WO2016038346A1

WO2016038346A1 - Anaerobic digestion systems and methods of installing the same

Info

Publication number: WO2016038346A1
Application number: PCT/GB2015/052576
Authority: WO
Inventors: Paul Michael Mason
Original assignee: Paul Michael Mason
Priority date: 2014-09-09
Filing date: 2015-09-07
Publication date: 2016-03-17
Also published as: GB2546427A; GB201415916D0; GB201704016D0

Abstract

An anaerobic digestion plant system (10) and method of installing an anaerobic digestion plant system. The anaerobic digestion plant system (10) comprises a plurality of containers (11, 12, 13, 14) having external walls (11a, 12a, 13a, 14a) arranged to define an enclosed area. The anaerobic digestion plant system (10) further comprises a flexible membrane (18) for holding a liquid phase of an anaerobic digestion reaction, the membrane (18) disposed within the enclosed area so as to be supported by one or more external walls (11a, 12a, 13a, 14a) of the containers (11, 12, 13, 14) when holding the liquid phase in use.

Description

ANAEROBIC DIGESTION SYSTEMS AND METHODS OF INSTALLING THE

SAME

FIELD OF THE INVENTION

The present invention relates to an anaerobic digestion system and method of installing the same, in particular to a transportable and modular system. The present invention also provides a kit for forming such an anaerobic digestion system. More particularly, the present invention provides a supported flexible membrane that can hold a liquid phase of an anaerobic digestion process (and optionally gas). The present invention also provides a container for use in installing an anaerobic digestion system.

BACKGROUND OF THE INVENTION

Anaerobic digestion is a collection of processes by which microorganisms break down biodegradable material in the absence of oxygen. The products of am anaerobic digestion process can include biogas (principally methane and carbon dioxide), and digestate in the form of a solid residue and/or liquid liquor that can be used as a fertiliser. Conventionally, anaerobic digestion plants are fixed or stationary fermentation plants that handle biological waste. Such conventional anaerobic digestion plants cannot be easily transported or installed in different locations; for example, close to where the waste is located. In recent years, efforts have been made to provide anaerobic digestion plants that can be transported and/or installed in different locations.

DE 20 2010 000 437 shows containers arranged end-to-end that allow for anaerobic digestion within the containers. A gas storage bag is located above the containers such that the biogas resulting from anaerobic digestion can be collected in the bag. The containers of DE '437 can be transported to waste sites.

WO 2013/039407 provides digester modules in the form of steel reaction chambers that can be connected to a technical module to control the anaerobic digestion parameters. Each digester module contains a gastight bag or lining e.g. PVC membrane. The digester modules of WO '407 form an ambulatory modular system that can be transported to waste sites.

It is an aim of the present invention to provide an alternative system and method to those described above.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention provides an anaerobic digestion system comprising: a plurality of containers having external walls arranged to define an enclosed area; and a flexible membrane for holding a liquid phase of an anaerobic digestion reaction, the membrane disposed within said enclosed area so as to be supported by one or more external walls of the containers when holding the liquid phase in use. Such an anaerobic digestion system may allow for transportation of the plurality of containers to a site where an anaerobic digestion plant is desired. Advantageously, the flexible membrane is supported by the external walls of the containers so that it is able to hold a liquid phase. The supported volume of liquid phase is defined by the enclosed area and surrounding external walls. For example, a ring of containers may define an enclosed area having three, four, five, six (or more), etc. supporting walls. This can be contrasted with inflatable membranes conventionally used to collect biogas, which are simply attached on top of a digestion site and would expand outwardly without any structural support. Of course, a liquid phase is much denser than a gas and the support of the external container walls thereby enables the membrane to hold a volume of liquid.

Any external side wall(s) or end wall(s) of the containers may define the enclosed area in which the flexible membrane is disposed. Preferably, the external walls of the plurality of containers are arranged in a closed ring to provide the enclosed area. The ring may have any suitable shape e.g. triangular, rectangular, square, polygonal, etc. Preferably, the plurality of containers is positioned on the ground to define the enclosed area in which the flexible membrane is disposed. It is contemplated that the liquid phase may be contained by a ground sheet connected to the flexible membrane so as to define a three-dimensional enclosure. However, it is preferable that the flexible membrane itself defines an enclosed volume for holding the liquid phase. This advantageously reduces the number of components required to install the system, and may also simplify repair and/or replacement of the membrane. The enclosed volume is advantageously supported by the surrounding external walls of the plurality of containers. The flexible membrane may be positioned on the ground within the enclosed area defined by the external walls. For example, the flexible membrane may take the form of a closed bag that is positioned on the ground within the enclosed area. Such a bag may be integrally formed from a single flexible membrane so as to minimise the risk of leakage e.g. at any seams. The enclosed volume provided by the flexible membrane e.g. bag would tend to spread out under liquid pressure except that, when the liquid phase is held by the flexible membrane, the flexible membrane is supported by the external side walls of the plurality of containers. The size of the flexible membrane e.g. bag and its enclosed volume may be chosen depending on the volume of liquid phase to be contained and/or the enclosed area available within the external walls.

The flexible membrane is preferably attached to one or more of the plurality of containers to advantageously secure the flexible membrane in the enclosed area. Further, attachment helps to define the shape of the enclosed volume of the flexible membrane.

The flexible membrane is optionally arranged to collect gas above the liquid phase. Gas produced by a further anaerobic reaction in the flexible membrane can advantageously be held above the liquid phase e.g. for temporary storage before being pumped out of the flexible membrane.

Any suitable material may be used as a feedstock for the anaerobic digestion system. The feedstock does not have to be waste; any biodegradable plant or animal matter can be used as a biomass feedstock. Preferably, at least one of the plurality of containers contains feedstock undergoing hydrolysis as part of an anaerobic digestion reaction to produce said liquid phase. This allows for a hydrolysis process to be carried out, within one or more containers, at the site where an anaerobic digestion plant is located.

The flexible membrane is preferably connected in fluid communication with one or more of the plurality of containers (e.g. the interior(s) thereof) so as to transfer e.g. receive the liquid phase. This allows for a liquid phase of an anaerobic digestion reaction (e.g., post-hydrolysis liquid) to be transferred into and/or out of the flexible membrane at the site. The liquid phase may contain some fine solid material in suspension. The liquid phase is preferably a post-hydrolysis liquid. The liquid phase may include material undergoing one or more of acidogenesis, acetogenesis and/or methanogenesis. Such processes may produce a gas that can be removed from the flexible membrane immediately or, as mentioned above, collected above the liquid phase in the flexible membrane. For example, one or more of hydrogen, C0₂, or methane may be collected above the liquid phase.

Preferably, at least one of the plurality of containers includes a partition wall extending therethrough to define a first space and a second space, said flexible membrane being permanently attached to said partition wall and being able to be stored in said first space before use. This allows for the flexible membrane to be conveniently transported inside one or more of the containers. For example, the flexible membrane e.g. bag may be folded up or otherwise compacted in the first space. Advantageously, when the containers reach a site for anaerobic digestion, the flexible membrane may be removed from one or more containers and arranged to be supported by the plurality of containers when holding the liquid phase in use. Pre-attachment to the partition wall can help with rapid deployment. The partition wall may be moveable, e.g. so as to expand the second space once the membrane has been removed from the container.

Preferably, the partition wall includes inlets and/or outlets that extend into the flexible membrane for transferring the liquid phase during use. This allows for the introduction, or removal, of liquid to or from one or more of the containers. By pre- connecting inlets and/or outlets with the partition wall, difficult parts of construction (e.g. requiring fluid-tight seals) may be installed at a factory rather than connecting fluid inlets and/or outlets on site.

Preferably, the system is modular. The containers are easily arranged in many different configurations to provide an anaerobic digestion system that can process a desired volume of feedstock. The components of the system may be demountable so as to be re-assembled in different configurations. By changing the number and/or size and/or orientation of the containers the system can be scaled up or down. Preferably, the containers are moveable or transportable. Therefore, the containers of the system can be transported to a desired site and the containers can be moved to change the enclosed area defined by the external walls of the containers.

Preferably, the plurality of containers comprises a plurality of ISO containers. ISO containers are a standard form of shipping containers that may be used to transport cargo and, preferably in this case, to contain feedstock undergoing hydrolysis and/or equipment relating to anaerobic digestion processes. The containers, e.g. ISO containers, may have steel walls. One or more of the containers may be used to house anaerobic digestion components for upstream and/or downstream processes e.g. solid waste treatment (maceration etc.), settling, aeration, dehydration, dewatering of post-hydrolysis solids, gas storage, gas scrubbing, etc... In addition, or alternatively, one or more of the containers may house power generation equipment.

According to a second aspect, the present invention provides a method for forming an anaerobic digestion system, the method comprising: arranging a plurality of containers having external walls so as to define an enclosed area; disposing a flexible membrane for holding a liquid phase of an anaerobic digestion reaction in the enclosed area so as to be supported by one or more external walls of the plurality of containers. Such a method therefore enables an anaerobic digestion plant to be installed at a desired site, e.g. close to feedstock. This arrangement allows for transportation of a plurality of containers to the site and an anaerobic digestion plant to be built to a scale as desired. Advantageously, the flexible membrane is supported by the external walls of the plurality of containers so as to counteract the hydraulic pressure of the liquid phase being held in use.

According to another aspect, the present invention provides a kit for installing an anaerobic digestion system, the kit comprising: a plurality of containers; and a flexible membrane defining an enclosed volume for holding a liquid phase of an anaerobic digestion reaction. Advantageously, an installer or an end user may use such a kit to conveniently transport a plurality of containers to a site where an anaerobic digestion plant is desired and/or arrange the containers to build a plant having a desired capacity. As part of the kit, the flexible membrane may be deployed to hold a liquid phase of an anaerobic digestion reaction.

In some embodiments the flexible membrane may be pre-attached to one or more of the plurality of containers. This can aid with rapid installation. Alternatively, or additionally, the kit may further comprise means for attaching the membrane to one or more of the plurality of containers. This may provide the installer with flexibility in choosing a particular arrangement of the containers and attaching the membrane so as to shape the enclosed volume as desired.

As is mentioned above, preferably the plurality of containers comprises a plurality of ISO containers. Preferably one or more of the containers are moveable or transportable.

According to a further aspect of the present invention, there is provided a container for an anaerobic digestion system, the container comprising: a removable side wall; a partition wall extending through the container to define a first space and a second space; and a flexible membrane for holding a liquid phase of an anaerobic digestion reaction attached to the partition wall such that the flexible membrane can be stored within the first space before use. Advantageously, this allows for a flexible membrane to be transported within one or more of the containers so that, when the containers reach a site where an anaerobic digestion plant is desired, the flexible membrane can be deployed.

Preferably, the flexible membrane is folded up to fit inside the first space. Preferably the partition wall includes inlets and/or outlets that extend into the flexible membrane for transferring the liquid phase during use. As is mentioned above, this means that the membrane is pre-connected in fluid communication with one or more containers, for example ready to receive post-hydrolysis liquid. According to a yet further aspect of the present invention, there is provided a method of deploying a flexible membrane from the container, the method comprising: providing a container comprising a removable wall and a flexible membrane stored within the container; removing said removable wall; and arranging said flexible membrane so as to hold a liquid phase of an anaerobic digestion reaction. Once the container is brought to a site where anaerobic digestion is desired, a user can then advantageously deploy the flexible membrane so that this can be filled with a liquid phase of an anaerobic digestion reaction. As is described above, preferably the flexible membrane defines an enclosed volume for holding the liquid phase, for example, the flexible membrane may take the form of a closed bag.

In embodiments of any aspect of the invention discussed above, it is described how the external walls of the plurality of containers may preferably be arranged in a closed ring to provide the enclosed area. However, it is also envisaged that the enclosed area may not be wholly defined by the external walls of the plurality of containers. The plurality of containers may be arranged in conjunction with another wall to define the enclosed area. For example, the plurality of containers may be arranged next to or around an existing wall (e.g. the external wall of a building or other structure) so as to define the enclosed area therebetween.

Although various embodiments and preferred features of the present invention have been described above, it is to be understood that these features can be provided separately or in conjunction with one another.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an anaerobic digestion system in accordance with an embodiment of the present invention.

Figure 2 shows an anaerobic digestion system in accordance with another embodiment of the present invention. Figure 3A shows an anaerobic digestion system in accordance with a third embodiment of the present invention.

Figure 3B shows a further view of the anaerobic digestion system of Figure 3A.

DETAILED DESCRIPTION

Referring now to Figure 1 , there is shown an anaerobic digestion system 10 that includes a plurality of containers 1 1 , 12, 13, 14. A flexible membrane 18 is attached to the plurality of containers 11 , 12, 13 and 14 e.g. at the corners or along the length of side walls. The flexible membrane 18 holds liquid 17 that is undergoing anaerobic digestion and, optionally, gas 16 that is a result of the anaerobic digestion. In one embodiment, the plurality of containers 11 , 12, 13, 14 may be ISO containers that can take the form as is known in the art. For example, the ISO containers may be 20 or 40 foot ISO containers. In the example shown in Figure 1 , each ISO container 1 1 , 12, 13, 14 includes a first side wall 1 1a, 12a, 13a, 14a and a second side wall 11 b, 12b, 13b, 14b. Each ISO container 1 1 , 12, 13, 14 also includes a first end wall 11 c, 12c, 13c, 14c and a second end wall 1 1d, 12d, 13d, 14d. In the arrangement shown in Figure 1 , the ISO containers are arranged such that the first side walls 11 a, 12a, 13a, 14a define an enclosed area in which the flexible membrane 18 is disposed. For example, as shown in Figure 1 , the first side walls 1 1a and 14a of ISO containers 1 1 and 14 oppose each other and the first side walls 12a and 13a of ISO containers 12 and 13 oppose each other. The first end wall 11 c of ISO container 1 1 is positioned adjacent and perpendicular from the second end wall 13d of ISO container 13. Similarly the first end walls 12c, 13c and 14c of ISO containers 12, 13 and 14 are positioned adjacent and perpendicular from the second end walls 11 d, 14d and 12d of ISO containers 11 , 14 and 12, respectively. ISO containers 1 1 and 14 are touching, and preferably connected to ISO containers 12 and 13 at the corners to define an enclosed area within which the flexible membrane 18 is to be disposed. Figure 1 shows an example in which there are four ISO containers 11 , 12, 13 and 14. However, it is to be understood that any number of ISO containers could be used; i.e., more than four or less than four. At least some ISO containers may also be replaced with steel walls that help to define an enclosed area for the flexible membrane 18 to be disposed.

The flexible membrane 18 of Figure 1 is attached to the corners of each of the side walls 11 a, 12a, 13a, 14a of the ISO containers 1 1 , 12, 13, 14. The flexible membrane 18 has an opening (not shown) for receiving liquid 17. The flexible membrane 18 acts as a rigid liquid holder to the depth supported on all sides by, for example, the ISO containers 1 1 , 12, 13 and 14, or steel walls. The flexible membrane is preferably non-elastic, impermeable and UV proof e.g. PVC.

One or more of the plurality of ISO containers 1 1 , 12, 13, 14 may contain organic feedstock that is undergoing an anaerobic digestion process. Preferably, the feedstock in one or more of the ISO containers 1 1 , 12, 13, 14 is undergoing a hydrolysis process. As the feedstock turns into a post-hydrolysis solution or liquid 17, this is then transferred through the opening of the flexible membrane 18. The flexible membrane 18 is then filled with post-hydrolysis liquid 17 that then undergoes further processes of anaerobic digestion, such as acidogenesis, acetogenesis and methanogenesis. Optionally, any gas 16 that is produced from these further processes can then be collected, and optionally, stored above the liquid 17 in the flexible membrane 18. An outlet (not shown) may also be provided in the flexible membrane 18 to remove the gas 17 that is produced during the anaerobic digestion process. Although not shown, the gas could be pumped out of the flexible membrane immediately for separate storage or use. This may be a batch wise or continuous process. In the example shown in Figure 1 , the ISO containers 1 1 , 12, 13, 14 act as a support for the flexible membrane 18. Advantageously, the flexible membrane 18 and ISO containers 11 , 12, 13 and 14 allow for a temporary and transportable anaerobic digestion system 10. Figure 2 shows an alternative arrangement of that shown in Figure 1. A plurality of containers 21 , 22, 23, 24, 25, 26 and 27 are shown as an example in Figure 2. A flexible membrane 202 similar to flexible membrane 18 of Figure 1 is disposed within an area defined by the plurality of containers 21 , 22, 23, 24, 25, 26 and 27. Containers 21 , 22 and 27 are arranged in a similar way as containers 11 , 12 and 13 of Figure 1. The containers 23, 24, 25 and 26 of Figure 2 replace container 14 of Figure 1 and have side walls 23a, 24a, 25a and 26a. As can be seen in Figure 2, the containers 23, 24, 25 and 26 are stacked adjacent each other and the side walls 23a, 24a, 25a and 26a extend vertically from end walls (not shown) provided on a base (not shown). The flexible membrane 202 can then be attached to the top of the vertically extended side walls 23a, 24a, 25a and 26a. This provides a greater volume in the flexible membrane 202 for gas storage above the liquid phase.

From Figures 1 and 2, it can be seen that the modular system is very flexible and allows the arrangement of containers to be adjusted on site to change the enclosed area and provide any desired volume supported by the container walls.

As with Figure 1 , the plurality of containers 21 , 22, 23, 24, 25, 26 and 27 may be ISO containers. The arrangement of Figure 2 shows, as an example, seven ISO containers. The ISO containers 21 , 22 and 27 are arranged in a similar manner to ISO containers 1 1 , 12 and 13 of Figure 1. ISO containers 23, 24, 25 and 25 are stacked adjacent each other and the side walls 23a, 24a, 25a and 26a extend vertically from end walls (not shown) provided on a base (not shown). The ISO containers 21 , 22, 23, 24, 25, 26 and 27 provide an enclosed area in which the flexible membrane 202 can be disposed.

Figure 2 shows, as an example, seven ISO containers 21 , 22, 23, 24, 25, 26 and 27. However, it is to be understood that any number of ISO containers could be used; i.e., more than seven or less than seven. At least some ISO containers may also be replaced with steel walls that help to define an enclosed area for the flexible membrane 202 to be disposed.

The flexible membrane 202 is attached to the top of the vertically extended side walls 23a, 24a, 25a and 26a. The flexible membrane 202 is also attached to the ISO containers 21 , 22 and 27 in a similar way that the flexible membrane 18 is attached to ISO containers 1 1 , 12 and 13 of Figure 1 , e.g. at corners. The flexible membrane 202 therefore has a greater volume for gas storage, as shown in Figure 2. As with the flexible membrane 18 of Figure 1 , the flexible membrane 202 has an opening (not shown) to receive liquid 204. The flexible membrane 202 acts as a rigid liquid holder up to the depth supported on all sides by, for example, the side walls of the ISO containers 21 , 22, 23, 24, 25, 26, 27 (and any steel walls). The flexible membrane is preferably non-elastic, impermeable and UV proof.

One or more of the plurality of ISO containers 21 , 22, 23, 24, 25, 26, 27 may include feedstock that is undergoing an anaerobic digestion process. Preferably, the feedstock in one or more of the ISO containers 21 , 22, 23, 24, 25, 26, 27 is undergoing a hydrolysis process. As the feedstock turns into a post-hydrolysis solution or liquid 204, this is then transferred through the opening of the flexible membrane 202 . The flexible membrane 202 is then filled with post-hydrolysis liquid 204 that then undergoes further processes of anaerobic digestion, such as acidogenesis, acetogenesis and methanogenesis. Optionally, any gas 200 that is produced from these further processes can then be stored above the liquid 204 in the flexible membrane 202. An outlet (not shown) may also be provided in the flexible membrane 202 to remove the gas 200 that is produced during the anaerobic digestion process. Although not shown, the gas 200 could be pumped out of the flexible membrane 202

immediately, e.g. for use or separate storage. Referring now to Figure 3A, there is shown an example of prefixing and transporting a flexible membrane in an ISO container. The anaerobic digestion system 3 is similar to anaerobic digestion system 10 shown in Figure 1.

Figure 3A shows ISO containers 31 , 32, 33 and 34 arranged in a similar way to the ISO containers 1 1 , 12, 13, 14 of Figure 1. However, ISO container contains a partition wall 35 located in the ISO container 34. The partition wall 35 may extend longitudinally through the ISO container 34 to provide a holding space 37. Of course, the partition wall 35 could also extend transversely through the ISO container 34. In the example of Figure 3A, the flexible membrane 30 is permanently attached to the partition wall 34. Inlets and/or outlets 36 may be provided in the partition wall 35 and the flexible membrane 30 to provide an inlet and/or outlet of liquid, as described previously. The advantage of providing a partition wall 35 is that the flexible membrane 30 may be stored in the holding space 37 of ISO container 34 so as to be transported and later unfolded/expanded into an enclosed area provided by an arrangement of ISO containers 31 , 32 and 33, as described in relation to ISO containers 1 1 , 12, 14 of Figure 1. The ISO container 34 could also be used as a substitute for ISO containers 21 , 22 and 27 of Figure 2.

The ISO container 34 may also include feedstock in a second space 38 that is undergoing anaerobic digestion. As the feedstock moves from a hydrolysis process to a post-hydrolysis process, the resulting liquid may be introduced through the inlets and/or outlets 36.

Figure 3B shows an exploded view of the ISO container 34 of Figure 3A. Here, the partition wall 35 is clearly seen extending longitudinally through the ISO container 34. The partition wall 35 creates a holding space 37 for storing the flexible membrane 30 and a second space 38 which would be used for anaerobic digestion of organic waste, or could include components that control the anaerobic digestion environment of the flexible membrane 30.

Although the containers described above have been described to contain, preferably, feedstock, it is to be understood that these containers could also house components relating to anaerobic digestion. For example, one of more of the plurality of containers described above may house anaerobic digestion components for upstream/downstream processes, for example solid waste treatment (e.g.

maceration etc.), settling, aeration, dehydration, dewatering of post-hydrolysis solids, gas storage, gas scrubbing, etc.

The feedstock can be any suitable biomass material. Some common examples of biomass feedstock include: grains and starch crops e.g. sugar cane, maize, wheat, sugar beets, industrial sweet potatoes, rice, etc.; agricultural residues e.g. corn stover, wheat straw, rice straw, orchard prunings, etc.; food waste; forestry materials e.g. logging residues, forest thinnings, etc.; animal by-products e.g. tallow, fish oil, manure, etc.; crops grown specifically for anaerobic digestion e.g. switchgrass, miscanthus, hybrid poplar, willow, algae, cacti, etc.; urban organic waste e.g. municipal solid wastes (MSW), lawn wastes, wastewater treatment sludge, urban wood wastes, waste cooking oil, etc.

Generally, the plurality of containers and flexible membrane described above can also be provided in a kit to form an anaerobic digestion system. Such a kit may be designed to create a standalone anaerobic digestion system, for example with the containers arranged in a closed ring as seen in the Figures. However, such a kit may also be used to assemble an anaerobic digestion system against an existing wall, for example an external wall of a pre-existing building or other structure.

Further modifications will be apparent to those skilled in the art without departing from the scope of the present invention as defined by the following claims.

Claims

1. An anaerobic digestion system comprising:

a plurality of containers having external walls arranged to define an enclosed area; and

a flexible membrane for holding a liquid phase of an anaerobic digestion reaction, said membrane disposed within said enclosed area so as to be supported by one or more external walls of said containers when holding said liquid phase in use.

2. The anaerobic digestion system of claim 1 , wherein the flexible membrane defines an enclosed volume for holding the liquid phase.

3. The anaerobic digestion system of claim 1 or 2, wherein the flexible membrane is positioned on the ground within the enclosed area defined by the external walls.

4. The anaerobic digestion system of any preceding claim, wherein at least one of the plurality of containers contains feedstock undergoing hydrolysis as part of an anaerobic digestion reaction to produce said liquid phase.

5. The anaerobic digestion system of any preceding claim, wherein said liquid phase is a post-hydrolysis liquid that includes material undergoing one or more of acidogenesis, acetogenesis and/or methanogenesis.

6. The anaerobic digestion system of any preceding claim, wherein the flexible membrane is attached to one or more of the plurality of containers.

7. The anaerobic digestion system of any preceding claim, wherein said flexible membrane is arranged to collect gas above said liquid phase.

8. The anaerobic digestion system of any preceding claim, wherein the flexible membrane is connected in fluid communication with one or more of the plurality of containers to transfer said liquid phase into and/or out of the membrane.

9. The anaerobic digestion system of any preceding claim wherein at least one of the plurality of containers includes a partition wall extending therethrough to define a first space and a second space, said flexible membrane being permanently attached to said partition wall and being able to be stored in said first space before use.

10. The anaerobic digestion system of claim 9, wherein the partition wall includes inlets and/or outlets that extend into the flexible membrane for transferring said liquid phase during use.

1 1. The anaerobic digestion system of any preceding claim, wherein said plurality of containers comprises a plurality of ISO containers.

12. The anaerobic digestion system of any preceding claim, wherein said system is modular.

13. The anaerobic digestion system of any preceding claim, wherein one or more of said containers are moveable or transportable.

14. A method of installing an anaerobic digestion system, said method comprising:

arranging a plurality of containers having external walls so as to define an enclosed area;

disposing a flexible membrane for holding a liquid phase of an anaerobic digestion reaction in said enclosed area so as to be supported by one or more external walls of said plurality of containers when holding said liquid phase in use.

15. The method of claim 14, further comprising arranging the flexible membrane to define an enclosed volume for holding the liquid phase.

16. The method of claim 14 or 15, further comprising positioning the flexible membrane on the ground within the enclosed area defined by the external walls.

17. The method of any of claims 14-16, further comprising arranging at least one of the plurality of containers to contain feedstock undergoing hydrolysis as part of an anaerobic digestion reaction to produce said liquid phase.

18. The method of any of claims 14-17, wherein said liquid phase is a post- hydrolysis liquid that includes material undergoing one or more of acidogenesis, acetogenesis and/or methanogenesis.

19. The method of any of claims 14-18, further comprising attaching the flexible membrane to the plurality of containers.

20. The method of any of claims 14-19, further comprising arranging the flexible membrane to collect gas above said liquid phase.

21. The method of any of claims 14-20, further comprising connecting the flexible membrane in fluid communication with one or more of the plurality of containers to transfer said liquid phase into and/or out of the membrane.

22. The method of any of claims 14-21 , further comprising introducing said liquid phase, during use, through an opening provided in the flexible membrane.

23. The method of any of claims 14-22, wherein at least one of the plurality of containers includes a partition wall extending therethrough to define a first space and a second space, said flexible membrane being permanently attached to said partition wall, said method further comprising storing said flexible membrane in said first space before use.

24. The method of claim 23, said method further comprising removing said membrane from said first space before disposing said membrane in said enclosed area.

25. The method of claim 23 or 24, wherein the partition wall includes inlets and/or outlets that extend into the flexible membrane and said method further comprising transferring said liquid phase through one or more of said inlets and/or outlets during use.

26. The method of any of claims 14-25, said method further comprising rearranging one or more of the plurality of containers so as to change said enclosed area defined by said external walls.

27. A kit for forming an anaerobic digestion system, said kit comprising:

a plurality of containers; and

a flexible membrane defining an enclosed volume for holding a liquid phase of an anaerobic digestion reaction.

28. The kit of claim 27, wherein the flexible membrane is pre-attached to one or more of the plurality of containers.

29. The kit of claim 27 or 28, said kit further comprising means for attaching said membrane to one or more of the plurality of containers.

30. The kit of any of claims 27-29, wherein said plurality of containers comprises a plurality of ISO containers.

31. The kit of any of claims 27-30, wherein one or more of said containers are moveable or transportable.

32. A container for an anaerobic digestion system, said container comprising: a removable wall;

a partition wall extending through said container to define a first space and a second space; and

a flexible membrane for holding a liquid phase of an anaerobic digestion reaction attached to said partition wall such that said flexible membrane can be stored within said first space before use.

33. The container of claim 32, wherein said membrane is folded up to fit inside said first space.

34. The container of claim 32 or 33, wherein the partition wall includes inlets and/or outlets that extend into said flexible membrane for transferring said liquid phase of an anaerobic reaction during use.

35. A method of deploying a flexible membrane from said container of any of claims 32-34, said method comprising:

removing said removable wall;

removing said flexible membrane from said first space on site; and arranging for said flexible membrane to hold said liquid phase of an anaerobic digestion reaction.

36. The method of claim 35, said method further comprising:

introducing said liquid phase of an anaerobic digestion reaction through outlets and/or inlets provided in the partition wall that extend into said flexible membrane.

37. A method of deploying a flexible membrane from a container, said method comprising:

providing a container comprising a removable wall and a flexible membrane stored within the container;

removing said removable wall; and

arranging said flexible membrane so as to hold a liquid phase of an anaerobic digestion reaction.

38. A method of installing an anaerobic digestion system as hereinbefore described with reference to the accompanying drawings.

39. An anaerobic digestion system or kit for forming an anaerobic digestion system as hereinbefore described with reference to the accompanying drawings.

40. A container for an anaerobic digestion system as hereinbefore described with reference to the accompanying drawings.

41. A method of deploying a flexible membrane as hereinbefore described with reference to the accompanying drawings.