Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This application is divided out of copending Canadi~n application
No. 260,809, filed September 9, 1976.
This invention relates to methods and apparatus for recovering
livestock feed supplements from animal wastes. More particularly, the present ;
invention relates to methods and apparatus for separating the solids and
liquids from animal wastes from a flush-type facility and the treatment of
these separated materials in a manner suitable for recycling as animal feed
supplements. The present invention is particularly use~ul for confinement
~eeding facilities such as for feeding of livestock.
As evidenced in recent years the world demand or feedstuffs,
usually considered to be livestock feed ingredients, has outs~ripped supply
at least at historic price levels. As the world population continues to in-
crease, and the living standards of these populations also increases, upward
price exertions will remain on those feed ingredients for which livestock
and people dlrectly compete. All phases of the cattle producing industry
have been continually cost-price sensitive. The cost of energy, roughage
and protein sources available to the cattle industry have significantly
increased and the value of the finished product has been drastically reduced.
It is imperativ~ that production costs be reduced by lower ingredient costs
or improving efficiencies.
The concentration of production and availability of feed grain
and cellulose in certain geographical areas such as the so-called Corn Belt
of the United States indicates an economic advantage in raising and feeding
livestock in those areas. For various reasons such as protection from
climatic hazards, it is particularly attractive to feed such livestock in
confinement. Wherever there is proximity to more densely populated areas,
the control of air and water pollution relative ~o such confinement feeding
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systems is further important particularly relative to the waste handling and
treatment. Thus, it is attractive to provide systems which permit recycling
of the wastes as animal feed supplements.
Certain classes of livestock are much more ineficient users of
feedstuffs than others. For instance, beef cattle on a fattening ration
require a~ least seven pounds of ration (10% moisture) to produce one pound
of gain. According to the National Academy of Science investig~tions on
nutrient requirements of beef cattle, beef cattle require an equal amount of
energy for production and body maintenance if they are performing at a near
optimal level. Tllerefore, only 28 1/2% of all of the eed consumed by beef
cattle on a fattening ration is actually utilized. The remainder is passed
through in the form of animal excrement.
Livestock waste continues to represent a major problem to society
and to the livestock feeding industry. To comply with pollution regulations,
many livestock operators have improved their facilities to meet these re-
quirements, but their produc~ion costs have also increased. The most practi-
cal solution to the problems of pollution and increased ration costs is to
reclalm, process and recycle the waste from cattle that are being fed in
confinement feed lot facilities. Accordingly, various efforts have been
directed towards waste recycling in the agricultural industry. For many years
cattle feeders have allowed swine to follow cattle in the feed lot. The
purpose of this practi.ce was to allow swine to recover a portion of the un-
digested sollds from the cattle waste and convert ~hem into pork. Consider-
able research, and practical application, has been conducted in the area of
recycling poultry waste litter through other classes of livestock. Further,
one system ~or producing feed supplements from poultry is shown in United
States Patent No. 3,831,288 by Stribling et al.
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During recent years many research projects have been conducted
to measure the performance of beef cattle that were fed a ration that con-
tains processed beef cattle waste as a portion of their ration. The pre-
mise behind these research tests was to substitute not only energy, but all
or a portion of the protein in the ration with protein derived from beef
cattle waste. It would appear that feedlot cattle waste when properly
collected and processed can be included to make up a part of cattle rations
and the performance of cattle on feed is not adversely affected.
Numerous chemical tests have been conducted on feedlot cattle
waste to determine levels of protein, ~ry matter digestibility, calcium, etc.
Such research has determined that the amount of protein in fresh feedlot
cat~le excrement was 6.01%. When converted to a dry matter basis this excre-
ment contained 30.74~ protein.
Assuming that an 850 pound steer consumes 21.50 pounds of air
dry ration ~10% moisture) per day, along with a 28 1/2% utilization factor,
only 5.50 pounds of a typical "hot feedlot ration" is utilized by the animal.
The remainder of the ration, 13.85 pounds, is passed through in the excrement.
`As shown in certain "in-vitro" tests, about 70% of the dry matter in this
portion of the ration passed through the animal undigested. On a dry matter
analysis the digestibility of cattle excrement compares favorably to typical
corn silage.
Recent research conducted at Iowa State University has shown
that cattle performance when fed ensiled waste excrement is equal to the per-
formance of cattle that were fed whole-plant corn silage. Thus, there is a
tremendous economic potential to the confinement cattle feeding industry if
the undigested solid portion of the ration is reclaimed.
Summarizing, various efforts have been applied to recover the
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food value from the ~nimal wastes as supplements. For confinement cattle
feeding barns~ there are further a variety of flushable flume configurations
for recovering wastes such as are shown iTI United States Patent Nos.
2,233,766 by Bogert, 3,137,270 by Rigertin~ et al and 3,530,831 by Conover.
Further, oxidation of these wastes such as through intensive aeration in
storage reservoirs has been pursued. Various methods of inducing air into
such collected wastes have also been used. Some research has indicated
that Up to 50% of the animal wastes from feedlot cattle can be recycled as
food supplements except for the final month or two before marketing. Various
processes of treatment and silage storage have been suggested, and the re-
covered silage ration indicates weight gains comparable to cattle fed on
whole corn silage ration supplemented with various other additives. Some
examples of treatment and separation systems can be found in United States
Patent Nos. 2,270,869 by Ditto et al, 3,462,275 by Bellamy and 3,633,547 by
Stevens et al. The Stevens et al patent shows a closed loop type confine-
ment feed mg system wherein fermented and sterilized solids are automatically
added to the feed slurry.
Accordingly, it is a primary object of the present inVeTltiOn to
provide a method and apparatus for recovering animal feed value from animal
wastes.
According to one aspect of the present invention there is provid-
ed apparatus for separating solids and liquids rom a mixture thereof compris-
ing:
screen means having an upper substantially flat surface oriented
at an angle for permitting gravitational flow of said mixture over said
surface,
means for introducing said mixture to the upper portion of said
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screen means surface, said flat surface of said screen means being formed by
a plurality of parallel bars arranged in a spaced relation for defining a
plurality of transverse slots, the width of said slots being arranged to ac- ;
commodate passage of the liquid from said mixture therethrough while blocking
passage of the solids from said mixture,
liquid filter meansJ
means receiving said mixture from the lower portion of said screen
meanS for compressing said mixture against said liquid filter, and
means for receiving the liquids passing through said screen means
and said liquid filter means whereby the mixture after passing over said
screen means as a result of the gravitatlonal flow and after being compressed
against said liquid filter means will have a reduced liqui.d content.
According to another aspect of the invention there is provided
apparatus for separating solids and liquids from a mixture comprising:
a cylindrical drum means,
means for imparting rotary motion to said drum means,
filter means arrayed around the lower peripheral area of said
drum means, said filter means including a plurality of spaced bars arranged
for forming an arcuate surface in surrounding relation relative to the lower
peripheral area of said drum means,
porous endless belt means arranged to move against said spaced
bars and said drum means for compressing said mixture against said drum me~ns,
means introducing said mixture between said drum means and said
filter means at the point the peripheral edge of said drum means is rotation~
ally moving downward for compressing said mixture between said drum means and
said filter means, and
means for collecting the liquid passing through said endless belt
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and the spaces between said spaced bars, whereby the liquid fTom said mix-
ture will pass through said filter means while solids will pass between said
drum and the endless belt means and will be discharged at the peripheral
edge of said drum when said drum is moving upward.
Further objects, advantages and features of the present invention
will be more readily apparent in view of the following detailed description
of a preferred embodiment.
Figure 1 illustrates an arrangement for livestock feed supple-
mentation recovery in accordance with the present invention relative to a con-
finment feeding facility.
Figure 2 is a partially cross-sectional view of the press roll
separator shown in Figure 1.
Figure 3 is a front view of the press roll separator of Figure 2.
Figure 4 shows a partially sectioned view o the apparatus of
Figure 2 taken along section line 4-4.
Figure 5 shows the detail of the interrelationship of the drum,
belt and wedge wire basket of Figures 2, 3 and 4.
Figure 6, on the same sheet as Figures 2 and 3, is a section view
~ of a typical wedge wire section taken along line 6-6 of Figure 3; and
Figure 7 shows the detail of an aerator system.
The present invention is preferably useful in conjunction with
flush type livestock confinement barns and will be described in detail rela-
tive to a typical such barn 28 but it is to be recognized that the invention
is not limited to the confinement barn configuration as shown. Fresh water
is introduced at pipe 10 and the system is initialized by filling primary
aeration tank 11 therefrom. Tank valve 12 is provided for allowing water
iTito tank 11, which will eventualIy become the liquid portion of the wastes
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recycling system. Further) ~he content of tank 11 flows by gravity through
underground pipe 13 to the upper end of the confinemen~ feeding barn. The
effluent from tank 11 enters the bottom o~ the splitter box 14 to be divided
into as many parts as there are flumes or surge tanks 15. Flumes 15 can be
continuously or periodically flushed clean by flooding either sequentially
or all at once as desired.
The liquid from flumes 15 flows to the lower end of the barn
by gravity feed and carries the wastes to the sump 16. Sump pump 17 pumps
the wastes through pipe 18 to the wedge wire filter appara~us 19 where much
of the liquid is removed. The solids gravitate down the screen to the rotary
press 20. Press 2~ extracts more liquid from the solid portion of the wastes
and discharges the solids at approximately 6S% moisture into the solids hold-
ing bin 21. The liquid portion of the wastes flows through pipe 22 back into
primary aeration tank 11 for aerobic treatment. Overflow from tank 11 flows
over the additional wedge wire screen filter 23. Wedge wire screen filter
23 typically is a screen with approximately .005 inch openings between solid
wedge shaped bars. The small opening slots of such a screen remove most
of the liquid from the remaining solids from the overflow of tank 11 and
these solids will be primarily inert since they have been aerobically digest-
ed in tank 11. These solids are likewise discharged into holding bin 21.
The liquid flows from screen filter 23 through pipe 2~ into a final aeration
tank 2~5. Fresh water from source 10 can also be piped into tank 25 through
fresh water line 26 and a level maintained constantly in tank 25 by a conven-
tional float valve 27.
Sloped wedge wire screens for liquid separation by gravity feed
have been applied in several industries. A variety of such screens are com-
mercially available. As applied in conjunction with this invention, the
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screen size may vary depending upon such factors as the type of animal involv-
ecl, the type of ration being fed to the animals, etc. For a typical cat~le
feeding environment, the screen for filter 19 typically will have .010 inch
spacings between bars with the flat surface of such bars being approximately
3/16 inch and the thickness of the bars in the top screen being approximately
1/4 inch.
In a typical configuration such as for supporting abou~ five
hu~dred s~eers, tank 11 and tank 25 extend approximately 11' and 9', respec-
tively, above the surface of the confinement area. This allows enough head
pressure to flush the barn by gravity flow from tank 11 and also provides
enough head pressure from tank 25 to force the aerobic treated waste liquids
mixed with fresh water to the automatic livestock waterers in the barn (not
shown~ .
As shown in Figure 7, the aerators installed in tanks 11 and 25
utilize high volume, low pressure pumps 30 with the impeller mounted horizon-
tally. The power shaft 31 runs vertically from the bottom of each tank ~o
the surface or top of the aeration tanks 11 and 25 where electric motors 32
are mounted for belt driving pulleys such as 33 and thus drive power shaft
31. The llquid is received into the pump from the center of both top and
bottom of the housing of pump 30 which is positioned slightly above the bot-
tom of the tank. The liquid is forced through the pump discharge 34, the
flow is split and forced through two venturi units 35 and 36, air is supplied
to these venturis through a plastic pipe 38 that extends from the bottom of
a tank to above the liquid surface as shown in Figure 7. Air pump 40 drives
the air into plenu~ chamber 41 where it is appropriately split and introduced
to pipes 38 and 42, the latter terminating in a similar venturi assembly in
tank 25. The air is broken up and dispersed into the liquid by means of
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diffusers ~5 and 46. Due to the depth of the pump and baffles in the tank
(not shown), the air is retained in the liquid to transfer a high percent of
the oxygen into the liquid. It has been found that 10 cubic feet of air per
minute per horsepower can be put ~hrough the venturis with nearly 75% of the
oxygen transferring into the liquid of this type of application.
It should be noted that the air intake into air pump 40 of
Figure 7 is advantageously supplied by an Aran generator 39 which is somewhat
similar to an ozone generator. The main difference is that Aran is composed
of four and five oxygen atoms per molecule instead of three oxygen atoms as ~ -
in Ozone. The advantage of using Aran generator 39 is that the efficiency
of transfer of o~ygen into the liquid in the storage tank is significantly
enhanced since Aran and Ozone which are actually both produced by generator
39 are highly unstable. A still further advantage of using Aran is that it
provides a sterili~ation effect as it is introduced into the tanks via the
ventllris. This can be further controlled by the plenum 41 which splits the
flow from blower 40 and Aran generator 39. Note that air duct pipes 38 and
42 which extend from~above the surface of the tanks to the venturis (35 and
36) on the pumps can under some circumstances be all that is needed to supply
the air flow to satisfy the reduced pressure created in the venturi. However,
blower 40 between generator 39 and plenum chamber 41 can be arranged to main-
tain positive static air pressure such as by pumping ~15 cubic feet per minute
.md maintaining a static pressure of 3 inches. Thus the system not only
satisfies the venturi vacuum but, by the positive pressure, potentially
doubles the amount of air induced into the liquid. This could result in re-
ducing the horsepower demand on pumps 30% by 50% since the purpose of pumps
30 is to induce air and oxygen into tanks 11 and 25.
In the system thus descrlbed, every precaution is taken to conserve
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the wastes being removed from the confinement feeding facility. The waste is
flushed from the flumes with aerobic material from the primary aerator tank 11
on a continuous basis. The solids are separated and removed in a matter of
minutes and made available to be put into a silo for fermentation from storage
bin 21. After the solids portion of the waste has been placed in a silo and
allowed to ferment for typically twenty-one to twenty-eight days, the pro-
pionic, acetic an~ lactic acids which evolve in the ensiling or fermentation
process of such materials tends to enhance the digestibility and palatability
for potential recycling or feeding.
The unique filter and rotary press combination shown generally in
Figure 1 is particularly advantageous for separating solids from liquids and
illustrated in greater detail in Figures 2-6. This rotary press is particular-
ly advantageous for this application since it is relatively simple but still
economical and efficient in operation. As seen in Figure 2, the discharge
from pipe 18 from sump pump 17 is introduced to chamber S0 until it reaches
the apex of solid back wall 51 and overflows down wedge wire screen 19. ~s
can be seen in Figures 2~ 3, and 6, wedge wire screen 19 is composed of a
series of wedge-shaped horizontal bars such as 47 and 48 with a small lateral
gap 49 therebetween. Typically, bars 47 and 48 have an upper surface of
3/16 inches which are separated by 0.010 inches of open space, e.g. gap 49.
Thus, as reservoir 50 overflows so that waste material 43 flows down the face
of screen 19~ the liquids will be permitted to enter collection chamber 52
and eventually escape from pipe 22 back into ae~rator tank 11 (note Figure 1).
Eventually the materials sliding down the surface of screen 19 will reach
rotary spreader wheel 53 which rotates as indicated against the Elow of the
materials and prevents jamming against the drum 54.
Drum 54 is arranged in proximity to an endless belt 55 which
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typically is a nylon material. By applying rotary power to drum 54~ ma~erials
which reach the bottom o screen 19 are squeezed between ~elt 55 and drum 54,
thereby removing further moisture for collection in chamber 52. By making belt
55 somewhat porous such as by a woven configuration, the liquid escape from
between nylon belt 55 and drum 54 into collection chamber 52 will be augment-
ed. Typically, belt 55 would be o a net configuration with up to 3/16 inch
spacings but any ~luidically porous arrangement can be used. The primary
purpose of belt 55 is to support liquid flow therethrough while allowing
positive feed of solids 66 into the roller press. Belt 55 also reduces
friction between dr~l 54 and filter basket 75 (note Figure 5). ~:
Belt 55 is retained in position relative to drum 54 by an idler
roller 56, a slotted tube 57, and an additional idler roller 58, the latter
being vertically adjustable to maintain appropriate tension in belt 55. The
endless ioop of belt 55 is completed via rollers 59 and 60. The solids
which have been thus compressed are removed by rotating brush 61 so as to drop
over the front surface 62 of collection chamber 52 and thence into storage
bin 21.
Figure 4 shows the interrelationship of the drum and belt and
represents a section along line 4-4 of Figure 2. More particularly, drum 54
has a rubber coating 65 for interfacing with nylon belt 55 with the compress-
ed waste material being shown therebetween at 66. The edge o~ belt 55 is
guided by slotted tube 57 which extends for approximately one-half of the
circumference oE drum S~ as is shown in Figure 2 and is attached to sidewall
68 of the rotary press. The opposite sidewall 69 shown in Figure 2 has a
slotted guide tube attached thereto similar to 57. The idler rollers such
as 60 as can be seen in Figure ~ have slotted grooves (70) around the peri-
phery at each end thereof which receives the edge bead 71 of belt 55 and
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further provides guidance therefor.
The interrelationship of the slotted guide tube 57 and edge bead
71 is more clearly seen in Figure 5. In addition, Figure 5 illustrates the
relationship of a wedge wire basket 75 which extends around the circumference
of drum 54 in substantially the same manner as guide slot 57 shown in Figure
2. The particular cross-section of the arcuate bars forming basket 75 as
shown in Figure 5 is advantageous in that it provides a generally rigid means
for retaining endless belt 55 in proximity to drum 54 while still providing
relatively free flow of liquid therethrough. In a typical example, screen
filter 75 has approximately ~010 inch spacings with a screen thickness of
about 1/2 inch.
For a typical cattle confinement feecling application, drum 54
has a diameter of 31.5 inches and is driven at 1 rpm of rotation, spreader
53 has a 6.5 inches diameter and 30 rpm of rotation, and scraper brush 61 is
of a 4 inch diameter with 40 rpm of rotation. More particularly, drum 54 is
composed of a 30 inch diameter steel cylinder with a 3/4 inch thick forty
durometer rubber coating 65 molded on the outside with a 31.5 inch outside
diameter finish. Wedge wire 19 is of the dimensions mentioned with a 6 foot
width and 5 foot slope at 50 to the horizontal. The use of a stainless
~steel wedge wire screen 19 and the relatively low rotating speed ~one to two
rpm) of dr~m 54, minimum energy is required and friction and wear are also
minimized while obtaining maximum separation. The efficiency of the system
can be improved and operating costs reduced by including a fan 40 pressuriz-
ed plenum 41 from which air ducts 38 and ~2 are run to the vent pipes 38 and
~2 leading to the venturis in the bottom of the aeration tanks 11 and 25.
By way of example, assume the present invention is being adapted
to accommodate confinement feeding of two thousand steers which average 40
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pounds of waste per day. This waste is 85% moisture containing 1.5 pounds
Biological Oxygen Demand. If 60% of the 40 pounds were removed as liquid
containing 6% solids~ there would be 24 pounds of liquid that would contain
1.58 pound of solids. In the 40 pounds of waste there was 6 pounds of dry
matter and they contained 1 1/2 pounds Biological Oxygen Demand; then 1.58
pound of dry mat~er in liquid portion would contain .2531 pounds Biological
Oxygen Demand per steer per day times twQ thousand steers equals 506.2 pounds ;~
Biological Oxygen Demand daily. A 5 horsepower pump would add 50 cubic foot
of air per minute or 72,000 cubic foot of air per day and would equal 65
cubic eet per 1 pound of oxygen or 1108 pounds dissolved oxygen. With 50%
oxygen transfer, a 5 horsepower motor 40 in Figure 7 on a pump would furnish
enough oxygen for two thousand cattle.
A 21 foot diameter by 21 foot deep tank 11, allowing 1 foot
freeboard provides a capacity of 6927 cubic feet, OT 51,954 gallons. This
amount of storage will allow 9.2 days retention time for the liquid por*ion
of the waste from two thousand cattle, assuming no loss through aeration,
and disregarding the volume of liquid that would be in the flushing system
of the barn (1,000 feet long) continuously.
With a 5 horsepower motor 40 being used on a Parma pump 30 with
a double venturi, 10 cubic feet of air per minute per horsepower can be put
,
- into the liquid at a~depth of approximately 18 feet below the surface. At
this rate, 72,000 cubic feet of air would be induced every twenty-four hours.
If we assume 1 pound of oxygen in each 65 cubic feet of air, there would be
10,191 pounds of oxygen induced for each daily production of Biological
Oxygen Demand with the calculated Biological Oxygen Demand being 506.2 pounds
per day. Thus, aeration treatment will be completed in the 9.2 days retention
time.
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In converting the Dissolved Oxygen requirements to pounds o
Dissolved Oxygen per horsepower hour in thi5 particular application: 5
horsepower times twenty four hours times 9.2 days retent;on equalsllO4
horsepower hours. 506.2 pounds of Biological Oxygen Demand times 2 pounds of
Dissolved Oxygen required equals 1012.4 pounds of Dissolved Oxygen. 1012.4
pounds of Dissolved 0xygen required per 1104 horsepower hours equals .317
pounds Dissolved Oxygen per horsepower hour which would be required to fur-
nish 2 pounds Dissolved Oxygen per 1 pound Biological Oxygen Demand.
Since the industry has accepted the rate of Oxygen Transfer per
horsepower hour to be 2 pounds per horsepower hour~ when working a mechanical
aerator in a 2% solids liquid, containing a constant 1 P.P.M. - Dissolved
Oxygen - a safe and general margin is projected. Instead of mechanical
type aerators such as surface aerators of paddle wheel types prevalent in the
prior art, the present invention via the venturi configuration assures that
the air is broken up into minute portions and mixed well into the liquid
well below the surface. The solids involved in this liquid are typically
of 10/lOOQ of an inch or less. Surface area per pound of Biological Oxygen
Demand in the solids involved are much greater than the average waste material.
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