An example of a waste treatment system in the form of a decomposition toilet is described in GB-A-2248641. This describes a toilet, particularly for use in a passenger vehicle, comprising a mass receiving chamber and a heat exchanger which heats the decomposing material at the base of the chamber. Stirring means, operable in two directions, stir decomposable material in the chamber in a first direction to thoroughly mix the material and ensure sufficient decomposition, and in a second direction to enable the chamber to be emptied completely. Emptying is achieved by reversing the direction of rotation of the stirring means, causing most of the material to pass through a permanent opening into a disposal chamber. There is no need for further heating in the disposal chamber because the material is heated to between 45°C and 80°C in the decomposition chamber, and the chamber is only emptied when full pasteurisation has taken place. After emptying, the decomposition chamber is re-seeded with new compost.

A similar type of decomposition toiled is described in WO-A-80/00962.

GB-A-1489974 and SE-A-368699 describe decomposition toilets with stirring means, rotatable in one direction, which move decomposed material through an opening closable by means of a hatch. When the hatch is opened, the decomposition chamber is emptied completely, and the chamber must be re-seeded with new compost prior to further use.

These conventional composting toilets have a number of disadvantages. Firstly they require a second chamber into which the composted waste is transferred prior to an emptying operation. This chamber may be equipped with a second heater which is used to pasteurise the waste prior to disposal. The provision of a second chamber adds to both the cost of the toilet and adds greatly to its size as

a small chamber would require frequent emptying. A second disadvantage is that an opening is required between the decomposition and disposal chambers and this can become blocked particularly if non-biodegradeable items such as drinks cartons and other refuse are deposited into the decomposition chamber. Such refuse can also jam the stirring means. The emptying process cannot take place until this debris is removed and in certain circumstances it may be necessary to dismantle the toilet in order to correct the problem. The risk of blockage can be reduced by using the stirring means to move material away from the opening but this reduces the effective capacity of the chamber.

In accordance with the present invention waste treatment apparatus is provided having a housing; a chamber supported by the housing in which waste material is decomposed; a stirrer for stirring the contents of the chamber; and heating means for heating the contents of the chamber characterised in that the chamber is mounted to the housing in a manner allowing it to be removed and the contents emptied.

The problems encountered by conventional composting toilets are overcome by the present invention in that a single removable decomposition chamber is provided which is easily removed from the housing allowing emptying and thereby negating the need for a second chamber. This invention provides advantages in that only a simple change of dimensions is required to increase its capacity, the volume of the decomposition chamber is typically greater in comparison with the total volume of the toilet, and greater simplicity reduces manufacturing costs.

The stirrer could be operated manually but preferably is powered with a motor. In addition the stirrer is preferably permanently mounted within the decomposition chamber to simplify the emptying procedure but alternatively it could be removable separately.

The heating means is typically situated beneath the removable decomposition chamber and is preferably built into a saddle provided to support the chamber. Although the heating means could be situated inside the chamber this would reduce the chamber's capacity, add to its weight and would require more corrosion resistant materials to be used in the heater's construction.

Preferably level sensing means for example comprising a material level detector is provided to detect when the position of the material within the chamber attains or exceeds a predetermined level. A liquid sensing means comprising a liquid detector is also preferably provided in order to detect the absence of liquid at a predetermined position.

Both the material level detector and the liquid detector are also preferably attached to the removable decomposition chamber.

Typically, electrical connection between the decomposition chamber and the saddle is achieved using a cooperating plug and socket connection means, one of the plug or socket being mounted to the chamber, the other preferably built into the saddle and arranged in such a way that electrical connection is established when the decomposition chamber is correctly placed within the housing. Alternatively this connection may require manual coupling or could be permanent using a cable that is long enough to allow emptying of the chamber.

One or both of the detectors can be directly connected to an indicating means in the case of a manually controlled example. In such an example manual switching of the heating means is required, typically in response to information from at least one of the detectors.

Alternatively the provision of a temperature sensor and a processor allows the temperature of the decomposition chamber to be controlled automatically by controlling the heating means. The operation of the stirrer may also be controlled by the processor.

A display means controlled by the processor may also be provided to display information concerning for example the temperature inside the chamber in addition to indicating when the chamber is full or dried out.

The waste management system described is particularly suitable for use in continuous decomposition toilets for use domestically or for example, in a vehicle.

Some examples of continuous decomposition toilets in accordance with the present invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a cross-section of a first example; Figure 2 is a plan view from above with the lid removed, of the first example; Figure 3 is a second cross-section of the first example; Figure 4 is a cross-section of a second example; Figure 5 is a plan view from above with the lid removed, of the second example; and Figure 6 is a second cross-section of the second example.

A first example of a continuous decomposition toilet with removable decomposition chamber is shown in Figures 1- 3. The toilet comprises a housing 1 containing a heated saddle 2, a detachable lid 3 forming a seat to which a cover 4 is hinged, and a removable decomposition chamber 5.

Other arrangements of seat and cover readily apparent to a person skilled in the art are also envisaged. Composting material is typically continuously decomposed within the decomposition chamber 5. The composting material (not shown) comprises a mixture of seeding material such as vegetable or coir powder which is placed in the chamber prior to use or after emptying, and a mixture of solid and liquid waste. The chamber 5 contains a stirrer 6 which stirs the composting material whilst in the chamber. The stirrer 6 comprises a number of stirring arms 7, for example six, arranged preferably equally spaced and attached, circumferentially around a split axle 8 mounted

in opposing walls of the chamber 5. The stirring arms 7 are approximately"U"shaped, the bottom section of the"U" being of substantially similar length to the distance between the ends of the composting chamber. The stirrer 6 is driven by a motor 9 and a gearbox 10 both mounted to an outer surface of the wall of the decomposition chamber 5.

The shaft 8 could also be driven from a more remote motor via a friction, shaft, chain, belt or gear connection. The bottom surface 11 of the chamber is substantially cylindrical having a radius of curvature only slightly in excess of the radius swept out by the stirring arms 7 ensuring that their action redistributes composting material adjacent to this bottom surface 11. The end panels of the decomposition chamber need not be flat, but may be curved to increase the swept area of the decomposing material exposed to airflow to speed up decomposition. The sloped surface of the material caused by the action of the stirrer 6 is exposed to the air promoting aerobic decomposition, the redistribution of material ensuring that unwanted aerobic decomposition is prevented.

A composting material level detector comprising a light beam, an infra-red beam or any other known method is used to detect when the level of composting material has attained a certain position, typically between one third and halfway up one side of the chamber 5. In this preferred example an infra-red emitter 12 is mounted to one end wall 20 of the decomposition chamber and an infra-red detector 13 is mounted to the opposing end wall 21, in this case in a position just above the level of the stirrer split axle 8. At least the adjacent sections of chamber wall are transparent to the infra-red radiation. In a continuously composting toilet it is important that the composting material remains moist but not liquid and therefore a liquid detector 14 is provided to alert the operator when the chamber is flooding. An opening 15 positioned substantially at the lowest point of the decomposition chamber and covered by a filter such as a

grill, allows liquid from the chamber 5 to contact the liquid detector 14 mounted on the outside of the chamber wall.

Electrical connections between the toilet housing and both the motor and detectors, are provided by male plug connectors 16 attached to the chamber wall and female socket connectors 17 attached to the toilet housing or preferably built into the saddle 2 thereby reducing both the manufacturing and servicing time. Alternatively, the electrical connection may be achieved by replacing connectors 16,17 with more flexible versions requiring manual coupling. This avoids reliance upon the accurate positioning of the chamber to align and engage the connectors. In such a case, either or both connectors might be connected to the housing or the chamber with a cable. Examples of such alternatives include using a socket and power lead system as found in domestic appliances such as a kettle or using a conventional plug and socket as might be used to supply power to a lamp. A permanent electrical connection between the chamber 5 and the housing 1 or saddle 2 could also be provided for example using a cable long enough to allow removal and emptying of the chamber 5 whilst remaining connected.

Figure 2 shows a plan view of the toilet housing 1 with the decomposition chamber 5 fitted in the correct position for use. In this example correct repositioning of the chamber following removal is achieved using guides 18 attached to this housing (not shown in Figure 1). These hold the chamber firmly in position and ensure that the electrical connectors 16,17 of both the chamber and the housing engage correctly on replacing the emptied chamber.

The guides could be provided adjacent to or as part of the saddle 2 to achieve similar correct alignment of the connections 16,17. Alternatively the chamber 5 and saddle 2 could be held together using any known fastening method, for example catches could be attached to the saddle 2 in order to hold the chamber 5 in contact with the saddle 2.

Power may be supplied to the toilet, typically from an external source, by any known method such as using a simple cable and plug or preferably using a socket 19 and a power lead (not shown in the Figure) as described above.

The front and rear chamber walls 20,21 are provided with handles which in this example are simply formed by holes 22 (Figure 3) cut centrally at a position close to the top of each of these walls. The handles allow easy removal of the decomposition chamber assembly including the chamber 5 itself, the internal stirrers 7, the motor 9, gearbox 10, attached detectors 13,14 and male electrical connector 16.

On replacing the emptied chamber 5, the guides 18 direct the chamber onto the saddle 2 which preferably forms part of the toilet housing 1. The upper surface of saddle 2 is also formed in a cylindrical manner so as to have a substantially complementary upper surface to the bottom external surface of chamber 5. A heating means 23 forms the upper surface of this saddle, engaging directly with the base of the chamber 5. The heating means may be attached to or built in to the saddle 2. Alternatively the heating means 23 may be attached to the outside of the base of the compost chamber 5. In this example the heating means 23 is built into the saddle 2 and comprises a simple electric filament heater but alternatively any other suitable known heating method could be used such as a gas heater or hot water for example. This is required to maintain the temperature in the chamber between approximately 45°C and 80°C, the thermophilic temperature range, in which decomposition and pasteurization occur. The heating means 23 can also be used to evaporate excess liquid which is detrimental to the composting process. A sudden influx of liquid is also undesirable in that it can reduce the temperature in the chamber 5. This could be detected for example with a second liquid detector. In the present example control of the heating means 23 is achieved using manually operated switching means 29 and visual

inspection is required to detect any excess liquid. A device such as a thermostat 50 could be additionally provided to control the operating temperature.

The detachable lid 3 contains an air vent or vents 26 as shown in Figure 1, to allow aerobic composting of the material. A fan (not shown) may also be provided for enhanced aeration of the material. Fasteners 27 (Figures 2 and 3) attached to the side walls of the housing and/or the saddle and/or the lid are used in such a manner that the decomposition chamber 5 beneath is pressed against the heating means 23 promoting the required good thermal contact. These fasteners may for example take the form of clips or any similar known method, the preferred method in this example being the use of industrial velcro, as shown in Figures 2 and 3.

A display unit 28 also coupled to the detectors 13,14 and attached to the outer surface of the housing 1 indicates to the operator when the decomposition chamber requires emptying or has dried out. The display may alternatively be positioned within the housing if the toilet might become subjected to vandalism. The display unit 28 may constitute one or more lights, light emitting diodes, a liquid crystal display or any other means for providing information to an operator. In this manually operated example of a composting toilet, light emitting diodes are used to indicate when the chamber requires emptying or has dried out. A switch 29 is provided to control the heating means 23 and could additionally be used for controlling the stirrer 6. Such a switch 29 could be provided by any known method but preferably would be achieved using switches mounted adjacent to the light emitting diodes. In this example a switch 30 controls the heating means, a switch 31 controls the stirrer 6 and a switch 32 is a power ON/OFF switch, as shown in Figure 2.

In a second example of the present invention shown in Figures 4-6, an automated composting toilet is provided for use with a motor vehicle. In this case the heating means

23 comprises a heat exchanger containing a fluid heated in a fluid jacket by the cooling system of an engine of the vehicle although any other system deliberately or coincidentally dissipating heat into such a fluid could be used, for example the cooling fluid from a lubricating system. Fluid flows to and from the heating means via pipes 40 and 41 as shown in Figures 4 to 6. In Figure 4 a temperature sensor 24 is also provided forming part of the bottom of the decomposition chamber 5. Automation of the composting toilet is achieved using a control processor 25 which controls the operation of the stirrer 6 and the heating means 23 in response to signals from the detectors 13,14,24 to produce the optimum composting conditions for the material. In the preferred example the display comprises a liquid crystal display 37 attached to the toilet housing 1. Figure 6 shows the position of the display 37 although the display 37 could be provided internally, for example attached to an inner surface of the housing 1. Manual operation of the system is achieved using buttons 34,35,36 of a control means 33 attached at a position adjacent to the liquid crystal display 37. The buttons allow the operator to manually override or adjust the functions of the processor in association for example with choices displayed on the display means. For example such functions might include control of the target temperature within the system and the speed or frequency with which the stirring means is operated. Buttons 34 and 35 move a cursor up and down respectively through the choices displayed on display means 27 whereas button 36 is used for selection of a particular choice.

Prior to emptying the chamber it is desirable to pasteurise the material to destroy any noxious organisms.

Pasteurising takes several hours and although this could be controlled by manually timing and operating the heating means 23, the process could be simply automated using a timer coupled to or forming part of the control processor 25. The completion of a pasteurising procedure could be indicated by the display means 37 or alternatively a device could be provided to alert the operator audibly.