GB2474331A

GB2474331A - A synthetic soil product

Info

Publication number: GB2474331A
Application number: GB1015521A
Authority: GB
Inventors: Richard Kay
Original assignee: GREEN TECH Ltd
Current assignee: GREEN TECH Ltd
Priority date: 2009-09-17
Filing date: 2010-09-16
Publication date: 2011-04-13
Anticipated expiration: 2030-09-16
Also published as: GB201320836D0; GB2474331B; GB201015521D0; GB0916325D0; GB2505588A; GB2505588B

Abstract

A synthetic soil product is disclosed which comprises a conditioned sewage sludge material and an aggregate material. The product may further contain a composted green waste and wood chips. Also disclosed is a method of conditioning sewage sludge by causing annual rye grass to grow in the sludge.

Description

A Synthetic Soil Product The present invention relates to a synthetic soil product. In particular, the present invention relates to a synthetic topsoil material and a method of preparing the same.

Topsoil is used in gardens and fields around the world and generally has a concentration of organic matter, thus allowing plants growing therein to obtain nutrients.

Over time, the nutrients in top soil become depleted and it is required to refresh top soil to allow plants to efficiently and effectively grow. Fresh topsoil can be added to an area to remove and replace contaminated soils or to completely reinstate the soil in a particular area.

Top soil can be retrieved from various sources, such as by composting or by digging up soil from one area to redistribute to another. Typically, such topsoil would be referred to as naturally occurring topsoil or "as dug". However, such soils can have inherent problems in that they may have unacceptable physical and chemical characteristics. Also, as dug soils can vary widely in consistency over small areas and as dug soils may not have the required amount of drainage or organic material.

A further problem associated with such soils is the detrimental environmental impact associated with digging earth from one part of the world and shipping it to another part of the world.

It is an object of aspects of the present invention to provide one or more solutions to the above mentioned problems.

According to a first aspect of the present invention there is provided a synthetic soil product comprising a conditioned sewage sludge material and an aggregate material.

By the term "conditioned sewage sludge material" it is meant a sewage sludge material that has undergone a process to reduce the level of biological hazard posed by the material. The sewage sludge material may be conditioned in a number of ways including being gradually biologically broken down in lagoons, for example.

The synthetic soil product may optionally comprise green waste. The term green waste as used herein refers plant material and may include for example grass cuttings and other foliage, such as hedge trimmings, tree clippings etc. The green waste may be composted, preferably prior to adding to the conditioned sewage sludge material. For example, the green waste may be composted for a period of at least 8 weeks and more preferably at least 12 weeks.

In a particularly preferred embodiment, green waste may be composted for at least 16 weeks, preferably prior to addition to the conditioned sewage sludge material.

After composting, the green waste may be referred to as composted green waste.

The green waste may be shredded, which shredding may occur prior to composting the green waste. For example, the green waste may be shredded to a size of less than 100mm, preferably less than 80mm and most preferably less than about 60mm.

In a particularly preferred embodiment, the green waste may be shredded to a size of about 40mm, preferably prior to composting the green waste.

The green waste is preferably blended with the conditioned sewage sludge.

The synthetic topsoil may also contain wood chip material. The wood chip material may be added to help dry out the conditioned sewage sludge.

Preferably, the aggregate material comprises less than 8% by weight of very coarse sand, more preferably less than about 5% by weight. The aggregate material may comprise 1 to 5% by weight of very coarse sand.

In a particularly preferred embodiment, the aggregate material comprises between about 2 and 4% by weight of very coarse sand, for example, about 3% by weight.

The term "very coarse sand" refers to particles having a size of between about 1.0 to 2.0mm.

Preferably, the aggregate material comprises less than 9% by weight of coarse sand, more preferably less than about 7% by weight. The aggregate material may comprise 2 to 6% by weight of coarse sand.

In a particularly preferred embodiment, the aggregate material comprises between about 3 and 5% by weight of coarse sand, for example, about 4% by weight.

The term "coarse sand" refers to particles having a size of between about 0.5 to 1.0mm.

Preferably, the aggregate material comprises less than about 30% by weight of medium sand, more preferably less than about 25% by weight.

Preferably, the aggregate material comprises more than about 5% by weight of medium sand, more preferably more than about 10% by weight. The aggregate material may comprise 10 to 22% by weight of medium sand.

In a particularly preferred embodiment, the aggregate material comprises between about 15 and 20% by weight of medium sand, for example, about 16, 17, 18 or 19% by weight.

The term "medium sand" refers to particles having a size of between about 0.25 to 0.5mm.

Preferably, the aggregate material comprises less than about 70% by weight of fine sand, more preferably less than about 60% by weight and most preferably less than about 55% by weight.

Preferably, the aggregate material comprises more than about 20% by weight of fine sand, more preferably more than about 30% by weight. The aggregate material may comprise 30 to 55% by weight of fine sand.

In a particularly preferred embodiment, the aggregate material comprises between about 40 and 50% by weight of fine sand, for example, about 42, 43, 44, 45, 46, 47 or 48% by weight, about 45% by weight being particularly preferred.

The term fine sand" refers to particles having a size of between about 0.15 to 0.25mm.

Preferably, the aggregate material comprises less than about 40% by weight of very fine sand, more preferably less than about 35% by weight.

Preferably, the aggregate material comprises more than about 10% by weight of very fine sand, more preferably more than about 15% by weight. The aggregate material may comprise 20 to 30% by weight of very fine sand.

In a particularly preferred embodiment, the aggregate material comprises between about 22 and 26% by weight of very fine sand, for example, about 23, 24 or 25% by weight.

Q 15 The term "very fine sand" refers to particles having a size of between about 0.05 to 0.15mm.

Preferably, the aggregate material comprises less than about 10% by weight of silt, more preferably less than about 7% by weight.

Preferably, the aggregate material comprises more than about 0.5% by weight of silt, more preferably more than about 1% by weight. The aggregate material may comprise 1 to 3% by weight of silt.

In a particularly preferred embodiment, the aggregate material comprises about 2% by weight of silt.

The term "silt" refers to aggregate particles having a size of between about 0.002 to 0.05mm.

Preferably, the aggregate material comprises less than 10% by weight of clay, more preferably less than about 8% by weight. The aggregate material may comprise 2 to 7% by weight of clay.

In a particularly preferred embodiment, the aggregate material comprises between about 4 and 6% by weight of clay, for example, about 5% by weight.

The term "clay" refers to particles having a size of less than 0.002mm.

Preferably, the synthetic soil product has a pH value of between about 5.5 and 8.5, more preferably between about 6 and 8. Preferably, the synthetic soil product has a pH value of between about 6.5 and 7.5.

In a particularly preferred embodiment, the synthetic soil product has a pH value of between about 6.6 and 7.4, for example a pH value of about 7 is particularly preferred.

Preferably, the synthetic soil product has between about 40 and 100 mg/I of available Phospohorus, more preferably between about 60 and 80 mg/I.

Preferably, the synthetic soil product has between about 200 and 600 mg/I of available Potassium, more preferably between about 300 and 500 mg/I, for example, preferably between about 300 and 400, such as between about 340 and 380 mg/I.

Preferably, the synthetic soil product has between about 50 and 250 mg/I of available Magnesium, more preferably between about 100 and 200mg/I, for example, between about 120 and 160mg/I, between about 130 and 150mg/I being especially preferred.

Preferably, the synthetic soil product comprises between about 0.01 and 1.5% by weight of nitrogen, more preferably between about 0.1 and 1% by weight and most preferably between about 0.2 and 0.9% by weight.

In a particularly preferred embodiment, the synthetic soil product comprises between about 0.25 and 0.75% by weight of nitrogen.

Preferably, the synthetic soil product has between about 10 and 30 mg/I of available sodium, more preferably between about 15 and 20mg/I, for example, 16.5mg/I.

Preferably, the synthetic soil product has between about 800 and 900 mg/I of extractable calcium, more preferably between about 820 and 850 mg/I, for example, 838mg/I.

Preferably, the synthetic soil product comprises between about 1 and 100 mg/kg of copper, more preferably between about 10 and 80 mg/kg, for example, between about and 70mg/kg.

Preferably, the synthetic soil product comprises between about 50 and 300 mg/kg of zinc, more preferably between about 100 and 250 mg/kg, for example, between about and 200mg/kg.

Preferably, the synthetic soil product comprises between about 20 and 100mg/kg of lead, more preferably between about 40 and 80mg/kg, for example between about 55 and 75mg/kg.

Preferably, the synthetic soil product comprises less than about 20mg/kg of arsenic, more preferably less than about 10mg/kg.

Preferably, the synthetic soil product comprises less than about 1 mg/kg of cadmium, more preferably less than about 0.6mg/kg.

Preferably, the synthetic soil product comprises less than about 40mg/kg of nickel, more preferably less than about 30mg/kg.

Preferably, the synthetic soil product comprises less than about 150mg/kg of chromium, more preferably less than about 100mg/kg.

Preferably, the synthetic soil product comprises less than about 1mg/kg of mercury, more preferably less than about 0.8mg/kg.

Preferably, the synthetic soil product comprises less than about 1mg/kg of selenium, more preferably less than about 0.5mg/kg, for example, less than about 0.4mg/kg.

Preferably, the synthetic soil product comprises between about 0.001 and 2g/l of water soluble sulphate, more preferably between about 0.1 and lg/l.

Preferably, the synthetic soil product comprises less than about lg/l of water soluble sulphate.

Preferably, the synthetic soil product comprises less than about 15mg/kg of acid volatile sulphide, more preferably less than about 10mg/kg.

Preferably, the synthetic soil product comprises less than about 100mg/kg of elemental sulphur, more preferably less than about 50mg/kg.

Preferably, the synthetic soil product comprises less than about 5mg/kg of total phenols index, more preferably less than about 1 mg/kg.

Preferably, the synthetic soil product comprises less than about 5mg/kg of cyanide, more preferably less than about 1 mg/kg.

Preferably, the synthetic soil product comprises less than about 100mg/kg of TPH (C8 -034), more preferably less than about 50mg/kg.

Preferably, the synthetic soil product comprises less than about 10mg/kg of PAH (epa-i 6), more preferably less than about 9mg/kg.

Preferably, the synthetic soil product has an exchangeable sodium percentage of between about 0.1 and 5%, more preferably between about 2 and 4%.

Preferably, the synthetic soil product has a conductivity (1:2.5 water) of between about 100 and 2000 us/cm (microsiemens per centimetre), more preferably between about 500 and 1 SOOus/cm, for example, about 1 000us/cm.

Preferably, the synthetic soil product contains less than about 2mg/kg, more preferably less than about 1.5mg/kg, more preferably less than about 1 mg/kg and most preferably less than about 0.5mg/kg of the following materials, each independently: acenaphthylene; acenaphthene; fluorine; anthracene; benz(a)anthracene; chrysene; benzo(b)fluoranthene; benzo(k)fluoroanthene; benzo(a)pyrene; indeno(1, 2, 3-cd)pyrene; dibenz(a, h)anthracene; benzo(g, h, i)perylene; naphthalene; phenanthrene; fluoranthene; pyrene; Preferably, the aggregate material comprises a total carbon content of between about 0.01 and 1% by weight, more preferably between about 0.1 and 0.2% by weight, for example, about 0.13% by weight.

The conditioned sewage material, optional green waste and optional wood chippings may be referred to as a "composted premix".

Preferably, the synthetic soil product comprises the aggregate material and the composted premix in the ratio of between about 5:1 and 0.5:1, more preferably between about4:1 and 1:1.

Preferably, the synthetic soil product has a bulk density of between about 1 kg per 2 litres and 1 kg per 0.5 litres of product, more preferably between about 1 kg per 1.5 litres and 1kg per litre of product, most preferably about 1kg per 1.1 litre.

According to a further aspect of the present invention there is provided a method of providing a conditioned sludge material, the method comprising the steps of arranging an amount of sewage sludge to an average depth of less than about 1 metre and causing annual rye grass to grow in the sewage sludge.

Preferably, the process further comprises substantially harvesting the annual rye grass. The harvested rye grass may be used as a bulking agent in a further composting process.

Preferably, the annual rye grass is non-self seeding.

According to a further aspect of the present invention there is provided a method of preparing a synthetic soil product, the method comprising blending an amount of conditioned sewage sludge material with an amount of aggregate material.

All of the features contained herein may be combined with any of the above aspects in any combination.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the following examples:

Example I

The topsoil of example 1 is a manufactured material which is produced from a batch process and consists of 3 primary components.

* Conditioned Sewage Sludge.

* Processed Green Waste from Local Authorities.

* Graded High Quality Aggregate, Quarried Sand Conditioned Sewage Sludge.

Sewage is deposited into Large Lagoons where over a period of years the sludge is gradually broken down (conditioned). The primary aim of sludge conditioning is to reduce the volume and degree of hazard posed by this material. to a l.evel. which permits effective disposal., or 1 5 recovery as a suitable component of topsoil manufacturing.

The matured conditioned' sludge material is mechanically extracted, screened, de watered Q and left to stabilised. Then blended with woodchip, green waste and screened and placed into windrows.

(\J 20 Processed Green Waste Unprocessed green waste is brought into Council kerbside collections. The material is screened to eliminate as much Litter as possible and then shredded to 40mm, windrowed and composted for a minimum of 16 weeks. As the windrows heat up during the resulting compostthg process, any redundant weed or seed is eliminated.

Co-composted Material After a period of 16 weeks the material leaves the initial fast composting process and is transferred into larger windrows until it can be mixed with the conditioned sewage sludge.

Post blending with the conditioned sewage sludge the co-composted material is stockpiled awaiting disposal (to landfill, agricultural land as pure compost) or recovery as a suitable component of topsoil manufacturing.

Graded High Quality Aggregate, Quarried Sand A high quality aggregate is selected from a local source and initially bucket blended with the co-composted material. The subsequent rough blend is then screened using a 15mm trommel screener and windrowed awaiting transportation.

Example I -Process Overview Material Action Output Stabilised Sewage Sludge Screened, de watered and Conditioned sludge suitable left to stabilised. as a component in the topsoil manufacturing process.

Green Waste Unprocessed green waste Material used in the sludge received then screened and conditioning process and the shredded, reduced in size oversize used as mulch.

before adding woodchip.

Woodchip Material incorporated and Co-composted and blended blended with the green material used on site for waste and stabilised sewage Green-tree topsoil sludge prior to windrowing. manufacturing.

High Quality Aggregate Mixed with the treated and Topsoil. Blended material is subsequently screened co-re-screened to 15mm to composted material to meet exacting specifications.

create a topsoil blend.

Mixing Rates in Example I Compost Mix Fill Sand 9.0 Ton 12.0 Ton @650 gram per Litre @1400 gram per Litre 13.8 m3 8.6 m3 End result required is a bulk density of 1kg I 1.1 litre of product This is the initial blend ratio at topsoil conception. Actual bulk densities are recorded under the quality pro toco(s.

Mixing rates are devised through a number of tested and trialed blends. Each of these trial blends is submitted for a topsoil suitability test. This will highlight any obvious problems i.e. contamination, ph or lack of nutrient before we progress to full scale manufacturing.

The latest British Standard for topsoil BS: 3882:2007 is used as a benchmark for any preliminary testing.

New mixthg rates are considered at any point if any of the three primary components change in any way. Although we will try to maintain all components from a single source, from time to time it may be appropriate to amend the mixing rates, dependent on the quality/availability of sand or age of the compost.

Example 2

Example 2 topsoil is a manufactured material which is produced from a batch process and consists of 2 primary components.

* Conditioned Sewage Sludge, SPC * Graded High Quality Aggregate, Quarried Sand Processed Green Waste Unprocessed green waste is brought into Council kerbside collections. The material is Q screened to eliminate as much litter as possible and then shredded to 40mm, windrowed and composted for a minimum of 16 weeks. As the windrows heat up during the resulting composting process, any redundant weed or seed is eliminated.

Conditioned Sewage Sludge, SPC The sludge conditioning process is handled differently in example 2 using a new process called SPC, Sludge Phyto Conditioning.

The SPC process reduces the overall volume of material (sewage) through evapo-transpiration and ameliorates the sewage reducing the pathogen contents to very low levels (see testing protocols).

Processed green waste may be added to the sludge prior to or after conditioning via SPC.

Sewage sludge is extracted and matured and de-watered to a degree. The matured sewage sludge is transported to a concrete pad and laid out over a large area 0.6-0.8m deep. The laid out sewage sludge is then seeded with an annual rye grass which penetrates the full depth of the material. This process adds root structure to the sewage sludge and the growth of the crop further de waters the material to a point where it becomes friable, workable and suitable component of topsoil manufacturing.

The annual crop is removed although is subsequently used as a bulking agent in the further composting process. The now matured, stable, ameliorated and composted material is now windrowed and stockpiled awaiting disposal (to landfill, agricultural land as a pure compost) or recovery as a suitable as a component of topsoil manufacturing.

Graded High Quality Aggregate, Quarried Sand A high quality aggregate is selected from a local source (see product selection) and initially bucket blended with the co-composted material. The subsequent rough blend is then screened using a 20mm trommel screener and windrowed awaiting transportation.

Example 2 -Process Overview Material Action Output Stabilised Sewage Sludge Screened, de watered and Matured and proportionally left to stabilise. de-watered sludge suitable as a component in the SPC process.

SPC Compost Sown with an annual rye Resulting de-watered and grass to add root structure friable compost now suitable and further de-water the for topsoil manufacturing.

compost High Quality Aggregate Mixed with the treated Blended material is re-composted material to screened to 20mm to meet

create a topsoil blend. exacting specifications.

Mixing Rates for Example 2 Compost Mix Fill Sand 6Tonne l8Tonne @650 gram per Litre @1400 gram per Litre 9.23 m3 12.85 m3 End result required is a bulk density of 1kg 1 -1.1 litre of product This is the initial blend ratio at topsoil conception. Actual bulk densities are recorded under the quality protocols As with example 1, mixing rates are devised through a number of tested and trialed blends.

Each of these trial blends is submitted for a topsoil suitability test. This will highlight any obvious problems i.e. contamination, ph or lack of nutrient before we progress to full scale manufacturing. The latest British Standard for topsoil BS: 3882:2007 if used as a benchmark for any preliminary testing.

Quality Protocol, Examples I and 2 To ensure a consistent blend and quality of topsoil, regular checks of material were done.

These are visually assessed for quality, friability, moisture content and any litter or other visible contaminants.

At the point of measuring the material for stock take purposes a physical analysis is done to ascertain the bulk density of each component.

Q Samples were taken over a 4 month period from a minimum of five different locations on each stock pile to create a representative, consolidated sample of each component. A bulk (\.J density assessment was then done in accordance with BS 12580. An example of the recorded data is detailed below.

Topsoil -Weights And Bulk Density Record Blend Ratio Sand -Compost -Total -Compost Estimated Bulk Actual Bulk Date tonnes tonnes tonnes Sand (kg per I) (kg per I) Total -weight Density tonnes/m3 Density tonnes/m3 Variance Variance % 17/32 12 9 21 125 05 195 0929 09 19/02 12 9 21 1 18 0.58 1938 0923 0795 -1/13 27/02 12 9 21 1 05 0.58 1782 0849 0.79 -1/122 12/03 12 9 21 1 05 0.56 1764 0.840 0.62 -0/1/10 12/03 12 9 21 1.05 0.75 1935 0.921 0.75 -/1 1/1 -12% 22/03 12 9 21 1 0.54 16.86 0.803 0.825 /1 0/1/1 2% 01/04 12 9 21 0.98 0.74 18.44 0.878 0.76 -0 112 3% 09/04 12 9 21 1.001 0.51 16.57 0.789 0.7385 -11.05/1 -2% 24/04 12 9 21 1.0045 0.60 17.45 0.831 0.6735 1213 01/05 12 9 21 1.081 0.60 18.37 0.875 0.714 -1) 1531 -113% 20/05 12 9 21 1.0945 0.58 18.31 0.872 0.7215 -/1121 -17% 08/06 12 9 21 1.1 0.59 18.54 0.883 0.706 --/1 177 -/1/1% M3 10.91 15.16 TM3 13091 136.4095655 26732 BLEND 49% 51% Product Selection Graded High QuaUty Aggregate, Quarried Sand An integral component of the topsoil is the quarried sand. The criteria for sand selection is reasonably straight forward: we would Look to source a medium to fine grade as dug quarried sand with very low silt, clay and stone content.

Although some clay s desfrable too much clay can change the textural classffcaton of Green-tree. Ideally we look to blend and create topsoil with a sandy loam textural classification, which is considered the ideal landscaping media. In addition too much clay can retain too much water affecting the bulk density of the topsoil dramatically depending how moist it is. Further more high clay content soils can suffer from structural degradation and self compaction.

Initially the sand would be subjected to a particle analysis report and then an analysis for 1 5 contamination before it is considered as a component for topsoil manufacturing. Although as dug quarried sands are usually pretty clean we would look for any potential contaminates Q that could affect the classification of the soil or lead to any further issues post installation.

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Testing Protocols, Topsoil The most commonly used method for TPH determination in soil is Gas Chromatography Flame lonisation Detection (GCFID), as it is relatively cheap, quick and effective for most soil types. However, it is not suitable for organic-rich soils. Using this method, the Topsoil of the present nventon usually produces a chromatogram wfth a large mass of unresolved complex materials mainly in the carbon banding range C25 to C40.

1 0 The Gas Chromatography Mass Spectrometry (GCMS) Broadscan method is a preferable method in this instance as it enables further characterisation of the hydrocarbon and non-hydrocarbon compounds and therefore a more detailed interpretation of the results.

Our testing criteria are as follows:-CLAY ( <0.002MM) % Q SILT (0.002-0.063MM) % SAND (0.063-2.0MM) % (\.J TEXTURE CLASS (UK CLASSIFICATION) -STONES (2-20MM) % DW N.. STONES (20-50MM) % DW STONES (>50MM) %DW PH VALUE (1:2.5 WATER EXTRACT) UNITS ELECTRICAL CONDUCTIVITY (1:2.5 WATER EXTRACT) Us/CM ELECTRICAL CONDUCTIVITY (1:2 CaSO4 EXTRACT) Us/CM EXCHANGE SODIUM PERCENTAGE (ESP) % ORGANIC MATTER (WB) % TOTAL NITROGEN (DUMAS) % C:NRATIO:1 EXTRACTABLE PHOSPHORUS mg/I EXTRACTABLE POTASSIUM mg/I EXTRACTABLE MAGNESIUM mg/I TOTAL ARSNIC As mg/kg TOTAL CADIUM Cd mg/kg TOTAL CHROMIUM Cr mg/kg TOTAL COPPER Cu mg/kg TOTAL LEAD Pb mg/kg TOTAL MERCURY Hg mg/kg TOTAL NICKEL Ni mg/kg TOTAL SELENIUM Se mg/kg TOTAL ZINC Zn mg/kg TOTAL CYANIDE mg/kg TOTAL (MONO) PHENOLS mg/kg ELEMENTAL SULPHUR 5 mg/kg ACID VOLATILE SULPHIDE S mg/kg WATER SOLUBLE SULPHATE SO4 g/1 TPH BY GC-MS BROADSCAN (C8-C34) mg/kg NAPTHALENE mg/kg ACENAPHTHYLENE mg/kg ACENAPHTHENE mg/kg FLUORENE mg/kg Q PHENANTHRENE mg/kg ANTHRACENE mg/kg (\J FLUORATHENE mg/kg PYRENE mg/kg BENZO (A) ANTHRACENE mg/kg CHRYSENE mg/kg BENZO (B) FLUORATHENE mg/kg BENZO (K) FLUORATHENE mg/kg BENZO (A) PYRENE mg/kg INDENO (1,2,3-CD) PYRENE mg/kg DIBENZO (A,H) ANTHRACENE mg/kg BENZO (G,H,I) PERYLENE mg/kg TOTAL PAHs (SUM USEPA16) mg/kg Testing Protocols, Sewage Sludge.

Ongoing tests of the conditioning sewage sludge are carried out before it is made available for any further projects. Fundamentally this testing is looking at some of the more common PAHs but with an additional focus on Ecoli and Salmonella. Examples of the test results are as follows:-(\J nd3 S3t3.

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Attention is directed to all papers and documents which are fi'ed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic 1 5 series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1. A synthetic soil product comprising a conditioned sewage sludge material and an aggregate material.
2. A synthetic soil product according to claim 1 which further comprises green waste.
3. A synthetic soil product according to claim 2, wherein the green waste is composted prior to adding to the conditioned sewage sludge material.
4. A synthetic soil product according to claim 3, wherein the green waste is shredded prior to composting the said green waste.
5. A synthetic soil material according to any preceding claim which further comprises wood chip material.
6. A synthetic soil material according to any preceding claim, wherein the aggregate material comprises less than 8% by weight of very coarse sand.
7. A synthetic soil material according to any preceding claim, wherein the aggregate material comprises less than 9% by weight of coarse sand.
8. A synthetic soil material according to any preceding claim, wherein the aggregate material comprises less than about 30% by weight of medium sand.
9. A synthetic soil material according to any preceding claim, wherein the aggregate material comprises less than about 70% by weight of fine sand.
10. A synthetic soil material according to any preceding claim, wherein the aggregate material comprises less than about 40% by weight of very fine sand.
11. A synthetic soil material according to any preceding claim, wherein the aggregate material comprises less than about 10% by weight of silt.
12. A synthetic soil material according to any preceding claim, wherein the aggregate material comprises less than 10% by weight of clay.
13. A synthetic soil material according to any preceding claim which has a pH value of between about 5.5 and 8.5.
14. A synthetic soil material according to any preceding claim which comprises between about 40 and 100 mg/I of available Phospohorus.
15. A synthetic soil material according to any preceding claim which comprises between about 200 and 600 mg/I of available Potassium.
16. A synthetic soil material according to any preceding claim which comprises between about 50 and 250 mg/I of available Magnesium.
17. A synthetic soil material according to any preceding claim which comprises between about 0.01 and 1.5% by weight of nitrogen.
18. A synthetic soil material according to any preceding claim which comprises between about 10 and 30 mg/I of available sodium.
19. A synthetic soil material according to any preceding claim which comprises between about 800 and 900 mg/I of extractable calcium.
20. A synthetic soil material according to any preceding claim which comprises between about 1 and 100 mg/kg of copper.
21. A synthetic soil material according to any preceding claim which comprises between about 50 and 300 mg/kg of zinc.
22. A synthetic soil material according to any preceding claim which comprises between about 20 and 100mg/kg of lead.
23. A synthetic soil material according to any preceding claim which comprises less than about 20mg/kg of arsenic.
24. A synthetic soil material according to any preceding claim which comprises less than about 1mg/kg of cadmium.
25. A synthetic soil material according to any preceding claim which comprises less than about 40mg/kg of nickel.
26. A synthetic soil material according to any preceding claim which comprises less than about 150mg/kg of chromium.
27. A synthetic soil material according to any preceding claim which comprises less than about 1 mg/kg of mercury.
28. A synthetic soil material according to any preceding claim which comprises less than about 1mg/kg of selenium.
29. A synthetic soil material according to any preceding claim which comprises between about 0.001 and 2g/l of water soluble sulphate.
30. A synthetic soil material according to any preceding claim which comprises less than about lg/l of water soluble sulphate.
31. A synthetic soil material according to any preceding claim which comprises less than about 15mg/kg of acid volatile sulphide.
32. A synthetic soil material according to any preceding claim which comprises less than about 100mg/kg of elemental sulphur.
33. A synthetic soil material according to any preceding claim which comprises less than about 5mg/kg of total phenols index.
34. A synthetic soil material according to any preceding claim which comprises less than about 5mg/kg of cyanide, more preferably less than about 1 mg/kg.
35. A synthetic soil material according to any preceding claim which comprises less than about 100mg/kg of TPH (C8 -034).
36. A synthetic soil material according to any preceding claim which comprises less than about 10mg/kg of PAH (epa-i 6).
37. A synthetic soil material according to any preceding claim which comprises an exchangeable sodium percentage of between about 0.1 and 5%.
38. A synthetic soil material according to any preceding claim which has a conductivity (1:2.5 water) of between about 100 and 2000 us/cm (microsiemens per centimetre).
39. A synthetic soil material according to any preceding claim which comprises less than about 2mg/kg of the following components, each independently: acenaphthylene; acenaphthene; fluorine; anthracene; benz(a)anthracene; chrysene; benzo(b)fluoranthene; benzo(k)fluoroanthene; benzo(a)pyrene; indeno(1, 2, 3-cd)pyrene; dibenz(a, h)anthracene; benzo(g, h, i)perylene; naphthalene; phenanthrene; fluoranthene; pyrene;
40. A synthetic soil material according to any preceding claim, wherein the aggregate material comprises a total carbon content of between about 0.01 and 1% by weight.
41. A synthetic soil material according to any preceding claim, wherein the aggregate material and the composted premix are contained in a ratio of between about 5:1 and 0.5:1.
42. A synthetic soil material according to any preceding claim which has a bulk density of between about 1 kg per 2 litres and 1 kg per 0.5 litres.
43. A method of providing a conditioned sludge material, the method comprising the steps of arranging an amount of sewage sludge to an average depth of less than about 1 metre and causing annual rye grass to grow in the sewage sludge.
44. A method according to claim 43, which further comprises substantially harvesting the annual rye grass.
45. A method according to claim 44, wherein the harvested rye grass is used as a bulking agent in a further composting process.
46. A method according to any of claims 43 to 45, wherein the annual rye grass is non-self seeding.
47. A method of preparing a synthetic soil product, the method comprising blending an amount of conditioned sewage sludge material with an amount of aggregate material.
48. A synthetic soil material substantially as hereinbefore described and with reference to the examples.
49. A method of providing a conditioned sludge material substantially as hereinbefore described and with reference to the examples.
50. A method of preparing a synthetic soil product substantially as hereinbefore described and with reference to the examples.