Waste handling method

A method of handling waste is disclosed. The invention includes providing a transport vehicle or the like having a material-receiving cavity and a waste-receiving bladder carried within a portion of the cavity. A flowable waste material is loaded into the bladder at a waste collection site and delivered to a treatment facility located remotely of the collection site. A portion of the material-receiving cavity of the transport vehicle is filled with a non-waste material and is transported to a drop-off site located remotely of the treatment facility. In one embodiment, the drop-off site is located relatively closely to the waste collection site. The bladder may also be collapsed into a generally flat shape for use as a tarpaulin for covering the non-waste material.

FIELD OF THE INVENTION 
The present invention relates generally to the field of waste handling, 
treatment and disposal. In particular, the invention provides a method for 
efficiently transporting, treating and utilizing a flowable waste 
material. 
BACKGROUND OF THE INVENTION 
Researchers are continually searching for new methods to treat and dispose 
of waste materials. Finding a cost-effective, environmentally safe method 
of dealing with waste has always been problematic, and the problem is 
particularly acute in large cities and other areas with high population 
densities in such areas, the value of land tends to be rather high, adding 
significantly to the capital costs of providing a proper waste disposal 
site. Operational costs associated with transporting the waste, however, 
may offset the capital cost savings gained by moving the waste to a remote 
location where land values are lower. This is particularly true in the 
case of waste water, primarily because the cost of building and 
maintaining a waste water pipeline between the city and a distant location 
often vastly outweighs the cost savings associated with the land itself. 
Accordingly, it would be desirable to provide a reliable, cost efficient 
method for transporting waste water from one location, such as a city, to 
another location, such as a rurally located treatment facility. 
Waste materials, including both solid wastes and waste water, represent 
significant potential sources of energy. Some municipalities have 
attempted to recove this energy and reduce the amount of solid waste 
deposited in landfills by incinerating solid waste. However, such garbage 
incinerators are meeting increased resistance due to their high cost and 
the risks they impose to the environment. 
As an alternative to incineration, others have used anaerobic 
decomposition, i.e., decomposition in a low oxygen or oxygen-free 
environment, as a means of treating organic waste on a small scale. The 
main products of anaerobic decomposition include carbon dioxide 
(CO.sub.2), methane (CH.sub.4), hydrogen sulfide (H.sub.2 S), and 
nitrogen-rich solids. As methane is a primary component of natural gas and 
is readily combustible, methane produced by anaerobic decomposition of 
waste can be burned to produce energy without posing any significant 
environmental hazard such as those presented by common incinerators. 
Furthermore, the nitrogen rich solids which are produced in this type of 
decomposition tend to be dispersible in water and may be used as a 
fertilizer or soil conditioner. Because anaerobic decomposition is an 
environmentally safe method for utilizing the energy stored in waste 
materials and because this process can provide a valuable fertilizer 
source, it would be desirable to have a method of utilizing this natural 
biochemical process on a large scale. 
It has long been known that the growth rate of plants generally bears a 
proportional relationship to the concentration of carbon dioxide in the 
ambient atmosphere--a low carbon dioxide concentration tends to stunt the 
growth of the plant while an elevated carbon dioxide concentration can 
significantly increase the rate at which the plants grow. Although 
enhanced carbon dioxide concentration has been used in enclosed 
environments, such as greenhouses, utility of this technique in growing 
plants under field conditions is rather limited because the carbon dioxide 
becomes diluted by the ambient atmosphere and is blown away by the wind. 
Accordingly, it would he desirable to provide a means of utilizing 
enhanced carbon dioxide concentration to grow plants, such as trees, under 
field conditions. 
SUMMARY OF THE INVENTION 
The present invention provides a method of handling waste that is both 
commercially advantageous and environmentally safe. In one embodiment, the 
invention provides a method for economically transporting waste from one 
location to another, treating the waste to produce a biogas, and utilizing 
a portion of that biogas to enhance plant growth and/or as a fuel source. 
Another embodiment of the invention comprises a method of handling waste 
which utilizes a waste-receiving bladder carried within a 
material-receiving cavity. A flowable waste material is loaded into the 
bladder at a waste collection or storage site and the waste material is 
transported to a remote treatment facility. The waste material is then 
removed from the bladder and delivered to the treatment facility, where it 
may be processed. The cavity within which the bladder rests may then be 
filled with a non-waste material and the non waste material is transported 
to a drop-off site. Thus, one may haul waste in one direction and a 
non-waste material in another direction, all using the same transport 
means, without contaminating the non waste commodity. 
In another embodiment, the invention provides a method of handling waste 
wherein waste material is loaded into a waste-carrying vessel and 
transported to a remote treatment facility, where it is unloaded. The 
waste is then anaerobically digested at the treatment facility and a 
portion of the biogas resulting from the anaerobic digestion is utilized 
to enhance the growth of vegetation. The portion of the biogas so used is 
desirably relatively rich in carbon dioxide. The remaining portion of the 
biogas, which is desirably relatively rich in methane, and relatively 
carbon dioxide-poor, may then be combusted as a fuel source.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In a first embodiment, the instant invention provides a method of 
economically transporting waste from one location to another. Referring to 
the schematic diagrams of FIGS. 1 and 2, a transport means (50 in FIG. 3) 
used in the invention includes a material receiving cavity (53 in FIG. 3), 
such as a common railroad car, and a waste-receiving bladder (11 in FIG. 
3, described in detail below) carried within at least a portion of the 
cavity. The transport means may include any number of cavities, with a 
bladder being associated with each cavity. In the case of a train, the 
transport means could include a large number of cavities, with each car of 
the train defining a separate cavity. 
A flowable waste material is loaded into the bladder at a waste collection 
site. For instance, the waste may be substantially untreated waste water 
from a municipality accumulated at a predetermined collection site, such 
as a preexisting water treatment plant. The flowable waste need not be a 
liquid, however; any material which is flowable may be loaded into the 
bladder. The waste may be a slurry of a municipal solid waste or the like, 
or even a flowable solid without any significant liquid content, e.g., a 
powdered solid such as coal ash. 
The waste is desirably loaded by known means into the bladder to fill 
substantially the entire volume of the material-receiving cavity of the 
transport means. When so filled, the bladder may line substantially the 
entire interior of the cavity. Once the bladder is filled, the waste may 
be transported to a remote treatment facility. Although this facility may 
be fairly close to the waste collection site, in most circumstances it 
will be located a significant distance away from that site. If the waste 
collection site is in a city or other high population density location 
where land value is relatively high, for example, it would be economically 
beneficial to locate the treatment facility relatively far away from the 
collection site at a place where the cost of real estate is significantly 
less and environmental and public health risks are minimized. In a 
particularly preferred embodiment set forth below, wherein coal unit 
trains are employed as the transport means, the treatment facility may be 
positioned hundreds of miles from the waste collection site without unduly 
increasing transportation costs. 
Upon reaching the treatment facility, the waste is unloaded from the 
bladder and delivered to a treatment facility for processing. The 
treatment of the waste may be carried out in any known manner, with the 
treatment chosen depending upon the nature of the waste. For example, in a 
preferred embodiment described below, organic wastes are anaerobically 
digested. If the waste is not capable of being broken down in this manner, 
it would obviously be preferable to utilize a different treatment regimen. 
Some waste materials may be essentially untreatable and their "treatment" 
may simply comprise interment in a landfill. 
Due to the fact that different classes of waste may require different types 
of treatment, it may be desirable to segregate the waste, particularly if 
the transport means includes a plurality of bladders This permits one type 
of waste, such as a relatively high-solid slurry, to be loaded into one 
bladder and another type of waste, such as a relatively low-solid waste 
water, to be loaded into another bladder in a different cavity. When 
delivering waste to a treatment facility, the various types of waste could 
be directed to different areas of the same treatment facility or could be 
directed to entirely different treatment facilities, with each facility 
being designed to handle a different type of waste. If the latter approach 
is used, additional waste could be collected at a second waste collection 
site to refill bladders emptied at one of the treatment facilities. 
When the flowable waste is delivered to the treatment facility, the bladder 
desirably is substantially emptied of its contents. This permits the 
bladder to be collapsed to a generally flat configuration, as described 
below The bladder may then be substantially removed from the 
material-receiving cavity, placing the cavity itself in condition for 
receiving material rather than holding the bladder. In removing the 
bladder from the cavity, it should be sufficiently disposed away from the 
opening or openings through which the cavity is commonly filled so that 
the cavity may be unobstructedly filled with another material. 
Also after the waste in the bladder is delivered to the treatment facility, 
the transport means is moved to a collection site for a non-waste 
material. This movement may occur before or after the bladder is removed 
from the cavity, or the bladder could be removed while the transport means 
is in transit. Any type of commodity may be stored or collected at this 
non-waste collection site, and virtually any such site may be served 
according to the present invention. For instance, the site may be a 
warehouse for goods of the type commonly carried by the chosen transport 
means. In a particularly preferred embodiment set forth below, the 
non-waste collection site may comprise a strip mining site where a 
mineral, such as coal, is extracted from the ground. 
Once the transport means reaches the non waste collection site and the 
bladder has been substantially removed from the cavity, the cavity may be 
filled with the non-waste material or materials held at this collection 
site. The non-waste material in the cavity is then transported and 
delivered to a drop-off site where the non-waste material is desired. As 
with the non-waste collection site, the nature of the drop off site served 
will depend upon the type of commodity being transported. For example, if 
the non waste material being hauled is coal, the drop off site may be a 
coal fired power plant. Although a single drop off site will usually 
suffice, at times it may be preferable that a single load of commodities 
carried by the transport means be delivered to a multiplicity of drop off 
sites, particularly if the transport means includes a plurality of 
material receiving cavities. 
The method set forth above may be readily repeated to provide a continuous 
means for hauling waste material to a treatment facility in one direction 
and transporting a non-waste material in the other direction. If such a 
repetitive circuit is desired, the bladder should be replaced in its 
original position in the material receiving cavity and transported to the 
waste collection site to be refilled with flowable waste. Such a 
repetitive circuit is particularly useful when the drop off site is 
located relatively closely to the waste collection site. In this case, the 
transport means may be transported a relatively short distance from the 
drop-off site to the waste collection site, minimizing the distance 
traveled without any payload to cover operating costs. 
As noted repeatedly above, the present invention is particularly useful in 
connection with a mining operation. In current coal mining practice, coal 
removed from a mining site, such as a strip mine, is delivered to a drop 
off site where the coal is used or processed. This is commonly 
accomplished by means of unit trains having a large number of individual, 
open-topped railroad cars. These unit trains run a circuit from the mining 
site to the drop off site and back. While the mine is commonly located in 
a rural area, the drop-off site is often a power generating facility, such 
as a coal-fired power plant, located close to a distant city or 
municipality which consumes the generated power. Once a train has 
delivered a load of coal, it usually "deadheads" back to the mine site; 
that is, they make the return trip without any payload. Such deadheading 
is economically unattractive in that it obviously does not generate any 
income to cover the cost of transporting the empty train. 
According to the method of the present invention, such deadheading can be 
substantially eliminated. Drop off sites for coal are commonly located in 
high population density areas which tend to generate a large amount of 
waste. Since the drop-off site and the waste collection site may readily 
be located relatively closely to one another as noted above, this holds 
deadheading down to a minimum because a payload of waste may be loaded 
into a bladder on the transport means shortly after a non waste material 
is delivered at a drop off site. At the opposite end of the circuit, the 
treatment facility may be located very near the mining site. Mines are 
commonly located in areas where the value of the land itself is relatively 
low, particularly once the minerals have been extracted from the land. 
Desirably, the treatment site is located at the mining site and, in a 
particularly preferred embodiment set forth below, the treatment facility 
may be incorporated into a strip mining site and is useful in helping to 
reclaim the strip mine land. Although unit trains are often required to 
operate on a fairly tight schedule in order to meet the coal requirements 
of some power generating facilities, if waste is collect from only a 
single site and delivered to a single treatment facility, a significant 
commercial advantage can be gained by carrying a payload on the otherwise 
empty return trip without significantly delaying the train's schedule. 
One preferred embodiment of a bladder for use in the present invention is 
shown in FIGS. 3-5 and described in the current inventor's U.S. Pat. No. 
4,909,156 (the teachings of which are incorporated herein by reference). 
The transport means depicted in these figures comprises an open-topped 
railroad car, such as those commonly used for hauling coal. The 
3-dimensional generally rectangular flexible bladder 11 is placed within 
the material receiving cavity 53 defined by the bottom and walls of the 
railroad car 50. This enables a flowable material 60 to be carried within 
the railroad car, as noted above. Desirably, the bladder is formed out of 
a strong, durable rubber material with adequate flexibility to allow it to 
conform to the interior of the railroad car 50. The bladder 11 is 
structurally supported by the railroad car 50 and preferably comprises the 
fully enclosed, substantially leak-proof bag suitable for transporting 
flowable waste. The material of which the bladder is made should possess 
good chemical resistance properties so that its performance is not 
substantially affected by the waste carried within it or the environment 
to which it is exposed. 
Carried by the upper portion of the bladder 11 are one or more closable 
filling ports 12 through which flowable waste may be introduced to the 
bladder. Preferably, the filling ports 12 comprise rigid threaded hose 
fittings 33 which are permanently attached to the upper portion of the 
bladder and contain a central opening through which the flowable waste may 
be added to the bladder. A threaded cap 34 may be screwed onto the hose 
fitting 33, providing a seal to keep the waste in the bladder. A locking 
device may be included on the filling ports to prevent unauthorized 
persons from gaining access to the inside of the bladder. A gas release 
valve 35 may be included to allow gases to escape when the bladder is 
being filled. The gas release valve 35 may also employ automatic pressure 
relief means for releasing accumulated gas from the bag as necessary, 
e.g., gas pressure accumulated under elevated temperature conditions. 
Carried by the lower portion of the bladder 11 are a plurality of emptying 
ports through which the waste may be emptied for delivery to the treatment 
facility. The emptying ports may comprise a plurality of closable 
discharge ports 36 which may be adjustable so that the flow rate of the 
waste exiting the bladder 11 ma be controlled. The discharge valves 36 may 
protrude into the proximity of the hopper doors 51 of the railroad car 50 
so that the valves can be easily opened when the hopper doors are opened. 
The flow of waste through the discharge valves may be induced by gravity, 
or may be facilitated by pressurization. The discharge valves 36 may be of 
an obstruction screw type which would allow the valves to be adjusted to 
the desired flow rate. The discharge valves may include a suspension rope 
so that they may be removed from the hopper doors 51 from a remote 
position. 
When the bladders 11 are not being used to transport waste, they may be 
collapsed into a generally flat shape, as noted above. If the material 
receiving cavity 53 of the transport means is open topped, as shown, the 
bladder may be used as a tarpaulin to cover non-waste material 61 carried 
by the railroad car 50. The bladder thus serves to provide a waterproof 
cover to protect the cargo 61 from the elements and to prevent the cargo 
from spilling or blowing out of the car during transport (e g., coal 
dust). 
The bladder 11 may be provided with attachment mean through which an 
anchoring line 32 may be passed for removable attachment to the railroad 
car 50. The anchoring line 32 is preferably secured to the railroad car by 
threading the anchoring line through anchoring means 52 carried by the 
railroad car. A pair of end lashing ropes may be used to secure the ends 
of the collapsed belabor to the respective ends of the railroad car and to 
stretch it across the non-waste material carried by the railroad car. 
Any suitable means may be used to substantially remove the emptied bladder 
from the material-receiving cavity 53. In the embodiment shown in FIGS. 
3-5, a movable rolling bar 40 and retaining means 41 for the rolling bar 
is provided to remove the bladder from the cavity. The emptied bladder 11 
is removed from the railroad car by attaching one end of the bladder to 
the rolling bar 40 and rolling this rolling bar closely along the top 
surface of the bladder, accumulating the bladder thereupon in a spiral 
roll configuration as exemplified in FIG. 2. This spiral roll may then be 
placed on the rolling bar retaining means 41 which is carried adjacent an 
end of the railroad car, with the opposing ends of the rolling bar being 
securely retained by the retaining means 41. Alternatively, the bladders 
may be collapsed into their generally flat configuration and stacked on 
top of one another on a separate railroad car, such as a flatbed car, 
dedicated for this purpose. 
In order to fill the bladder with the flowable waste material, the bladder 
is placed inside the material-receiving cavity of the railroad car 50 with 
its discharge valves 36 closed. The valves are placed adjacent the closed 
hopper doors 51 of the railroad car carried by the discharge valves 36. 
Once the valves are in place, the bladder 11 may be lowered into the car 
and positioned so that&it generally evenly covers the floor of the car 
throughout its length. In order to minimize wear on the bladder, a padding 
material, such as a durable blanket, may be placed within the 
material-receiving cavity between the bladder and the points in the 
railroad car causing the most wear on the bag. Obviously, the blanket 
should be provided with a hole or the like adjacent the discharge valve 36 
so that it does not hamper the discharge of the waste. 
The caps 34 carried by the filling ports 12 are opened and a filling hose 
may be applied to the filling port. The flowable waste may then be loaded 
into the bladder by means of a pump, an auger, or other suitable means. 
The bladder should be reasonably monitored during this loading process to 
ensure that it is properly and evenly seated in the car before the bladder 
becomes too heavy to adjust. As the bladder is filled with the flowable 
waste, it conforms to the shape of the material-receiving cavity When the 
bladder is filled to a predetermined level, preferably adjacent but below 
the top rim of the car, the flow of waste is stopped, the filling hose is 
removed, and the caps 34 are replaced. When unloading the waste from the 
bladder for delivery to the treatment facility, the hopper doors 51 are 
positioned over a suitable discharge point and then opened to expose the 
bladder's discharge valves 36. The discharge valves may then be opened 
sufficiently to achieve the desired flow rate. When the bladder is empty, 
the discharge valves are closed and the bladder is ready to be collapsed 
and removed from the material-receiving cavity, such as by utilizing the 
rolling bar described above. 
Bladders of this type may be used for a relatively large variety of 
railroad cars; preferably the bladders are tailored to fit the particular 
car configuration in which they are used. In the case of a rotary dump 
car, the car may be rotated and the bladder drained through the fill port 
12. Obviously, this would necessitate providing means for holding the 
bladder in the railroad car as it is upturned. Alternatively, the bladder 
contents may be siphoned out through the fill port, or the bladder may be 
pressurized at one port to expel the contents at another port, or the 
bladder may be compressed to expel the contents through one or more ports. 
If a higher flow rate were desired, more discharge valves 36 could be 
used, or a significantly larger opening could be provided, which opening 
may be elogate with a length approximately equal to the width of the 
hopper doors 51. 
In a second embodiment, the present invention includes the steps of 
anaerobically digesting the waste at the treatment facility an utilizing 
by-products of this anaerobic digestion as a fuel source and to enhance 
the growth rate of plants. 
As explained above, anaerobic decomposition is a natural biochemical 
process which occurs when organic materials decay in an environment with a 
limited oxygen content. The products of such a decomposition include 
CO.sub.2, CH.sub.4, and nitrogen rich solids. A system for anaerobically 
digesting waste is set forth in U.S. Pat. No. 4,897,195, which is also 
owned by the current inventor The teachings and disclosure of that patent 
are incorporated herein by reference. This digester may handle a wide 
range of wastes, including manures, refuse, human effluent, distillery 
by-products, vegetable processing by-products, and other waste materials 
which anaerobically decompose. 
A preferred anaerobic digestion system such as that set forth in U.S. Pat. 
No. 4,897,195 is illustrated schematically in FIGS. 6-11. The system 
includes a plurality of digester modules 110, which generally take the 
form of a somewhat flexible bag, lying on an inclined surface 118 enabling 
the modules to be rolled slowly, thus agitating the contents of the 
modules and facilitating the anaerobic digestion process. The digester 
modules 110 are filled with a suitable waste toward the upper-most end of 
the inclined surface 118 and allowed to slowly roll down this surface 
adjacent other digester modules 110 over a period of time sufficient to 
complete the decomposition process, known as the digester life cycle. The 
digestion process takes place within the digester modules and biogas, 
i.e., the gas produced in the digestion, may be removed from the digester 
modules while the digestion process is taking place as desired. Materials 
may also be added to the modules to promote the digestion process without 
interrupting the process. 
The anaerobic digestion system may include a heating unit (not shown) for 
heating the contents of the digestion modules 110 to a temperature 
preferably between 100.degree. F. and 140.degree. F. to hasten the 
anaerobic decomposition process. The heating means may be contained within 
the digestion modules or may be external to the digestion modules. In one 
preferred embodiment, the modules 110 are housed in a solarium type 
structure, described below, taking advantage of passive solar energy. This 
digestion system may also include testing means comprising a master gas 
control unit 138 for sampling the contents of the digestion modules to 
determine the extent of completion of the digestion process taking place 
within the modules and for determining what materials, if any, to add to 
promote the decomposition process. 
In a preferred embodiment, the digestion modules 110 comprise generally 
cigar shaped synthetic bags which are liquid-tight and provide an 
anaerobic environment (i.e., a low-oxygen environment) in which materials 
can be digested. The materials from which the bags are constructed should 
be generally non-reactive so as not to interact with the digesting waste. 
As shown in FIG. 8, bags preferably include a plurality of fluid transfer 
ports allowing entry and exit of materials, including the organic material 
port 156, biogas port/line 154, sampling line 150, and doping line 52 for 
introduction of other substances to facilitate the digestion process. 
The digestion bags are desirably generally circular in transverse cross 
section, enabling them to easily roll down an inclined surface. The bags 
may also include hardware on their external side for lifting and moving 
them. They may also be provided with internal agitation means for stirring 
and agitating the contents of the bag to promote the decomposition process 
and to move substances contained within the bag to a favorable location to 
be easily removed from the bag. This agitation means may comprise a 
plurality of agitator paddles 148, shown in FIGS. 8 and 10, contained 
within the digester bag 110 for agitating the contents of the bag as they 
roll down the incline 118. In a preferred embodiment, the sampling doping 
and gas lines (150, 152, and 154, respectively) may be suitably attached 
to an agitator paddle to facilitate in adding and extracting materials to 
and from selected portions of the module. 
The emptying means on the digester modules 110 may comprise a closable 
opening for draining the contents as by pumping or alternatively may 
include a generally larger opening, such as that shown as 168 in FIGS. 8 
and 9, enabling the contents to be dumped and may be of any suitable 
closable type. 
In treating the waste in this anaerobic digestion system the digester 
modules 110 are placed in an area adjacent the highest point of the 
inclined planar floor. The upper-most portion of this floor is referred to 
as the digester head 114. The digester modules are arranged on the 
digester head as shown in FIGS. 6 and 7 where they are filled with the 
waste material. Although the digester modules 110 may be nearly filled 
with waste, some volume should be left for expansion as gases are produced 
in the anaerobic decomposition process. Living anaerobic bacteria may then 
be added to the waste within the module along with carbon dioxide gas and 
lignite to begin the digestion process. 
Preferably, more than one digester module 110 is prepared in this manner on 
the digester head 114 before being released by the head gate 116. The head 
gate 116 is a movable barrier between the digester head and the inclined 
planar surface 118 for retaining the digester modules on the digester head 
until they are ready to be released. When the head gate 116 is moved out 
of the way of the digester modules 110, the modules are allowed to roll 
onto the inclined surface 118. 
The digester modules 110 are allowed to roll slowly in close contact with 
one another along the inclined surface with their axes aligned generally 
parallel to one another. The material transfer lines and sampling lines 
150, 152, and 154 attached to the digestion modules are preferably in free 
rotating engagement with the master gas control unit 138 and remain 
connected to the digestion modules throughout their entire journey down 
the inclined plane 118. The master gas control unit extends along the 
length of the inclined plane to continuously monitor the progress of the 
decomposition process. The contents of the digestion modules 110 may be 
sampled by the computer-controlled master gas control unit, which may 
automatically dope the contents of the modules as desired for the most 
efficient anaerobic decomposition. 
The angle of the inclined plane 118 may vary from one system to the next as 
necessary. In most systems, the angle would be between about 0.1.degree. 
and 5.degree., desirably between about 0.2.degree. and 3.degree., and most 
preferably about 1.degree.. The determinative factor is that the angle be 
steep enough to enable the digestion modules 110 to roll slowly down the 
inclined plane 118 while in close contact with other modules, but flat 
enough to prevent the modules from attaining excessive momentum. A number 
of positioning gates 134 may be included along the inclined plane for 
retarding movement of the digestion modules 110. 
The lower end of the inclined plane comprises a digester tail 122 
preferably sized to hold three digestion modules 110 carried by the 
inclined plane 118. A tailgate 120 is positioned at the end of the 
digester tail to limit movement of the modules down the inclined plane. 
The tailgate 120 is movable to allow one or more digestion modules 110 at 
a time to roll off the digester tail 122 down an accelerator ramp 128 and 
onto either a conveyor for removal or onto an extended cycle incline 130, 
depending on the extent of completion of the decomposition process. The 
majority of the digestion modules reaching the end of the inclined plane 
will desirably have completed the anaerobic digestion process and will be 
ready to have their contents emptied. 
In order to empty the modules, a separating gate 124 is moved to allow the 
digestion modules that have passed by the tailgate to roll down the 
acceleration ramp 128 and onto a conveyor belt 136 where they are 
restrained from moving any further by an extended cycle head gate 126. The 
modules may be emptied by pumping the contents out through an opening or 
by forcibly dumping them into a receptacle, such as the tank 166 shown in 
FIG. 7. Once emptied, the digestion modules are returned to the digester 
head 114 where they may be refilled and reused. 
The transporting means used to move the modules may, in a preferred 
embodiment, comprise a motorized cable system 160, as shown in FIGS. 6 and 
7, for pulling modules 110 along a smooth surface. The conveying system 
includes a plurality of support towers 172 between which extends a 
continuous cable 170 to which the modules may be attached. 
When a digester module 110 reaches the separating gate 124 containing waste 
which has not been fully digested, the separating gate 124 is opened, but 
the extended cycle head gate 126 remains retracted. This permits the 
module to enter an extended cycle incline 130 similar to the incline 118, 
where the module remains until the anaerobic digestion process is 
completed. A tailgate 132 is included with the extended cycle incline 130 
to retain the digester modules 110 on the extended cycle incline 130 while 
the contents are still being processed. When the digestion process has 
been completed, the tailgate 132 is retracted to allow the digester 
modules 110 to pass by and proceed down an acceleration ramp 164 to a 
second conveyor belt 162 for removal. 
In an alternative embodiment, the modules 110 are floated in a pond or 
other body of controlled temperature water. Rotation of the modules 110 to 
agitate the contents may then be accomplished mechanically, either 
manually at desired intervals or automatically by suitable mechanical 
linkages to a drive motor (not shown). Alternately, an incline 4 may be 
used in conjunction with such a pool. In either alternative embodiment, 
filling and emptying of the modules can be carried out substantially the 
same as with the inclined embodiment described above. 
In the preferred embodiment described above wherein the treatment facility 
is located adjacent a strip mining location, one of the elongate trenches 
formed during the strip mining process may be utilized for this anaerobic 
digestion process. The floor of such a trench may function as the inclined 
plane 118. Alternatively, such a trench may be fortified, such as by 
techniques well known in forming earthen dams or by lining the trench with 
a layer of concrete or a large rubber liner. This trench ma then be 
flooded with water within which the modules 110 may be floated, as noted 
above. An insulating dome would be placed over the strip to maintain the 
elevated temperature necessary for anaerobic digestion. 
As noted above, the biogas produced during this anaerobic decomposition 
process may be extracted through the biogas port/line 154 in the digestion 
module 110 The biogas extracted from each such module may be carried 
through the master gas control unit 138 to a central collection site. Once 
the biogas has been collected, it may be utilized as desired, such as by 
simply combusting this gas to produce heat, which heat may in turn be used 
to maintain the contents of the digestion modules at an elevated 
temperature. In the alternative embodiments employing a body of controlled 
temperature water, this energy produced may be used to heat the water and 
thereby maintain the digester modules at the elevated temperature. 
In a preferred embodiment, however, the biogas is separated into a 
relatively carbon dioxide rich gas and a relatively carbon dioxide poor 
gas. It is preferred that the carbon dioxide-rich gas have only a minimal 
methane content to minimize the flamability of this gas. The carbon 
dioxide-poor gas, therefore, has a higher methane content and is more 
inflamable, making it a more efficient fuel source. The separation of the 
biogas into its various components may be accomplished by any of a wide 
variety of means well known in the art. 
The biogas produced by the anaerobic decomposition may be utilized in any 
desire manner. However, in a preferred embodiment, a portion of the biogas 
is used to enhance the growth rate of plants. As noted above, the growth 
rate of the vegetation may be significantly increased by enhancing the 
concentration of carbon dioxide adjacent the plants. The present invention 
therefore utilizes a portion of the biogas--preferably a carbon 
dioxide-rich portion--produced at the treatment facility to augment the 
growth rate of vegetation. 
This may be done by any known means. The carbon dioxide-rich gas may simply 
be supplied to an enclosed greenhouse environment. This will obviously 
increase the carbon dioxide concentration of the ambient air within this 
enclosure, thereby increasing the growth rate of the plants. 
In a particularly preferred embodiment, however, the carbon dioxide-rich 
gas is supplied to plants growing under field conditions. Such a system is 
depicted in FIGS. 12-14. This system is described in detail in the present 
inventor's copending U.S. patent application Ser. No. 601,873, filed Oct. 
23, 1990, the teachings of which are incorporated herein by reference 
A system for enhancing plant growth according to the present invention is 
shown in FIGS. 12-14. The system includes at least one elongate trench 10 
in which a plurality of plants may be grown. The trench comprises a floor 
212 and a pair of sidewalls 214 which extend along the length of the 
trench. The sidewalls desirably slope generally outwardly and away from 
one another in an upward direction. The sidewalls 214 of the trench 210 
are designed to minimize loss of carbon dioxide from the environment of 
the trench; if the sidewalls are too short or the slope is too gradual, 
their ability to retain carbon dioxide within the trench will suffer. If 
the sidewalls 214 are too steep, however, the effects of erosion will be 
more pronounced, adversely affecting their long-term stability. Although 
erosion can be checked by known means, such as employing a ground cover of 
smaller vegetation with extensive root systems, the slope of the sidewalls 
must be optimized by balancing these two competing considerations. Other 
factors, such as the nature of the soil and average rain fall at the site, 
must also be taken into consideration. Accordingly, the slope of the 
sidewalls 214 will tend to be relatively site specific. 
If so desired, a layer of top soil 216 may be enriched with fertilizers, 
such as a nitrogen-rich fertilizer, or other known chemicals which are 
useful in enhancing the growth of vegetation or increasing its resistance 
to disease or parasites. The nitrogen-rich solids which result from the 
anaerobic digestion process in the treatment facility described above may 
be used as a fertilizer. 
Elongate ditches 218 may also be provided in the sidewall. These ditches 
may, for example, be used for irrigation or, as explained below, elongate 
conduits for delivering carbon dioxide to the trench may be placed within 
these ditches. Although a pair of trenches are shown spaced from the floor 
212 and one another on each sidewall 214, the number and location of 
ditches may be varied a desired. 
In a preferred embodiment, a plurality of such trenches 210 are provided, 
with the trenches being oriented generally parallel to one another. A 
sidewall 214 of each trench is positioned adjacent the sidewall 214 of 
another trench, with the adjacent sidewalls defining a ridge 220. Although 
the sidewalls may directly abut one another to define a narrow ridge at 
the apex of the sidewalls, the ridge is desirably somewhat wider and may 
be substantially horizontal, as shown. Such horizontal ridges not only 
help minimize erosion, but they also provide a suitable planting surface 
for additional vegetation which may act as a windbreak, serving to further 
reduce the wind currents. The plants grown on the ridge to create the 
windbreak may all be of the same variety, and at approximately the same 
stage of growth, but this is not preferred. Instead, it is desirable to 
provide a windbreak composed of both tall, mature plants, such as mature 
trees, and a variety of shorter plant life to more effectively shelter the 
trench from wind turbulence 
For reasons explained below in connection with the delivery of carbon 
dioxide to the trench, it may be desirable to provide a sloped floor 212. 
In a preferred embodiment, the floor slopes downwardly from one end of the 
trench toward the other at a gradient of between about 0% and about 10%. A 
gradient of about 10% was found to work well in a laboratory test. 
The trenches may be oriented as desired. Although the layout of the land 
may effectively dictate the direction of the trenches, they are preferably 
oriented generally perpendicularly to the "prevailing wind direction." 
Obviously, the precise direction of wind currents adjacent the trench will 
vary over time. However, the historic weather patterns of many areas 
indicate that weather systems, and hence wind, will more frequently tend 
to move in a certain general direction. This direction is referred to 
herein as the "prevailing" wind direction, and is indicated in FIGS. 13 
and 14 by the arrow designated "W." 
Orienting the trenches such that they extend generally perpendicularly to 
this prevailing wind direction improves retention of carbon dioxide within 
the trench. If the wind travels in a direction substantially parallel to a 
trench, it will carry carbon dioxide rich air within the trench along the 
length of the trench and out one end thereof. As the wind direction 
approaches from a direction substantially perpendicular to the length of 
the trench, though, the sidewalls 214 and the windbreak, if any, on the 
ridges 220 impede the flow of air into the trench. By so restricting the 
passage of air into and through the trench, the sidewalls and the ridges 
serve to prevent the carbon dioxide rich air which is supplied to the 
trench from being either diluted by or carried off with the ambient air. 
FIGS. 12-14 depict the trenches of the present system as being 
substantially straight along their length. While the depicted construction 
is preferred, the invention may be practiced in trenches which may 
significantly deviate from a straight path. 
The invention is particularly well suited for use in reforestation of 
denuded tracks of land. As noted above, in a preferred embodiment, the 
present invention is used in conjunction with a strip-mining operation. In 
the process of strip-mining of minerals, such as coal, the soil above the 
mineral deposit is systematically pushed aside to provide access to the 
deposit. In so doing, large, elongate mounds of the cleared earth are 
commonly formed. Those carrying out such mining are required by law (see, 
e.g., 30 U.S.C. .sctn.1201 et. seq.) to reclaim the land, i e., to 
repopulate the site with vegetation, after the mining is completed. The 
current standard practice in the industry is to redistribute these 
elongate mounds to more or less recreate the original contour of the land 
and then plant vegetation on this new landscape. 
Strip-mining sites may instead be modified according to the instant 
invention. An elongate mound of cleared earth produced in the mining 
process may be formed to define a ridge 220 and the adjacent sidewalls 214 
of two trenches of the invention. When two or more such ridges are so 
formed, suitable trenches may be defined. In the short term, this would be 
beneficial in that the cleared earth would not have to be as extensively 
redistributed from the series of long mounds. In the long term, this would 
transform the former site of a mine from a commercially unproductive 
eyesore into a productive tract of land. In particular, the land may be 
planted with trees which can be sold as timber or as a raw material for 
forming pulp or combustible fuels, rather than merely lying fallow. 
As noted above, a trench of the invention is provided with a supply of 
carbon dioxide rich gas to accelerate growth of the plants in the trench. 
Although it may vary slightly, the average concentration of carbon dioxide 
in the ambient atmosphere is on the order of 0.03%, or 300 ppm. It is an 
object of the present invention to augment this concentration within the 
trench to at least about 0.06-0.20% (1500-2000 ppm). Although this 
concentration may be increased significantly more than that, if carbon 
dioxide comprises 10% (100,000 ppm.) of the ambient air, this may be toxic 
to animals which may live in the trench and workers who tend the trench. 
Furthermore, the beneficial effects of the heightened carbon dioxide 
concentration on plant growth are believed to diminish at concentrations 
of about 5% or more. Hence, it is preferred that the carbon dioxide 
concentration in the air within the trench be maintained at a level 
between about 0.06% to about 5%, with a range of about 0.06% to about 2% 
being preferred. 
It is well known that at standard temperature and pressure, carbon dioxide 
gas is denser than atmospheric air. In particular, the density of carbon 
dioxide gas is approximately 1.5 times that of an average ambient air 
composition. Accordingly, if one were to release a carbon dioxide-rich gas 
into the trench adjacent the floor 212, this denser gas would tend to stay 
within the trench absent any disturbance by air currents. Thus, the 
sidewalls 214 and the vegetation, if any, planted on the ridge 220, serves 
an important function--by limiting wind turbulence in the trench, the loss 
of carbon dioxide from the trench is minimized. Under high-velocity wind 
conditions, though, these measures alone may prove to be insufficient to 
contain the carbon dioxide in a trench for an extended period of time. 
This is particularly true when vegetation in the trench is dispersed 
because the plants which are being treated with the carbon dioxide-rich 
gas will not actively prevent the loss of carbon dioxide. 
In a preferred embodiment, the plants grown in a trench of the invention 
are "overstocked," i.e., they are planted more closely together than their 
optimum spacing under normal conditions. This will encourage the formation 
of a "closed canopy" as the upper portions of the plants grow rather close 
together. In the case of trees, for example, the upper branches of 
adjacent trees may tend to become interlaced with one another if the trees 
are planted too closely together. Such a closed canopy tends to result in 
the depletion of carbon dioxide from the air beneath the canopy because 
the supply of replenishing air is restricted by the presence of this 
closed canopy. While the leaves on a plant which are positioned above the 
"canopy" are exposed to the circulating ambient air, leaves below the 
canopy scavenge carbon dioxide from the air underneath the canopy. The 
level of carbon dioxide beneath the canopy is therefore reduced quite 
rapidly. Whereas the closed canopy restricts the flow of fresh air 
supplies to the underside of the canopy, this same restriction of gas flow 
through the canopy will trap the carbon dioxide-rich gas in the trench. 
Although a wide variety of plants may be grown in a trench of the 
invention, trees which grow well under overstocked conditions are 
generally preferred. Such trees include, for example, salixaceae populas 
tremuloides (quaking aspen). Alternatively, sorgham, a grain, may be used 
instead, as it has shown an ability to grow well when heavily stocked. 
Carbon dioxide may be supplied to the trench by a wide variety of methods. 
In a preferred embodiment, the carbon dioxide-rich gas produced in 
treating the waste is held in a storage facility 230 (schematically 
depicted as a building in FIG. 1) and is delivered to the trench through 
conduit means 232. If more than one trench is formed at the site, the 
conduit means 232 may include a manifold 234 for controllably distributing 
the gas to each of the trenches. 
The conduit means may deliver the carbon dioxide-rich gas in essentially 
"pure" form. However, as explained above, carbon dioxide can be toxic to 
animal life at a concentration of about 10%. If such highly-concentrated 
carbon dioxide gas were to be delivered into the trench 210, this would 
create a gradient of carbon dioxide concentration along the length of the 
trench as the gas mixes with ambient air, and may present toxic levels of 
carbon dioxide adjacent the conduit means. It is preferable, therefore, to 
deliver an admixture of the carbon dioxide-rich gas and air at higher 
volumes to achieve the desired concentration within the trench. Both the 
flow rate and the concentration of carbon dioxide in this carbon 
dioxide-rich gas supply may be varied according to known principles in 
order to effectively ensure that the desired concentration is achieved, 
and that the carbon dioxide concentration is substantially constant along 
the length of the trench. 
In one preferred embodiment, the conduit means includes a spur 236 which 
extends between the manifold 234 and a position adjacent the first end of 
the trench. This spur may simply discharge the carbon dioxide-rich gas 
directly into the trench, but it is preferred that a series of baffles 
(not shown) or the like be provided adjacent the discharge end of the spur 
to more effectively spread the gas supply across the floor of the trench. 
Alternatively, each trench may be supplied by a plurality of spurs 236 
which are spaced horizontally across the width of the floor 212 of the 
trench. If conduit means according to the present embodiment are utilized, 
it is desirable that the floor of the trench slope generally downwardly in 
a direction away from the spur 236, as noted above. Since carbon dioxide 
is heavier than air, this will lead to a more uniform distribution of 
carbon dioxide along the length of the trench because the carbon dioxide 
will tend to flow downhill, i.e., away from the spur 236. If so desired, 
this tendency may be enhanced by increasing the density of the gas exiting 
the spur, such as by cooling the gas by maintaining it under relatively 
high pressures in the conduit means 232. 
In another preferred embodiment, the spur 236 of the previous embodiment is 
replaced with a supply duct 238 which may extend along substantially the 
entire length of the trench 210. The supply duct may be provided with a 
number of discharge ports (not shown) which are substantially equally 
spaced along the length of the supply duct to more evenly distribute the 
carbon dioxide-rich gas along the length of the trench. If the trench 210 
includes a ditch (218 in FIG. 14), the supply duct 238 may rest in such a 
ditch. If so desired, more than one supply duct 238 may be provided in a 
trench, but it is not believed that this will be necessary under normal 
circumstances. 
Thus, the present invention provides an efficient, cost-effective method of 
transporting, treating, and utilizing a flowable waste material. This 
method is particularly useful in connection with a strip-mining operation. 
Waste ca be transported from a city or the like to the strip mining site 
at very low cost because the train hauling coal from the mine to the city 
would otherwise have to deadhead from the city to the mine. A large-scale 
treatment facility utilizing anaerobic digestion can be located at the 
mine site, where land value tends to be significantly less than in 
metropolitan areas. Finally, the products of this large scale anaerobic 
digestion can be used as a fuel source and to assist in reclamation of the 
strip-mining site by enhancing the growth of commercially valuable plants 
in trenches already present at the site. 
While a preferred embodiment of the present invention has been described, 
it should be understood that various changes, adaptations and 
modifications may be made therein without departing from the spirit of the 
invention and the scope of the appended claims.