receiving an outflow COD reading from the outflow COD sensor, the controller calculating a difference between the outflow COD reading and the inflow COD reading to obtain a COD difference reading. Optionally, the outflow COD sensor is arranged in a flowline conveying enhanced feedstock from said cavitation apparatus. Optionally, the system further comprises an additive dosing apparatus, the controller activating the dosing apparatus in response to the COD difference reading. Optionally, the cavitation apparatus rotates at a range of speed, wherein the controller adjusts the speed of rotation of the cavitation in response to the COD difference reading. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a schematic diagram of a known anaerobic digester; Figure 2 is a schematic diagram of a known anaerobic digester; Figure 3 is a flow diagram showing steps in a process in accordance with the present invention; Figure 4 is a schematic diagram showing a system following the process shown in Figure 3; Figure 5 is a schematic top view of a micronisation apparatus used in the system shown in Figure 4; Figure 6 is a side schematic view of the micronisation apparatus shown in Figure 5; Figure 6A is a top view of a cavitation apparatus of the micronisation apparatus shown in Figure 5; Figure 6B is a sectional view of a cavitator unit of the cavitation apparatus shown in Figure 6A; Figure 7 is a side view of the micronisation apparatus shown in Figure 5 connected to an anaerobic digester tank; Figure 8 is a flow diagram showing steps in an alternative process in accordance with the present invention; Figure 9 is a schematic side view of a micronisation apparatus suitable for use in the process of Figure 8, the micronisation apparatus being feed by feedstock from an anaerobic digester to be returned thereto; Figure 10 is a flow diagram showing steps in an enhanced process in accordance with the present invention, the enhancement comprising a dark fermentation step; Figure 11 is a schematic view of a dark fermentation apparatus used in the process shown in Figure 10; Figure 11A is an anaerobic digester for use in the enhanced process shown in Figure 10; Figure 12 is a flow diagram of a further enhanced process in accordance with the present invention the further enhancement comprising an ammonia stripping step; Figure 13 is a schematic view of an ammonia stripping apparatus suitable for use in the process of Figure 12; Figure 14 shows an example of a feedstock; Figure 14A shows an example of an enhanced feedstock; and Figure 14B shows an example of a solids digestate; Figure 15 shows an additive dosing apparatus for use in dosing an additive to a stream of feedstock flowing through a feed pipe, the additive dosng apparatus in accordance with the present invention; Figure 16 shows an apparatus for preparing a dry-feed stock for use in an anaerobic digester as shown in any embodiment disclosed herein, the apparatus in accordance with a further aspect of the invention; Figure 17 shows an apparatus for preparing a feed stock for use in an anaerobic digester as shown in any embodiment disclosed herein, the apparatus configured for dark fermentation re-circulation, the apparatus in accordance with a further aspect of the invention; and Figure 18 shows the apparatus of Figure 17 together with a control and monitoring system in accordance with a further aspect of the invention. DETAILED DESCRIPTION Referring to Figure 1 there is shown an anaerobic digester (AD) generally identified by reference numeral 1. The AD 1 comprises a tank 2 having a cylindrical wall 3 with a planar circular base 4, but may be of any suitable shape such as square or oblong for containing a feedstock 5. A lid 6 encloses the tank 2, which may be a separate part or integrated with the cylindrical wall 3. The lid 6 may be domed (as shown) or planar or any suitable shape for collecting biogas 7 produced from breakdown of the feedstock 5. An inlet pipe 8 is provided towards a top of the cylindrical wall 3 for introducing feedstock 5 into the tank 2. The feedstock 5 may be any feedstock discussed herein, such as OFMSW (Organic Fraction of Municipal Solid Waste) washed from processing black bin bag waste. The organic fraction rises a top of the water and floated off through a separate channel. The organic fraction comprises cellulosic material. The result is a solids and liquid feedstock suitable for flowing through the inlet pipe 8. The inlet pipe 8 may be solid walled pipe or a flexible hose. An outlet pipe 9 is provided at a bottom of the cylindrical wall 3 to drain off digestate 15, which is generally a solids laden slurry which settles at the bottom of the tank 2. The outlet pipe 9 may be a solid walled pipe or a flexible hose, or indeed simply an outlet selectively opening allowing solids laden slurry to flow into a skip, hopper or the like (not shown). A valve 11 is provided to selectively open, close and vary flow through the outlet pipe 9, thus controlling the rate at which the settled solids are drained off through the outlet 9. The greater the flow rate through the outlet pipe 9, the shorter the residency time of the feedstock 5 in the tank 2; the lower the flow rate through the outlet pipe 9, the longer the residency time of the feedstock 5 in the tank 2. The valve 11 may thus control the residency time of the feedstock 5 in the tank 2. Typically, the tank 2 is sized to contain 200 cubic metres of feedstock 5, which is suitable for use on large farms and in waste processing plants. Although the tank 2 may be of any suitable size, such as to contain 50 cubic metres of feedstock 5 for small farms to 10,000 cubic metres for large farms and large waste processing plants. The tank 2 may be smaller for use in small communal village waste processing. A gas outlet pipe 12 is provided above the level of the feedstock contained in the tank 2, thus may be located in the lid 6 for facilitating collection and transportation of the biogas 7. The tank 2 does not need to be pressure rated. Any biogas 7 produced by breakdown of the feedstock 5 is only at a low pressure sufficient to induce a flow of biogas through the gas outlet pipe 12. The pressure of the biogas in the top of the tank 2 may be slightly above ambient atmospheric pressure. In use, the feedstock 5, which may be of any type disclosed in the introduction, and generally simply comprises water or urine and solid organic material, may simply be left to naturally break down in the tank 2. However, the residency time for the feedstock 5 to break down is high, typically greater than 60 days. Furthermore, the feedstock 5 may not sufficiently break down before being drained off. Furthermore, parts of the feedstock 5 may break down at a greater rate than others, such breakdown may occur faster at the top of the tank 2 than the bottom or in warmer parts of the tank 2. In order to speed up the process and induce a more uniform breakdown of the feedstock 5, a stirrer 13 may be used. The stirrer 13 generally comprises a motor (not shown) rotating a drive shaft provided with an impeller 14 arranged in the feedstock 5 to agitate and induce movement in the feedstock 5. A heater 15 may also be provided to heat the feedstock 5 to induce a faster breakdown of the feedstock 5 and thus reduce the residency time needed. Even with these additional features, the residency time will be in the region of 30-60 days. Additives may be added directly into the tank 2 to speed up and aid complete breakdown of organic material held within the feedstock 5. Such additives may be inorganic and/or biological. Figure 2 shows an anaerobic digester AD, generally identified by reference numeral 101. The AD 101 is generally similar to the AD shown in Figure 1, with like reference numerals referencing like parts in the one hundred series. The AD 101 comprises a tank 102 having a cylindrical wall 103 with a planar circular base 104, but may be of any suitable shape such as square or oblong for containing a feedstock 105. A lid 106 encloses the tank 102, which may be a separate part or integrated with the cylindrical wall 103. The lid 106 may be domed (as shown) or planar or any suitable shape for collecting biogas 107 produced from the breakdown of the feedstock 105. An inlet pipe 108 is provided towards a top of the cylindrical wall 103 for introducing feedstock 105 into the tank 102. A feedstock such as solid organic matter, such an energy crop and crop residues are premixed with a liquid, such as water or urine in a pre-mixing pit 108’ to form a slurry 105 comprising a solids laden liquid. The slurry 105 is then pumped through inlet pipe 108 into the tank 102. The inlet pipe 108 may be solid walled pipe or a flexible hose. An outlet pipe 109 is provided at a bottom of the cylindrical wall to drain off digestate 115, which may comprise solids which settles at the bottom of the tank 2 and a liquid in the form of a thick slurry. The outlet pipe 109 may be solid walled pipe or a flexible hose, or indeed simply an outlet opening selectively allowing the digestate 115 to flow into a skip, hopper or the like (not shown). A valve (not shown) is provided to selectively open, close and vary the rate at which the digestate 115 is drained off through the outlet 109. The greater the flow rate through the outlet pipe 109, the shorter the residency time of the slurry 105 in the tank 102; the lesser the flow rate through the outlet pipe 109, the longer the residency time of the slurry 105 in the tank 102. The valve thus controls the residency time of the slurry in the tank 102. The solids laden settled slurry which is drained off may be separated in a further apparatus and used as or used in commercial production of a liquid fertiliser and a solid fertiliser. Typically, the tank 102 is sized to contain 200 cubic metres of slurry 105, which is suitable for use on large farms and in waste processing plants. Although the tank 102 may be of any suitable size, such as to contain 50 cubic metres of slurry 105 for small farms to 10,000 cubic metres for large farms and large waste processing plants. The tank 102 may be smaller for use in small communal village waste processing. A gas outlet pipe (not shown) is provided above the level of the slurry contained in the tank 102 for facilitating collection and transportation of the biogas 7. In order to speed up the process and induce a more uniform breakdown of the slurry 105, the slurry 105 is agitated by pressurised biogas 107. A return pipe 113 taps off biogas 107 from the top of the tank 102. The biogas in return pipe 113 passes through a pump 114 which pressurises the biogas. The biogas under high pressure passes out into the slurry 105 through perforations in a perforated tube 116, agitating the slurry 105. This reduces the residency time needed. Even with these additional features, the residency time will be in the region of 30-60 days. The lid 106 may have a hatch (not shown) for allowing solid organic matter to be added to the slurry 105 in the tank 102. Referring to Figure 3, there is shown a flow diagram showing steps in a process in accordance with the present invention. Feedstock 201 may be in the form of a slurry comprising solid organic waste and a liquid. The feedstock 201 may be predominantly solids containing sufficient moisture to form a slurry when processed using the following method. Alternatively or additionally, the feedstock 201 may have already been pre-treated to be a mixture of solids and liquid. A stream of feedstock 201 flows through a feed pipe.The solids in the feedstock 201 may be of a random particle size and may include a large portion of solids in the range of 1mm to 20mm and may be in the range 5mm to 10mm. A typical feedstock 201 is shown in Figure 14. An additive 200 is added to the stream of feedstock 201 to produce an additive rich feedstock 203. The additive 200 may added by dosing the stream of feedstock 201 whilst the stream of feedstock flows through a feed pipe, such as a solid walled pipe or a flexible hose or in a mixing apparatus or mixing tank immediately prior to the micronisation step. The additive-enriched feedstock 203 is subjected to a micronisation step 204 to produce an enhanced feed stock 205. The enhanced feedstock 205 typically takes the form of a slurry with a high proportion of small solids content with very few large solids. The enhanced feedstock 205 flows through an inlet pipe, such as inlet pipes 8, 108 of an AD, such as AD 1, 101, which produces a biogas stream 207, and a digest stream comprising liquid and solids which is separated into a liquid digestate stream 208 and a solids digestate stream 209. The liquid digestate stream 208 may be further processed or packaged for use as a liquid fertiliser. The solids digestate stream 209 may be further processed or packaged for use as a solid or granular soil improver. The additive 200 may be or may comprise a bio-organic catalyst (BOC) which may increase the solubility and bio availability of organic material and may also enhance the enzymatic breakdown of cellulose and hemicellulose. The BOC may protect the natural enzymes from being absorbed onto the substrate and being rendered inactive. This allows access to hereto unreactive substrate, the substrate optionally being cellulosic material. The additive 200 may be a surfactant composition to reduce surface tension, interfacial tension, and critical micelle concentration. Surfactants may be regarded as compounds composed of both hydrophilic and hydrophobic or lipophilic groups. The surfactant composition may be a protein-based surfactant synergist. The surfactant may be of the type disclosed in US8735338. The surfactant composition may comprise a protein component that has the effect of improving the surface-active properties of the surfactants contained in the compositions. The surfactant composition having the protein component demonstrate significantly lower critical micelle concentrations (CMC), reduced surface tensions, and reduced interfacial tensions than do comparable compositions having no protein component. In addition, the surfactant-containing compositions having the protein component has the effect of converting greasy waste contaminants to surface active materials. The surfactant composition may comprise one or more surfactants. One of the surfactants may be an anionic surfactant, and the surfactant composition comprising a protein component having a concentration sufficient to substantially increase the surface activity of the one or more surfactants relative to the surface activity of the one or more surfactants in the absence of the protein component. The anionic surfactant may be selected from fatty acid alkylolamide sulfosuccinate, sodium lauryl sulfate, sodium lauryl ether sulfate, and alkyl benzene sulfonate. The protein component may be a mixture of multiple intracellular proteins, at least a portion of the mixture may include yeast polypeptides, which may be obtained from a yeast fermentation process and yeast heat shock proteins resulting from subjecting a mixture obtained from the yeast fermentation process to heat stress. The additive 200 is added to the stream of feedstock 201 at a dose rate of optionally 1.5 litre/tonne of volatile solids, but may be in the range of 0.5 to 3 litres per tonne of volatile solids or any other suitable dose rate. The dose rate is approximately three times what would be expected if the additive was added directly into an AD tank 1, 101. The inventors noted that the micronisation step may split solids within the feedstock into a larger number of smaller particles, increasing overall surface area of the total number of smaller particles. The additive 200 may thus have more surface area with which to react with the solids to produce an enhanced feedstock 205. Referring to Figure 4, there is shown a schematic diagram of a system in accordance with the present invention, comprising a micronisation apparatus 300. The feedstock 201 flows through a large diameter feed pipe 203 from a feedstock source 210 through a mixing valve 211. The large diameter feed pipe 212 may have an internal diameter in the order of 50 to 200mm and optionally 90mm diameter. An additive 200 flows into the mixing valve 211, whereupon the additive is mixed with the feedstock 201 to produce a flow of additive rich feedstock 203 which flows through a large diameter feed pipe 212, through an optional isolating valve 213 into macerator 214. The mixing valve 211 may be located close to the macerator 214 and may be located within 10m of the macerator 214 and may be within 3m of the macerator 214 and may be within 1m of the macerator 214 and may be between 0.5m and 1m of the macerator 214. The macerator 214 comprises a set of blades or flails 215 which may be sharp or blunt, which pound and/or cut any large solids in the additive rich feedstock 203. The set of blades 215 are driven by a motor 216. The macerated additive rich feedstock 217 flows into a progressive cavity pump 218, such as a screw pump or moineau pump, which may comprise a conveying screw 219, which may be an Archimedes helical conveying screw driven by a motor 220. The macerated additive rich feedstock 217 is pushed through a feed pipe 221 into a cavitation apparatus 222. The progressive cavity pump 218 may be driven by an inverter (not shown). The progressive cavity pump 218 may be controlled by a PID controller connected to the motor 220, which may control the speed of rotation of the conveying screw 219 by altering alternating current electrical frequency. The PID controller (not shown) may obtain an input from a flow rate transducer 223 and base the frequency on such input value. The PID controller forms part of control apparatus 245. The cavitation apparatus 222 is generally a pump which uses cavitation and high energy microbubbles to explode the particles within the macerated additive rich feedstock 217 and break down the solids into smaller more reactive particles. The cavitation apparatus 222 may provide a controlled hydrodynamic cavitation. The cavitation apparatus 222 may be suitable for inducing cavitation in any biological fluid, manure, sewage, waste, mud or any other fluid which incorporates solid particles that may create friction. The cavitation apparatus 222 comprises a cavitator unit 224, a motor 225 and a cooling circuit 226, as shown in Figure 6A. The motor 225 may be driven by an inverter (not shown) and controlled by a PID controller, such as controller 903 (see Figure 18). The cavitator unit 224 may be of the type shown in Figure 6B and disclosed in EP 3,278,868. The cavitator unit 224 shown in Figure 6B comprises a shaft 230 rotated by the motor 225, a housing 231 defining a chamber 231’, a fluid inlet conduit 233 and a fluid outlet conduit 234 in the housing 231 and a rotor 232 rotationally fixed to the shaft 230 and rotatably arranged within the chamber 231’. The inlet direction (B- B) of the inlet axis (B) of the fluid inlet conduit 233 is perpendicular to the axial direction (X-X) of the rotor axis (X) of the shaft 230, the outlet direction (C-C) of the outlet axis (C) of the fluid outlet conduit 234 is perpendicular to the axial direction (X-X). The inlet and outlet ports 233’,234’ of the housing 231 are positioned at an axial position spaced apart from the rotor 232, which is shaped as a conical frustum. The rotor 232 may be shaped as a conical frustum and a peripheral surface 235 shaped as a conical surface which extends in a tapered manner between said first and second side surfaces 236, 237. At least two arrays of bores or recesses 237 may be formed in the peripheral surface 235, the bores 237 of each array of bores being arranged in a row extending around said peripheral surface 235, each bore 237 extending radially into said rotor 232 from said peripheral surface 235 and may have a cavitation zone 238 defined inside the bores 237. Referring to Figure 4, the cavitation unit 224 may be cooled with a coolingcircuit 226, which comprises coolant conveying tubes 227, accumulators 228 and a compressed air supply 229. The micronisation apparatus 300 suitable for a 10,000 cubic metre AD has a flow rate in the order of 6 to 24 cubic metres per hour, with a peak flow rate of 24 cubic metres per hour at an inlet pressure of 1.5 bar to 3 bar of feedstock 201 at the inlet of the macerator 214. The enhanced feedstock 205 comprises >50% at <100micron. The macerated additive enhanced feedstock 203 flows under pressure from the progressive cavity pump 218 through inlet conduit 233 into the chamber 231’ under pressure, and through a small annular gap between the rotating rotor 232 and the housing 231, where the macerated additive enhanced feedstock 203 is accelerated to a high velocity and vapour bubbles form within the macerated additive enhanced feedstock 203 at low-pressure regions, such as in bores 237. This action may improve dispersion of the additive within the macerated additive enhanced feedstock 203 and may speed up the action of the additive within the macerated additive enhanced feedstock 203. An enhanced feedstock 205 exits the chamber 231’ through outlet conduit 234 and into a small diameter pipe 240, through a pinch valve 241 and on to the inlet of an AD 242. The AD 242 may be any disclosed herein, such as AD 1 or AD 101. The small diameter pipe 240 may be in the order of 50mm, but may be of any suitable dimension for such as between 30mm and 100mm. The micronisation apparatus 300 for preparing the feedstock may be containerised, as shown in Figures 5 and 6. A container 350, which may be a standard size ISO container of 8’ by 8’6” by 20’, is used to contain all of the components making up the micronisation apparatus 300, such as the macerator 214, the progressive cavity pump 218, the cavitation apparatus 222, control apparatus 245, pinch valve 241, a power supply board 246 and pressurized air supply port board 247. Large diameter feed pipe 212 is provided with a connecting flange 248 for attachment to a large diameter pipe or hose leading from a source of feedstock and passes through a wall of the container connecting with the macerator 214. The mixing valve 211 is located in the large diameter feed pipe 212 immediately outside the container, although may be arranged within the container. The small diameter pipe 240 passes through the wall of the container 350 to a quarter turn ball valve 250 and an annular male thread 249 for attachment to a hose 251, as shown in Figure 7 or rigid pipe to lead to an inlet stub 252 in the AD 242. The enhanced feedstock 205 is under a significantly greater pressure in the hose 251 provided by the progressive feed pump 218 than the head of enhanced feedstock 205 in the AD, so the inlet stub 252 may be located in a lower or upper portion of the tank cylinder 253. The enhanced feedstock 205 is retained in the AD 242 until biogas 207 is released therefrom and extracted to a full amount and the digestate in a suitable form for a suitable purpose. It is believed that residency time in the AD can be reduced to twenty days by using the process of the invention. Referring to Figures 8 and 9, there is shown a schematic diagram of a variation on the process and system of the invention described above. Like numerals are used to refer to like parts. The AD 242 is essentially used as a buffer tank, as well as an anaerobic digester. The feedstock 201 is introduced directly into the AD 242 through an inlet 8 to be stored and to breakdown, whereupon the feedstock from the AD is tapped out of the AD 242 through an outlet 256 located towards the top of the AD 242, slightly below the surface 258 of the feedstock 201’. The feedstock 201’ flows through a through a large diameter feed pipe 257 to which additive 200 is added using mixing valve 211 to produce an additive rich feedstock 203, which is then introduced to the micronisation apparatus 300, as described above to produce a stream of enhanced feedstock, which is then returned to the AD 242 at inlet stub 252. The mixing valve 211 may be located at any point in, or at either end of the large diameter feed pipe 257. The mixing valve may be located within 10m, 3m or 1m of the macerator 214 of the micronisation apparatus 300 and may be located immediately outside or inside a container 350 containing the micronisation apparatus 300. The enhanced feedstock 205 is retained in the AD 242 until biogas 207 is released therefrom and extracted to a full amount and the digestate in a suitable form for a suitable purpose. Referring to Figures 10, 11 and 11A, there is shown a schematic diagram of an enhanced process and system of the invention described above with reference to Figures 4 to 7, although the enhancement may be used in the process and system shown in Figure 8 and 9. Feedstock 201 may be in the form of a slurry comprising solid organic waste and a liquid. The feedstock 201 may be predominantly solids containing sufficient moisture to form a slurry when processed using the following method. Alternatively or additionally, the feedstock 201 may have already been pre- treated to be a mixture of solids and liquid. Referring to Figure 10, an additive 200 is added to the feedstock 201 to produce an additive rich feedstock 203. The additive rich feedstock 203 is subjected to a micronisation step 204 to produce an enhanced feed stock 205. The enhanced feedstock 205 typically takes the form of a slurry with very few large solids which is further processed in a dark fermentation apparatus 400, Figure 11. The dark fermentation apparatus 400 comprises a dark fermentation tank 402 having a cylindrical wall 403 with a planar circular base 404, but may be of any suitable shape such as square or oblong for containing the enhanced feedstock 205. A lid 406 encloses the dark fermentation tank 402, which may be a separate part or integrated with the cylindrical wall 203. The lid 206 may be domed (as shown) or planar or any suitable shape for collecting fermentation gas 407 produced from fermentation of the enhanced feedstock 205. An inlet pipe 401 is provided towards a top of the cylindrical wall 403 for introducing the enhanced feedstock 205 into the dark fermentation tank 402. A hatch 405 is provided in the lid 406 through which fermentation additives 408 and/or pH balancing acids or alkali may be added to the enhanced feedstock 205 residing in the dark fermentation tank 402. A small diameter solid walled feed pipe or a flexible hose (not shown) may be connected to the inlet stub 401 to convey the enhanced feedstock 205 into the dark fermentation tank 402. An outlet pipe 410 is provided at a bottom of the cylindrical wall 403 to drain off fermented feedstock 411. The outlet pipe 410 may be solid walled pipe or a flexible hose with a valve 412 provided to selectively open, close and vary flow through the outlet pipe 410 and thus controls the rate at which the fermented feedstock 411 is drained off through the outlet 9. The greater the flow rate through the outlet pipe 411, the shorter the residency time of the fermented feedstock 411 in the tank 402; the lower the flow rate through the outlet pipe 410, the longer the residency time of the fermented feedstock 411 in the tank 402. The valve 412 thus controls the residency time of the fermented feedstock 411 in the tank 402. Typically, the tank 402 may be sized to contain 200 cubic metres of enhanced feedstock 205, which is suitable for use on large farms and in waste processing plants. Although the dark fermentation tank 402 may be of any suitable size, such as to contain 50 cubic metres to 500 cubic metres. A stirrer 414 comprising a motor (not shown) rotating a drive shaft provided with an impeller 415 arranged in the enhanced feedstock 205 is used to stir, agitate and induce movement in the feedstock 205. A heater 416 may also be provided to heat the enhanced feedstock 5 to enable thermal hydrolysis, inducing a dark fermentation of the feedstock 205. The heater 416 may comprise an electric heating element or coil or be a coil of pipe with hot fluid flowing therethrough and may be located within the dark fermentation tank 402. The enhanced feedstock 205 is feed through inlet stub 401 into the dark fermentation tank 402, whereupon the level of enhanced feedstock 205 in the tank 402 may be substantially maintained. The enhanced feedstock 205 is continuously stirred using stirrer 214 and heated by heater 416 to maintain a temperature of 55 Celsius and may be between 45 and 65 Celsius. The fermentation additive 408 may be added through hatch 405 to the enhanced feedstock 205. The fermentation additive may be an inoculation of bacteria and may comprise a glycerol. The inoculation may comprise specially isolated bacteria, allowing the bacteria to multiply and break down or ferment the feedstock. The isolated bacteria colonies may be at include or comprise one or more of the following bacteria: ENTEROBACTERIACEAE • Citrobacter freundii: Carrier induced granular particles comprising Enterobacter cloacae and Citrobacter freundii were used to generate H2 from sucrose in an anaerobic fluidized bed bioreactor. At a hydraulic retention time of 4.5 h, 95.8% of the sucrose was consumed and the rate of H2 production reached 180 mmol H2 l h–1. Biogas composition for H2 and CO2 was 42 and 55%, respectively. • Citrobacter freundii (KPC positive) • Klebsiella oxytoca: Compared with that of the wild strain, the ethanol concentration in DF broths of DeltaadhE HP1 decreased 69.4%, which resulted in a hydrogen yield in the PF stage and the total hydrogen yield over the two steps increased by 54.7% and 23.5%, respectively. • Morganella morganii (pathogen) CLOSTRIDIUM • Clostridium perfringens: https://www.sciencedirect.com/science/article/abs/pi i/S1389172317308654 • Paraclostridium bifermentans: https://www.sciencedirect.com/science/article/abs/pi i/S095965262032237X#:~:text=Paraclostridium%20contributed %20to%20the%20most%20efficient%20fermentative%20H,could%2 0be%20possibly%20used%20for%20H%202%20production. OTHER ORGANISMS • Enterococcus durans • Enterococcus faecium https://www.sciencedirect.com/science/article/abs/pii/S03 60319918337868 • Lactococcus lactis: Lactic acid production • Peptostreprococcus russelii • Bacillus coagulans (At 55°C): Lactic acid production Among all, Bacillus coagulans MO11 could produce hydrogen gas using molasses and ethanol refinery wastewater effectively (1.634 molH2/mol hexose) as detected by Drager tube, which was the maximum yield in this study. https://www.sciencedirect.com/science/article/abs/pii/S03 60319920325647 Isolated Colonies found in the dark fermentation tank 402 after the residing therein may be: ENTEROBACTERIACEAE • Proteus vulgaris • Proteus hauseri • Citrobacter ferundii: • Providencia rustigianii • Serratia marcescens CLOSTRIDIUM • Clostridium sporogenes: • Clostridium butyricum: i/S0360319908014444 The operational parameters for the dark fermentation step may be: pH 4.5 (%77 con. H2SO4) at 55 C, with a %10 mixed culture (%5 inoculated broth, %5 synthetic media without inoculation) The pH of the enhanced feedstock 205 is maintained acidic and may be maintained at pH 4 and may be between pH 5 and pH 3 by injecting an acid, such as sulphuric acid through injection point 417 in the inlet stub 401. The feedstock is acidified to facilitate acid hydrolysis promote the conditions necessary for the specific bacteria to survive. A gas outlet pipe 413 is provided in the lid 406 above the level of the enhanced feedstock 205 contained in the dark fermentation tank 402 for facilitating collection and transportation of the fermentation gas 407. The tank 402 does not need to be pressure rated. Any fermentation gas 407 produced by breakdown of the enhanced feedstock 205 is only at a low pressure sufficient to induce a flow of fermentation gas through the gas outlet pipe 413. The pressure of the fermentation gas 407 in the top of the tank 402 may be slightly above ambient atmospheric pressure. The enhanced feedstock 205 is generally held in the dark fermentation tank 402 for approximately 12 hours but may be between 12 to 24 hours, although this may be between 6 and 48 hours, depending on the originating type of feedstock 201. In the right conditions in the dark fermentation tank, hydrogen and carbon dioxide are formed. This can be extracted and separated and used as the individual gases or reinjected into the main AD to enhance the methane concentration in the biogas which can be up to 80% (normal AD concentration is 50-62%). The fermentation gas 407 may comprise hydrogen, methane and carbon dioxide. The fermentation gas 407 may comprise in the region of 40% hydrogen and 60% carbon dioxide with 1-2% methane. The dark fermented feedstock 411 flows from outlet pipe 410 into an inlet pipe, such as inlet pipes 408 of an AD 450 (Figure 12). The AD 450 is generally similar to the AD 101 described above. The AD 450 comprises a tank 452 having a cylindrical wall 453 with a planar circular base 454, but may be of any suitable shape such as square or oblong for containing the fermented feedstock 411. A lid 456 encloses the tank 452, which may be a separate part or integrated with the cylindrical wall 453. The lid 456 may be domed (as shown) or planar or any suitable shape for collecting biogas 207 produced from the breakdown of the fermented feedstock 411. An inlet pipe 458 is provided towards a top of the cylindrical wall 453 for introducing fermented feedstock 411 into the tank 402. An outlet pipe 459 is provided at a bottom of the cylindrical wall to drain off digestate 460. The size of the AD tank may be between 50 cubic metres and 12,000 cubic metres, but in this example 10,000 cubic metres is preferred. The dark fermented feedstock 411 is produced at a rate of 200 cubic metres per 12 to 24 hours, which may be sufficient to feed an AD tank 450 which can contain in the order of 10,000 cubic metres for a 20-day retention. A gas outlet pipe 461 is provided above the level of the fermented feedstock 411 contained in the tank 452 for facilitating collection and transportation of the biogas 207. The fermentation gas 407 may be injected into the fermented feedstock 411. The fermentation gas 407 passes though pipe 463 passes through a pump 464 which may raise the pressurise of the fermentation gas 407. The fermentation gas 407 passes out into the slurry 105 through perforations in a perforated tube 465, which may agitate the fermented feedstock 411. This potentially reduces the residency time and may improve yield from the feedstock. The digestate generally comprises a solids phase and a liquid phase, the solid phase may be suitable for use as a solid soil improver 209 and a liquid phase which is suitable for a nitrogen rich liquid fertilizer 208. The solids digestate 209 may be further processed or packaged for use as a solid or granular soil improver. The digestate may contain a very high nitrogen content. Furthermore, the digestate may contain a high percentage of ammonia. Referring to Figures 12 and 13, there is shown a schematic diagram of a further enhanced process and system of the invention. The system and process is identical to the system and process described above with reference to Figures 10 to 11A, save for the addition of an ammonia stripper 500, which strips ammonia from the liquid digestate stream 209. It should be noted that the further enhancement of an ammonia stripper 500 may be added to any of the processes and systems shown in any of the Figures. A higher yield of biogas stream 207 may be expected that following the previously described process. The inventor has noted that increasing the efficiency of an AD means that the formation of ammonia by-product is more likely. Ammonia becomes toxic to the process microbia at a certain level. The process of the invention removes digestate from the system and strips ammonia and reacts it with acids to form ammonium salts, usually sulphate and nitrate but can be ammonia hydroxide. This means that the digester is no longer inhibited and also the digestate can be recycled into the hydrolysis step to dilute solids loading with a free source of liquid and also reduce the amount of digestate that has to be spread to land thus reducing transport and disposal costs. The ammonia recovery also reduces fugitive ammonia emissions to atmosphere which are regulated by the Environment Agency. The system and process comprise all of the steps and apparatus shown in Figures 10 to 11A, with the addition of an ammonia stripping apparatus 500 shown in Figure 12 and 13 for stripping ammonia out of the liquid digestate stream 209. The stream of methane and carbon dioxide is then re- injected into the AD 450 with the fermentation gas 407. The liquid digestate 209 from AD 450 is likely to have a high ammonia content. The liquid digestate stream 209 is pumped with pump 502 through a tube-in-tube heat exchanger 503 to elevate the temperature of the liquid digestate stream 209 and into the top of a stripper unit 504, where air is blown through the liquid digestate stream 209 in counterflow mode. Ammonia is captured by the air. The air, partially saturated with water vapor and ammonia, is blown through a series of ammonia scrubbers 505, 506. There, the ammonia is removed from the air with sulphuric acid and water to form ammonium sulphate. A transparent liquid, pH neutral ammonium sulphate with 8% nitrogen and 40% dry matter is produced, suitable for use as a high-quality fertilizer. The clean moist air is fed back to the stripper. All columns operate at nearly the same temperature. In a wet environment the gaseous ammonia (NH3) is in equilibrium with ammonium (NH4+). At higher temperatures or higher pH-values the equilibrium shifts to ammonia that can be captured by the air. The pH of the stream of liquid digestate 209 may be raised with an alkaline agent before or after an optional CO2-stripping step. The treated stream of liquid digestate 209 leaves the ammonia stripper 504 with low ammonium values, but at almost the same temperature as the incoming fluid. If desired, this heat can be recovered by exchanging incoming and outgoing substrate streams to and from the ammonia stripper 504. The ammonia stripping apparatus 500 may also comprise an air supply 507 and a fan 508 for moving air to and from the ammonia stripper 504 and a compressed air supply 509 for supply compressed air to the ammonia strippers 504, 505 and the ammonia scrubber 506. An acid supply 510 and acid pump 511 may be provided for dosing acid for use in the ammonia scrubber 506 to yield ammonia sulphate. The system, apparatus and process of the invention may be a retrofitted pre-treatment stage to enhance biogas outputs feedstock inputs from Anaerobic Digesters (AD). Various alterations are envisaged to the above described systems, apparatus and processes. It is envisaged that the additive, such as BOC, is introduced into the feedstock 200 at any point before the cavitation apparatus 222, such as between the macerator 214 and the progressive cavity pump 218 or between the progressive cavity pump 218 and the cavitation apparatus 222. A simple sampling valve may be used in place of the mixing valve 211, and the additive 200 may be held at an equal or higher pressure than the pressure of the feedstock 201 at the point the additive 200 is added and/or mixed into the feedstock 201. It is envisaged that at least part of the fermentation gas 407 comprising mainly hydrogen and carbon dioxide stream is split into a hydrogen stream and a carbon dioxide, the hydrogen stream bottled and sold on for use in the hydrogen economy. Figure 14 shows an example of a suitable feedstock 201. Figure 14A shows an example of a suitable enhanced feedstock 205. Figure 14B shows an example of a solids digestate 209. Figure 15 shows an additive dosing apparatus generally identified by reference numeral 600 for use in dosing an additive 200 to a stream of feedstock 201 flowing through a feed pipe 212 to produce an additive rich feedstock 203 to feed micronisation apparatus 300. The additive dosing apparatus 600 comprises two containers 601 and 602. Each container 601 and 602 may be 1 cubic metre opaque or transparent plastic Intermediate Bulk Containers (IBC) for containing the additive 200 and accessing the level of additive contained therein by manual sight and/or using a level sensor (not shown) optionally with a low level alarm. The containers 601 and 602 may be bunded to inhibit possible escape of the additive 200 to the environment. An isolation valve 603, 604 is located at the foot of each container 601, 602 for allowing or disallowing flow of additive from each container into flow line 605 and 606 respectively. The flow lines 605, 606 are typically 15mm diameter and at a distal end provided with half inch BSP threaded end fittings for providing a means for attachment to the isolation valves 603, 604 respectively. At a proximal end, the flowlines 605,606 are connected to a manifold, T or Y-fitting 607 leading into a common flow line 608, allowing flow of additive to a dosing pump 609, such as a diaphragm pump to increase pressure in the flow of additive through flowline 610 to a spring-loaded pressure sustaining non-return valve 611. An isolation valve 612 is provided to selectively isolate the additive in the flow line 610 from the large diameter feed pipe 212. An injection quill 613 leads from the isolation valve 612 into the feed pipe 212. In use, at least one of the isolation valves 603, 604 is opened and the other may be closed. Pressure in the additive in the flowline 608 is dictated by the head of additive in the container 601, 602 with the open isolation valve 603,604. In order to increase pressure in the additive in flowline 610, a diaphragm pump 609 is used. The spring-loaded pressure sustaining non-return valve 611 ensures the pressure in the additive to be dosed into the feed pipe 212 is at or above the pressure of the feedstock 201 therein. Preferably, 5 millibars above the pressure of the feedstock 201 in the feed pipe 201 at the point at which the additive is added through the injection quill 613. The additive enriched feed stock 203 then enters the micronisation apparatus 300, which is located within optionally less than 10m and optionally less than 5m and optionally between 0.5 and 1m of the point of injection of the additive into the feed pipe 212. When the supply of additive 200 is nearing depletion in the container 601, 692 with the open valve, the container is removed and a fresh container is added. Alternatively or additionally, the container 601, 602 may be refilled through a lid 614, 615 at the top of the container 601, 602. Figure 16 shows an apparatus for preparing a dry-feed stock for use in an anaerobic digester AD, the apparatus generally identified by reference numeral 700. Reference to like parts used in previous embodiments in the 200 series are referred to in this embodiment in the 700 series. An example of a dry feedstock 701 comprises 35% and 40% solids and the residual made up of liquid. The solids may comprise maize, rye and chicken litter. Another example of a dry feedstock is 60% solids and the residual made up of liquid. The apparatus 700 comprises a dry feed hopper 770 having a frusto-conical lower portion funnelling into a screw conveyor 771 for conveying dry feed 701a from the dry feed hopper 770 to a blending tank 710. The blending tank 710 has a stirrer 775 therein for mixing, agitating and/or stirring the contents of the blending tank 710. The stirrer 701 may comprise a stirring blade, a drive shaft and a motor (not shown) connected to a controller, such as a Programmable Logic Controller. Residual digestate 708 is fed from the AD 450 through flowline 773 into the blending tank 710. A motorised valve 774 controls the flow of residual digestate 207 into the blending tank 710. In use, the dry feed 701 is blended in the blending tank 710 with the residual digestate 708 by activation of the stirrer 775 to form a feed slurry 701 comprising, for example 25% to 10% solids by weight and optionally 15% solids by weight, the residual being liquid phase. A flowline 709 leads from a bottom portion of the blending tank 710 to micronisation apparatus 300. The flowline 709, or any flowline disclosed herein may be: a solid wall pipe; a flexible wall pipe, which may retain its structural shape with or without feed slurry therein; a hose, which may change its structural shape dependent on whether a feed slurry is flowing therethrough or not; an open trough; or a pipe with openings therein above the flow level of the feed slurry therein. The flowline 709 has a slurry pump 772 located at a proximal end of the flowline 709, as well as a valve 777 to control the flow of the feed slurry 701 therethrough. A mixing valve 711 or injection quill (such as that shown in Figure 15) is arranged in the flowline 709 in close proximity to micronisation apparatus 300. The micronisation apparatus 300 may comprise a macerator, a progressive cavity pump and a cavitation apparatus, which may comprise a hydrodynamic cavitator. In use, the slurry pump 772 pumps the feed slurry 701 through the flowline 709to facilitate flow of feed slurry 701 through the flowline 709 to induce a stream of feed slurry 701. Immediately before the micronisation apparatus 300 (optionally, within 10m, optionally within 5m and optionally between 0.5 and 1.5m) additive 200 is added to the stream of feed slurry 701 flowing through the flowline 709. This may be achieved using a mixing valve 711 or using the additive dosing apparatus 600 shown in Figure 16. The additive enriched feed slurry 702 continues flowing through the flowline 709 into the micronisation apparatus 300 to macerate solids in the additive enriched feedstock and subject the slurry to cavitation to facilitate breakdown of the elements of the enhanced feed slurry 702 to produce a stream of enhanced feedstock 705. The stream of enhanced feedstock 705 flows from the micronisation apparatus 300 through a motorised valve 779 to dark fermentation apparatus 400. The dark fermentation apparatus 400 may be of the type disclosed with reference to Figure 11, comprising dark fermentation tank 402, heater 416 and stirrer 415. Sensors are provided to monitor various parameters at various points in the dark fermentation apparatus. A temperature indicator and controller (TIC) 780 is provided to monitor temperature of the treated feedstock 705 held in the dark fermentation tank 702. A pressure indicator controller (PIC) provides an indication of the gaseous pressure in the top of the dark fermentation tank 402 above the surface of the treated feedstock 705 held therein. A level indicator and controller (LIC) 782 provides an indication of level of the treated feedstock held in the dark fermentation tank 402. An aciditiy/alkalinity sensor 783 provides a indication of the acidity /alkalinity of fermented feedstock 410 in flowline 411. A gas analyser 784 provides an analysis of fermentation gas 407 passing out of the dark fermentation tank 402. In use, the enhanced feedstock 705 enters the dark fermentation tank 402, whereupon inoculum 405 is manually added thereto through a hatch in the dark fermentation tank. The temperature in the enhanced feedstock 705 is maintained at a desired temperature, which may be between 45 and 65 Celsius and optionally 55 Celsius for use with a biological inoculum. Additional heating is provided by heater 416 in order to maintain the desired temperature in the enhanced feedstock 705 in the fermentation tank 402. The enhanced feedstock 705 held in the dark fermentation tank 402 is continuously stirred, agitated or mixed with activation of the stirrer 415. The treated feed stock 705 is retained in the dark fermentation tank 402 for between 6 hours and 72 hours residency time. During fermentation, fermentation gas 705 is continuously emitted from the enhanced feedstock residing in the dark fermentation tank 402. The fermentation gas 407 is collected within the top of the dark fermentation tank 402 and selectively allowed to flow through flowline 413 through a pressure regulating valve 785 controlled by a pressure threshold measured by PIC 781. Pressure regulating valve 785 is optionally a motorised valve controlled by PIC 781. The pressure threshold may be between 0.5 and 10 millibars and optionally between 1 and 5 millibars and optionally between 2 and 3 millibars above atmospheric pressure. The fermentation gas 407 which flows through the pressure regulating valve 785 flows through flowline 413 through gas agitator 465 in AD 450 shown in Figure 11A and bubbled through the fermented feedstock 411 held therein. Fermented feedstock 411 flows out of the dark fermentation tank 402 through flowline 410 and may be pumped with pump 786 through one of two routes: recirculated through open re-circulation valve 787 back into a top of the dark fermentation tank 402; or to AD 450 through inlet pipe 458. The re-circulation loop may simply be used for sampling purposes, the sampling may be used for measuring parameters such as pH level. The micronisation apparatus 300 may be provided with a flushing water flowline 776 for facilitating cleaning and flushing of the component parts, such as macerator, progressive cavity pump and cavitation apparatus. Figure 17 shows a dark fermentation re-circulation apparatus, generally identified by reference numeral 800, in a system for preparing feedstock for processing in an anaerobic digester. The system for preparing feedstock is generally similar to that disclosed in Figure 16, with like reference numerals used for like parts. However, in the present embodiment, the feed slurry 701, is fed directly into the dark fermentation tank 402 and the micronisation apparatus 300 obtains and returns feedstock from the dark fermentation tank 402. As can be seen from Figure 17, part fermented feedstock 810 from the bottom portion 801 of the dark fermentation tank 402 passes through flowline 803 through a valve 804 and is dosed with additive 200 through mixing valve 711 or injection quill of the additive dosing apparatus of Figure 15 to produce an additive enriched feedstock. The additive enriched feedstock flows into the micronisation apparatus 300 which returns enhanced feedstock 705 to a top portion 802 of the dark fermentation tank 402 through flowline 805 and valve 806. In the present embodiment, static head in the dark fermentation tank provides sufficient pressure to initiate flow of feed to the micronisation apparatus 300. However, a pump (not shown) may be provided if the head does not induce sufficient pressure to induce a sufficient flow rate to the micronisation apparatus 300. An optional buffer tank 788 and associated valving can be placed in the flowline 709 to temporarily store the feed slurry 701 before onward flow to dark fermentation tank 402. Figure 18 shows an embodiment of a system for preparing feedstock for processing in an anaerobic digester which is generally similar to the embodiment shown in Figure 17, together with a control and monitoring system in accordance with a further aspect of the invention. The present embodiment differs from the embodiment of Figure 17, in that it further comprises: a micronisation and additive dosing control system 900; a pH balancing system 1000; a defoamer control system 1100; a hydrogen sulphide control system 1200; and an Oxidation-Reduction Potential sensor 1301 and Electrical Conductivity sensor 1302. The micronisation and additive dosing control system 900 comprises an inflow Chemical Oxygen Demand (COD) sensor 901 in flowline 803, an outflow Chemical Oxygen Demand (COD) sensor 902 in flowline 805, each sending the sensed COD results electronically to a controller 903. The controller 903 is in communication with a dosing pump 609 of the additive dosing apparatus 600. The controller 903 is also in communication with the Variable Frequency Drive motor 225 of the cavitation apparatus 232. In use, the inflow COD sensor 901 monitors the amount of oxygen required to chemically oxidize the organic material and inorganic nutrients, such as ammonia and nitrates, present in the flowline 803 before any additive 200 is added.The outflow COD sensor 902 monitors the amount of oxygen required to chemically oxidize the organic material and inorganic nutrients, such as ammonia and nitrates, present in the enhanced feedstock in flowline 805, after the feedstock has been enriched by the additive 200 and subjected to micronisation in micronisation apparatus 300. The controller 903 receives readings from the inflow COD 901 and outflow COD 902 and calculates the difference therebetween to yield a COD difference figure. In response, the controller 903: adjusts the frequency, such as between 52Hz and 58Hz of the VFD motor 225, which adjusts the speed of rotation of the rotor 232 of the cavitation apparatus 222; and/or adjusts the speed of the dosing pump 609 dosing additive into the flowline 803 at injection point 711. The higher the COD difference figure, the better the enhanced feedstock is for onward processing in the dark fermentation tank and/or in the anaerobic digester. The additive 200 may be dosed in a proportional manner, such that if the COD differential is high, the dosing rate is adjusted proportionally and the speed of rotation of the VFD motor 232 in the cavitation apparatus is adjusted. It should be noted that the optional macerator 214 in the micronisation apparatus 300, may be left to operate at its normal speed of operation. The macerator 214 is used to ensure large pieces of solid matter are reduced to a size suitable for cavitation apparatus 222. The pH balancing system 1000 comprises a pH sensor 783 in the outlet pipe 410 for measuring the pH level of fermented feedstock 411. An acid controller 1001 receives a reading from the pH sensor 783. The controller 1001 is in communication with an acid dosing pump 1002 for dosing acid 1003 from an acid holding container 1004 through a flowline 1005, through acid dosing valve 1006 into the top of the dark fermentation tank 402. The pH balancing system 1000 also comprises an alkali controller 1011 receives a reading from the pH sensor 783. The controller 1011 is in communication with an alkali dosing pump 1012 for dosing alkali 1013 from an alkali holding container 1014 through a flowline 1015, through alkali dosing valve 1016 into the top of the dark fermentation tank 402. In use, a target pH of optionally between 4.5 and 5.5 is desired in the dark fermentation tank. The pH sensor 783 may simply provide a pH reading of in the fermented feedstock 411 in the outlet pipe 410. Alternatively or additionally, a circulation loop flowline 1020 is provided with a loop valve 1022 normally maintained shut and a loop valve 1021 in the outlet pipe 410 normally maintained open. When a sample pH is desired, loop valve 1021 is shut and loop valve 1022 is opened. Fermenting feedstock 810 from within the fermentation tank is circulated through the loop flowline 1020 and a pH sensor reading taken. If the pH sensor reading is above the target pH, the acid controller 1001 activates the dosing pump 1002 and opens acid valve 1006 to dose acid 1003 into the dark fermentation tank 402. If the pH sensor reading is below the target pH, the alkali controller 1011 activates the dosing pump 1012 and opens alkali valve 1016 to dose alkali 1013 into the dark fermentation tank 402. The defoamer control system 1100 comprises a visual inspection of the fermenting feedstock 810. The foaming controller 1101 is in communication with an defoamer dosing pump 1102 for dosing defoamer 1103 from an defoamer holding container 1014 through a flowline 1105, through defoamer dosing valve 1106 into the top of the dark fermentation tank 402. In use, a visual inspection of the fermenting feedstock is performed. If there is a large quantity of foam observed in the dark fermentation tank 402, the controller 1101 is set manually to activate the dosing pump 1102 and opens defoamer valve 1106 to dose defoamer 1103 into the dark fermentation tank 402. The hydrogen sulphide control system 1200 comprises a hydrogen sulphide controller 1201 receives a reading from the gas analyser 784. The hydrogen sulphide controller 1201 is in communication with a ferric chloride dosing pump 1202 for dosing ferric chloride 1013 from a ferric chloride holding container 1204 through a flowline 1205, through ferric chloride dosing valve 1016 into the top of the dark fermentation tank 402. In use, the gas analyser 784 continuously or intermittently monitors the gas flowing through flowline 413. If there is an excessive quantity of hydrogen sulphide in the gas in flowline 413 i.e. above a threshold level, the controller 1201 activates the dosing pump 1202 and opens ferric chloride dosing valve 1206 to dose ferric chloride 1203 into the dark fermentation tank 402. An optional valve 1207 may isolate the gas analyser 784 from the flowline 413. The Oxidation-Reduction Potential sensor 1301 and Electrical Conductivity sensor 1302 are arranged to sense ORP and Electrical conductivity in the fermented feedstock flowing in the outlet pipe 410. Use of the ORP and EC sensors 1301,1302 may be made using the in loop 1020. Any of the systems disclosed herein are to be used in a near continuous fashion, such that the residency times in each of the dark fermentation tank 402 and AD are likely to be achieved by the majority of the feedstock, but perhaps not all. Alternatively or additionally, the systems could be used in a batch configuration, in which the residency times in each of the dark fermentation tank and/or the AD can be achieved for each batch for the complete contents of each batch. ^

Claims

CLAIMS 1. A system for processing a feedstock comprising solids laden liquid, at least a portion of said solids being cellulosic material, the system comprising a stream of said feedstock (201), a cavitation apparatus (222) for processing the feedstock (201) by subjecting the feedstock to cavitation thereby reducing the size of at least a portion of said solids characterised in that an additive (200) is added to said stream of feedstock prior to being processed by the cavitation apparatus (222) to produce a stream of enhanced feedstock (205).

2. A system as claimed in Claim 1 wherein the additive comprises a surfactant.

3. A system as claimed in Claim 1 or 2 wherein the additive comprises a bio-organic catalyst.

4. A system as claimed in Claim 1 wherein the additive comprises a protein-based surfactant synergist.

5. A system as claimed in any preceding claim, wherein the stream of feedstock flows through a feed pipe comprising a valve, the additive added to the stream of feedstock through the valve.

6. A system as claimed in any preceding claim, the system further comprises a macerator (214) for macerating the solids in the stream of feedstock to produce a stream of macerated feedstock (203) and feeding the macerated feedstock into the cavitation apparatus (222), the macerator apparatus (214) having an inlet and an outlet whereinthe additive is added to the stream of feedstock at the inlet of said macerator or optionally at the outlet of said macerator.

7. A system as claimed in any preceding claim, wherein the system further comprises a pump (218) for pumping the stream of feedstock into the cavitation apparatus (222), the pump having an inlet and an outlet and optionally, the additive is added to the stream of feedstock at the inlet of said pump or optionally at the outlet of said pump.

8. A system as claimed in any preceding claim, wherein the cavitation apparatus comprises a cavitator unit (224), a motor (225) and a control apparatus (245), the cavitator unit (224) comprises a shaft (230) rotated by the motor (225), a housing (231) defining a chamber (231’), a fluid inlet conduit (233) and a fluid outlet conduit (234) in the housing (231) and a rotor (232) on the shaft (230) and rotatably arranged within the chamber (231’) and a cavitation zone (238).

9. A system as claimed in Claim 8, wherein the rotor (232) may be shaped as a conical frustum and a peripheral surface (235) shaped as a conical surface which extends in a tapered manner between said first and second side surfaces (236, 237). Optionally, at least two arrays of bores or recesses (237) may be formed in the peripheral surface (235), optionally the bores (237) of each array of bores being arranged in a row extending around said peripheral surface (235), each bore (237) extending radially into said rotor (232) from said peripheral surface (235) and may have a cavitation zone (238) defined inside the bores (237).

10. A system as claimed in any preceding claim, wherein the system further comprises an anaerobic digester (1,101,242,450), the stream of enhanced feedstock feeding the anaerobic digester.

11. A system as claimed in Claim 10, wherein the anaerobic digester comprises an inlet pipe (8,108,458) for the stream of enhanced feedstock (205), an outlet pipe (9,109,159) for facilitating removal of digestate and a gas outlet pipe (461) for facilitating removal of biogas.

12. A system as claimed in Claim 10 or 11, wherein the anaerobic digester comprises a stirrer (13) or gas agitator (116,465).

13. A system as claimed in any preceding claim, wherein the system further comprises a dark fermentation apparatus (400), the stream of enhanced feedstock (205) feeding the dark fermentation apparatus to produce a stream of fermented feedstock (411) and a stream of fermentation gas (407).

14. A system as claimed in any of Claims 1 to 12, wherein the feedstock is obtained from a dark fermentation tank (402) and the enhanced feedstock is returned to the dark fermentation tank.

15. A system as claimed in Claim 14, wherein the feedstock is obtained from a bottom portion of the dark fermentation tank of a dark fermentation apparatus (400) and flows through a flowline (803) in which the additive is added to enrich the feedstock and fed into the cavitation apparatus and the enhanced feedstock is returned through a flowline (805) to a top portion of the dark fermentation tank.

16. A system as claimed in Claim 13, 14 or 15, wherein the fermented feedstock is fed to an anaerobic digester (450).

17. A system as claimed in any one of Claims 13 to 16, wherein at least a portion of said stream of fermentation gas (407) is fed to said anaerobic digester (450).

18. A system as claimed in any one of Claims 13 to 17, wherein the dark fermentation apparatus (400) comprises an enclosed tank (402) an inlet pipe (401) for the stream of enhanced feedstock (205), an outlet pipe (410) for facilitating removal of fermented feedstock (411) and a gas outlet pipe (413) for facilitating removal of fermentation gas (407), a heater (416) and a stirrer (414).

19. A system as claimed in any one of Claims 13 to 18, wherein the stream of enhanced feedstock (205) and/or enhanced feedstock (205) residing in the dark fermentation apparatus (400) is inoculated.

20. A system as claimed in Claim 19, wherein the inoculation includes or comprises at least one of: Enterobacteriaceae; and Clostridium.

21. A system as claimed in Claim 20, wherein the Enterobacteriaceae comprises at least one of: Citrobacter freundii, Citrobacter freundii (KPC positive); Klebsiella oxytoca; and Morganella morganii.

22. A system as claimed in Claim 20, wherein the Clostridium comprises at least one of: Clostridium perfringens; and Paraclostridium bifermentans.

23. A system as claimed in Claim 19, wherein the inoculation comprises at least one of:Enterococcus durans; and Enterococcus faecium.

24. A system as claimed in Claim 11 or any Claim dependent on Claim 11, wherein the system further comprises an ammonia stripper (500) wherein the digestate flows through the ammonia stripper.

25. A system as claimed in Claim 24, wherein the system further comprises a heat exchanger (503) for raising the temperature of the digestate.

26. A system as claimed in Claim 24 or 25, wherein the system further comprises an ammonia scrubber (506) for yielding ammonia sulphate.

27. A system as claimed in any preceding claim, the system further comprising an inflow COD sensor (901) for sensing the COD (Chemical Oxygen Demand) level in the feedstock (201,701) and an outflow COD sensor (902) for sensing the COD level in the enhanced feedstock (205,705).

28. A system as claimed in Claim 27, the system further comprising a controller (903) for receiving an inflow COD reading from the inflow COD sensor (901) and receiving an outflow COD reading from the outflow COD sensor (902), the controller calculating a difference between the outflow COD reading and the inflow COD reading to obtain a COD difference reading.

29. A system as claimed in Claim 28, the system further comprising an additive dosing apparatus (600), the controller (903) activating the dosing apparatus to dose or adjust the dosing rate of the additive into the stream of feedstock in response to the COD difference reading.

30. A system as claimed in Claim 28 or 29, wherein the cavitation apparatus (222) rotates the enriched feedstock at a range of speeds, wherein the controller (903) adjusts the speed of rotation in response to the COD difference reading.

31. A system as claimed in any preceding claim, the additive is added to the stream of feedstock using an additive dosing apparatus (600) comprising at least two containers (601,602), a dosing pump and an injection quill (613).

32. A system as claimed in any preceding claim, further comprising a pretreatment apparatus (700) for pre-treating dry feedstocks, the system further comprising a dry feed hopper (770), a blending tank (710) and a flowline (773) for flowing residual digestate from an anaerobic digester to the blending tank (710).

33. A system as claimed in Claim 32, wherein the resultant feedstock comprises between 10% and 20% solids by weight and optionally 15% solids by weight, the residual being liquid phase.

34. A system for processing a feedstock comprising solids laden liquid, at least a portion of said solids being cellulosic material, the system comprising a stream of said feedstock (201), a macerator apparatus (214) for processing the feedstock (201) by subjecting the feedstock to maceration thereby reducing the size of at least a portion of said solids characterised in that an additive (200) is added to said stream of feedstock prior to being processed by the maceration apparatus (214) to produce a stream of enhanced feedstock (205).

35. A system for processing a feedstock comprising solids laden liquid, at least a portion of said solids being cellulosic material, the system comprising a cavitation apparatus (222) for processing the feedstock (201) by subjecting the feedstock to cavitation thereby reducing the size of at least a portion of said solids characterised in that an additive (200) is added to said feedstock prior to being processed by the cavitation apparatus (222) to produce a stream of enhanced feedstock (205).

36. An inoculation for inoculating a feedstock to be fermented in a dark fermentation tank, the inoculation comprising at least one isolated bacteria culture chosen from the group: Citrobacter freundii, Citrobacter freundii (KPC positive); Klebsiella oxytoca; Morganella morganii; Clostridium perfringens; Paraclostridium bifermentans; Enterococcus durans; and Enterococcus faecium.

37. A dark fermentation apparatus comprising a dark fermentation tank (402) for containing an enhanced feedstock, the dark fermentation tank comprising a top enclosed portion (802) to collect fermentation gas and a fermentation gas flowline (413) leading from the top enclosed portion and a pressure regulating valve (781,785) for selectively allowing fermentation gas to flow from the top enclosed portion through the fermentation gas flowline.

38. A system as claimed in Claim 37, wherein the pressure regulating valve comprises a motorised valve (785), a controller and a pressure sensor (781), the pressure sensor arranged to measure the pressure of the gas held within the top enclosed portion (802) of the dark fermentation tank (402), the controller set or programmed to activate the motorised valve to maintain the pressure of the fermentation gas held in the top enclosed portion of the dark fermentation tank at a predetermined pressure.

39. A control system for controlling and processing a feedstock comprising solids laden liquid, at least a portion of said solids being cellulosic material, the system comprising a stream of said feedstock (701), a cavitation apparatus (222) for processing the feedstock by subjecting the feedstock (701) to cavitation thereby reducing the size of at least a portion of said solids characterised in that an additive (200) is added to said feedstock to produce an additive enriched feedstock prior to being processed by the cavitation apparatus, the output from the cavitation apparatus to produce a stream of enhanced feedstock, the system further comprising an inflow COD sensor (901) for sensing the COD level in the feedstock and an outflow COD sensor (902) for sensing the COD level in the enhanced feedstock.