CA1175961A - Method and apparatus for composting waste - Google Patents
Method and apparatus for composting wasteInfo
- Publication number
- CA1175961A CA1175961A CA000406143A CA406143A CA1175961A CA 1175961 A CA1175961 A CA 1175961A CA 000406143 A CA000406143 A CA 000406143A CA 406143 A CA406143 A CA 406143A CA 1175961 A CA1175961 A CA 1175961A
- Authority
- CA
- Canada
- Prior art keywords
- waste
- compost layer
- recited
- cutting roller
- compost
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
- Y02A40/10—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture
- Y02A40/20—Fertilizers of biological origin, e.g. guano or fertilizers made from animal corpses
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- Processing Of Solid Wastes (AREA)
- Fertilizers (AREA)
Abstract
Abstract of the Disclosure:
The disclosure relates to a method and an appara-tus for composting waste. The waste is deposited in a compost layer of a height of up to 9 m and the base sur-face dimensions of at least 5 m x 5 m, preferably at least 10 m x 30 m; The waste is fed from the compost layer to a rapidly rotating cutting roller which comminutes the waste and, under intermixing and vortex motion, flings it through a conditioning compartment for degasification and aeration, whereafter the waste is discharged and de-posited in a new compost layer. The apparatus according to the invention substantially comprises a chassis with a motor, wheels and steering, on which there are mounted a feeding assembly, two feeding screws, a cutting roller between the feeding screws, a conditioning compartment whose bottom preferably consists of a conveyor belt, as well as a discharge assembly which preferably consists of a conveyor belt which is pivotal laterally and verti-cally.
1b
The disclosure relates to a method and an appara-tus for composting waste. The waste is deposited in a compost layer of a height of up to 9 m and the base sur-face dimensions of at least 5 m x 5 m, preferably at least 10 m x 30 m; The waste is fed from the compost layer to a rapidly rotating cutting roller which comminutes the waste and, under intermixing and vortex motion, flings it through a conditioning compartment for degasification and aeration, whereafter the waste is discharged and de-posited in a new compost layer. The apparatus according to the invention substantially comprises a chassis with a motor, wheels and steering, on which there are mounted a feeding assembly, two feeding screws, a cutting roller between the feeding screws, a conditioning compartment whose bottom preferably consists of a conveyor belt, as well as a discharge assembly which preferably consists of a conveyor belt which is pivotal laterally and verti-cally.
1b
Description
~L~7~
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 .
,. . .
.
~'7 .
landfill area and is thereafter not subjected to any par-, 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 .
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 ., 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 ....
:: . . . .
.. .
:, , - :
. . , 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 .
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 .q - .
: , . .
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~
S
;
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 , ,.;, ; 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 ~, ~
`~ 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 ~ 6 9.~:
' ;' ~ . ' , -' .
: ' .
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 . .
~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 .; .
~ 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, ~ .
~'7S~
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 .
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 . .
:~'7 ~;:
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 ;:
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 . ' i9~:~
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 :, ." ~
.
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 ~' ' , S~
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
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 .
,. . .
.
~'7 .
landfill area and is thereafter not subjected to any par-, 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 .
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 ., 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 ....
:: . . . .
.. .
:, , - :
. . , 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 .
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 .q - .
: , . .
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~
S
;
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 , ,.;, ; 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 ~, ~
`~ 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 ~ 6 9.~:
' ;' ~ . ' , -' .
: ' .
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 . .
~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 .; .
~ 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, ~ .
~'7S~
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 .
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 . .
:~'7 ~;:
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 ;:
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 . ' i9~:~
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 :, ." ~
.
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 ~' ' , S~
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 .
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 :,.;
and easily maneuvered.
`~ A movable feeding assembly 5 is mounted on the . "
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, ;, ~ 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 , ~f~5~
.. .
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 . , 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 , , ;; , ' .
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.
,. .
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 ~ ' ' jl ' , ~ , ., 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 ;: -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-., 19 ~ ~5~
'.' 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 . ,, , : ' :
~75i~
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.
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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:i 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.
,;';
According to this Example~ treatment was effected on waste which consisted of one part sludge of the same . ~
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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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 .
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 :,.;
and easily maneuvered.
`~ A movable feeding assembly 5 is mounted on the . "
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, ;, ~ 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 , ~f~5~
.. .
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 . , 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 , , ;; , ' .
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.
,. .
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 ~ ' ' jl ' , ~ , ., 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 ;: -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-., 19 ~ ~5~
'.' 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 . ,, , : ' :
~75i~
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.
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.
",, .
, ~ ~ .
~ ,.
:i 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.
,;';
According to this Example~ treatment was effected on waste which consisted of one part sludge of the same . ~
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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Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of composting waste, wherein the waste is deposited in a compost layer of a length of at least 5 m, a width of at least 5 m and a height of up to 9 m, and wherein 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 supplied with oxygen, whereafter the conditioned waste is deposited in a new compost layer and the above treatment is repeated perio-dically from once every tenth minute to once every sixtieth day for a total from 1 to 120 days.
2. The method as recited in claim 1, wherein the waste is deposited in a compost layer of a length of at least 30 m and a width of at least 10 m.
3. The method as recited in claim 1, wherein the cutting roller moves in relation to the compost layer, and wherein said new compost layer is deposited next to the original compost layer and, in the next treatment, is moved to the site of said original compost layer, such that the compost layer, in the repeated treatments, exe-cutes an oscillating movement substantially at right angles to the direction of movement of the cutting roller.
4. The method as recited in claim 1, wherein the BOD17 of the waste is reduced by at least 80%.
5. The method as recited in claim 1, wherein the removal of carbon dioxide and supply of oxygen in the conditioning compartment are promoted by a fan.
6. An apparatus for composting waste which is deposited in a compost layer of a length of at least 5 m, a width of at least 5 m and a height of up to 9 m, the apparatus comprising a chassis with wheels and a motor, and the apparatus further comprising A) a movable feeding assembly mounted on the forward portion of the apparatus for feeding waste from the compost layer to two rotary feeding screws located beneath the feeding assembly;
B) a conditioning assembly having a rotary cutting roller provided with cutters and disposed between the feed screws and a conditioning compartment disposed after the cutting roller, seen in the direction of feed of the waste; and C) a discharge assembly for receiving the waste from the conditioning compartment and discharging and depositing said waste in a new compost layer.
B) a conditioning assembly having a rotary cutting roller provided with cutters and disposed between the feed screws and a conditioning compartment disposed after the cutting roller, seen in the direction of feed of the waste; and C) a discharge assembly for receiving the waste from the conditioning compartment and discharging and depositing said waste in a new compost layer.
7. The apparatus as recited in claim 6, wherein the cutting roller is disposed coaxially with the feed screws and rotatable independently thereof.
8. The apparatus as recited in claim 6, wherein said feed screws have a diameter of about 0.3 to 3.0 m, a thread height of about 0.1 to 200 m, a pitch of about 4 to 60°, a length each of about 0.3 to 3.0 m, and are rotatable at a speed of about 1 to 500 rpm.
9. The apparatus as recited in claim 6, wherein the cutting roller has a length of about 0.3 to 3.0 m, a diameter of about 0.3 to 3.0 m and is rotatable at a (continued claim 9) (continued) speed of about 1 to 1000 rpm.
10. The apparatus as recited in claim 6, wherein said conditioning compartment has openings for feed in and discharge of the waste, whereas the remainder of the compartment is defined by walls, floor and top.
11. The apparatus as recited in claim 10, wherein said floor consists of a conveyor belt.
120 The apparatus as recited in claim 6, wherein the conditioning compartment is provided with a fan and/or water supply means,
13. The apparatus recited in claim 6, wherein the discharge assembly consists of a conveyor belt which extends from the discharge end of the conditioning compart-ment and is raisable and lowerable from 0 to 9 m, and horizontally pivotal through an angle of about 0 to 150°
with respect to the longitudinal axis of the apparatus.
with respect to the longitudinal axis of the apparatus.
14. The apparatus recited in claim 13, wherein the conveyor belt of the discharge assembly has, at its discharge end, a rotary spreader disc.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000406143A CA1175961A (en) | 1982-06-28 | 1982-06-28 | Method and apparatus for composting waste |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000406143A CA1175961A (en) | 1982-06-28 | 1982-06-28 | Method and apparatus for composting waste |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1175961A true CA1175961A (en) | 1984-10-09 |
Family
ID=4123109
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000406143A Expired CA1175961A (en) | 1982-06-28 | 1982-06-28 | Method and apparatus for composting waste |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1175961A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5395417A (en) * | 1993-01-26 | 1995-03-07 | Double T Equipment Manufacturing Ltd. | Apparatus and process used in working windrowed ingredients to produce pre-wet cycle mushroom compost |
-
1982
- 1982-06-28 CA CA000406143A patent/CA1175961A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5395417A (en) * | 1993-01-26 | 1995-03-07 | Double T Equipment Manufacturing Ltd. | Apparatus and process used in working windrowed ingredients to produce pre-wet cycle mushroom compost |
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