GB2288598A

GB2288598A - Covering a landfill site for waste disposal

Info

Publication number: GB2288598A
Application number: GB9407807A
Authority: GB
Inventors: Paul Watson Wheeler; Christopher William Huckle
Original assignee: Geohess UK Ltd
Current assignee: Geohess UK Ltd
Priority date: 1994-04-20
Filing date: 1994-04-20
Publication date: 1995-10-25
Also published as: GB9407807D0

Abstract

A land-fill site for waste disposal is operated by covering the waste material at the end of each day with a permeable textile material. The material may be laid in pieces which are then stitched together to form an integral covering. A bio-degradable material such as hessian is particularly preferred as it can be re-used several times and then left in place, where it will not inhibit the extraction and control of gas or leachate.

Description

WASTE DISPOSAL The present invention relates to waste disposal, and in particular to an improved method of operating landfill sites.

Currently there are a number of ways of disposing of household waste, and in the United Kingdom the most common method is to deposit the waste in landfill sites. These are often disused extraction sites, such as quarries and brick pits, where the waste is deposited in layers and compacted.

The operator of a landfill site is able to recoup operating costs by charging for the tipping of waste at the site, and may also make additional revenue by extracting gas, mainly methane, from the decomposing waste. The gas is used to produce electricity which can be used at the site, sold to the national grid etc.

Waste disposal authorities usually require the landfill site operator to cover the surface of the waste at the end of each working day. The main performance criteria that the covering for the waste material needs to satisfy are that it must - present an acceptable and uniform visual appearance; - eliminate the problem of wind blown refuse; - reduce the emission of odours; and - limit the ingress of vermin.

At present, an inert material such as clay is used as the daily cover, a layer of clay being deposited over the day's refuse at the end of the working day. There are various disadvantages in using an inert material of this sort: - clay and similar naturally occurring inert materials are non-renewable resources; - many sites do not have a readily available supply of the material; - transporting and handling the material is costly; - the material itself occupies valuable void space in the landfill site, thereby reducing the capacity and hence the useful life of the site; - the material is generally not recoverable for re-use as a covering material the next day because it is contaminated with the waste; and - the material is generally impermeable to gas and liquid, and the intermediate layers of inert material within a landfill site make gas and leachate control and extraction difficult.

A particular problem is that the inert material layer causes gas to migrate sideways to the edge of the site, where it exhausts into atmosphere instead of being collected for use by the site operator.

Additionally, the operator will incur additional expense in trying to control the effluent generated by the decomposition of the waste (known as leachates). The inert layers cause the leachates to migrate sideways to weak points in the side walls of the site, leading to contamination of the water table.

Decomposing refuse also generates heat, which is trapped by the inert layers. This can lead to fires deep below the surface of the landfill site. These fires are difficult to locate and control,and generate toxic fumes which vent into the atmosphere and/or contaminate the ground water with their residues.

It is generally accepted that the use of inert materials such as clay is not ideal, and various solutions have been proposed and tested, including the use of synthetic membranes and tarpaulins which can be laid on the waste at the end of the day and then removed at the beginning of the next day, and the application of a covering of foam.

These other solutions have not proved very successful in practice because they ameliorate only some of the problems outlined above. In particular, synthetic membranes and tarpaulins are expensive to use, they can be difficult to lay and join together, and they are generally impermeable to gases and liquids.

The present invention provides a method of operating a land-fill site for waste disposal, in which a covering of permeable sheet material is laid over the deposited waste material.

Preferably the sheet material is permeable to allow both gas and liquid to pass through the covering.

Preferably the covering is re-usable, being removed at the start of the day and re-laid over the waste material at the end of the day.

Preferably the sheet is a biodegradable material, and preferably formed of natural fibres. The sheet may be of cloth, and in particular it may be a textile material.

The covering can be re-used from day to day. However, the covering may also be left in place, for example if it is damaged or contaminated, and covered with the next day's refuse. The permeable material layer remaining in the site will not inhibit the escape of gases or cause leachates to migrate sideways across the site.

Additionally, a biodegradable material will pose no long term problems in extracting gases or controlling leachates.

Preferably the covering is laid in pieces from a roll, which results in a considerable saving in plant and labour costs.

According to another aspect of the invention, waste material in a landfill site is covered by pieces of sheet material which are then stitched together. The pieces may then be unstitched to allow the covering to be easily removed.

The particularly preferred material is a close weave hessian Preferably the material has a weight of from about 175 to about 350 gsm. and more preferably between about 200 and about 320 gsm.

Hessian is particularly suitable as it can be easily laid in strips which can be stitched together to form an integral covering and unseamed for removal the next day. It is a readily available, renewable resource which is relatively inexpensive and can be easily repaired if damaged.

The invention will be further described by way of example.

A roll of close woven hessian formed from jute fibre and of length about 500 metres and width about 4. 7 metres is rolled around a cylinder and rotatably supported on a frame carried by a site excavation machine.

At the end of the working day, the free end of the roll is fixed at one edge of the site, for example by being weighted by sandbags. The excavator is then driven slowly across the site to unroll the material and lay it across the surface of the waste. At the far edge of the site the roll is cut, and the free end fixed in place.

A second strip is then layed adjacent the first strip of material in a similar fashion. The process is repeated until the whole site is covered.

Preferably, the strips of material are then sewn together at their adjacent edges using a hand held industrial sewing machine, and the outer edges of the end strips may be fixed in place.

At the start of the next day, the stitching may be pulled free and the material rolled up ready to be laid down again at the end of the day.

Generally the covering may be re-used several times.

Where the covering or particular strips of covering, are damaged or too contaminated for re-use, they may be left in place and covered with the next day' s waste material.

It will be appreciated that various widths and weights of hessian may be used. Fabric wegihts of 214, 229 and 305 grams per square metre have been found suitable.

It is believed that other materials may be used, for example a woven cotton or coconut-fibre.

The covering material may be treated in various ways.

For example, it may be dyed to give a suitable colouration, it may be treated with a fire retardant, and it may be treated with a deodoriser to slowly release deodorant.

Claims

CLAIMS:

1. A method of operating a landfill site for waste disposal, in which a covering of permeable sheet material is laid over deposited waste material.

2. A method as claimed in claim 1, wherein the covering is formed of cloth.

3. A method as claimed in claim 2, wherein the cloth is a textile.

4. A method as claimed in claim 1, 2 or 3, wherein the covering is bio-degradable.

5. A method as claimed in any one of claims 1 to 4, wherein the covering is of natural fibre.

6. A method as claimed in claim 3, wherein the covering is hessian.

7. A method as claimed in any one of claims 1 to 6, wherein the covering is laid in pieces.

8. A method as claimed in claim 7, wherein adjacent pieces are releasably connected together after laying.

9 A method as claimed in claim 8, wherein the pieces are stitched together.

10. A method as claimed in any one of claims 1 to 9, wherein the covering is removed to allow additional waste material to be deposited, and then re-laid over the site.

11. A method as claimed in any one of claims 1 to 10, wherein the covering is laid from a roll.

12. A method of disposing of waste material, comprising providing a landfill site, depositing waste material in the site and placing a covering of permeable sheet material over the deposited waste material.

13. A method as claimed in claim 12, wherein the covering is removed to allow additional waste material to be deposited, and then re-laid over the site.

14. A method of disposing of waste material, comprising providing a landfill site, depositing the waste material in the site and placing a covering of sheet material over the waste material from time to time, wherein the covering is laid in pieces across the site and adjacent pieces are stitched together, the covering being removable to allow more waste to be deposited in the site.

15. A method as claimed in claim 14, wherein the pieces are permeable to both gas and liquid.

16. A method as claimed in claim 13 or 14, wherein waste material is deposited on a layer of the covering, the layer becoming part of the landfill.

17. A method of waste disposal substantially as hereinbefore described with reference to the foregoing example.