Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a method andan apparatus for composting waste.
Waste, which is taken to mean residual products
which have been assessed as being of no useful value and
discardedl may be treated in a number of different ways,
substantially dry, combustible waste which is biological-
ly degradable to a slight or moderate degree being suitable
~or use a fuel, whereas wet or moist biologically degrad-
able waste is treated in one of the following manners:
spreading on fields; use in land fillingj thermostabiliza-
tion (pasteurization); combustion with fuel additives;
anaerobic bioligical degradation (fermentation); aerobic
biological degradation (composting), vaxious other methods
such as encapsulation in cement, use together with bin-
ders as material for the preparation of building tlles~
use as fish feed in fish forming, etc.
On condition that transport and spreading costs
are reasonable and that the applicable environmental re-
quirements have been satisfied, spreading on fields and
use in land filling are often the cheapest and most suit-
.
able treatment methods. However, in view of today's ener-
gy costs and trends within technical development, compost-
ing is otherwise to be preferred both from the economical
and from the technological points of view.
In years gone by, a number of different tech-
ni~ues have been developed for composting waste, the most
important of these techniques being discussed briefly
below.
; The waste is deposited in a so-called long-term
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landfill area and is thereafter not subjected to any par-
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ticular treatment. This technique is extremely doubtful
and its functiorl is uneven. Among other things~ leachate
problems occur.
Another technique is to deposit the waste in
a landfill area having an aerated slab. In this technique,
the material is placed, as ~ rule aftex premixing of the
various components of the material, up in layers of a
determined height, length and width on a concrete slab,
whereafter air is sucked or blown through the waste ac-
cording to a predetermined plan. Apart from the fact that
the storage site proper requires high installation and
maintenance costs, this method has a number of disadvan-
tages. Por example, the process progresses unevenly because
of channel formation in the material, the process is slow
and difficult to control, the quality of the product is
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low and uneven, and finally the process gives rise to
unpleasant smell.
; These two methods are so-called static methods,
,
that is to say after deposition, no further handling takes
place of the waste during the composting time. Apart from
such static composting methods, there are also dynamic
methods in which the waste is worked during the composting~
One such dynamic method is so-called reactor
composting or closed composting in which the waste which
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is to be treated passes through a reactor such as a drum,
a column or the like and in this reactor is turned, degasi~
; fied for the removal of carbon dioxide, aera~ed for the
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supply of oxygen, and is regulated for moisture and tempera-
ture. A serious disadvantage inherent in reactor composting
is that the reactor cannot, for reasons of economy, be
made too large, with the result that the duration of stay
in the reactor will be short and degradation of the waste
incomplete. Consequently, a controlled maturing stage
is necessary.
Another dynamic method, so~called windrow compost-
ing, employs a self-propelled machine which simultaneous-
ly moves through the waste and treats it. Here, the waste
is laid openly in rows on a suitable substrate, such as
a concrete slab, possibly under cover if the weather condi-
tions so require. Each row is of a relatively slight width
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of roughly 2-4 m and a maximum height which is dependent
upon the angle of repose related to the width of the row,
and which is normally from 102 to 1.7 m. The width of
the row is in general adapted to the machine employed,
50 that the machine may straddle the row and treat it
during a single passage. Windrow composting is associated
:
with a number of disadvantages, such as the fact that
a large substrate surface is required for laying out the
waste, that is to say the material loadinq per surface
unit is low. In its turn, this entails a high level of
effect on the waste in variations in the weather (such
as precipitation) which results in an uneven product qua-
lity.
The object of the present invention is to ob-
viate several of the disadvantages inherent in prior art
composting methods and to realize a composting method
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which is economically viable and results in a stable product.
Like the windrow composting method, the present
invention relates to dynamic composting with a self-pro-
pelled maclline, but as opposed to the windrow composting
method, the waste is, in the present invention, deposited
in a large compost layer of a width of at least 5 m, pre-
ferably at least 10 m, a length of at least 5 m, preferably
at lest 30 m, and a height of up to 9 m. Deposition of
the waste in such a compost layer en-tails that the material
loading per surface unit will be favorably high according
to the invention, that is to say the installation will
be compact and economical. Furthexmore~ the waste is not
appreciably influenced by changes in the weather even
if no roof cover is provided over the waste.
According to the invention, the compost layer
is treated by means of a new type of self-propelled machine
which successively and in repeated periods works through
the compost layer and feeds the was~e, by means of a feeding
assembly and two feeding screws, into a conditioning as-
sembly where the waste is conditioned, under the action
of a cutting roller, with respect to particle size, particle
distribution, carbon dioxide content, oxygen content,
moisture content and temperature~ in order thereafter
to be discharged by means of a discharging assembly and
deposited in a new compost layer.
The machine according to the invention is highly
maneuvrable, for which reason demands on the evenness
of substrate can be reduced. Thus~ it is not necessary~
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according to the present invention, to provide expensive,
specially constructed concrete slabs, it being instead
suf f icient to provide a simple asphalted substrate. This
is a further economical saving made possible by the pre-
sent invention.
Hence, it is a major object of the present inven-
tion to realize a method of composting waste whereln the
waste is deposited in a compost layer having a lengtn
of at least S m, a width of at least 5 m and a height
of up to 9 m, and wherein the waste is successively fed
from the compost layer to a rotary cutting roller which
comminutes the waste and flings it, under intermixing
and vortex motion, through a conditioning compartment
in which the waste is freed of carbon dioxide and is sup~
plied with oxygen, whereafter the conditioned waste is
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; deposited in a new compost layer; and wherein the above
:~; treatment is repeated periodically from once every tenth
minute to once every sixtieth day for a total of from
~ l to 120 days.
~ It is a further majox ob~ect of the present
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`~ invention to provide an apparatus for composting waste,
. the apparatus comprisiny a chassis with wheels and a motor,
and the apparatus further comprisin~:
A) a movable feeding assembly mounted on the
`~ forward end of the apparatus, for feeding waste from the
compost layer to two rotary feed screws located beneath
; the feeding assembly;
i. B) a conditioning assembly having a rotary cutting
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roller provided with cutters and disposed between the
feeding screws and a conditioning compartment located,
seen in the feeding direction of the waste, after the
cutting roller; and
C) a discharge assembly for receiving the waste
from the conditioning compartment and discharging and
depositing the waste in a new compost layer~
Compared with the prisr art, the present invention
involves a number of advantages.
As was intimated earlier, one important advantage
is that the surface area required for the process is small,
that is to say the material loading per surface unit is
high in the present invention. As a result, installation
costs may be kept at a minimum. The high material loading
i5 realized not least as a result of the manner of driving
the machine through the compost layer, as well as of depo~
siting a new compost layerO In the treatment process,
the machine is driven through the compost layer along
a row whose width corresponds to the width of the machine.
After the treatment is completed, the compost`is deposited
in a new row of substantially the same width for building
up a new compost layer The new row is deposited close
to the machine and normally obliquely behind or at the
side of the machine, that is to say on that side of the
machine which is located opposite the original compost
layer. In the treatment process, the machine moves recipro-
cally through the compost layer, thereby simultaneously
building up the new compost layer with new rows which
are disposed approximately at one machine width's distance
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~rom the original compost layer. When the entire compost
layer has been treated once, a new compost layer has thus
, been built up at approximately one machine width~s distance
from the original compos~ layer. In the subsequent treatment,
the compost layer is moved back approximately one machine
width in the lateral direction and will thereby be placed
on the site of the original compost layer. In a manner
of speaking~ the compost layer, in the repeated treatments,
;~ oscillates laterally, substantially at right angles to
`~ the direction of advancement of the machine. It will be
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~ appreciated that the total surface which is required accord-
,~ ing to the invention for storing and working a compost
~ layer substantially comprises but the surface area for
-~ the compost layer proper, together with the surface area
of one row of a width correspondin~ to one machine width.
.;.
A further advantage in the present invention
is that the exposed surface per unit of volume of waste
is small, which entails that the state of the weather
will have but slight influence.
~; Compare~ with other composting methods~ such
"~ as with positive aeration or with a reactor~ the method
according to the present invention requires low investment
,, and running costs.
These and other advantages inherent in the pre
sent invention will be further apparent to the skilled
~; reader of the following description of the method and
apparatus according to the present invention.
In the method according to the present invention,
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biologically degradable material from various sources,
such as domestic waste, sewage sludge, waste from the
foodstuffs industry, for example scraps from the vegetable
indus~ry and slaughterhouse offal, etc. is treated in
the substantially solid phase in an aerobic~ mesophilic
or preferably thermophilic process.
As was indicated above, the waste is deposited
in a compost layer of considerable dimensions, the height
of the layer being up to 9 m and, in practicel suitably
at least 1 m, preferably from about 2 to about 4 m. Prior
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to the deposition in the compost layer, the waste is suit-
ably intermixed and homogenized. Further intermixing and
homogenization take place in conjunction with the treat-
ment according to the present invention.
The treatment according to the present invention
provides even and homogeneous conditions in ~he treated
material with a good degree of control of particle size
and distribution, while at the same time eliminating un-
favourable channel formation which is an important contribu-
tory factor to the formationqof cold and hot zones, wet
and dry zones, and aerobic and anaerobic zones.
Apart from the parameters of particle size and
particle distributionl the present invention calls ~or
the control and optlmation of the carbon dioxide content
(degasification), the oxygen content (aeration), the mois-
ture content, the temperature, the treatment frequency
and the total processing in time.
By optimum regulation of the process parameters
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according to the present invention, there will obtained
a rapid and complete degradation of the biologically de-
gradable material in the waste, which may be demonstrated
by a measurement of the biochemical oxygen demand (BOD).
The biochemical oxygen demand is, here, measured during
two ~BOD2), five (BOD5) and seventeen (BOD17) days, respec
tively, BOD17 being the most stringent criterium for sta-
bilization of the biologically degradable material. In
the invention, BOD17 is reduced by more than 80~. ~oreover,
the presence of pathogenes or parasites cannot be demonstrat-
ed in the finished compost This entails that the waste
will attain, in the present invention, a very high degree
of stability and hygiene.
In ~this context, it might be mentioned that,
in the field, it is often impractical to measure BOD17,
since this takes too long a time. Instead, a correlation
to units which may be determined rapidly, such as ash
content, carbon dioxide content or pH may be drawn. In
order~ after deposition of the waste in a CompQSt layer
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according to the above~ to treat waste under optimum control
of the above-mentioned parameters, the waste is successively
ed from the compost layer to a cond-itioning assembly,
where the waste~ after intensive working and comminution
with a rotary cutting roller, is flung through a condi~
tioning compartment under intermixing ahd vortex motion,
in order thereafter to be discharged from the conditioning
compartment and deposited in a new compost layer.
The conditioning compartment is in the form
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of an elongate zone in which at least the forward and
rear ends are open for receiving and discharging waste,
whereas the rest of the conditioning compartment may be
provided with defining walls. Even if such defining walls
are not necessary, they are suitable for realizing guid
ing of the waste during its conveyance through the con-
ditioning compartment. ~t the very least, it is prefer-
able that the undermost section of the condi~ioning com-
partment be provided with a defining floor which is pre-
ferably designed in the form of a conveyor belt which
is movable from the forward to the rear end of the con~
` ditioning compartment.
; Because of the kinetic energy which is impartedi ~
; to the waste material by the cutting roller, the waste
material is flung out through the conditioning compart-
~; ment. Since the waste material is here brought into mo-
tion in slightly different directions by the cutting roller,
the material will be flung through the conditioning com-
partment under powerful intermixing and vortex motion,
that is to say even if the major direction of movement
of the material is from the forward towards the rear end
of the conditioning compartment~ the discrete material
particles also move vertically and horizontally, at~right
angLes to the major direction of movement. This inter-
mixing and vortex motion in the material entail an extreme-
ly effective degasification and aeration of the waste,
that is to say carbon dioxide which has been formed is
removed from the waste and oxygen is added to the waste.
~ This degasification and aeration may be further amplified
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by providing the conditioning compartment with a fan.
As a result of the comminution of the waste
by the cutting roller and the subsequent aeration of the
waste, a certain requlation of the moisture content of
the waste will be obtaine~ normally a reduction. If it
is desired to further reduce the moisture content of the
waste, the conditioning compartment may be provided with
a drier, but in view of the great amounts of waste which
are treated, this is often less viable from the economic
point of view A simple and effective method of further
reducing the moisture content of the waste is to increase
the intensity in the process treatment by increasing the
treatment frequency or the speed of the cutting roller
with respect to the rate of movement of the machine. If,
on the other hand, it is desired to increase the moisture
content of the waste, the conditioning compartment may
be provided with a sprinkler or humidifier device, for
example, in the orm of a water nozzle.
Once the waste material has passed through the
conditioning compartment, it arrives at a discharge assembly
which conveys the treated waste further and deposits it
in a new compost layer of the same dimensions as the ori-
ginal layer.
Despite the effective treatment afforded according
to the present invention~ it is o~ten not sufficient to
provide but a single treatment in order that the waste
be completely composted. Consequently~ the above-described
treatment must normally be repeated one or more times
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for a shorter or longer period. The treatment frequency
and total treatment time are dependent upon the composition
of the waste, as well as the ambient conditions, that
is to say climate and prevailing weather conditions, and
may vary within very broad limits. Thus, the treatment
frequency may vary from once every tenth minute to once
every sixtieth day, whereas the total treatment time may
vary from about 1 to 120 days.
In order to carry the method according to the
invention into effect, use is made, as was mentioned above,
of a new type self-propelled machine. This will now be
described in greater detail with reference to the accompa-
nying drawings which illustrate one embodiment of the
apparatus according to the present invention, and on which:
Fig. 1 is a side elevation of a machine according
,,
to the invention;
igO 2 is a top plan view of the machine accord-
ing to Fig. l; and
Fig. 3 is a rear view of the machine according
to Fig 1.
As is apparent from Fig. 1, the machine accord-
ing to the invention comprises a frame or chassis 1~ wheels
2, 3~ a cabin ~ various auxiliary assemblies 5~ 6~ 7~
8, 9, 10 and a motor 17 for driving the machine and its
auxiliary assemblies.
The chassis, the wheels, the cabin, the motor
and its drive are of conventional type and need no further
description here. However, it might be mentioned that
the forward driving means is suitably disposed on the
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forward wheels 2, whereas the the rear wheels 3 are the
~` steering wheels and are disposed as closely ~ogether as
~'''!' possible in order to render the machine stable, compact
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and easily maneuvered.
`~ A movable feeding assembly 5 is mounted on the
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forward portion of ~he machineO This assembly is intended
to loosen and tear down waste from the high compost layer
11, so that the waste may be treated by the machine. Ac-
cording to the presently preferred embodiment illustrated
in Figs. 1 to 3~ the feeding assembly consists of a con-
veyor belt which is mounted~on the forward portion of
the machine so that it is movable upwardly, downwaxdly,
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~ forwardly and to the sides. The rolIers of the conveyor
.,
belt are, in a per se known manner, hydraulically driven
by means of the motor of the machine. The conveyor belt
is disposed about the rollers in order to be driven by
them, and is, on its outside, provided with pins or dogs
(not shown) for loosening and tearing down the waste.
As is most clearly apparent from Fig. 2 9 two
feeding screws 6 and 7 are ~lso mounted on the forward
portion of the machine. These feeding screws are coaxial,
that is to say they have the same major axis, whereas
the screws may be provided with the same or differènt
drive shafts. In the latter case9 the screws 6 and 7 may
be driven at diferent speeds. Driving of the feeding
screws is effected by means of the prevlously mentioned
motor in a per se known manner, either hydraulically or,
preferably, by means of chains as intimated at 12 in Figs.
1 and 2. The speed of the feeding screws may, depending
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upon the amount of waste and the forward driving rate
of the machine, be varied within the range of from 1 to
500, preferably about 1 to 200 rpm. The diameter of the
screws is about 0.3 to 3.0, preferably about 0.5 to 1.5
m, including a thread heiyht of about 0.1 to 2.0, preferably
about 0.15 to 0.5 m For feeding-in the waste towards
a cutting roller 8 disposed between the feeding screws,
the threads of the feeding screws have a pitch of about
4 to 60, preferably about 15 to 45. In order further
to improve the entraIning of the waste by means of the
screw threads, the threads are preferably provided with
teeth which are disposed at an angle of from 0 to 180
with respect to the threads. The feeding screws are each
of a length of about 0.3 to 3.0, preferably about 0.5
to 1.5 m.
A cutting roller 8 is disposed between the feed-
ing screws 6 and 7 and coaxially therewith, the cutting
roller being driven independently of the feeding screws,
for example, by means of a chain 13. The length' of the
cutting roller 8 is about 0.3 to 3.0 preferably about
0.5 to 2.0 m and its diameter is about 0.3 to 3.0, prefer-
ably at 0.5 to 1.5 m. A multiplicity'of knife means 14
is disposed about the surface of the cutting roller', the
knife means having a height of about 0.1 to 0.6 m. These
knife means may be of greatly varying designs, such as
T~shaped flails, straight, edged knives~ curved knives,
oblique knives etc. but they all have the feature in com-
mon that they are pivotally jointed in the cutting roller
8. The pivot shaft of the joints is substantially at right
":
angles to the direction of rotation of the cutting roller
so that the knives, on rotation of the cutting roller,
are caused by centrifugal force to assume a radially out-
wardly directed position for the most effective working
of the waste. Like the feeding screws1 the knives 14 of
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the cutting roller are preferably disposed in helical
rows (not shown) in such a manner that the waste, on be-
ing worked by the cutting roller, is moved in a fe~ding
direction from the outer edges of the cutting roller towards
its centre. The cutting roller 8 rotates at a higher speed
than that of the feed screws 6 and 7. This speed may be
varied within the range of from 1 to 1000 rpm.
On operation of the machine, the waste material
is fed in by means of the screws 6 and 7 to the rapidly
rotating cutting roller 8 which works the waste intensively~
with its knife means and comminutes the waste. By suitably
regulating the speed of the cutting roller and the rate
of advancement of the machine~ it is possible to obtain
the desired particle size and particle distribution in
the waste. In such an instance~ an 1ncrease in the~speedi-
of rotation and reduction in the rate of advancement of
the machine result in more intensive working of the waste
with consequential smaller particle size and closer particle
distribution. Apart from comminuting the waste, the cutting
roller flings it rearwardly under intensive intermixing
and vortex motion through the conditioning compartment
9. This in~ermixing and vortex motion are realized in
that the waste particles, during their rearward movement
through the conditioning compartment, collide with each
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other, this being assisted to a great extent by the fact
that the waste, apart from the rearwardly directed movement~
is also caused to move sideways by the feeding screws
and preferably also by the cutting roller This means
that an average waste particle moves from the cuttin~
roller 8 and obliquely rearwardly through the conditioning
compartment 9, the particlel during its movement, colliding
with other particles such that it executes, apart from
its rearward movement, also sideways and vertical movemçnts.
This intensive vortex motion and intermixing entail that
extremely good contact is achieved with the ambient atmos-
phere so that the waste rapidly and effectively is de-
gasified, that is to say freed from carbon dioxide, and
îs aerated, that is to say supplied with oxygen. The im-
portance of rapid and effective degasification and aera-
tion cannot be overemphasized.
Simultaneously with degasification and aeration,
the waste is brought into contact with the ambient atmos-
phere in the conditioning CQmpartment 9 which entails
a temperature reduction from the temperature of about
60C which the waste normally holds in the compost layer
11. If the waste is not treated according to the invention,
but is allowed to remain in the compost layer, anaerobic
processes will gradually col~lence~ the temperature in
these zones xising to about 80-95C, a~ the same time
as other zones remain cold and without being influenced
by these processes. If~ on the other hand, the waste is
regularly treated in accordance with the invention, the
temperature oE the waste will fall and there will not
be enough time to develop the optimum temperature level
;;; of about 60C in the compost layer between treatments.
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Consequently, an accurate balancing of the treatment fre-
quency is an important means for a regulated temperature
and optimum process.
In the treatment of the often moist waste by
comminution, gasification and aeration, a reduction of
the moisture content of th~ waste is also often achieved,
which~ as was mentioned earlier, may be further reduced
by intensifying the process working. Moreover, the moisture
content can be influenced by some form of drier ~not shown)
which is disposed in the conditioning compartment. This
driex may consist of an air fan which involves the further
advantage that the degasification and aeration of the
waste are intensified and improved. Instead of an air
fan, it is conceivable to provide a heating element which
gives off heat to the waste, but in view of the great
amounts of energy which this woul~ require, th~s alternative
is unsuitable from the economic point of view
If, on the other hand, the waste is too dry,
that is to say its moisture content too low, the moisture
content can slmply be increased by the provision, :Ln the
conditioning compartment~ of a moisturizer (not shown),
such as a water container with a discharge conduit and
a nozzle for sprinkling the waste with fin01y divided
water.
On the drawings, the conditioning compartment
9 has been shown as a open compartment which comprises
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the portion above and along the conveyor belt 15, the
belt, thus, forming the bottom or floox of the conditioning
compartment. In most cases, such a design of the condition-
ing compartment is fully sufficient, but in cer-tain cases
it may be desirable and suitable to provide the conditioning
compartment with defining side walls and top in order
to create a more enclosed c~mpartment. Irrespective of
whether the conditioning compartment is provided with
open, perforated or enclosed defining surfaces, it is,
hvwever, important that the conditioning compartment be
provided with a forward opening for feeding in of the
waste flung from the cutting roller, ana a rear opening
for discharge of the waste. It is to be preferred that
the lower portion of the conditioning compartment be defined
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by a conveyor belt 15 which catches falling waste materialand conveys it towards the discharge opening of the con-
ditioning compartment, but this is not necessary, the
bottom section can instead be deslgned in a different
manner, for example as smooth metal sheeting.
The dimensions of ~he conditioning compartment
may be varied within broad limits, but preferably the
length of the compartment lies within the range of rom
1 to 5 m and its cross-sectional area in the range of
about 1 to 8 m~.
A discharge assembly 10 is provided af~er the
conditioning compartment 9 for discharging the treated
waste and for depositing the waste in a new compost layer.
As shown on the drawings, the discharge assembly 10 pre-
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ferably consists of a conveyor belt~ but may also consist
of a bucket elevator or similar means for removal of the
:
waste from the discharge end of the conditioning compart-
ment. In order that it be possible to deposit the waste
evenly in a compost layer of a height of up to 9 m
the discharge assembly is preferably raisable and lowerable
in the vertical direction. Moreover, the discharge assembly
is preferably rotatable in the horizontal direction through
from 0 to 150 on one or both sides of the longitudinal
axis of the machine so that the waste can be discharged
as desired from a position straight behind the machine
to a position obliquely ahead of the machine. Furthermore,
the discharge assembly 10 can be provided with a rotary
spreader disc 16 in order that the discharged waste be
spread as evenly as possible in the new compost l~yer,
thereby preventing the formation of ridges.
On the accompanying drawings, the machine has,
for purposes of simplicity, been shown with a fixed dis-
charge assembly 10, but the skilled reader will appreciate
that the assembly may readily be made raisable and lower-
able as well as pivotal~ One of several manners of realizing
this is to mount the discharge assembly rotatable about
a vertical axis near the cabin 4O For free rotatabiiity,
the conveyor belt is, in lts entirety, disposed above
the chassis 1, such that it does not engage with the chassis
on pivoting. The conveyor belt 15 is simultaneously extend
ed so that it terminates above the discharge assembly
10, that is to say such that the waste from the conveyor
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belt 15 is transferred to the discharge assembly 10.
The following non-restrictive Examples of the
present invention are here presented in order further
to illuminate the various aspects of the invention.
EXAMPLE 1
According to this Example, treatment was effected
of waste which consisted of two parts of screen fraction
which had been obtained as heavy fraction in the separation
of domestic waste from which magnetic material has been
separated, and one part of partly digested and dewatered
biological sludge and chemical sludge from a municipal
sewage treatment plant having a total solids tT.S.) of
23 weight %.
The waste was deposited in a compost layer of
a height of 3 m, the bottom surface of the layer having
the dimensions 50 m x 50 m.
The compost layer was treated by the method
according to the present invention with the assistance
of the above-described machine The machlne was driven
by a motor which developed 200 h.p., the diameter of the
feeding screws was 1.0 m~ their length was 1.5 m each,
whereas the cutting roller had a diameter of 1.0 m a length
of 1.75 m and rotated at a speed of ~00 rpm.
The waste was treated with the machine once
every third day during a total treatment time of four
weeks. The obtained, finished compost was odorless, dis-
played a BS17 reduction of just above 88~ and lacked patho-
genes, parasi~es and parasite eggs.
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EXAMPLE 2
According to this Example, treatment was effected
of waste which consisted of one part sludge of the same
type as in Example 1, one part scraps from the vegetable
inclustry having a total solids of 30 weight ~, one part
bark, and two parts recirculated compost.
The waste was cleposited in a compost layer of
a height of 2.5 m and a bottom surface having the dimensions
~ 30 m x 60 m.
:~ The waste was treated with the same machine
as in Example 1, the speed of the cutting roller being,
however, 275 rpm. The treatment was carried out once every
other day for a total treatment time of 24 days~ when
a stable finished product was obtainedl The mature compost
was odorless, displayed a BS17 reduc~ion of just above
B5% and lacked pathogenes or parasites and parasite eggs.
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EXAMPLE 3
According to this Example~ treatment was effected
on waste which consisted of one part sludge of the same
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type as in Example 1, and two parts of horse manure from
riding stables.
The waste was cleposited in a compost layer of
a height of 3.2 m and a bottom surface of the dimensions`
40 m x 60 m.
The waste was treated with thè same machine
as in Example 1, but the speed of the cutting roller was
350 rpm. The treatment was carried out once every fifth
day for a total treatment time of 30 days, when a stable
,
-
'7~
finished product was obtained. The mature compost product
was odorless and displayed a BS17 reduction of just above
87%. Pathogenes, parasites and parasite eggs could not
be found.
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