GB2494192A - Two composters - Google Patents

Abstract

A first composter (Fig. 1) comprises an above ground solar chamber with an access lid and a below ground digestion basket which forms a base for the chamber. The basket is substantially cuboid with an open top and is made from wire mesh with a mesh structure on its wire base to provide air pockets under compost in the composter. Also a wire mesh barrier can be located in the ground around the basket. A second composter comprises a tray 36 located below a composting chamber 56, and hydrophilic matting 42. Leachate collected in the tray 36 is wicked or pumped into the matting 42 from where it evaporates. In figure 7 leachate is pumped into an annular reservoir 40 located around a lid 52. Leachate is then wicked from the reservoir. The lid 52 provides access to the composting chamber 56 and has a solar panel 50 mounted thereon which provides electricity for operating a fan 44 used to assist evaporation and a pump 38 used for pumping the leachate.

Description

Composter The present invention relates to a composter, and in particular composters with improved composting efficiency.

Background

There are two basic approaches for dealing with household food waste, namely collection and treatment at a centralised facility and household treatment using systems referred to by a variety of names such as household food waste digesters or composters. A range of household treatment methods is available on the market, which includes aerobic composting methods, wormeries and anaerobic fermentation systems. However, household food waste should not be put into the traditional unsealed, garden compost bin, particularly non-green food waste, because of a number of health, safety and environmental issues. These include attracting vermin and potential access, through animal and human activity, to the surface soil around the compost bin and the compost material itself However, other organic materials can be included in some food waste composters.

The Green Cone food waste composter as originally disclosed in BP0449927 was a purpose designed and built unit that can be located in a household's garden for the disposal of all food waste, including vegetable scraps, raw and cooked meat or fish, bones, dairy products and other organic food waste such as bread and pasta. It operates as a passive, continuous feed, aerobic system, where the primary products of the decomposition process are water, carbon dioxide and a small residue of humic substances comprising lignin and protein remains. The Green Cone system fulfils the waste management objectives of volume reduction, sanitation through the destruction of pathogens and stabilisation of the residue end product. It was placed on the market, and tens of thousands of units were sold worldwide.

That original design, although effective, had various inefficiencies. The present applicant, however, has identified a number of developments that can be applied to it, or to other composting systems, to offer a range of improvements to composting efficiency.

Operation and function of the prior art Green Cone System The function of the Green Cone has been to: * Accelerate the natural decomposition process by raising temperatures; -maintaining aerobic conditions; and -encouraging the growth of micro-organisms.

* Contain and enclose the food waste to prevent dispersion and eliminate odours.

* Create barriers to human, farm animal, wild animal, pet and bird activity.

* Prevent surface and top soil contamination.

* Meet all relevant health, safety and environmental legislation.

The Green Cone food waste composter (hereinafter the "Green Cone") has been a four-part plastic injection moulded system comprising a digestion basket that is installed below ground and which forms the base for an above ground double-walled solar chamber with an access lid.

The design of the Green Cone utilises solar heating in the double-walled chamber to facilitate and accelerate the aerobic decomposition process within the digestion basket.

The nominal dimensions of the existing Green Cone are as follows. The diameter of the 440 mm deep digestion basket is 550 mm at the top and 400 mm at the bottom. A series of slots designed into the basket commence 190 mm below ground level and effectively remove about half of the side wall and base material. The inner and outer walls of the conical solar chamber are 20 mm part, providing a gap that is open at the top and bottom of the unit. The diameter of the outer chamber reduces from 550 mm at its base to 285 mm at the lid end. The chamber is 680 mm high but when assembled and installed, the Green Cone stands 650 mm above ground level and extends 460 mm below ground level. Access is through a 200 mm diameter hole in the top of the solar chamber, which is sealed by a hinged lid with a twistlock security catch.

A Green Cone will dispose of up to about 5 kg of food waste a week. In a well operating system the residue will occupy the bottom part of the digestion basket after the decomposition of about a twine of food waste. This small quantity of residue must be removed and dug into the garden sub-soil after a few years of operation.

The successful decomposition of food waste in a Green Cone is a function of a range of external factors: * Temperature and level of direct sunlight.

* Rainfall, drainage and moisture ingress into the digestion basket.

* Fertility of waste and soil (pH. minerals, fauna, organisms and micro-organisms).

* Uniformity and stability of aerobic conditions.

* Composition of the food waste.

* Quantity and rate of the food waste input to the system.

The Green Cone above ground chamber fulfils a number of functions: * Containing the food waste.

* Ensuring secure access for the disposal of the food waste.

* Providing a barrier to human, animal, bird, reptile and insect activity.

* Protecting the decomposing food waste from the elements, particularly rainfall.

* Preventing the release of odours.

* Preventing the release of airborne biological aerosols and endotoxins.

* Raising the teniperawre in the below ground digestion basket to improve the efficiency of the decomposition process.

* Creating air circulation to assist in maintaining aerobic conditions.

* Maintaining distance between the decomposing food waste and the user to avoid visual and physical contact.

As with the above ground chamber, the Green Cone digestion basket fulfils a number of functions: * Containing the food waste.

* Being of sufficient size to store the food waste during the periods when the temperature is not high enough to support significant decomposition.

* Providing a barrier to human, animal, bird, reptile and insect activity.

* Assisting in maintaining aerobic conditions.

* Preventing the release of odours.

* Limiting the ingress of rainfall.

* Avoiding the contamination of surface water.

* Allowing free drainage.

* Allowing the movement of organisms in and out of the basket.

* Providing an "anchor" for the upper chamber.

The prior art Green Cone, however, has now been developed further, and in that regard a first aspect of the present invention provides: A digestion basket for a food waste composter, the digestion basket being for installation below ground and forming a base for an above ground solar chamber with an access lid, the digestion basket being substantially cuboid, with four sides, a base and an open top. The open top is covered by the solar chamber, once installed thereover, but the basket remains open at the top, for receiving the food waste.

Prior art digestion baskets were always cone shaped (frustoconical) or cylindrical. Examples of such prior art digestion baskets are shown in EP0449927. Those prior art shapes were helpful for an ease of assembly of the solar chamber onto it, since the shapes generally matched.

Preferably the digestion basket is supplied together with the solar chamber, so as to be supplied as a food waste composter. Preferably that solar chamber is double-walled.

Other features of the so'ar chamber, and the basket, can be in accordance with features disclosed in EP0449927, its disclosure therefore being incorporated herein by way of reference.

Preferably the digestion basket is provided in a flat-pack condition, rather than in a preformed or prefabricated "in-use" shape. For that purpose, each side can be disconnectable from, or foldable relative to, one or more of the adjacent sides, or the base.

This invention performs all the functions of the existing Green Cone digestion basket (the Mark I basket), but it can include or facilitate additional features or capabilities. These features or capabilities can be related to any one or more of its delivery, installation, operation and

applicability.

The new shape of digestion basket for the Mark II Green Cone digestion basket can offer the following improvements and benefits: * Increased basket volume to provide a greater throughput for large multi-occupancy households, groups of households and small institutions and commercial premises with a suitable enclosed outdoor space.

* Increased basket surface area to volume ratio for improved aeration and performance.

* The new basket shape for simpler installation of both a single unit and clusters of units (for increasing throughput further).

While increasing the surface area to volume ratio increases the potential for aerobic conditions, the balance of heat absorption and losses is affected by both the size and shape of the basket.

Investigations have concluded that a preferred arrangement for the basket is a basket having sides with a length of about 0.55m. Another preferred dimension for the sides is a depth of about O.4m. Preferably the sides are about O.55m long and O.4m deep, and the base is preferably about O.55m square.

Preferred dimensions, such as those above, provide a significant volume increase for the basket for a similar surface area to volume ratio for the food waste/compost, relative to the existing conical Green Cone basket. However, the changing shape of the continuous-feed compost pile and the physical constraint imposed by the digestion basket are significant factors in terms of the actual ratio and the degree of aeration achievable. Testing of the square digestion basket however, has shown a tendency of the deposited food waste to form a cone shape that levelled and spread during the decomposition process. Nevertheless, a benefit of a square Mark II digestion basket relative to the round Mark I basket is that an air region is maintained around the pile for some time during the decomposition cycle, particularly at the corners, since levelling is not instantaneous.

In preferred embodiments of the present invention the square digestion basket could incorporate a mesh structure built into the base to create air pockets under and within the compost pile.

These would improve aeration ftrther. With this approach, the volume could be increased significantly while at the sane time providing an improvement in aeration overall.

The Green Cone system should not attract vermin and animals such as badgers and foxes as no smells come from the sealed system if properly installed and operated. However, vermin and other animals could be attracted if food waste is spilt near the system during disposal. In addition, burrowing vermin, such as rats, could unintentionally come across the underground digestion basket. Rats can readily chew through the side walls of a plastic digestion basket, particularly in a slotted region, even though such features are preferred for ease of manufacture or for cost purposes. However, especially for areas that experience a large number of vermin, a preferred arrangement is for a wire mesh barrier to be installed around the digestion basket to prevent access to the Green Cone. This results, however, in additional complexity, and increased cost of production and delivery of a purpose designed and built system. This in turn can make this an unattractive solution. The present invention therefore further provides a digestion basket made directly from wire mesh. Unlike prior art round, nioulded, plastic digestion baskets, the wire mesh digestion basket is particularly suited to be supplied fiat-packed. This reduces the costs of production and delivery.

In preferred arrangements of the present invention, the digestion basket can be assembled without screwdrivers or spanners, for example using a specially designed fastener system, or wire/crimp connections.

The present invention also provides a digestion basket that is constructed of vermin proof material, such as impregnated plastics, metal wire or cut metallic-sheet materials.

The present invention also provides a connection mechanism between a below-ground digestion basket and an above ground solar chamber with an access lid, whereby a simplified removal of the upper chamber from the basket, for access to the compost residue, is achieved.

Preferably the connection mechanism comprises four corner brackets, each with mesh attachment lugs. Preferably a sloping surface is incorporated into the brackets, from the mid-edge of each side to each corner. This is to assist in rainwater removal.

In use, the brackets are installed on top of the basket, but still below the surface of the soil, preferably just below the surface.

Prcferably the connection mechanism comprises boltless clips for clipping the upper inner and upper outer chambers to the basket, or to the brackets at the top of the basket. Preferably only four clips are required. Preferably the clips can clip or connect flanges on the upper inner and upper outer chambers to the basket, otto a flange on the brackets at the top of the basket.

Preferably an odour barrier is incorporated around the upper portion, or half, of the basket.

Preferably the odour barrier is a polypropylene panel. Preferably it is about 1.5mm thick.

Preferably it lines the inside of the upper portion of the basket. It can be held in place by clips.

The present invention also provides a block of such baskets installed in the ground in an array, or in a line, all in a single hole or a single trench. In such arrangements, preferably the baskets are each formed primarily from metal materials, such as steel.

It is also to be observed that composting systems produce a liquid that is either collected or allowed to drain into the surrounding environment. It is important to contrast the liquid that exits well-managed household composting systems and the leachate generally associated with waste management operations. Leachate is described by a range of definitions, such as a liquid that has been polluted or made toxic by percolating through or draining from rubbish or hazardous waste. Legislation requires that leachate from large-scale waste treatment systems is collected and suitably treated to remove or destroy any contaminants. This does not generally apply to household composting systems.

Leachate from large-scale waste treatment systems could cause a range of environmental and health problems. The most significant environmental issue is its potential to lower the dissolved oxygen content of a watercourse. Leaehate normally contains high concentrations of dissolved nutrients and these act as a food source for aerobic aquatic micro-organisms. As a result, these organisms grow rapidly and consume large amounts of oxygen. This reduces the dissolved oxygen in the water, which seriously affects an aquatic ecosystem. Leachate can also cause pollution by introducing poisonous heavy metals or depositing materials that physically cover species, preventing them from breathing or receiving the sunlight required for photosynthesis.

In terms of the risks to human health, the hazardous and non-hazardous components may render an aquifer unusable for drinking-water purposes and other uses.

Free draining household composting systems are located outside, usually in the household's garden. The decomposition of garden and food waste produces a significant quantity of water.

A fraction of this water evaporates from the system, some remains within the waste matrix and the remainder drains into the surrounding soil. The extent to which the compost pile is open to the elements and the level of rainfall will affect the total quantity of water draining into the soil and the degree of leaching. Maintaining a suitable moisture content of the compost pile is important to the efficiency of the decomposition process. However, achieving this for all the prevailing conditions during the decomposition process in a passive system is extremely difficult. The moisture content is largely a function of the mix of feedstock materials. However the moisture content is also affected by the efficiency of the decomposition process, which is & influenced by the variability of the weather conditions e.g. ambient temperature, level of direct sunshine and amount of rainfall.

Household composting systems that include food waste in the feedstock have the potential for producing a liquid that is contaminated. The liquid draining from a household composting system will have been in contact with the decomposing food waste and potentially contain varying levels of nutrients and minor contaminants. The liquid may migrate into the soil surrounding the system and downwards through the unsaturated zone to the water table and the saturated zone of an aquifer, where it follows the hydraulic gradient of the groundwater.

Food sold as fit for human consumption may contain contaminants that pose a potential health hazard. Contamination can also occur during food storage and preparation. Waste food may be further contaminated through being left uncovered or being disposed of with other organic and inorganic substances.

The potential health hazards in food waste are pathogenic organisms (pathogens), prions that result in Transmissible Spongiform Encephalopathies (TSEs) or chemicals, such as pesticides and antibiotics. Foodborne illness is usually caused by food contaminated by pathogens such as bacteria, viruses and parasites, or their toxins.

A large proportion of animal products carry particular pathogens and the food implicated in an outbreak of food poisoning is usually undercooked meat, poultry, seafood or unpasteurised milk. There are also increasing concentrations of antibiotic-resistant bacteria in agricultural animals resulting from the therapeutic and growth-promotion use of antibiotics in animal production.

Outbreaks of intestinal infections in humans have also been associated with pathogens ingested with vegetables and fruit. Some of these pathogens are naturally present in soil and their occurrence on produce is not uncommon. Animal manure is generally used more frequently in organic production than in conventional fruit and vegetable production, although it is not proven that the risk of contamination is higher for organic foods. Contamination of fruit and vegetable crops with pathogens from manure may take place via the roots, by splashing water from the ground onto leaf surfaces, by direct contact of the leaves with manure or transmission by soil organisms. Enteric pathogens can reside on or inside the plants.

Meat or other products of animal origin fit for human consumption are classified as low risk animal by-products. Raw meat is the most likely fraction of food waste to contain the highest levels of pathogens and therefore only the off-outs from normal household food preparation should be disposed of in a household food waste composter. The thorough cooking of food destroys most of the organisms responsible for foodborne illness and can be used as a strategy to minimise the number arid range of pathogens in the food waste.

Limited national and international guidelines are available for the siting of household composters. On the basis of the requirements for large scale operations and human and pet burial sites, the siting of a composter in the vicinity of standing or running surface water (e.g. lake, pond, drainage ditch, river or spring) and ground water abstraction (e.g. well or borehole) may require a site specific risk assessment when: * There are a significant number of other composting systems in the area.

* The proposed site is particularly close to sources of non-potable surface water or there are significant local features, such as steep gradients, raised beds or extensive periods of heavy rainfall in the area.

* The proposed site is close to a water source used to supply potable water.

Responsible suppliers of free draining household coinposting systems mitigate the health and environmental threats from the potentially contaminated liquid by the design of the system and issuing guidelines for users. For example, with the Green Cone system the health and environmental threats are mitigated by: * The Green Cone being dedicated to food fit for human consumption that is not contaminated by external sources, i.e. no other organic (e.g. faeces, paper, garden waste) and inorganic (glass, metal, plastic, household disinfectants and drugs) materials or substances are disposed of in the Green Cone.

* Raw meat, which is the most likely fraction of food waste to contain the highest levels of pathogens, only accounting for a small percentage of the typical mix of household food waste.

* The effectiveness of the decomposition process in pathogen destruction and contaminant degradation.

* The very small quantities of water, nutrients, pathogens and contaminants leaving the system.

* The design of the sealed Green Cone system to limit the ingress of rainfall and potential leaching.

* The design of the below ground digestion basket to protect surface water.

* The siting of the Green Cone in areas with low water tables and that are not susceptible to surface and ground water flooding.

* The siting of the Green Cone in ground areas with high natural physical, chemical and biological pollutant attenuation capacity.

* The siting of the Green Cone in areas with intergranular ground water flow.

* The siting of the Green Cone at appropriate distances from standing or running surface water, such as a lake, pond, drainage ditch, river or spring. It should not, therefore, be installed on a very steep slope, on a raised bed or within the maximum potential migration distance to the surface water.

* The siting of the Green Cone at appropriate distances from where surface water source or ground water abstraction is used to supply potable water for human consumption, such as wells, boreholes or springs.

The requirement for users of garden compost systems to interpret and apply the siting guidelines is a major shortcoming of such systems> in particular where there is a need for a site-specific risk assessment. This invention allows composting systems to be sited in a wider range of locations and removes the need for many of the guidelines. In addition to eliminating potentially contaminated liquid from leaving the composter, the invention increases the overall performance of the system by improving the moisture content, temperature distribution and aeration of the compost pile.

The present invention therefore also provides a system by way of which contaminates can be removed from the leachate through evaporation, allowing the contaminants to be captured and clean water to exit the system. According to the present invention there is therefore provided a composting system in which a tray is located beneath a location for the waste pile in the composting system, the tray being for collecting leachate, and through capillary action or pumping the leachate is wicked or pumped onto a hydrophilic matting material, which acts as an evaporation surface for the leachate.

In a preferred arrangement, a fan is also provided, preferably directed at the evaporation surface.

The fan can further improve the rate of evaporation. The fan can also provide additional advantages.

The resulting evaporated water, which will be free, or substantially free, of contaminants, can be arranged to exit through aeration holes provided for that purpose within the systemlcomposter.

Alternatively, or additionally it can condense and run down an inner surface of the system to the base of the system, and away.

This type of system would eliminate or substantially reduce the amount of pathogens and other contaminants in the leachate that exits the system. However, volatile organic compounds that can be present, albeit generally in minimal quantities (if any) in a household system, could still evaporate and condense with the water. Such exiting quantities, however, are not of a sufficient volume to present an environmental risk in a household environment, This aspect of the present invention is therefore provided to remove, or substantially remove, contaminants from the leachate that exits the system. Further it offers three additional benefits.

Since oxygen is consumed and carbon dioxide is generated in the aerobic composting process, the oxygen needs to be continuously replenished. Appropriately installed, the evaporation system, and particularly a fan assisted evaporation system, can be an aid to maintaining aerobic conditions by removing the by-product gases and introducing fresh air into the system. The fan can also be used to improve the temperature distribution, and to reduce the moisture content of the compost pile.

Depending on requirements, the invention allows for a range of options, which include in common or separate embodiments: 1. Under-pile leachate treatment systems comprising a leachate collection tray, a wicking and evaporation surface and an evaporation fan, the fan being located under the compost pile.

2. Low-pile leachate treatment systems comprising a leachate collection tray, a wicking and evaporation surface and an evaporation fan, the fan being located on the inner chamber wall at a low-pile height governed by the wicking efficiency of the hydrophilic matting material.

3. Mid-pile leachate treatment system comprising a leachate collection tray, a pump to raise leachate to a reservoir at the top of the system, a wicking and evaporation surface and an evaporation fan, the fan being located on the inner chamber wall at a mid-pile height.

Outdoor free-draining systems using any of the above options are the usual arrangement. They would allow the condensed clean water to drain from the system into the surrounding soil.

Indoor and outdoor collection systems can also be provided, again using any of the above options, They would collect the condensed clean water for disposal in the garden or sewage system.

The fan, and where provided the pump, may be operated using either mains or solar power.

Solar power systems may incorporate a rechargeable battery to allow the device(s) to operate when insufficient solar energy is available.

The various aspects of the invention fnay be used all together, or in isolation of the others.

These and other features of the present invention will now be described in greater detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 schematically shows a square wire mesh digestion basket installed in the ground with an existing green cone solar chamber mounted above it; Figure 2 shows side and base basket attachment brackets and a mode of assembly; Figure 3 shows upper basket attachment brackets; Figure 4 shows upper basket attachment brackets and an inner chamber assembly; Figure 5 shows an odour barrier attachment system; Figure 6 shows upper chambers and basket securing system; and Figure 7 shows a free draining household composter with a leachate treatment system.

Referring first of all to Figure 1, the Mark II digestion basket 10 comprises a 0.55 m square base 12 and four side walls 14, each 0.55 m x 0.40 m. The base 12 and four side walls 14 are constructed from a galvanised steel 12.5 mm square mesh made from wire of minimum 0.7 mm diameter. The basket 10 is installed in the ground or soil 20.

The base 12 and four side wall panels 14 are secured together using 8 angle iron supports 16 incorporating fasteners 18 designed for tool-free construction. See Figure 2. These structural brackets or supports 16 also provide sufficient reinforcement at the corners, which are particularly vulnerable to vermin attack. Other connections are also possible, such as a wire or crimp connections. Angle iron supports 16, however, provide a long-lasting solution.

The top edge of the basket 10 is fitted with T-section galvanised steel brackets 22 (Figure 3), again of tool-free design. These novel brackets 22 are specifically designed and sized to provide the structure for securing the inner and outer above ground chambers to the digestion basket, while at the same time maintaining a gap between the two chambers to vent into the square digestion basket as in the plastic Mark I basket. Referring also to Figure 4, four such 1 5 brackets are used per basket.

As well as securing the upper chambers to the digestion basket 10, the attachment brackets 22 fulfil the function of an upper odour and rain barrier. Figures 3 and 4 show that a 5mm slope is incorporated from the mid-edge of each side to each corner. This assists rainwater removal.

Further, when installed, soil covers the upper attachment brackets.

A distance of about 0.2 m of soil is preferred to filter out odours. Thus an odour barrier 24 is incorporated around the upper half of the wire basket 10 adjacent to the soil 20. The upper half of the side walls 14, as shown in Figure 1, and in Figure 5 in more detail, is lined internally with 1.5 mm thick polypropylene panels 24 to provide the odour barrier, each panel 24 being held in place by ten clips 26 as illustrated in Figure 5. As there are four sides, there are four panels 24 in this illustrated embodiments, each panel having dimensions of about 520mm by 180mm, although other arrangements or sizes for the panels 24, such as a single sheet wrapped around the inside of aU four sides, would be within the understanding of a skilled person.

The upper chambers 28, 30 are anchored to the digestion basket 10 using four boltless clips 32, as illustrated in Figure 6. In contrast to the Mark I system, the attachment of the upper chambers to the digestion basket does not require the use of tools. The boltiess clip 32 anchoring system therefore greatly simplifies the removal of the upper chambers for access to the residue every few years.

Another important benefit of the Mark II digestion basket is that it has been found to be easier to install than the existing round Mark I digestion basket. Firstly, it is simpler to dig a square hole than a round hole, and further, the square shape makes it more feasible to use a mechanical digger. Yet further, while the square digestion basket provides some increase in throughput for single households, or larger multi-occupancy households, it greatly increases throughput where multiple units are installed near one another. This is useful for groups of households, small institutions and commercial premises with a suitable enclosed outdoor space, since it is easy to install a group of the new square Green Cone systems side by side, or in a line. A mechanical digger can simply prepare trenches for installing groups of the Mark II Green Cone system there along.

A consequence of such lines or blocks of green cone systems, however, can be an increase in vermin activity, which could have more serious health and financial consequences. However, the Mark II system reduces that problem as a result of its wire mesh, whereby it is particularly applicable to this market.

Although the above embodiment arose from a series of investigations performed in relation to the inter-relationship between the size and shape of the digestion basket required to meet the objectives of improved aeration, increased throughput and simpler installation, for commercial reasons, the developed design was aimed to be compatible with the upper chambers of the existing Green Cone. However, the Mark H digestion basket could also be adapted in size or form, i.e. with different connection mechanisms, for making it suitable for working with other upper chamber designs, as would be apparent to a skilled person.

Referring finally to Figure 7 there is shown a schematic view of a typical system in accordance with the final aspect of the present invention. The illustrated embodiment is a mid-pile leachate treatment system 34 comprising a leachate collection tray 36, a pump 38 to raise leachate to a reservoir 40 at the top of the system, a wicking and evaporation surface 42 and an evaporation fan 44, which is located on the inner chamber wall 46 at a mid-pile height h. This arrangement will generally offer an improved composting performance over other possible arrangements of leachate treatment system because of the location of the fan.

This illustrated system is also an outdoor free-draining system that allows the condensed clean water to drain from the system into the surrounding soil. However, it can be converted to an inside/outside collection system by providing tubes (not shown) from the drainage holes 48 to an external reservoir (not shown).

The schematic embodiment includes a solar panel 50 mounted in the access lid 52 for generating power for the evaporation fan 44 and water pump 38 (wiring not shown).

The system illustrated in Figure 7 comprises the following additional components: * An outer chamber 66 consisting of a circular base and wall 46.

* The diameter of the outer chamber 66 is slightly greater at the bottom than the top to encourage any condensed water inside the system to run down to the water drainage holes 48 -it will lie on the inverted inner surface, and will thus tend to run downwards.

* The top of the chamber contaths slots 54 to allow evaporated water to escape with foul air.

* A compost chamber 56 that can either contain numerous holes or it can be constructed of a mesh material, or both, to assist aeration of the compost pile.

* A leachate collector (tray 36) covered by a debris catch plate 60, which prevents compost debris from reaching the collector 36. The plate 60 can slope from the centre 62 to the edges to direct the leachate to drainage slots 64.

* An electric pump 38 to transfer leachate from the leachate collector 36 to an upper reservoir 40, which can be annular as shown. The pump 38 can contain a safety cut-out for when there is insufficient leachate in the collector to pump.

* The preferably annular reservoir 40 located around the compost chamber 58, at the top of the outer chamber 66, can have an overflow 68 provided to feed fluids back into the compost chamber 58 from the reservoir 40 for occasions when an excessive volume of leachate is present in the system. The reservoir 40 can be arranged to clip together the outer chamber 66 and the compost chamber 58. It can also incorporate a rainproof upper surface to which the access lid can be attached. An overhang from the upper surface can be provided to prevent the ingress of rain through aeration slots 54 in the outer chamber.

* A hydrophilic wicking and evaporation matting material 42 that can be anchored between the reservoir 40 and debris catch plate 62. During the composting cycle, the quantity of contaminants adhering to the matting material will increase to the extent that its efficiency reduces significantly. The matting material will therefore require occasional removal for washing or replacement.

* An electric fan 44 positioned adjacent to the wicking and evaporation matting 42 on the inside 46 of the outer chamber 66.

The use of an evaporation system within a household composter is a novel approach for removing potential contamination from the liquid leaving the composter.

This aspect of the invention can be included into the design of future systems and back-fitted to many existing household composting systems.

The present invention has therefore been described above purely by way of cxample.

Modifications in detail may therefore be made within the scope of the invention as defined by the appended claims.

Claims (1)

1. <claim-text>CLAIMS: 1. A digestion basket for a food waste composter, the digestion basket being for installation below ground and forming a base for an above ground solar chamber with an access lid, the digestion basket being substantially cuboid in use, with four sides, a base and an open top.</claim-text> <claim-text>2. The digestion basket of claim 1, being provided together with the solar chamber, so as to be supplied as a food waste composter.</claim-text> <claim-text>3. The basket of claim 2, wherein that solar chamber is double-walled.</claim-text> <claim-text>4. The basket of any one of the preceding claims, wherein the basket is provided in a flat-pack condition.</claim-text> <claim-text>5. The basket of any one of the preceding claims, wherein the sides have a length of about 0.5 Sm.</claim-text> <claim-text>6. The basket of any one of the preceding claims, wherein the sides have a depth of about 0.4m.</claim-text> <claim-text>7. The basket of any one of the preceding claims, wherein the base is about 0.55m square.</claim-text> <claim-text>8. The basket of any one of the preceding claims, further incorporating a mesh structure built into or onto the base to create air pockets under and within the compost pile when in use.</claim-text> <claim-text>9. The basket of any one of the preceding claims, provided together with a wire mesh barrier to be installed around the digestion basket in the ground.</claim-text> <claim-text>10. The basket of any one of the preceding claims, wherein the sides and base are made from wire mesh.</claim-text> <claim-text>11. The basket of any one of the preceding claims, wherein the sides and the base are connected together, in use, using eight angle iron brackets, one along each joining edge.</claim-text> <claim-text>12. The basket of any one of the preceding claims, wherein a connection mechanism for connecting the basket to the above ground solar chamber comprises four corner brackets, each with mesh attachment lugs for connecting the brackets to the basket, the basket being made of one or more sheets of wire mesh.</claim-text> <claim-text>13. The basket of any one of the preceding claims, wherein a connection mechanism for connecting the basket to the above ground solar chamber comprises a sloping surface incorporated into four corner brackets, each slope extending from a mid-edge of each side to each corner.</claim-text> <claim-text>14. The basket of any one of the preceding claims, wherein a connection mechanism for connecting the basket to the above ground solar chamber comprises boltless clips for clipping the upper inner and upper outer chambers to the basket, or to brackets at the top of the basket.</claim-text> <claim-text>15. The basket of any one of the preceding claims, wherein an odour barrier is incorporated around the upper portion, or half, of the basket.</claim-text> <claim-text>16. The basket of claim 15, wherein the odour barrier lines the inside of the upper portion of the basket.</claim-text> <claim-text>17. A digestion basket for a food waste composter substantially as hereinbefore described with reference to any one or more of Figures ito 6.</claim-text> <claim-text>18. A block of food waste composters, each comprising a basket as defined in any one of the preceding claims, and each basket being installed in the ground either in an array, or in a line, all in a single hole or a single trench.</claim-text> <claim-text>19. A composting system comprising a tray, located beneath a location for the waste pile in the composting system, the tray being for collecting leachate, and adapted such that through capillary action or pumping the leachate will be wicked or pumped onto a hydrophilic matting material, which acts as an evaporation surface for the leachate.</claim-text> <claim-text>20. The composting system of claim 19, further comprising a fan.</claim-text> <claim-text>21. The coniposting system of claim 20, wherein the fan is directed at the evaporation surface.</claim-text> <claim-text>22. The composting system of claim 20 or claim 21, further comprising a pump.</claim-text> <claim-text>23. The composting system of claim 22, wherein the pump pumps the leachate into a reservoir.</claim-text> <claim-text>24. The composting system of claim 23, wherein the reservoir is an annular reservoir.</claim-text> <claim-text>25. The composting system of claim 23 or claim 24, wherein the reservoir is positioned at or in a top portion of the composting system.</claim-text> <claim-text>26. The composting system of any one of claims 20 to 25, further comprising a solar panel for operating one or more electrically operated element of the system.</claim-text> <claim-text>27. The composting system of any one of claims 19 to 26, further comprising aeration holes.</claim-text> <claim-text>28. The composting system of any one of claims 19 to 27, further comprising drainage slots or drainage holes through which condensate that runs down an inner surface of the system towards the base of the system can drain away.</claim-text> <claim-text>29. The composting system of any one of claims 19 to 28, being arranged fully outdoors such that any condensed clean water therefrom can drain from the system into the surrounding soil.</claim-text> <claim-text>30. The composting system of any one of claims 19 to 29, being arranged part indoors and part outdoors such that food waste can be put into it indoors.</claim-text> <claim-text>31. A composting system substantially as hereinbefore described with reference to Figure 7.</claim-text> <claim-text>32. A method of composting substantially as hereinbefore described with reference to any one of more of the accompanying drawings.</claim-text>