High efficiency waste placement system for municipal landfills

A high efficiency waste placement and disposal method for disposing of solid waste in a landfill includes size reducing the solid waste, moisture adjusting the solid waste, placing the solid waste in a preselected geometric form thereby forming a waste pile, coating the exposed portion of the waste pile with a synthetic covering compound comprising a liquid, binder, cellulose fibers, and plastic fibers, biostabilizing the waste pile and compacting the waste pile. The waste is preferably placed in a matshaped stockpile for efficient biostabilization through sufficient aeration and moisture adjustment and compaction.

TECHNICAL FIELD 
The present invention relates to the field of waste management. More 
particularly, the invention relates to a method for efficiently and 
effectively placing and disposing of waste for municipal landfills. 
BACKGROUND OF THE INVENTION 
It is well-known today that both commercial and domestic activities produce 
an enormous amount of solid waste. Almost all of this waste is deposited 
into municipal landfills causing existing landfills to quickly fill to 
their capacity. Therefore, landfill space is significantly limited making 
it a valuable commodity. It is, therefore, necessary to efficiently 
utilize presently existing landfill space to its maximum landfill 
capacity. Developing new landfill sites or expanding existing ones could 
help alleviate the problem of dwindling landfill space. However, obtaining 
the necessary approvals for construction of new landfills on virgin land 
is extremely difficult. Therefore, this problem is preferably solved by 
maximizing the amount of solid waste existing landfill sites can handle. 
U.S. Pat. No. 4,838,733 issued to Katz teaches that by compacting municipal 
waste, to increase its density, an existing landfill can contain a greater 
amount of solid waste. However, the problem with this technique is that 
biostabilization of the existing municipal solid waste is not facilitated. 
Compacting merely increases the density of the solid waste present within 
the landfill, without actually decreasing the amount of solid waste within 
the landfill. In fact, compaction of the waste impedes its 
biostabilization. 
Techniques typically utilized in the disposal of other types of wastes 
create a number of problems when used for municipal solid waste disposal, 
particularly, within a landfill. For example, static pile aeration is 
conducted on concrete, other solid pavement, or virgin land and not on the 
landfill. When used in the landfill static pile aeration facilitates the 
intrusion of methane gas emanating from subsurface buried waste, 
differential settlement of the working surface, variation of water 
saturation elevations, and elevated water emissions. Also landfills are 
typically infested with nuisance vectors such as flies, insects, birds and 
animals which are attracted to municipal solid waste. 
It is therefore an object of the present invention to provide a method for 
increasing the effective density (that is, the number of tons of waste 
received, measured by a weight scale, divided by the number of cubic yards 
of landfill volume consumed, measured by a topographic survey) of a 
typical municipal solid waste landfill which thereby conserves landfill 
capacity and is of significant commercial value to the landfill owner. 
It is also an object of the present invention to provide a method of 
increasing the effective density of a landfill that does not impede the 
biostabilization process but rather enhances it, thereby reducing the 
actual amount of municipal solid waste. 
It is a further object of the present invention to provide a method of 
landfill management capable of dealing with the unique problems associated 
with municipal landfills. 
It is also an object of the present invention to provide a method for 
efficiently placing solid waste which utilizes readily available recycled 
waste materials. 
SUMMARY OF THE INVENTION 
The aforementioned objects are achieved by utilizing a high efficiency 
waste placement system for municipal landfills in accordance with the 
present invention. 
The system encompasses a process for efficiently placing and disposing of 
municipal solid waste in landfills. The process includes size reducing and 
moisture adjusting the municipal solid waste; placing the waste in a set 
form; coating the exposed portion of the waste pile with a synthetic 
covering compound; biostabilizing the solid waste within the waste pile; 
and, compacting the waste pile. Waste may be aerated may also be placed in 
a substantially mat-shaped form. Aeration means may be placed within the 
waste when stockpiled and used to aerate the waste. This method may be 
repeated upon the same area thereby forming a series of layers of 
compacted biostabilized solid waste. 
The synthetic covering compound utilized in the method described above may 
comprise a mixture of a liquid, a binder, cellulose fibers and plastic 
fibers. The liquid used within this synthetic covering compound may 
comprise water, landfill, leachate, and/or industrial waste water. The 
binder may comprise cement kiln dust, fly ash with portland cement or 
portland cement. The cellulose fibers may include shredded paper and/or 
finely shredded wood fibers. The plastic fibers may comprise polyethylene 
terephthalate fibers. 
The mixture may comprise approximately thirty percent to sixty percent by 
weight liquid, approximately forty percent to seventy percent by weight 
binder, approximately one half percent to ten percent by weight cellulose 
fibers, and approximately two percent or less by weight plastic fibers.

DETAILED DESCRIPTION 
The present invention involves a system that creates an increased effective 
landfill density thereby conserving landfill capacity while fostering the 
biostabilization of the municipal solid waste. This system includes: 
shredding the waste, moisture adjusting the waste, placing the waste in a 
specific configuration, installing an aeration system in the waste pile, 
covering the waste pile with a synthetic cover, performing static pile 
aerobic decomposition (biostabilizing), compacting the waste pile and 
covering the compacted waste pile with a synthetic cover. 
An initial step of the present invention is to reduce the solid waste into 
smaller sized particles. This is referred to as size reducing and is 
commonly accomplished by shredding the municipal solid waste. Typically 
much of the municipal solid waste deposited in a landfill is received in 
densely packed plastic bags which effectively prevents decomposition and 
biostabilization. Shredding decreases the density of the solid waste 
thereby facilitating biostabilization. Size reduction, by shredding or 
otherwise, may be performed using a wide variety of commercially available 
technology and equipment specifically designed for reducing waste. 
Examples are shear shredders, hammer mills, and even bulldozers utilized 
in the appropriate manner could suffice. Preferably the waste should be 
shredded to a nominal 2 to 6 inch particle size to facilitate 
biostabilization. 
The solid waste to be disposed should be moisture adjusted to such a degree 
that the moisture content sufficiently promotes aerobic biostabilization. 
If the moisture content is too low, biostabilization will be impeded and 
the time for the municipal solid waste to completely biostabilize will 
increase. However, if the moisture content is too high, the municipal 
solid waste may generate leachate which is highly undesirable since there 
is a tendency for it to seep into the ground water and other areas of 
concern. Ideally the moisture content of the municipal solid waste should 
be 40 to 60 percent by weight. Often, visual inspection of the municipal 
solid waste will enable one to determine if the moisture content is 
adequate. Visible liquid and/or puddles within the waste may indicate that 
the moisture content is too high. One technique for moisture adjusting 
municipal solid waste having a moisture content that is exceedingly high 
is by mixing the overmoisturized municipal solid waste with dry municipal 
solid waste. An inadequate moisture content may be visibly apparent if all 
of the solid waste is not wet and there are dry sections. The moisture 
adjusting should result in municipal solid waste that has no excess 
amounts of water and yet has no dry areas. 
Moisture adjusting may be performed with use of agricultural type spray 
irrigation units which are capable of supplying approximately 500 
gallons/minute of water to the selected area of stockpiled waste. The 
amount of water to be applied can be easily determined by calculating the 
appropriate weight of the dry waste using density and volume values and 
adding an amount of water which would yield a moisture content of 40 to 60 
percent by weight. 
The municipal solid waste may be reduced and moisture adjusted 
simultaneously. This allows the water, or other liquid, to be uniformly 
distributed and absorbed into the solid waste. This will help to maintain 
desired relative humidity conditions in interstitial gases generated 
during the subsequent biostabilization. Also, simultaneous shredding and 
wetting of municipal solid waste greatly aides in saprobe (aerobic decay 
microbes) distribution resulting in a more uniform biostabilization rate 
throughout the mass of waste. 
After the municipal solid waste has been shredded and moisture adjusted, it 
may be placed into a specific and predetermined form. Forms that are 
substantially geometric and symmetrical are preferred because they will 
typically be the most convenient for the landfill owner to effectively 
duplicate and will also aid in the biostabilization process discussed 
herein below. The shredded and moisture adjusted municipal solid waste may 
be placed in the appropriate form with the use of a conventional track 
loader. 
Referring to FIG. 1, it is preferred to place the material into a mat-like 
shaped pile 1 having a length and width which is substantially greater 
than its thickness. For example, the mat 1 of solid waste may be 
approximately 9 feet thick or 100 feet wide with the length of the 
stockpile mat-shaped waste being dictated by the requirements of the 
specific landfill. The optimum depth is typically 6 to 9 feet, however, it 
may be as high as 30 feet and as low as 4 feet. Other geometric and 
preferably symmetrical configurations for the stockpile may be utilized 
without departing from the scope of the invention. For example, use of 
geometric shapes such as windows and the like which are capable of 
repeated mechanical manipulation may adequately suffice for this 
invention. 
While the municipal solid waste is being placed or stockpiled in its 
predetermined form, a network of piping 15 may be placed therein in order 
to facilitate the biostabilization of the municipal solid waste. However, 
it is also possible to initially construct the pipe network 15 and 
thereafter place the municipal solid waste in a preselected configuration 
over the aeration means. Pipes 3 within the network act as an aeration 
means. The pipes are preferably located within the stockpiled municipal 
solid waste to create a substantially uniform air pressure at each 
location within the waste pile. 
The placement of the pipe network 15 should be preferably at least 4 feet 
above the landfill surface 7 to protect against elevated water saturation 
levels. The air injection pipes 3 should, preferably, be placed at a level 
5 feet above the bottom of the mat. When the piping network 15 is 
saturated by water or leachate, it may not be capable of effectively 
aerating stockpiled municipal solid waste. Therefore, the pipes 3 may be 
placed in their respective positions after 4 to 5 feet of municipal solid 
waste has been initially stockpiled. In addition, the exact placement of 
any aeration means, including pipes 3, will be dictated by the particular 
shape of the stockpiled waste 1. For example, when using a rectangular or 
mat-shaped waste pile 1, as is shown in FIG. 1, the pipes 3 should run 
perpendicular to the length of the pile 1 and parallel to the width at a 
distance of one-half the height of the pile 1. The pipes 3 should be 
spaced at equal distances from each other with perforations 8 in the pipes 
equally spaced throughout the entire stockpile 1. The maximum spacing 
between the pipes may be approximately 30 feet or less, any greater 
distance may yield unequal biostabilization. Each of the pipes extends 
from the waste pile 1 and is connected via an isolation valve 4 to a 
manifold 5. This manifold 5 may include a water control means 14 and is 
connected to a blower 6. The water control means 14 may inject water into 
the air from the blower to help maintain the moisture content of the 
stockpiled municipal solid waste 1. The blower 6 pumps air through the 
manifold 5 and through a series of isolation valves 4 and pipe 3. The air 
enters the waste pile 1 from perforations 8 within the pipes 3. 
Schedule 80 PVC may be used for the injection pipes 3. The manifold 5 may 
be constructed of SDR 35 PVC, flexible ADS or other materials which are 
well-known in the art. DRUM model 600 blower driven by a DEUTZ diesel 
engine suffices for the needs of this invention. However, other blowers 
and engines will also suffice. The blower 6 should move air at a low 
pressure (0.5 to 5 psig) and at a high volume (i.e., greater than 500 cfm 
for each 200 tons of stockpiled municipal solid waste) into the air 
injection manifold 5. It will be apparent to one skilled in the art that 
other types of blowers, drive motors and/or piping may be used in 
accordance with the principles of the present invention. 
The stockpiled municipal solid waste may be compacted, preferably after 
biostabilization has been achieved with conventional landfill compactors 
which are well-known in the art. The pipes 3 may be left in the pile 1 
after the waste has fully biostabilized. Thereafter, the waste pile may be 
compacted thereby crushing and disposing of the pipes with the 
biostabilized municipal solid waste. 
After the material has been placed in its appropriate configuration, the 
portion of the stockpile exposed to the air may be covered with a 
synthetic cover coating. The application of this coating on the outside of 
the stockpile protects the stockpile from vectors and blowing litter. The 
synthetic cover coating must itself be capable of disposal within a 
municipal landfill. Furthermore, in order to achieve the objects of the 
present invention, the synthetic cover cannot occupy a significant amount 
of space within the landfill. The synthetic cover may comprise a liquid, a 
binder, cellulose fibers and plastic fibers. 
The constituents used in the liquid portion of the mixture may include 
water, landfill leachate, and/or industrial waste water. Although either 
of these three types of liquids will suffice, water is the preferred 
liquid constituent because it is easily available. Many different 
qualities of water may be used including turbid, polluted and non-potable 
water. Industrial waste water may also be used, provided that it does not 
contain pollutants which react with the other constituents during mixing. 
Landfill leachate, created by percolation of water through the varied 
refuse at a landfill, may also be used as a liquid constituent. Since 
disposal and treatment of landfill leachate are troublesome and expensive, 
use of landfill leachate may provide an effective method of its disposal. 
However, the use of landfill leachate and industrial waste water as a 
liquid constituent may require increased safety precautions. 
The constituents which may be used as cellulose fibers include shredded 
newspaper, mixed types of shredded paper and/or shredded wood fiber. These 
cellulose fiber constituents may be used separately or in various 
combinations. Preferably, shredded newspaper or shredded mixed waste paper 
should be used because of its absorbability and availability. Newspapers 
may be shredded into particles, preferably less than one-half inch in any 
dimension. In order to insure proper liquid content in the total mixture, 
the shredded newspaper should not have more than a 6 percent, by weight, 
moisture content prior to mixing with the liquid constituent. Also, other 
finely shredded mixed papers usable as the cellulose fiber constituent 
should preferably be less than one-half inch in any dimension. These mixed 
paper fibers may include shredded magazines, phone books, corrugated 
containers, junk mail, office paper, etc. These shredded mixed papers 
should also be less than 6 percent by weight moisture content prior to 
mixing. Shredded wood fibers may also be used as a constituent provided 
that the wood fibers are finely shredded. The shredded wood fiber must be 
in a string or hair-like shape such as flexible excelsior. Wood chips are 
not satisfactory for use as the cellulose fiber constituent. 
The constituents which may be used as plastic fibers include high density 
polyethylene, polyvinyl chloride as well as other types of plastics 
shredded into thin hair-like fibers. These hair-like fibers 
Polyethylene terephthalate fibers, such as TETROFLEX.RTM. Type 401 fiber 
which are hair-like in diameter in between one-quarter to one-half inch 
long in length are preferred as the plastic constituent usable in the 
present invention. These fibers are manufactured from recycled products 
such as plastic soda containers. 
The constituents which may be used as binders in the present invention 
include mineral binders such as cement kiln dust, fly ash with portland 
cement, cement kiln dust with bentonite, or stone dust with portland 
cement. Cement kiln dust, the preferred binder used in the present 
invention, is captured during the manufacture of portland cement by air 
pollution control devices. Although cement kiln dust is the preferred 
binder constituent, other pozzolonic binders may also be used. Also, 
bentonite may be added to kiln dust to form the binder constituent. The 
bentonite enhances the smoothness and consistency of the mixture and also 
increases its tactness and viscosity, enabling the mixture of the 
constituents forming the synthetic cover to better adhere to waste and 
cohere to itself. Approximately 5 percent, by weight, of the total 
mixture, of bentonite may be added. However, it is usually not necessary 
or required to have bentonite with the cement kiln dust as the binder 
constituent. 
Fly ash and portland cement may also be used as the binder constituent. Fly 
ash are fine solid particles of ashes, dust and soot which evolve from 
burning fuel. The amount of portland cement used with the fly ash should 
be approximately 10 to 15 percent by weight of the total mixture. In lieu 
of fly ash, stone dust, derived from commercial stone crushing operations, 
may be used along with portland cement as a binder constituent. 
Accordingly, the amount of portland cement used with stone dust should 
also be between 10 to 15 percent, by weight of the total mixture. 
The constituents of the mixture forming the synthetic cover: liquid, 
binder, cellulose fibers and plastic fibers should be combined within 
specific ratios. The amount of liquid should be between 30 and 60 percent, 
but preferably, between 38 and 45 percent, by weight of the total mixture. 
The amount of binder in the total mixture should be between 40 and 70 
percent, but preferably, between 38 and 45 percent, by weight. The total 
amount of cellulose fiber in the mixture should be between 1/2 and 10 
percent, but preferably between 1/2 and 2 percent, by weight. The amount 
of plastic fiber used in the mixture may be up to 2 percent, or less, of 
the mixture by weight. 
The exact percentage of each constituent used to create the mixture may 
depend upon the weather conditions which exist during mixing and 
application of the synthetic cover. For example, at relatively higher 
temperatures, the amount of liquid used in the total mixture will be 
higher than the amount of liquid used at lower temperatures. However, the 
total amounts used should stay within the above stated ranges despite such 
weather variations. The amount of binder used in the mixture, unlike the 
liquid, will be higher on a cold day compared to the amount of binder used 
in the mixture on a hot day. The amount of cellulose fiber used is also 
dependent upon rain fall. On a day when rainfall is present, the amount of 
cellulose fiber should be a relatively higher percentage of the total 
weight of the mixture. Accordingly, the higher the rainfall, the higher 
the amount of cellulose fiber used. However, the amount of constituents 
used should remain within the aforementioned ranges despite changes in 
weather conditions. 
Using the aforementioned materials as constituents will result in a mixture 
which may be applied, by spraying or another manner, to a waste pile to 
form a cover which will minimize odor and prevent vectors such as birds, 
flies and other insects from feeding off the waste. 
Since there is a large amount of municipal solid waste to be disposed of 
within the landfills, the waste piles themselves will be large. 
Accordingly, it is necessary to utilize a synthetic cover capable of 
economical use on large areas. Synthetic cover application equipment 
manufactured by Landfill Service Corporation of Apalachin, NY, may be used 
to mix and supply the ingredients necessary to produce the synthetic 
cover. 
The synthetic cover for waste piles may be mixed by filling a mixture tank 
with a predetermined amount of liquid constituent such as water, landfill 
leachate, industrial waste water or any other water based compound that 
does not react with the constituents therein. The proper amount of 
cellulose fibers and plastic fibers are then loaded into the mixture tank 
containing the liquid. Optionally, a coloring agent, also available from 
Landfill Service Corporation, may be added if desired. An agitator is then 
activated such that the cellulose fibers and plastic fibers are mixed with 
the liquid. Typically, it is necessary to activate the agitator for 
approximately one minute or longer to adequately mix the liquid, cellulose 
and plastic fibers together. The binding agent is then placed into the 
mixer where it is thoroughly agitated with the liquid, cellulose fibers 
and plastic fibers. The mixing time necessary to yield a mixture with the 
proper consistency may vary depending on the percentage of each 
constituent added to the mixture. In addition, weather conditions such as 
temperature and humidity may affect the length of time that the binder 
must be mixed with the liquid, cellulose fibers and plastic fibers. 
However, in all cases the materials should be mixed until the mixture 
becomes a thick viscous slurry having a "milk shake" type consistency. 
When the mixture is properly agitated, a spray applicator is moved to the 
working area and the mixture is sprayed onto the waste pile surface using 
a motion similar to spray painting. The mixture is sprayed in such a 
manner that a uniform layer approximately one-eighth to one-quarter inch 
thick exists. After the entire surface area of the waste pile has been 
sprayed in this manner, the material will harden if undisturbed. When the 
mixture is applied at the proper consistency, it will resemble a coagulant 
type material which will adhere to the waste pile and cohere to itself. 
Typically, the material will dry and harden to resemble a stucco type 
finish within 24 hours. After the entire waste pile has been covered, the 
applicator and mixing unit must be cleaned out thoroughly when not in use 
so that the mixture remaining within the apparatus does not harden. 
Typically, water will suffice in cleaning the apparatus. For convenience, 
cleaning may occur directly on the landfill itself. 
The manufacture, use and application of the synthetic cover for waste piles 
is more thoroughly described in U.S. Pat. application Ser. No. 674,864 
filed on Mar. 25, 1991 and U.S. Pat. application Ser. No. 966,269 filed on 
Oct. 26, 1992, each of which is incorporated herein by reference and made 
a part of this disclosure. 
Once the waste pile is covered and the synthetic cover has hardened, static 
pile aerobic decomposition of the waste pile may be conducted. Although 
aeration of the stockpiled waste may be accomplished in a multitude of 
ways, the piping network may be used as a means for directing forced air 
into the municipal solid waste in order to adequately aerate the municipal 
solid waste. Having a system of aeration pipes within the pile allows one 
to effectively control the interstitial gas conditions with considerably 
less effort. Such aeration allows for effective control over temperature 
as well as the resupply of oxygen within the substrate. The aeration of 
the stockpiled waste, referred to as static pile aerobic decomposition, 
facilitates biostabilization of the waste. When static pile aerobic 
decomposition is occurring, the municipal solid waste will generate heat. 
Substrate waste levels will reach temperatures ranging from 120.degree. to 
140.degree. F. for several weeks indicating that biostabilization is 
occurring in the thermophylic range. If the temperature of the substrate 
exceeds 140.degree., undesirable bacteria begin to flourish and the 
desired bacteria which thrive on the low to medium range temperature will 
be harmed. Adequate aeration of the waste pile will effectively keep the 
temperature within the appropriate range. If the temperature has been 
brought down from over 140.degree. to the appropriate 
120.degree.-140.degree. range, the substrate temperature may again rise to 
140.degree.. When this occurs, the municipal solid waste may need to be 
reaerated. Again the piping network may be used as the aeration means and 
air pumped therethrough. If the temperatures never reaches the 
120.degree.-140.degree. temperature range, or it falls below this range, 
it may be necessary to once again moisture adjust the waste within the 
stockpile. The waste may need to be reaerated and moisture adjusted more 
than once. 
The synthetic cover will not impede the aeration of the stockpiled waste. 
Because the waste has been shredded, the surface of the stockpiled waste 
is not smooth and non-porous. Therefore, the applied synthetic cover does 
not result in a smooth uniform non porous coating. The coating, due to its 
consistency as applied to piles of solid waste, contains various pores and 
openings therein which allow air and interstitial gases to be exhausted 
therethrough during aeration. The aeration and biostabilization should be 
allowed to remain in the thermophylic stage of aerobic decomposition for a 
period of 60 to 90 days. The major portion of biostabilization will have 
taken place when the substrate temperature decreases from the 
120.degree.-140.degree. range to a temperature of 70.degree.-80.degree.. 
When the temperature so decreases, a major portion of the biostabilization 
process has been achieved and most of the organic waste has been converted 
into a brown humus-like material. 
Following the biostabilization, the mat-shaped waste may be compacted with 
standard landfill equipment such as a landfill compactor. Once compacted, 
fresh waste may be processed using the identical system. However, as shown 
in FIG. 2, the fresh waste 11 may be stockpiled directly on top of the 
previously stockpiled and now completed waste 1. After the fresh waste has 
fully biostabilized, it may be compacted thereby creating a series of 
layers of compacted mats. A 9 foot high mat-shaped stockpile will be about 
3 feet thick after compaction. It is possible to cover the compacted 
material with the synthetic cover prior to reperforming the steps herein 
but it is not required. 
Although the invention has been disclosed in relation to the embodiments 
described herein, it is apparent that the various modifications, 
substitutions, equivalents and other changes may be utilized without 
departing in any from the spirit of the invention. Any such modification 
are intended to be within the scope of the invention as defined by the 
following claims.