Waste treatment

Landfill sites or other refuse deposits are temporarily covered by sheet material between successive filling or dumping operations. The sheet material may be left in place and more refuse deposited on top, or removed and re-used. The material is preferably woven, biodegradable and permeable, such as hessian. A number of sheets of the material may be placed together side-by-side and joined together such as by stitching, stapling or staking.

BACKGROUND OF THE INVENTION 
The present invention relates to a method of covering waste, refuse or 
other material. The invention is applicable to the handling of waste, 
refuse or other material which is disposed of in areas such as landfill 
and land raising sites, waste and refuse establishments and mineral 
quarries. 
It is current practice to provide daily cover for landfill sites at times 
when they are not actually being filed e.g. overnight. The covering is 
provided for several reasons including the following: 
(i) to reduce odors from decaying waste; 
(ii) to deter vermin, birds and flies; 
(iii) to minimize wind-blown litter; 
(iv) to improve the aesthetic appearance of the site. 
At the moment, valuable non-renewable mineral resources are being used to 
provide this daily cover. Where clay is used, it is very lumpy and 
non-flexible making it almost impossible to lay it less than 200 mm deep 
to provide a reasonable cover. The next day's waste is deposited over the 
cover layer and thus layers of waste are separated by cover layers which 
can be impermeable. As a result they inhibit gases released by the 
decaying matter from migrating and these have to be removed in other ways. 
A number of disadvantages arise from the use of minerals such as clay as 
daily cover, e.g.: 
(i) a potentially valuable, non-renewable, mineral resource is wasted; 
(ii) the material cannot readily be recovered and occupies valuable void 
which could otherwise be used, for example, for depositing refuse; 
(iii) if the cover is impermeable it has the effect of dividing the 
landfill into relatively small, individual, sub-cells which makes 
long-term management difficult because the sub-cells will tend to behave 
as individuals and not en masse; and 
(iv) if the daily cover is impermeable it will prevent the migration of 
fluids, gases and/or liquids and delay final stabilization of the site. 
SUMMARY OF THE INVENTION 
The present invention provides a method of covering waste, refuse or other 
material daily, the waste being placed in layers and a layer of woven or 
non-woven sheet material used to cover each layer and either left or 
removed before the next layer of waste is deposited. 
The sheet material may be removed before the next layer of waste, refuse or 
other material is deposited so that it simply provides a temporary cover 
or it may be left and waste deposited on top thereby providing a stack 
comprising layers of waste separated by layers of sheet material. However, 
in the preferred embodiment of the invention the material may be removed 
and reused until such time as it is no longer in a condition where it is 
reusable, at which point it will be left on and the next layer of waste, 
refuse or other material placed on top. 
The layers of sheet material are preferably permeable so that the gases and 
liquid, produced by the decaying material, can migrate rather than 
building up. For each layer of waste, a number of pieces of material may 
be used, preferably stitched or jointed together or fixed down. Thus, in 
the case of permeable material, escaping fluids or rainwater can migrate 
either through the material or from between the stitched or jointed 
pieces. 
Alternatively, or additionally, the sheet material itself may be 
biodegradable. Given that the waste which the sheet is to contain is 
relatively large, the sheet material may be in the form of a net or mesh. 
It is generally preferable if the holes in the material are no larger than 
the average size of the material being covered or are small enough to 
prevent access by vermin, whichever size is the smaller, in the case of 
waste a maximum of about 12.5 mm (0.5 inches) might be best. 
The new sheets of material are preferably dispensed from a roll which may 
be pulled by a tractor or other off-road vehicle which can be driven 
across the waste. A special implement for attachment to the vehicle either 
directly or indirectly on a towed sled or trailer may be designed for this 
purpose. Once used the material will be laid and removed using a bar to 
which the sheets will be attached and the bar pulled to and fro across the 
day's layer of waste or other material using either a machine such as a 
tractor or off-road vehicle or manpower. 
The preferred sheet material which appears to be most appropriate is jute, 
which is biodegradable and relatively inexpensive. This can be dyed, 
soaked with water or treated with chemicals, as required. Other 
possibilities include material having similar properties to jute such as 
TARPOL (TM), Wavelock sheeting, p.v.c. netting, p.v.c. sheet, canvas 
matting and hessian. 
The sheets of material, once laid, may be stitched or jointed together or 
fixed down at their edges and the material loaded down, as necessary, to 
prevent the sheets from being lifted. Such stitching, jointing or fixing 
will preferably be removable in order that the material can be re-used or 
re-positioned and then re-stitched, re-jointed or fixed down again.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Waste and refuse is frequently deposited in large holes in the ground, 
these are commonly referred to as landfill sites. The landfill site shown 
in FIG. 1 comprises a hole 1 which is lined with an impermeable linear 2 
(not to scale). The site may cover an area of many hectares. 
For the purpose of filing, the area of the hole 1 is divided into smaller 
areas known as cells. Each cell is usually built up layer by layer to the 
ground level 3 before the next cell is filled. Each layer is commonly 
referred to as a "lift". Thus, a cell consists of vertically adjacent 
lifts. FIG. 1 shows two full cells, 4 and 5, and a third cell, 6 being 
filled. Cell 4 is made up of lifts 4a, 4b etc., cell 5 is made up of lifts 
5a, 5b etc. 
Each cell is covered with a layer of sheet material overnight whilst it is 
being filled, this is preferably removed before the next day's waste layer 
is deposited. A typical day's waste layer might be about 2 m deep. FIG. 2 
is a top plan view of one cell with its overnight cover. The cover 
consists of several rectangular sheets 15 of jute matting, for example, 
laid edge to edge, such edges then pulled together to allow a lap required 
for stitching, jointing or fixing down. A vehicle 16 is shown dispensing 
the last sheet 17 from a large roll 18 which it is towing or carrying. 
When the last sheet has been laid the vehicle leaves and in most 
circumstances it is preferable that the vehicle does not drive over the 
cover material. 
The adjoining edges of each sheet will be either held together and machine 
stitched, jointed or fixed down 14 to provide total coverage of the day's 
waste layer and prevent each separate sheet of material from moving. Such 
stitching will be done preferably using a hand held industrial sewing 
machine and potentially mechanically laid and sewn automatically. Such 
stitching will be easily removable and the material simply re-sewn, 
re-jointed or fixed down the next time the sheets are placed over the 
waste. 
FIG. 3 shows a sheet material dispenser which may be used in connection 
with the invention. This consists of a large frame 20 on which the 
material roll 25 is rotatably mounted. The free edge of the material 17 
may be held down so that as the roll is moved in the direction of arrow 
`X` the material unwinds. 
The dispenser is designed to be towed or carried by a vehicle, or mounted 
on a sled or trailer. 
The use of material dispensed from a roll is suitable when the material is 
new. If the material is to be taken up between layers of waste, refuse or 
other material, it may simply be attached to a bar at one edge and drawn 
across the surface of the waste, as shown in FIG. 4. A sheet 15 is pegged 
or otherwise secured at one edge 15a and attached to a bar at its opposite 
edge 15b so that it can be drawn across the surface of the waste 30 to 
position it (FIG. 4(b)) or drawn back across itself to take it up (FIG. 
4(a)). The material in this case must be fairly strong but it should be 
borne in mind that the occasional hole made by the vehicle or the 
underlying waste, refuse or other material will not be a problem since the 
sheet can be repaired by stitching or other suitable means and is intended 
to be permeable anyway. 
When a landfill site is completely full it is usually covered with a layer 
of impermeable material This could be a natural cap made from a material 
such as clay with a low permeability or high density polyethylene, 
followed by soil, so that the area can be re-used, for example as 
agricultural land. This material, usually known as "capping" material, has 
to be of low permeability so that it reduces rainfall infiltration into 
the site and prevents gas migration. It must be of very high quality and 
strength so that vehicles can drive over it without causing damage, and it 
must not be biodegradable. In contrast, the material used for the 
intermediate covering of the present invention is not required to have any 
of these properties. 
Whilst the above description refers specifically to landfill sites, it will 
be appreciated that the invention is equally applicable to other waste 
disposal methods including land raising as well as mineral quarries and 
other areas of loose material where short term protection is required.