GB2332353A - A biodegradable mat - Google Patents

Abstract

A mat 1 contains seeds 7, fertilizer granules 8 and water retaining crystals 9. These are supported on an intermediate layer 6 which is made of a woven, biodegradable material such as jute. An upper and lower layer 2, 4 are made from non-woven fibres such as coir, jute and goat's hair. These three fibres may be present in equal quantities by weight. An envelope (fig.5) may be formed by attaching two mats together along their edges (19, fig.5). Soil or other growth media may be inserted between the mats, and only the top mat contains seeds. These envelopes can be used on very steep embankments which may not be able to sustain plant life (fig.11). The mat may also be used to cover items such as a gabion (24, fig.6), or it may be rolled into a tube (25, fig.8; 32, fig.10) or other shape to make a three-dimensional object which can sustain plant life. The mat is made by dispensing seeds onto a mesh of woven biodegradable fibres and attaching non-woven fibres on either side of the woven mesh. The non-woven fibres are attached to the woven mesh by needling or felting.

Description

2332353

Biodegradable Mat Field of the Invention

This invention relates to biodegradable mats, and particularly to a biodegradable mat carrying seeds.

Background to the Invention

Materials known as geotextiles are widely used by landscapers in order to control soil erosion. One particular use of geotextiles is in the stabilization of embankments adjacent to roads, rivers and railway lines. The gradients of these embankments are often so steep that the embankments must be stabilized until plants, for instance grasses, have had time to establish. When plant cover has been established, the roots of the plants stabilize the embankment.

Geotextiles take the form of mats which can be laid on top of a surface to be stabilized, or which can be laid and covered with a thin layer of soil.

One known type of mat is disclosed in US 5226255. This mat comprises upper and lower portions of non-woven fibres, an intermediate layer of bilaterally stable plastics mesh of high strength relative to the portions of non-woven fibres, the intermediate layer being structurally joined to the fiber portions by needling. The mat includes seed, and may include fertilizer and/or water absorbing material.

The problems associated with the mat described in US 5226255 stem from the intermediate layer being formed from a plastics mesh. The length of time taken for the plastics mesh to biodegrade is many times longer than the time taken for the nonwoven fibres to biodegrade. This not only causes environmental problems, but also causes physical problems for those wishing to work the stabilized soil. For instance, it is often necessary for a road to be widened, and this need frequently arises within 10 to 20 years of first construction of the road and its original embankments. It is often found that the plastics netting forming part of the mat has not degraded and is still intact. It has been found that the netting tends to tangle around excavators and other soil working and grass cutting machinery. This leads to down time and can result in equipment being damaged.

US 5226255 advocates incorporating crop residue and the remains of the mat. Not only will there is a tendency for the plastics netting to wrap around parts of the implements used for incorporating the crop residue, but it is undesirable from an environmental standpoint to incorporate plastics into soil. This is due to the fact that plas5 tics materials take many years to bio-degrade.

Another problem associated with the mat described in US 5226255 is conflict between the requirement for the mat to be sufficiently heavy so that it will not blow away on the one hand, yet on the other hand the requirement that the mat be sufficiently thin for the seeds carried therein to germinate satisfactorily.

It has been found that grass seeds are generally capable of sending down roots of approximately 4mm in length, and are capable of sending up shoots of about 4mm in length before requiring a growth medium and sunlight respectively for further growth.

If the roots do not meet a growth medium, i.e. soil, and the shoots do not meet sunlight after growing by these amounts, the seedlings will not continue to grow and will even tually die. There is therefore an upper limit on the thickness of the mat.

Plastics netting material of the type used in US 5226255 is a lightweight mate rial, typically 0.004 kg/m. For this reason it is necessary for the thickness of the upper and lower portions to be increased so that the mat has sufficient weight to ensure that it does not blow away.

It has been found that if the thickness of the plastics netting is increased so as to increase its weight, the flexibility of the mat decreases. This makes it difficult to lay the mat on undulating surfaces and maintain adequate germination of the seeds carried by the mat because regions of the mat may not be in contact with the soil.

It would therefore be desirable to produce a mat carrying seeds, and which may carry fertilizer and/or water retaining crystals of the type described in US 5226255 but which does not suffer from the disadvantages mentioned above.

Summary of the Invention

The invention provides a seed containing biodegradable mat comprising an up per layer, a lower layer, and an intermediate layer, wherein the upper and lower layers are each formed substantially entirely from natural biodegradable non- woven fibre and 1 1 1 the intermediate layer is in the form of a mesh and is formed from woven biodegradable fibres, the fibres of the upper and lower layers penetrating the intermediate layer to attach the fibres of the upper and lower layers to the intermediate layer.

Preferably, the fibres of the upper and lower layers are needle punched into the intermediate layer.

Advantageously, the intermediate layer is in the form of a scrim.

Preferably, the mat is 6 to 9mrn thick. Even more preferably, the mat is 7 to 8mm thick.

Preferably, the mat weighs 0.3 to 1.5 kg/M2. and more preferably 0.6 to 0. 8 kg/M2. Even more preferably, the mat weighs 0.65 to 0.7 k&/M2.

The intermediate layer may be woven from jute and/or coir and/or hemp and/or flax for example. The intermediate layer may be 0.3 to 1 mm thick, and advantageously the intermediate layer is substantially 1 mrn thick. Preferably, the mesh size of the intermediate layer is 0.5 to 10mm, and more preferably 1.5 to 3.5mm. An espe15 cially suitable mesh size of the intermediate layer is 2 to 3mm.

The fibres of the upper layer may comprise one or more of jute, coir, hair, which hair may be goat hair or any other suitable animal hair and cotton. The upper layer suitably comprises jute and coir and hair in substantially equal proportions. Advantageously, the upper layer consists of one third jute fibres, one third coir fibres, and 20 one third hair.

The fibres of the lower layer may also comprise one or more of jute, coir, hair, which hair may be animal hair, for example goat hair, and cotton.

By increasing or decreasing the relative proportions of the different fibres used in the upper or lower layers, the physical properties of the mat can be varied. For instance, coir and hair are harder wearing than jute and therefore by increasing the proportion of hair and/or coir relative to jute the mat's resistance to wear can be increased.

Jute has better water-retaining capabilities than coir or hair. Therefore, by increasing the proportion of jute fibres relative to coir and hair, the water-retaining ca- pacity of the mat can be increased. For this reason it is preferable for the lower layer of the mat to have a higher proportion of jute fibres than the upper layer, in order that roots of the seeds may be provided with as much water as possible.

In one embodiment of the invention, the mat contains fertilizer and/or waterretaining means. Preferably, the fertilizer is in granular form. The water-retaining means suitably comprises water-retaining crystals. Advantageously, water-retaining crystals are added to the mat at a rate of 0.001 to 0.003k&/M2.

The seeds contained in the mat may be grass, flower, herb or vegetable seeds for example.

Another aspect of the invention provides an envelope comprising first and sec- ond biodegradable mats attached one to another along the edges thereof, each com- prising an upper layer, a lower layer, and an intermediate layer, wherein the upper and lower layers are each formed substantially entirely from natural biodegradable nonwoven fibre and the intermediate layer is in the form of a mesh and is formed from woven bio-clegraclable fibres, the fibres of the upper and lower layers penetrating the intermediate layer to attach the fibres of the upper and lower layers to the intermediate layer, wherein one of the first and second mats is seed containing, and wherein the tube is filled with a growth medium.

Preferably, the growth medium comprises soil and/or compost and/or mulch for example.

Advantageously, the first and second mats are advantageously attached one to another by means of stitching or quilting.

In a further aspect of the invention, the mat of the invention is formed into a tube, and the tube is filled with a growth medium. The tube may be of any desired cross-section, for example, the cross section may be substantially circular or square.

The growth medium may comprise soil and/or compost and/or mulch for example.

The invention also provides a method of making a seed containing biodegradable mat comprising the steps of- a) dispensing seed and/or fertilizer and/or water retaining particles onto a mesh of woven biodegradable fibres; and i b) attaching non-woven biodegradable fibres to the said mesh so as to form a mat having an upper layer of non-woven biodegradable fibres, an intermediate layer of woven biodegradable fibres and a lower layer of non- woven biodegradable fibres.

Preferably the non-woven biodegradable fibres are attached to the mesh by needling or felting.

The invention also provides a method of stabilizing soil comprising the steps of laying at least one mat according to the invention on the soil and applying water.

The invention also provides a method of establishing plants, comprising the steps of laying at least one mat according to the invention on a region of suitably prepared ground, and applying water.

The ground may be prepared by cultivation to form a seedbed.

The mat of the invention is particularly useful for establishing grass. When used on landscaped areas of soil which require stabilization it provides the stabilization, al- lowing the grass to establish and the roots of the grass to develop until it is the roots which stabilize the soil. The mat degrades within 3 to 6 years of being laid and therefore excavation of sites where the mats have been laid is not hindered. Also, due to flexibility of the biodegradable layer, it can be laid on undulating surfaces.

The invention provides a further method of establishing plants comprising the step of applying water to an envelope according to the invention.

The invention provides a further method of establishing plants comprising the step of applying water to a mat of the invention formed into a tube, the tube being filled with a growth medium.

The use of a biodegradable intermediate layer also permits a mat to be made which is of optimum thickness, the seeds contained therein only needing to send out roots and shoots of 3.5-4.5mm before meeting a growing medium and sunlight respectively, and which is of sufficient weight to conform to the shape of contours and which is not so susceptible to high winds.

In addition to its use for stabilizing soil, the mat can also be used simply to estab- lish plants, for example grass, and may be useful in the construction of sports fields, golf -6 greens, race tracks, grass surfaces being established simply by laying out a mat of the invention on a suitably prepared surface and applying water.

The mat may also be used for establishing arable crops such as cereals, vegetables, sugar beet, etc. The mat is particularly useful where accurate spacing of seeds and weed control during germination and early plant life is important, for example sugar beet. Brief Description of the Drawings

In the drawings, which illustrate the preferred embodiment of the invention:

Figure 1 is a cross-section of a biodegradable mat according to the invention; Figure 2 is a schematic representation of the mat shown in Figure 1 in a rolledup state; Figure 3 is a schematic representation of an embankment having a plurality of mats as shown in Figures 1 and 2 laid thereon; Figure 4 is a schematic representation of a steep embankment having envelopes according to the invention attached thereto; Figure 5 is a cross-section of an envelope according to the invention; Figure 6 is a schematic representation of a gabion having an envelope according to the invention attached thereto; Figure 7 is a schematic representation of an envelope according to the invention; Figure 8 is a schematic representation of a tube formed from a mat according to the invention; Figure 9 is a schematic representation of a hanging basket; Figure 10 is a schematic representation of a tube according to the invention; and Figure 11 is a schematic representation of an embankment having a plurality of mats as shown in Figures 1 and 2 laid thereon. Detailed Description of the Drawings

In Figure 1 there is shown a mat 1 having an upper layer 2, a lower layer 4 and an intermediate layer 6. The upper layer 2 is made up of non-woven fibres 3. Three different types of fibre are used: coir, jute and goat's hair (or other animal hair). The fibres are mixed in the proportion one third coir, one third jute and one third goat's i i i hair, by weight. The lower layer 4 is made up of non-woven fibres 5 which are jute fibres. The proportions of the different fibres may be varied to extend or reduce the longevity of the mat.

The non-woven fibres of the upper and lower layers, 2, 4, are needle punched into the intermediate layer 6 which is in the form of a jute scrim. The jute fibres are woven and the scrim is bi-laterally stable.

The overall thickness of the mat 1 is in the region of 7mm.

Within the mat 1 are seeds 7, fertilizer granules 8, and water retaining crystals 9.

By providing seeds, fertilizer granules and water-retaining crystals within the mat 1, far less manpower is required to establish viable germination of the seeds. This is because when a mats 1 are laid out as shown in Figure 3 on an embankment 12, beside a road or railway 13, it is only necessary for the mats to be watered initially, and then depending upon the weather conditions again at intervals of 7 to 14 days until the plants have germinated. The quantity of fertilizer granules and water-retaining crystals may be varied according to requirements.

Traditionally it has been necessary for a newly sown area of soil to be watered daily until germination of the plants has occurred. Not only does the labour requirement make this task particularly expensive, but also much water is wasted through leaching, and the water applied can even cause erosion of the soil before the plants have germinated.

Referring now to Figure 2, there is shown a roll 10 of matting 1. The rolled-up matting is held in a rolled-up state by suitable tapes or strings 11.

Referring now to Figure 3, there is shown an embankment 12 requiring stabilization. A plurality of mats 1 are laid upon the embankment, the surface of which will have been prepared so that it is substantially flat. The mats 1 may be laid by simply rolling out rolls 10 of matting. When the mats have been laid water is applied so that the seeds contained in the mat may germinate.

Where the embankment is sited in a region of high wind, it may be desirable to attach the mats to the embankment. The mats 1 may be fastened to the embankment using pegs 14, the pegs being passed through the mats 1 and into the embankment 12.

Pegs 14 may be made from wood or wire. Rather than using pegs to secure the mats to the stabilized embankment, pins or ties, such as cable ties, may be used.

Embankments are often stabilized with netting, geotextiles, or geogrids. Mats 1 may be laid on such stabilized embankments, and may be secured thereto using pegs as shown in Figure 3.

Figure 11, is similar to Figure 3, and like numerals are used to designate like objects. Figure 3 shows an alternative method of securing the mats 1 to the embank ment 12, a geotextile 14' being used. The geotextile 14' is secured to the embankment 12 using pins 15'. The geotextile may be replaced by a geogrid, or a simple netting. As well as keeping the mats 1 in place, geotextiles and geogrids provide for additional sta bilization of the bank 12.

Referring now to Figures 5 and 7, there is shown an envelope comprising a first seed containing biodegradable mat 35 attached to a second biodegradable mat 36, the two mats being attached along their edges 19. The first and second mats are also quilted 20 to provide pockets, which are filled with soil 15. In place of soil, other growth media, such as compost or mulch may be used. Water retaining crystals and/or fertilizer granules may be mixed with the growth media. The second biodegradable mat 36 does not contain seeds. Advantageously, the soil layer is 25 to 1 0Omm deep.

Figure 4 shows one particular use of the envelope shown in Figures 5 and 7. A plurality of envelopes 15 is fixed to a steep embankment 18, which may not be capable of supporting plant life. The envelopes are held in place on the embankment 18 by a mesh 16, and pins 17 fixed to the mesh pass through the envelope and into the em bankment 18. Mesh 16 may be a geotextile or a geogrid.

In Figure 6 there is shown a gabion 22, which has fitted to the inside of one of the faces thereof a large envelope 15. The gabion is made of a plurality of mesh panels 24. only the panels facing being shown for the sake of clarity. The envelope 15 is at tached to the panel 24 by clips 37.

Referring now to Figures 8 to 10, the mat may be of into any desired shape, and can be used as a hanging basket liner.

i Figure 8 shows a seed containing mat of biodegradable material according to the invention formed into a tube 25. A rope 26 having a hook 27 is attached to one end of the tube so that it can be hung from a bracket or beam for example.

Figure 9 shows a hanging basket 28 having a liner 29 of biodegradable material according to the invention. The basket 28 is provided with a chain 30 having a hook 31 so that the basket can be hung from a bracket.

Figure 10 shows a tube 32 of seed containing biodegradable material, the ends 33 of which are closed. The tube is filled with soil or another suitable growth medium, and plants 34 are growing from the seeds contained in the mat.

The mat may be made into three-dimensional objects such as a sphere, or a cube.

Claims (26)

1 A biodegradable mat containing seeds, the mat comprising an upper layer, a lower layer and an intermediate layer, wherein the upper and lower layers are each formed substantially entirely from natural biodegradable non-woven fibres and the intermediate layer is in the form of a mesh formed from woven biodegradable fibres, fibres from the upper and lower layers penetrating the intermediate layer to attach the upper and lower layers thereto.

2. A mat according to Claim 1, wherein fibres of the upper and lower layers are needle punched into the intermediate layers.

3. A mat according to Claim 1 or 2, wherein the intermediate layer is in the form of a scrim.

4.

5.

A mat according to Claim 1, 2 or 3, having a thickness of 6 to 9 mm. A mat according to Claim 4, having a thickness of 7 to 8 mm.

6. A mat according to any preceding claim, having a weight of 0.3 to 1.5 kg/ M2.

7. A mat according to Claim 6, having a weight of 0.6 to 0.8 kg/ M2.

8. A mat according to Claim 7. having a weight of 0.65 to 0.7 kg/M2.

9. A mat according to any preceding claim, wherein the intermediate layer comprises one or more of jute, coir, hemp and flax.

10. A mat according to any preceding claim, wherein the intermediate layer is 0.3 to 1 mm thick.

11. A mat according to any preceding claim, wherein the intermediate layer has a mesh size of 0.5 to 10 mm.

12. A mat according to Claim 11, wherein the mesh size is 1.5 to 3.5 mm.

13. A mat according to Claim 12, wherein the mesh size is 2 to 3 mm.

14. A mat according to any preceding claim, wherein the fibres of the upper and lower layers separately comprise one or more of jute, coir, animal hair, and cotton.

15. A mat according to Claim 14, wherein the upper layer comprises jute, coir and hair in substantially equal proportions.

16. A mat according to any preceding claim, containing fertiliser and/or water-retaining means.

17. A mat according to Claim 16, comprising water-retaining crystals at a concentration of 0.001 to 0.003 kg/M2.

18. A biodegradable mat containing seeds, substantially as described with reference to, or as shown in, the drawings.

19. An envelope comprising first and second biodegradable mats attached one to the other along the edges thereof, each comprising an upper layer, a lower layer, and an intermediate layer, wherein the upper and lower layers are each formed substantially entirely from natural biodegradable non-woven fibres and the intermediate layer is in the form of a mesh formed from woven biodegradable fibres, fibres from the upper and lower layers penetrating the intermediate layer to attach the upper and lower layers thereto, wherein one of the first and second mats contains seeds, and wherein the envelope is filled with a growth medium.

20. An envelope according to Claim 19, wherein the growth medium com prises one or more of soil, compost and mulch.

21. An envelope according to Claim 19 or 20, wherein the first and second mats are attached one to the other by means of stitching or quilting.

22. A mat according to any of Claims 1 to 18, formed into a tube and filled with a growth medium.

23. A method of making a biodegradable mat containing seeds, comprising the steps of:

a) dispensing seeds on to a mesh of woven biodegradable fibres, and b) attaching non-woven biodegradable fibres to the mesh to form a mat having upper and lower layers of non-woven biodegradable fibres, and an intermediate layer of woven biodegradable fibres.

24. A method according to Claim 23, comprising attaching the non-woven biodegradable fibres to the mesh by needling or felting.

25. A method according to Claim 23 or 24, wherein step (a) also comprises dispensing fertiliser and/or water-retaining particles on to the mesh of woven biodegradable fibres.

26. A method of making a biodegradable mat containing seeds, substantially as described.