GB2525695A

GB2525695A - A method of, and apparatus for, direct injection composting

Info

Publication number: GB2525695A
Application number: GB1419806.3A
Authority: GB
Inventors: Javier Rojo
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-11-06
Filing date: 2014-11-06
Publication date: 2015-11-04
Anticipated expiration: 2034-11-06
Also published as: GB201419806D0; GB2525695B

Abstract

A composting unit which may be a conventional wheeled bin or dumpster has a lid sides and base which may be insulated with a heat retaining means therein. An electrically driven air compressor or pump 50 may be situated in a housing 52 located on the composting unit. A hose 54 delivers air to a Y shaped distribution head 56 situated inside the base of the composting unit. The supply of pressurised air acts upon the vegetation etc inside the unit to aid in its breakdown into compost. The unit may be fitted with a drainage aperture 22,which may be located below an internal horizontal floor 70. A programmable logic controller PLC may be fitted to monitor the temperature of the unit and deliver air as required to promote breakdown of waste matter.

Description

A Method of, and Apparatus for, Direct Injection Compostinci The present invention relates to a method of, and apparatus for, direct injection composting. More particularly, the present invention relates to decentralised composting of organic matter using compressor arrangements to inject high-pressure au into a composting vessel. In embodiments, a standard wheeled bin ("wheelie bin") typically confirming to European standard DIN ENB4O, is utilised to form a tippable in-vessel composter by utilising a compressor system to inject air at high pressure.

Composting of organic matter is the inverse process of photosynthesis and it is of extreme importance to close the life cycle and to recycle valuable nutrients back to the ground. Oxygen availability and bacterial activity are the key elements that drive composting. Oxygen is the chemical catalyst that enables the composting activity of aerobic bacteria. Aerobic bacteria are sixteen times more efficient than anaerobic is bacteria at digesting organic matter.

When organic matter, namely food and garden waste, is not dealt with properly, it can lead to environmental problems including smells, vermin, insects and filtration of lixiviates. To mitigate the issues associated with the disposal and treatment of organic matter, the commercial waste management industry has traditionally developed large, centralised composting plants in remote locations. Such plants are able to exploit the economies of scale. However, this approach often results in high transportation costs (for example, food waste is -70% water) and large carbon footprints.

In such large-scale devices, it is known to use forced aeration to improve the composting rate. Traditional commercial-scale fixed-location solutions rely on transportation infrastructure to deliver the organic waste to them. Such infrastructure often utilises fans and blowers to introduce high volumes of air at low pressures as an affordable way to supply large amounts of oxygen.

However, such approaches have significant drawbacks. The low pressure of the injected air makes it hard for all regions of the compostable mass to be reached. This often requires mechanisms to physically turn the material.

Small scale composter designs are also known in the art. However, they are often complex and require detailed internal systems, for example: internal piping systems; drainage systems; perforations; and vents. This makes the manufacture of these units more expensive and the composting operations more cumbersome. For this reason small scale solutions are generally not used commercially as they are not competitive with the large scale centralised solutions.

Therefore, a technical problem exists in the art that known small-scale decentralised composting solutions are inefficient and uncompetitive with large scale centialised solutions. The present invention addresses, in one aspect, the above issues.

According to a first aspect of the present invention, there is provided a composting unit, comprising: a composting vessel comprising a base, side walls and a lid, the composting vessel defining an internal volume into which matter for composting can be placed; and an air compressor arranged to inject compressed air into the internal volume of the composting vessel through an aperture formed in the base of the composting vessel.

In one embodiment, the composting unit further comprises an air supply pipe connected at a first end to the air compressor and a second end connected to the aperture formed in the base of the composting vessel.

In one embodiment, the second end of the air supply pipe comprises a shaped outlet connector extending into the internal volume of the composting vessel.

In one embodiment, the outlet connector comprises at least two outlet apertures for introducing compressed air into the internal volume of the composting vessel.

In one embodiment, the outlet apertures are located at an angle to one another. In one embodiment, the outlet apertures are offset at an angle of 45 degrees to one another.

In one embodiment, the outlet connector comprises a Y-shaped connector.

In one embodiment, the air supply pipe comprises a braided pipe.

In one embodiment, the air compressor is operable to provide compressed air at a pressure of at least 200 mbar.

In one embodiment, the air compressor is operable to provide a flow rate of at least 50 litres/minute.

In one embodiment, the air compressor comprises a pulsation free air compressor.

In one embodiment, the air compressor is attached to an external surface of the composting vessel. In one embodiment, the air compressor is located within a housing attached to an external surface of the composting vessel.

In one embodiment, the lid comprises a pivotable lid.

In one embodiment, the composting vessel comprises a wheeled bin. In one embodiment, the wheeled bin is in accordance with European standard DIN ENS4O.

In one embodiment, the aperture in the base of the composting vessel comprises a drainage aperture in the base of the wheeled bin.

In one embodiment, the composting unit further comprises an electronic controller for controlling the operation of the air compressor.

In one embodiment, the electronic controller further comprises a temperature sensor operable to measure the temperature in the internal volume of the composting vessel.

In one embodiment, the electronic controller is operable to record data from the temperature sensor.

In one embodiment, the electronic controller comprises a programmable logic controller.

In one embodiment, the composting unit further comprises an insulation layer around at least a part of the external surface of the compost bin. In one embodiment, the insulation layer is provided on the sides and lid of the composting vessel.

In one embodiment, the composting vessel comprises an internal structure including a floor spaced from the base of the composting vessel.

According to a second aspect of the present invention, there is provided a method of decentralised composting utilising a composting vessel comprising a base, side walls and a lid, the composting vessel defining an internal volume into which matter for composting can be placed, the method comprising the steps of: placing waste matter for composting into the internal volume; and utilising an air compressor to supply compressed air into the internal volume of the composting vessel through an aperture formed in the base of the composting vessel to accelerate composting of waste matter.

In one embodiment, the compressed air is supplied to the composting vessel through air supply pipe connected at a first end to the air compressor and a second end connected to the aperture formed in the base of the composting vessel.

In one embodiment, the air compressor is operable to provide compressed air at a pressure of at least 200 mbar. In one embodiment, the air compressor is operable to provide a flow rate of at least 50 litreslminute.

In one embodiment, the composting vessel comprises a pivotable lid.

In one embodiment, the composting vessel comprises a wheeled bin. In one embodiment, the wheeled bin is in accordance with European standard DIN EN840.

In one embodiment, the method further comprises the step of: controlling the air compressor utilising an electronic controller.

In one embodiment, the electronic controller further comprises a temperature sensor and the method further comprises the step of: measuring the temperature in the internal volume of the composting vessel.

In one embodiment, the method further comprises the step of: recording data from the temperature sensor.

In one aspect, there is provided a high pressure in-vessel compost bin comprising: a body portion of an unmodified standard wheelie bin with a drainage hole; a pulsation free weather proof air compressor to inject the compressed air directly into the wheelie bin; and a braided external flexible pipe that delivers the compressed air straight into the bottom of the wheelie bin through its opening.

In one aspect, the high pressure in-vessel compost bin further comprises programmable electronic controls and a temperature probe for performance optimisation and data recording.

In one aspect, the high pressure in-vessel compost bin further comprises the use of any internal structure to hold the flexible pipe or to facilitate water drainage.

In one aspect, the high pressure in-vessel compost bin further comprises an insulation is layer on the top and to the sides of the container.

In one aspect, the high pressure in-vessel compost bin further comprises a weatherproof box that is hooked or attached to the wheelie bin and into which the compressor is placed.

In one aspect, the air is injected at high pressure (>200mbar).

In one aspect, the wheelie-bin has an internal structure comprising a raised floor.

In one aspect, the high pressure in-vessel compost bin further comprises a Y shaped connector at the end of the flexible pipe.

By providing such an arrangement and method, composting at high pressure means more energy per unit of air injected but this additional cost is compensated by the lower upfront investment, transportation and operational costs associated to decentralised solutions. High pressure decentralised solutions also benefit from the higher prices that the market assigns to locally produced organic fertiliser. Once organic waste and its associated problems (smell, vermin, etc) have been dealt with in a decentralised way, it becomes possible the decentralised recovery of other recyclable materials.

This invention is the result of a thorough combination of technologies and physical principles to create a new mobile device that enables the economical deployment of a decentralised high pressure accelerated composting solution. This invention allows taking technology closer to organic waste rather than transporting the waste over long distances to technology. The reduced scale and minimum energy consumption allows for this composting device to work under grid connected AC conditions (alternating current) or under a battery powered DC system (direct current), for example solar powered.

This invention is characterized by air injected at high pressure (>200mbar) instead of blown into the organic mass or naturally aerated as is typical in the traditional solutions.

The injection of air at high pressure brings several advantages. It makes unnecessary piping systems to distribute the air inside the composting mix that are characteristic of existing designs. As no piping is required, it makes tipping the container to empty the content a lot easier without damaging any structures or mechanisms. Also the absence of internal structures within the container make cleaning and operational maintenance much simpler. The high pressure of air injected is enough to raise the bin lid making unnecessary the drilling of any aeration vents while keeping the bin outdoors, closed and protected from rain.

Further, the disclosed invention takes advantage of the standard characteristics of the wheelie bin for both air injection and drainage. The absence of complex piping systems, and of the associated bends, drills and turns, reduce the losses in the transmission of pressured air hence reducing the energy consumption of the system and partially compensating for the increased amount of energy required to compress the air.

The air is compressed in a compression chamber significantly increasing its temperature. This higher than ambient temperature stimulates the commencement of the biological activity of the composting bacteria. This is especially important under low temperature conditions. The positive effects of the heat contained in the compressed air injected can be optimised, in optional embodiments, by the addition of an insulating layer around the container in the form of thermal blanket or insulating blocks.

With the proposed designs it is possible to use affordable, mass produced, standard containers that have been designed for a different purposes to manufacture an economically viable solution for the provision of decentralised high pressure in-vessel composting.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 shows a schematic front view of a composting unit according to an embodiment of the present invention; Figure 2 shows a side view of the composting unit of Figure 1; Figure 3 shows a "Y" shaped air diffuser; Figure 4 shows a detailed front view of a composting unit according to another embodiment; and Figure 5 shows a programmable logic controller.

The present invention relates to a mobile compressed air in-vessel composter with direct injection. In embodiments, the in-vessel composter includes an electric compressor attached to an unmodified standard wheelie bin and a flexible braided pipe that delivers the compressed air directly into the bin through the standard drainage opening in the bin.

The described configuration converts a standard wheelie bin into an in-vessel composter without any further modifications being required hence significantly reducing the cost of decentralised composting.

An embodiment of the present invention is described below. Whilst the present invention is described with reference to components such as, for example, a commercially-available wheeled bin, it is to be understood that this embodiment is exemplary and other arrangements may be utilised by the skilled person as appropriate.

Figures 1 and 2 show front and side views respectively of a composting unit 10. The a composting unit 10 comprises a composting vessel 12 which, in this embodiment, takes the form of an unmodified standard wheeled bin (wtieelie bin") The composting vessel 12 comprises sides 14, a base 16 and a pivotable lid 18 which define an internal volume 20. The recommended wheelie bin (known as a Eurobin) has an internal volume of 1100 litres capacity and conforms to European standard DIN EN840.

The preferred wheeled bin for use with the present invention has dimensions as follows (the reference letters corresponding to those shown in Figures 1 and 2): maximum total height (A) 1700 mm; maximum height to top of side walls (B) 1500 mm; maximum total length (C) 1600 mm; maximum longitudinal spacing between wheels (D) 1200 mm; maximum lateral spacing between wheels (E) 700 mm; and height of base 16 from ground surface (F) 300 mm.

The lid 18 is hinged at one side to enable the lid 18 to be swung open to deposit materials for composting into the internal volume 20. However, this is optional and the lid 18 may be simply fitted to the upper end of the composting vessel 12.

A drainage aperture 22 is formed in the base 16 of the composting vessel. In the described embodiment of the present invention, the drainage aperture 22 is a standard feature of a conventional wheeled bin and remains unmodified in the arrangement of the present invention.

Indeed, as set out above, through utilisation of an unmodified wheeled bin in the arrangement of the present invention, the manufacturing costs of bespoke composting items can be avoided. In addition, such wheeled bins are readily available at low cost, and many users already own such items and/or have storage areas sized and arranged to accept such wheeled bins. This reduces both the cost of manufacture and the cost of installation.

An air compressor 50 is also provided. The air compressor 50 may take the form of any suitable air compressor. However, in embodiments, the air compressor 50 takes the form of a pulsation-free weather-proof air compressor. The air compressor 50 may take the form of a piston air compressor or a membrane air compressor. For the size of composting vessel 12 described herein, the air compressor 50 is operable to provide a minimum flow rate of 50 litres/minute at a minimum pressure of 200 mbar (above atmospheric pressure). However, different pressures and flow rates may be selected for different sizes of composting vessel 12.

The air compressor 50 is located externally of the composting vessel 12 and, in embodiments, may be located on, or attached to, the composting vessel. For outdoor use, the air compressor 50 may be placed inside a weatherproof box 52 which may be attached to the composting vessel 12.

The air compressor 50 may be mains powered or battery powered. In other words, the air compressor 50 may be run from an AC power supply or from a DC battery system (which may typically be powered by solar panels). The air compressor 50 and power source selected will depend upon the minimum pressure and airflow levels required for a particular composting vessel 12.

The outlet of the air compressor 50 is in fluid communication with the internal volume 20 of the composting vessel by means of a pipe 54. The pipe 54 may take any suitable form. However, in the present embodiment, the pipe 54 comprises a 13 mm diameter PVC based braided external flexible pipe. A first end of the pipe 54 is connected to the outlet of the air compressor 50 and a second end of the pipe 54 is connected to the drainage aperture 22 in a substantially fluid-tight seal. The diameter of the pipe is selected to support the nominal flow rates and pressures required by a particular composting vessel 12.

The second end of the pipe 54 may be sized and arranged to fit into the drainage aperture 22. A seal (not shown) may then be provided to ensure a fluid-tight fit.

Alternatively, the pipe 54 may connect to an adapter (not shown) sized and arranged to sit in the drainage aperture 22 and form a connector for the pipe 54.

The pipe 54 may optionally comprise braids (for example, polyester braids) to ensure that the pipe 54 is operable to withstand the pressure and temperature conditions over time (and potentially up to pressures of 15 bars).

An outlet connector 56 is attached to the second end of the pipe 54. The outlet connector 56 is shown in more detail in Figure 3. The outlet connector 56 is located within the internal volume 20 of the composting vessel 12 and forms the outlet for compressed air entering the internal volume 20 of the composting vessel 12.

The outlet connector 56, in this embodiment, comprises a Y-connector diffuse and defines two outlet apertures 58 formed at an angle to one another. The angle is 45 degrees. The inventors have found that this configuration of outlet apertures maximizes the air distribution while minimising the pressure loss. It is also a simple, affordable and easy to install solution.

However, the skilled person will be readily aware of different configurations of outlet which could be used with the present invention. For example, a T-connector, a simple is single outlet or other configurations would be suitable.

An important aspect of the present invention is that the internal volume 20 of the composting vessel 12 remains free of any components such as nets, barriers, shelves or other devices. Only the outlet connector 56 extends into the internal volume 20. This maximises the space available for compost and facilitates cleaning of the interior of the composting vessel 12. This also reduces the cost of providing the composting vessel 12 since an unmodified wheelie" bin can be utilised.

However, variations may be implemented for specific purposes. Figure 4 shows composting unit 100 including additional components. The composting unit 100 may be configured to be automated and to monitor and control the composting process.

Therefore, the composting unit 100 according to an embodiment of the invention may comprise a programmable logic controller (PLC) 60, a built in clock, a temperature sensor 62 and a data recorder to enable the temperature profiles of the compostable mix to be monitored throughout the composting process to optimize the growing environment for the bacteria. An example of a PLC 60 is shown in Figure 5. However, alternative PLC models can be utilised.

The data recorder is operable to record the temperature profiles as measured by the temperature sensor and the programmable logic controller is operable to control the amount of air injected in order to maintain the temperature under 70 degrees centigrade and to minimise energy consumption.

In an embodiment, a low voltage set of basic programmable electronic controls are provided to optimise the performance of the composting unit 100. A combined digital and analogical system (minimum 2 input and 2 output relay ports) with a clock and data recording capabilities is recommended to comply with regulatory requirements in most European countries and to minimize energy consumption.

Further, the temperature sensor 62 is operable to manage the process and to ensure the proper pasteurization of the organic matter contained in the system. In an embodiment, a weather proof P1100 temperature sensor 600 mm long connected to the programmable logic controller is provided.

Further, in the embodiment of Figure 4, the composting unit 100 comprises a floor 70 is provided within the internal volume 20 and above the outlet connector 56. The floor is an optional feature which may be used in situations where organic matter may form excess liquid. The floor 70 is arranged to hold the solid matter above the level of any liquid within the internal volume 20 of the composting vessel 12.

Further, optionally, for optimal use in cold environments, and in order to accelerate the speed of the composting reaction, an insulation layer 80 may added to the top and to the sides of the composting vessel 12. A minimum thickness of 10mm is recommended for materials with thermal conductivities under 0.022 W/mK.

In summary, the present invention is operable to provide a local, low-cost composting unit comprising four key elements: a mobile "wheelie" bin; an electric compressor to enable the injection of air at high pressures (>200 mbar above atmospheric); an air delivery system to inject the compressed air directly into the organic mass; and a power system that can be grid connected or battery based.

By utilising a composting vessel such an unmodified "wheelie" bin, the cost of the composting unit is reduced and end users are provided with greater flexibility for operation. Further, by utilising the "wheelie" bin unmodified, the container remains undamaged so that it can be reused for its original purpose of waste storage or delivered to alternative locations should that be required.

In use, a user places organic material to be composted into the composting vessel 12.

The lid 18 can be lifted by the user to facilitate introduction of organic matter into the vessel 12. Once a particular amount of material has been added, the air compressor 50 may be started continuously or intermittently for particular time periods to introduce compressed air into the internal volume of the composting vessel 12. The compressed air is introduced through the apertures 58 in the outlet connector 56. By utilising compressed air at high pressure and relatively low flow rates, air can reach the whole of the composting matter and the temperature in the vessel 12 is increased. This improves the composting process. Should the air pressure inside the composting vessel 12 increase, a build up of pressure is prevented naturally by the lid 18 which will rise in response to the pressure. Alternatively, the lid 18 may be held open during use if desired.

The composting process may be controlled and monitored by the programmable logic controller 60 and temperature sensor 62 to optimise the growing environment for the bacteria.

Once the composting process is complete, the compost may be removed by lifting the lid 18 to gain access to the internal volume 20 of the composting vessel 12. Cleaning of the arrangement, if required, can be facilitated by removal of the outlet connector 56 and pipe 54 and rinsing the interior of the unmodified composting vessel 12. Waste water can then be flushed through the drainage aperture 22 in the composting vessel 12.

Variations of the above embodiments will be apparent to the skilled person. The precise configuration of hardware components may differ and still fall within the scope of the present invention.

Embodiments of the present invention have been described with particular reference to the examples illustrated. While specific examples are shown in the drawings and are herein described in detail, it should be understood, however, that the drawings and detailed description are not intended to limit the invention to the particular form disclosed. It will be appreciated that variations and modifications may be made to the examples described within the scope of the present invention.

Claims

CLAIMS1. A composting unit, comprising: a composting vessel comprising a base, side walls and a lid, the composting vessel defining an internal volume into which matter for composting can be placed; and an air compressor arranged to inject compressed air directly into the internal volume of the composting vessel through an aperture formed in the base of the composting vessel.
2. A composting unit according to claim 1, further comprising an air supply pipe connected at a first end to the air compressor and a second end connected to the aperture formed in the base of the composting vessel.
3. A composting unit according to claim 2, wherein the second end of the air supply pipe comprises a shaped outlet connector extending into the internal volume of the composting vessel.
4. A composting unit according to claim 3, wherein the outlet connector comprises at least two outlet apertures for introducing compressed air directly into the internal volume of the composting vessel.
5. A composting unit according to claim 4, wherein the outlet apertures are located at an angle to one another.
6. A composting unit according to claim 5, wherein the outlet apertures are offset at an angle of 45 degrees to one another.
7. A composting unit according to claim 4, 5 or 6, wherein the outlet connector comprises a Y-shaped connector.
8. A composting unit according to any one of claims 2 to 7, wherein the air supply pipe comprises a braided pipe.
9. A composting unit according to any one of the preceding claims, wherein the air compressor is operable to provide compressed air at a pressure of at least 200 mbar.
10. A composting unit according to claim 9, wherein the air compressor is operable to provide a flow rate of at least 50 litres/minute.
11. A composting unit according to any one of the preceding claims, wherein the air compressor comprises a pulsation free air compressor.
12. A composting unit according to any one of the preceding claims, wherein the air compressor is attached to an external surface of the composting vessel.
13. A composting unit according to claim 12, wherein the air compressor is located within a housing attached to an external surface of the composting vessel.
14. A composting unit according to any one of the preceding claims, wherein the lid comprises a pivotable lid.
15. A composting unit according to any one of the preceding claims, wherein the composting vessel comprises a wheeled bin.
16. A composting unit according to claim 15, wherein the wheeled bin is in accordance with European standard DIN EN840.
17. A composting unit according to claim 15 or 16, wherein the aperture in the base of the composting vessel comprises a drainage aperture in the base of the wheeled bin.
18. A composting unit according to any one of the preceding claims, further comprising an electronic controller for controlling the operation of the air compressor.
19. A composting unit according to claim 18, wherein the electronic controller further comprises a temperature sensor operable to measure the temperature in the internal volume of the composting vessel.
20. A composting unit according to claim 19, wherein the electronic controller is operable to record data from the temperature sensor.
21. A composting unit according to any one of claims 18 to 20, wherein the electronic controller comprises a programmable logic controller.
22. A composting unit according to any one of the preceding claims, further comprising an insulation layer around at least a pad of the external surface of the compost bin.
23. A composting unit according to claim 22, wherein the insulation layer is provided on the sides and lid of the composting vessel.
24. A composting unit according to any one of the preceding claims, wherein the composting vessel comprises an internal structure including a floor spaced from the base of the composting vessel.
25. A method of decentralised composting utilising a composting vessel comprising a base, side walls and a lid, the composting vessel defining an internal volume into which matter for composting can be placed, the method comprising the steps of: placing waste matter for composting into the internal volume; and utilising an air compressor to supply compressed air into the internal volume of the composting vessel through an aperture formed in the base of the composting vessel to accelerate composting of waste matter.
26. A method according to claim 25, wherein the compressed air is supplied to the composting vessel through air supply pipe connected at a first end to the air compressor and a second end connected to the aperture formed in the base of the composting vessel.
27. A method according to claim 25 or 26, wherein the air compressor is operable to provide compressed air at a pressure of at least 200 mbar.
28. A method according to claim 27, wherein the air compressor is operable to provide a flow rate of at least 50 litreslminute.
29. A method according to any one of claims 25 to 28, wherein the composting vessel comprises a pivotable lid.
30. A method according to any one of claims 25 to 29, wherein the composting vessel comprises a wheeled bin.
31. A method according to claim 30, wherein the wheeled bin is in accordance with European standard DIN EN840.
32. A method according to claim 30 or 31, wherein the aperture in the base of the composting vessel comprises a drainage aperture in the base of the wheeled bin.
33. A method according to any one of claims 25 to 32, further comprising the step of: controlling the air compressor utilising an electronic controller.
34. A method according to claim 33, wherein the electronic controller further comprises a temperature sensor and the method further comprises the step of: measuring the temperature in the internal volume of the composting vessel.
35. A method according to claim 34, further comprising the step of: recording data from the temperature sensor.
36. A method according to any one of claims 33 to 35, wherein the electronic controller comprises a programmable logic controller.
37. A compost bin substantially as hereinbefore described and/or illustrated with reference to the accompanying drawings.
38. A method of composting substantially as hereinbefore described and/or illustrated with reference to the accompanying drawings.Amendments to the claims have been filed as follows:CLAIMS1. A composting unit, comprising: a wheeled mobile waste container comprising a base, side walls and a lid located at an upper end of the mobile waste container, the mobile waste container defining an internal volume into which matter for composting can be placed the internal volume being free from internal support structures and the lid being pivotable to enable matter to be introduced into, and removed from the internal volume through an aperture at the upper end of the mobile waste container, and the mobile waste container being tippable to facilitate removal of matter from the internal volume through the aperture at the upper end, wherein the composting unit further comprises an electric air compressor arranged, in use, to inject compressed air continuously at a pressure of at least 200 mbar directly into the internal volume of the mobile waste container adjacent the base through a drainage aperture formed in the base of the mobile waste container, wherein the drainage aperture is operable to function as an air inlet to the waste container when in fluid connection with the air LI') compressor and as a drainage outlet for liquid evacuation when not in communication with the air compressor. C?)0 2. A composting unit according to claim 1, further comprising an air supply pipe 0 20 connected at a first end to the air compressor and a second end connected, in use, to C?) the drainage aperture formed in the base of the wheeled mobile waste container.3. A composting unit according to claim 2, wherein the second end of the air supply pipe comprises a shaped outlet connector extending into the portion of the internal volume of the wheeled mobile waste container adjacent the base.4. A composting unit according to claim 3, wherein the outlet connector comprises at least two outlet apertures for introducing compressed air directly into the internal volume of the wheeled mobile waste container.5. A composting unit according to claim 4, wherein the outlet apertures are located at an angle to one another.6. A composting unit according to claim 5, wherein the outlet apertures are offset at an angle of 45 degrees to one another.7. A composting unit according to claim 4, 5 016, wherein the outlet connector comprises a Y-shaped connector.8. A composting unit according to any one of claims 2 to 7, wherein the air supply pipe comprises a braided pipe.9. A composting unit according to any one of the preceding claims, wherein the air compressor comprises a pulsation free air compressor.10. A composting unit according to any one of the preceding claims, wherein the air compressor is attached to an external surface of the wheeled mobile waste container.11. A composting unit according to claim 10, wherein the air compressor is located within a housing attached to an external surface of the wheeled mobile waste container.LI') 12. A composting unit according to any one of the preceding claims, further comprising an electronic controller for controlling the operation of the air compressor. CY)2013. A composting unit according to claim 12, wherein the electronic controller further c comprises a temperature sensor operable to measure the temperature in the internal C, volume of the wheeled mobile waste container.14. A composting unit according to claim 13, wherein the electronic controller is operable to record data from the temperature sensor.15. A composting unit according to any one of claims 12 to 14, wherein the electronic controller comprises a programmable logic controller.16. A composting unit according to any one of the preceding claims, further comprising an insulation layer around at least a part of the external surface of the wheeled mobile waste container.17. A composting unit according to claim 16, wherein the insulation layer is provided on the sides and lid of the wheeled mobile waste container.18. A method of decentralised composting utilising a wheeled mobile waste container comprising a base, side walls and a lid located at an upper end of the mobile waste container, the wheeled mobile waste container defining an internal volume into which matter for composting can be placed, the internal volume being free from internal support structures and the lid being pivotable to enable mailer to be introduced into, and removed from the internal volume through an aperture at the upper end of the waste container, the mobile waste container being tippable to facilitate removal of composted matter from the internal volume through the aperture and the method comprising the steps of: placing waste matter for composting into the internal volume through the aperture at the upper end; and utilising an electric air compressor to supply, in use, compressed air continuously at a pressure of at least 200 mbar into the internal volume of the wheeled mobile waste container adjacent the base through a drainage aperture formed in the base of the wheeled mobile waste container to accelerate composting of waste matter; composting the waste matter; and LI') removing composted waste matter from the internal volume of the wheeled mobile waste container through the aperture at the upper end of the mobile waste C) container.O 20 19. A method according to claim 18, wherein the compressed air is supplied to the C) wheeled mobile waste container through air supply pipe connected at a first end to the air compressor and a second end connected to the drainage aperture formed in the base of the wheeled mobile waste container.20. A method according to any one of claims 18 to 19, further comprising the step of: controlling the air compressor utilising an electronic controller.21. A method according to claim 20, wherein the electronic controller further comprises a temperature sensor and the method further comprises the step of: measuring the temperature in the internal volume of the wheeled mobile waste container.22. A method according to claim 21, further comprising the step of: recording data from the temperature sensor.23. A method according to any one of claims 20 to 22, wherein the electronic controller comprises a programmable logic controller.24. A compost bin substantially as hereinbefore described and/or illustrated with reference to the accompanying drawings.25. A method of composting substantially as hereinbefore described and/or illustrated with reference to the accompanying drawings. IC)COCO