WO2010151101A1

WO2010151101A1 - Novel in-vessel high rate composter

Info

Publication number: WO2010151101A1
Application number: PCT/MY2009/000081
Authority: WO
Inventors: Mohd Ali Hassan; Khairul Anuar; Azhari Samsu Baharuddin; Alawi Sulaiman; Zubair Shafie; Hamidi Abdul Hamid; Moh. Fuad Sarun; Shahrudin Omar
Original assignee: Universiti Putra Malaysia; Ecobuilders Sdn. Bhd.
Priority date: 2009-06-26
Filing date: 2009-06-26
Publication date: 2010-12-29

Abstract

The present invention is an in-vessel high rate composting apparatus for processing of oil palm biomass, organic and municipal wastes to produce compost product. The composting apparatus consists of a vertical position and cylindrical shape vessel (100) with conical bottom (2) design, materials feeding (1) and product discharge systems (3), a screw impeller (12) for axial mixing, aeration (14) and carbon dioxide (CO₂) removal systems and a leachate collection system (15). The optimum composting conditions in the vessel will be maintained by means of programming logic controller (PLC) on key parameters such as temperature, oxygen (O₂) level, moisture level and carbon dioxide (CO₂) level. The compost product could be let to mature inside the vessel or let to cure elsewhere for the completion of the compost product

Description

NOVEL IN-VESSEL HIGH RATE COMPOSTER

FIELD OF INVENTION

The present invention is a novel high rate in-vessel vertical composter for the processing of oil palm biomass, organic and municipal wastes to produce compost product. The composter is equipped with a helical screw impeller for axial mixing, a composting materials feeding and a compost product discharge systems, a leachate collection system, an aeration system and a carbon dioxide (CO₂) and water vapor (H₂O) removal system.

BACKGORUND OF THE INVENTION

Nowadays, one of the serious problems faced around the world is the proper disposal of organic and agro wastes. The current trend of waste disposal is by incineration or landfill, but the incineration process discharges toxic substance such as dioxin, hazardous air pollutants and a large amount of CO₂. Policies are currently being formulated to improve the reduction and recycling of waste. One such policy involves the biological degradation of organic solid waste. Malaysia is also facing a problem with the waste management especially from the palm oil industry. Malaysia is the top producer of palm oil products in the world and at present, the total area under oil palm cultivation is about 4.05 million hectares, with the total palm oil production of 16.8 million tonnes. In 2004, it was estimated that 26.7 million tonnes of solid biomass and average of 30 million tonnes of palm oil mill effluent (POME) were generated from 381 palm oil mills in Malaysia.

The solid biomass generated was composed of 21-23% empty fruit bunch (EFB), 10-12% mesocarp, and 5-7% fiber and palm kernel shell. It is believed that the generation of oil palm biomass will continuously increase in proportion to the world demand of edible oils. In the near future, it is expected that the volume of organic and agro wastes will exceed the treatment capacity. Hence, reconsideration of current recycling system is an urgent requirement. Among the available technologies to recycle the organic solid wastes, the advantage of composting is superior due to its simple technology and lower investment. Thus, the composting process gained higher interest from the waste producer. Composting is a natural process of breaking down organic materials into a stable material which can be used as fertilizer. The composting process is influenced by a number of factors such as temperature, moisture content, carbon/nitrogen ratio, aeration, pH, and the composting material. Temperature is the most important indicator of the efficiency of the composting process. Most of the studies reported that the optimum temperature range for effective decomposition was at 50-70⁰C, with 60°C being the most satisfactory level. In thermophilic temperature, the dominant micro-organisms might attack rapidly the soluble, readily degradable compounds, high content of available nutrients and relatively small size of organic fraction particles. It also reported that composting temperature above 55⁰C could kill pathogens and sanitize the compost. Temperature of the composting mass must be below 75⁰C because higher temperature causes denaturation of enzymes in microbial cells. The moisture level is also the critical factor that determined the decomposition rate in composting. Although the range of 50-60% is generally recommended for composting, it is also reported that the range of 60-70% provided the maximum microbial activities. If the moisture less than 40%, the rate of biodegradation will falls, but if it is too high the material becomes waterlogged, thus limiting airflow. If the input material is too wet, water adsorbing and bulking materials are added to improve the structure of waste and increase the air circulation.

The composting is an aerobic process and oxygen level should not be lower than 3% throughout the process. The major problem of aeration systems is non-homogeneous distribution of oxygen in the composting piles. Many researchers reported that the optimum oxygen level is in the range of 10 to 15%. If the oxygen dispersion is not homogenous, it causes CO₂ accumulation and anaerobic conditions inside the pile. In order to maintain high rate biodegradation, oxygen must be available at all times. Composting process can be carried out in reactor systems to prevent the air pollution with CO₂. pH between 5.5 and 8.5 is optimal for the compost microorganisms. Bacteria and fungi digest the organic matter during which organic acids are released. If the system becomes anaerobic, acid accumulation will reduce pH to 4.5, which severely limits microbial activity. Compost maturity and stability are the key factors during composting. G/N ratio is always used as an indicator of compost maturation and should be stable with time. The ideal C to N mass ratio is considered to be around 30/1. A higher ratio is an indication of the shortage in nitrogen, otherwise indispensable for optimal microbial growth, whereas its scarcity slows down degradation. A lower value of the ratio generates excess of nitrogen compounds causing odors. During the composting process, the biologically degradable organic matter is converted into volatile CO₂ and H₂O and is removed from the compost. The total N content increases resulting in decreasing of C/N toward the end of composting. As composting is essentially an aerobic microbial process, the maintenance of sufficient oxygen in the pile is imperative. The method of delivering the oxygen to the microorganisms classifies the method of composting. Five common methods of composting are (1) Static Pile (2) Turned Windrows (3) Passively Aerated Windrows (4) Aerated Static Pile (5) In- vessel Composting. Most large on-farm and commercial composting facilities use a turned windrow system, passively aerated windrows, or aerated static piles. In the static pile composting system, the material is collected into windrows or piles and allowed to decompose over an extended period without mixing. Because none or very little mechanical agitation is used, the raw material must be initially mixed with a large volume of amendment to afford sufficient porosity for aeration. This is especially the case with manures. The size of the pile or windrow must be small enough to allow for passive aeration to occur. Occasional remixing and reformation of the pile is beneficial to rebuild the porosity. Sometimes trapped gasses and odors can become a major problem if the piles are not turned periodically. Passive pile composting takes a longer time to complete due to the low aeration frequency and temperatures. The piles tend to become anaerobic and odorous quickly if porosity is not adequate. Without enough dry amendment, material like manures can form leachate with high concentrations of organic constituents. Without mixing, there will be areas in the pile which do not attain the required composting temperatures and thus a proportion of the material will not be adequately composted. The outer layer may not undergo composting at all. Other limitations of static pile composting system are; 1) high manpower at formation and breakdown of the piles; 2) less choice of amendments and 3) material must be well mixed and sized from the beginning of the process.

Turned windrow composting system is also preferable conventional method in the field scale composting process especially when dealing with organic and agro waste. In windrow composting, the raw material are laid down in elongated piles, kept moist by watering, if necessary, and agitated and aerated by turning with either a loader or a specialized piece of equipment. The system can be expanded relatively easily to accommodate increasing material volumes. The length of windrows will vary with material quantity, but the width and height should be constructed to specific dimensions to optimize the composting process. If a windrow turner is used, the height and width of the turner generally dictates the height and width of the piles. Turning and mixing of the windrow pile is important to allow uniform moisture distribution and to aerate and agitate the material. Water should be added if the pile has dried out. The turner machines are designed specifically for agitating and aerating windrow piles, and accomplish the work quickly. The machines vary considerably in price depending upon the capacity and features. The size of the windrow for the maintenance of aerobic conditions is determined by the porosity of the material - wet denser material will require smaller windrows than more porous substrates. Large windrows will quickly become anaerobic in the core, requiring constant turning, while windrows which are too small will not attain the required temperatures for efficient composting and the destruction of weed seeds and pathogens. Turning frequency depends on the rate of the composting reaction. In the early stages when easily degradable material is being consumed, this could be called for daily. As the process slows down, turning frequency is reduced. Temperature, oxygen concentration and odors are good indicators for turning. Isolated cool regions in the pile (<45°C) indicate that better mixing is required and turning can remedy this. If the temperature is above 60⁰C, turning will dissipate the heat. If this does not alleviate the problem, smaller windrows need to be constructed. The limitations of the system such as; 1) requires more land area and more hard surface area. Due to the requirement of frequent turning and handling, this area would need to be hard surfaced; 2) cost of operations higher if requires for equipment storage, shelter, curing piles, and other on-site needs, therefore a total area of three to four acres would be needed; 3) paving of the additional surface is optional; 4) weather affects windrow composting systems. During a rainy season, piles may become saturated with water, causing leachate run-off and anaerobic conditions, and 5) additional labor costs may be needed to spread the windrow out to dry and then rebuild it.

Passively aerated windrow eliminated the requirement of turning due to the installation of perforated open-ended pipes which embedded across the base of the windrow and allow for air to diffuse through the material. As the material will not be turned, particular attention must be given to the size, structure, moisture and porosity of the material when constructing the windrow so as to maintain adequate aeration throughout the process. The raw materials must be thoroughly mixed before windrow formation and care must be given not to compact the material while building the windrow. The windrow can be constructed on a 1.5 to 2.0m high and 3m wide bed of finished compost which offers insulation and leachate absorption. The pipes are arranged on top of the bed and a windrow 1.5m high and 3m wide constructed on top of this arrangement. A 15cm layer of finished compost insulates the pile, discourages insects and helps with the retention of moisture and reduces odor.

In aerated static pile methods, a blower is used to force or draw air through the pile. No turning of the material is required once the pile is formed. As the pile is not turned, particular attention must be given to the blending of the material with structural amendments to maintain porosity throughout the composting period. It is important to achieve a homogeneous mixture and not compact the material with machinery while constructing the pile, so that air distribution is even and no anaerobic areas develop causing sections of un-composted material. Pile dimensions can be 1.5 - 2.5m high and 3 - 5m wide. Pile length is limited by the air distribution in the aeration pipe and depending on the aeration system otherwise little fresh air will reach the end of the pipe. Pile height is usually twice the pile width. A 15cm layer of finished compost may be used to cover the material to reduce drying, heat loss, fiies and act as a bio filter for odorous gasses. Two forms of piles are common - single and extended piles. With single piles the material should be of a single batch or several small batches of the same age. Extended piles are used when materials are generated daily and each day's intake is sufficient for a single cell. Placement of the temperature probe is critical to reflect the average temperature of the entire compost mass. Selection of the blower requires the knowledge of the air pressure loss in the system. Air must be supplied evenly along the entire length of the pipe and for evenly spaced holes; air becomes less evenly distributed as the pipe lengthens. Air can be blown or sucked through the material. Suction offers the opportunity to treat the exhaust for odor control through a bio-filter system. Condensate from the pile must then be collected in a sump before reaching the blower. With sucking there is an increased pressure drop to contend with which will demand a larger blower. This system provides better air flow from the same blower size and is more effective in cooling, so is preferred when temperature control is paramount. The disadvantages of the system are; 1) electric power required; 2) labor peaks at formation and breakdown of piles; 3) limited choice of amendments and 4) material must well mixed and sized from the start.

Closed composting or in-vessel systems are continuously improved by many researchers in order to eliminate the problems encountered in conventional methods. The choice of an in- vessel system will depend upon the raw material feedstock, the volume of material to be composted, the capital available, and the site characteristics. The general types of in-vessel systems are such as passively aerated bins mechanically aerated containers, agitated- aerated containers, rotating drums and agitated beds. These containerized systems all require the following; a container that is supplied with air flow and leachate drainage, a mixing and loading machine to thoroughly mix the raw materials and load them into the container, a bio-filter, which can be filled with finished compost, to control odors, process monitoring, an unloading system and a site for curing the compost. Most in vessel systems are designed to maximized microorganisms activity during the initial composting period, thus reducing composting time but do not provide sufficient retention time to produce mature compost. In an in vessel system, much of the composting process is carried out indoors or inside a large vessel, enclosed chamber in which mechanical mixing and/or forced aeration are performed where moisture, air and temperature can be controlled to create the optimal conditions for composting. The main advantages of closed system/in-vessel system over open system (non-reactor) are: (1) the shortening of mesophilic and thermophilic stages, together with higher process efficiency (2) fairly homogenous microbial activity within the whole composting process mass (3) external environmental factors do not affect the composting process (4) less land required and (5) better odor and operational control. Usually, in-vessel composting is employed when the primary ingredient to be composted is food waste or another high-nitrogen type of waste where pathogens may be an issue, such as manure or animal processing wastes. In-vessel systems are primarily designed to achieve the EPA requirement of three days at 50 degrees celcius or higher, to meet "Process to Further Reduce Pathogens" regulations. In general, the material composts inside the container for between 10 and 24 days, then is set outside to cure for an additional 30 to 60 days. Curing finishes the process of pathogen destruction, and allows the compost to cool down and biologically stabilize. Composting takes place within a structure, container or vessel with forced aeration and mechanical turning devices. In vessel composting system also requires operating and maintenance expertise.

Bin Composting is one of the examples of in vessel composting system. The walls of the bin may be constructed of wood slats or concrete blocks. There is usually an air supply manifold of perforated plastic piping laid on the floor to obviate the necessity of frequent unloading, mixing and reloading. Although bins allow for higher stacking of the material, this can cause compaction and an increased distance for air passage, resulting in anaerobic zones in the upper layers. In this instance, attention must be given to the structure and porosity of the material and adequate operating time for the blower to supply sufficient oxygen and cooling. However, excessive fan operation is likely to dry the material out, thus a fan cycle is chosen to prevent this but provide enough oxygen. The system can be automated to operate the fan on temperature or time. A sloping floor and drain take care of leachate collection. A series of bins will allow for occasional transfer and mixing which can speed up the process. Bins are often used indoors which allows for better temperature and odor control and eliminating weather effects.

Another type of in vessel composting system is a Bunker Composting. These are concrete channels up to 6m wide, 3m high and 50m long with a built in aeration system and leachate collection drain in the floor. A turning machine on rails tops the walls mixes and restores the porosity of the compost. The compost is at different stages of development along the length of the bunker, so independent temperature sensors and blowers control the temperature and aeration in the different zones.

Raw material is loaded at one end and during turning the machine gradually moves the material along the length of the bunker. Treated material is unloaded at the opposite end of the bunker. Several bunkers can be built side by side with a single turning machine servicing all the units by transferring the machine on a cradle between the bunkers. The material requires a curing phase after treatment in the bunkers.

Silo Composting is also one type of in-vessel system. A bottom unloading silo is used. Daily, an auger removes material from the bottom and an equal volume of raw material is loaded at the top. As there is no mixing of the material and it is stacked vertically, thorough blending of the substrate and adequate structural amendment is very important. The aeration system must also be adequate for sufficient oxygen supply and cooling throughout the vertical height. Exhaust air is collected from the top and treated for odor elimination. Curing of the product can take place in a second silo or in windrows or piles. Low cost per unit of working volume (packed bed reactor).

In a modern composting system, the application of rotary drum is a holistic approach for the composting process. Rotating drums, promote decomposition by tumbling material in an enclosed container and in horizontal position. The rotation exposes more of the surface area to air and oxygen, and releases heat and gaseous by products of decomposition. Rotating drums speeds up the composting process; some manufacturers claim that finished compost is produced in five to 10 days (as compared to open-air windrow-method composting which can take one to several months). The enclosed, controlled environment allows decomposition to proceed at a steady rate. Rotating drum compost vessels operate by very slowly turning a drum loaded with a specific volume of organic material, usually food waste combined with a carbon amendment, mixed thoroughly according to a specific recipe. The tumbling action that results agitates the material and accelerates the compost process. The drum does not turn constantly - it is usually turned once or twice a day for a 15-minute period, which coincides with loading and unloading. Usually the drum is placed at a very slight angle, so that the compost travels down the tube as it decomposes. The angle and the rotation speed are adjusted so that when the compost reaches the end of the chamber, it is sufficiently processed and may be removed and set outside in piles or windrows for curing. Some rotating vessels use a series of interior chambers, and the material passes through these chambers as it is reduced in volume. Some manufacturers adjust the amount of air forced into the chambers based on the degree of decomposition desired; for example, injecting extra air into the first chamber so that decomposition proceeds fastest on the newest material.

Some operations use specific techniques that they claim improve their process and end- product. The land required for an in-vessel composting system is minimal, especially if waste-only product is made that can be land-applied without a curing period. The hard surfaced area required would be significantly less than with a windrow system.

Many reports on the limitations of rotating drums operations such as: 1) potential for imbalances - even though the process is self-contained, and in the more expensive systems the monitoring, addition of process air, exhaust of gases, and leachate management are controlled and automated, it is still very important to remember that what happens inside the drum is a biological process. Even with 'all the latest sophisticated machinery, imbalances in the critical parameters of oxygen levels, moisture levels, temperature, and pH can occur; 2) imbalances more difficult to correct - If biological imbalances do occur, they are more difficult to correct in an enclosed container. In the worst case, the material may need to be removed from the container, spread out and re-mixed, the problems addressed, and then the material re-loaded. Aside from the odors and leachate that might result from exposing the material, the labor and time involved in such corrections could be significant; 3) less rapid processing time than with other waste streams - the time it would take to actually take to make compost from the composting material alone in a vessel is unknown, due to the different C/N ratio; 4) high capital costs - the capital cost of a system is high. The systems identified are equipped with auger conveyors for loading the drums, which may not be appropriate for different raw materials. 5) significant labor required - the expected reductions in day-to-day operations and maintenance costs, with respect to windrow systems, are not dramatic. In order to keep the process going, material must be loaded daily, unloaded daily, turned daily, and monitored daily. Corrections in air flow, temperature, and moisture still may have to be made. 6) high replacement costs - a vessel has a limited life span. Given the corrosive nature of the composting process, particularly if food waste were to be added, it may be worn out in seven to 10 years.

Various composters are currently commercially available. However, stable operation to maintain steady degradation over a long time span is difficult presumably due to the instability of the composting condition within the composter design. In view of the above, there is therefore a need for a simple centralized, automated composting system which alleviates some of the drawbacks of the prior art. Mechanical turning or mixing condition should achieves the following; 1) replenishes oxygen to the core of the material; 2) mixes the material to encourage thorough composting of all the particles and exposure to the hot zone in the core part; 3) restores porosity to maintain gaseous exchange; 4) blends raw material and increases surface area by particle break down; 5) exposes weed seeds, pathogens and insect larvae to the hot inner core and 6) allows excessive heat, water vapor and gasses to escape. Through our knowledge and prior art search, none of in-vessel system was applied for the composting process using oil palm biomass as a composting material. The present invention is designed in a vertical and cylindrical position, simple and automated operation and allow for homogenous mixing throughout the process as compared to other inventions. Many in-vessel composting systems were designed in a horizontal position. It can be seen from the invention for the decomposition process of food waste and organic materials as described by US patent no 6,352,855 (2002) and 6,071 ,740 (2000). Both inventions consists of a shredder/particle size, and a horizontal drum with three chambers with connecting ports of sequentially increasing diameter, incremental drum rotation, and process control system. The invention of US patent no 6,281 ,001 (2001 ) provide a process controlled for maintaining composting conditions of the organic materials within the pre-selected limits. The present invention could also allow for better controlling and maintaining the optimum condition of composting parameters throughout the process. The present invention also promoting aerobic microbial activity in the vessel by means of efficient aeration system and axial mixing pattern as compared to other invention such as US patent no 5,906,436 (1999). The unique of the present invention is in the design of impeller and the free flow pattern of composting materials inside the vessel during the feeding of composting materials and discharging the compost product as compared to the invention of US patent no 5,387,036 (1995). The US patent no 5,175,106 (1992) describes the methods and apparatus to improve efficiency of the fluid use and odor control in in-vessel composting systems. Other invention of US patent no 5,145,581 also describes on air recirculation system. In the present invention, the composter is equipped with water vapor and CO₂ removal system.

The present invention of a novel high rate composter is not only improving the oil palm biomass composting but also subjected to the problems solution in the conventional windrow system, minimizing the limitations as reported in horizontal drum system and the design also applicable for various potential waste in composting such as organic and municipal waste.

The economic feasibility has been considered in the present invention to make the system viable either in small medium scale or for commercialization. SUMMARY OF THE INVENTION

The present invention is an improved automated high-rate composting apparatus for the decomposition of organic wastes specifically oil palm biomass, organic and municipal wastes that utilizes a vertical position cylindrical with conical shape bottom vessel design and equipped with an axial mixing system, feeding and discharge systems, leachate collection system, aeration system and CO₂ removal system and the key process parameters such as temperature, moisture and oxygen level are controlled using a PLG.

It is therefore an object of the present invention to provide a conducive environments such as optimum temperatures (25-75⁰C), optimum oxygen level (3-20%) and optimum moisture level (40-80%) for the high rate decomposition of the organic matters by means of body insulation, minimal head space design, vertical position with closed system, external air addition and interval sludge addition from an external source using a pump and all these conditions are controlled with PLG system.

It is another object of the present invention to install the vessel in a vertical position, cylindrical shape top with conical bottom design so that less installation area is needed, more effective working volume available and eliminating dead zones during mixing compared to the similar capacity of a horizontal composting drum design and by having the conical shape bottom will provide an effective collection of the leachate run off so that the accumulated leachate can be either recycled to the vessel or sent to the storage.

It is another object of the present invention to install the loading chute at the top and unloading chute at the bottom of the composter in order to take full advantage of the gravity force in distributing the raw materials inside the vessel and allow the compost product to be discharged from the vessel by gravity force without any additional removal mechanism.

It is another object of the present invention to equip the composter with a vertical helical screw impeller for the purpose to generate a homogenous mixing through axial mixing by conveying the composting materials from the bottom to the top and free drop to the side by the gravity force to complete the mixing process

An even further intention of the unique helical screw impeller design is to create less friction between the composting materials and the impeller by reducing the mixing load due to the uniqueness of the impeller design compared to the conventional mixing paddle as well as to reduce the wearing of components in ensuring lower maintenance cost and provide longer lasting of impeller's material.

It is another object of the present invention to have an efficient aeration system inside the vessel by introducing the external air using an air blower and pumped into the vessel through the nozzles located at different position attached at the internal wall of the vessel and simultaneous air and material mixing by the impeller and the system is controlled by the O₂ controlled system.

It is another object of the present invention to enhance the composting process by removing the accumulated CO₂ inside the vessel and it will be removed using a centrifugal exhaust fan controlled by a CO₂ controlled system that will discharge the CO₂ at 16 meter above the installation.

It is another object of the present invention to install the safety switches at all openings and motorised equipment to prevent accidental occurrence during operation and maintenance of the composter system.

This equipment is also applicable for bigger capacity by means of expansion of up to 5 tonnes per day of compost product using the same size of impeller, gear box and motor or even higher capacity of up to 10 tonnes per day of compost product using the various sizes of vessel, impeller, gear box and motor or even further higher capacity by means of expansion of up to 50 tonnes per day or higher of compost product using the duplicate module with various sizes of impeller, gear box and motor.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a perspective view of the composter (100) showing the position of the feeding hopper (1), conical shape bottom (2), discharge chute (3), hand-rails (4), motor and reduction gear for mixing (5), cylindrical straight cut body (6) and the supports for the composter (7).

Fig. 2 shows the diagram of the composter with body insulation (10), the position of the probes for the key parameters (O₂, pH and temperature) (11), shape and position of the screw impeller (12), sludge addition system (13), aeration system (14) and leachate collection and removal system (15). Fig. 3 shows the position and location of the screw impeller. The axial mixing pattern is also shown where the composting materials move up (21) due to the mechanical action of the screw impeller and fall to the sides (20) once reach the top due to action of gravitational force.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

The present invention is susceptible to many variations, including scaling of capacity, in so long as process parameters and control logic are maintained and the drawings and following description of the composter are to be regarded as illustrative in nature and not as restrictive.

There are six main components which are combined to make the composter (100) which consist of a materials feeding (1) and product discharge system (3), helical screw impeller (12) for axial mixing, leachate collection system (15), aeration system (14) and CO₂ removal system.

The infeed component has a feed hopper (1) and lid and located at the top side of the composter. The incoming materials are recommended to be fed through a conveyor system. While feeding the screw impeller (12) is kept running to ensure good mixing. The feeding is stopped once the specified quantity of the feed materials is achieved.

The helical screw impeller (12) is located at the center of the composter in vertical position installation and powered by an electrical motor equipped with a reduction gear (5). The speed is slow and set at only between 3-5 rotations per minute. Due to the design of the impeller, once rotated the composting materials near the impeller will move up-ward and at the top it will move to the side. The gravity force will facilitate the down-ward flow of the composting materials and once reach the bottom, the impeller will carry the materials to the top again and the process continues until homogenous mixing is achieved.

The leachate run-off collection system consists of three main parts i.e conical shape bottom (2), collection sump and leachate pump. The conical shape bottom design is to ensure efficient removal and collection of the leachate from the system. To avoid contamination, the removed leachate is collected in a sump that is supplied with a pump so that the leachate could either be recycled sent to the storage tank.

The aeration inside the composter is achieved by introducing external air which is pumped into the composter using an air blower. For an efficient air distribution, the air diffusers or nozzles (14) are attached at the internal wall of the composter and located at different position inside the composter. To further enhance the air distribution, the screw impeller (12) could be operated when the air is blown into the composter.

High level of CO₂ could be toxic to the microorganisms. Thus the composter is also equipped with CO₂ removal system located at the top of the composter. The excess CO₂ inside the composter is removed using a centrifugal fan that will discharge the toxic gas at approximately 16 meters above.

Claims

1. The novel composter which an improved automated high-rate composting apparatus for the decomposition of organic wastes specifically oil palm biomass, organic and municipal wastes that utilizes a vertical position cylindrical with conical shape bottom vessel design and equipped with an axial mixing system, feeding and discharge systems, Ieachate collection system, aeration system and CO₂ removal system and the key process parameters such as temperature, moisture and oxygen level are controlled using a PLC.

2. The novel composter as claimed in claim 1 which can be operated with oxygen level between 3 and 20% by introducing external air using an air blower.

3. The novel composter as claimed in claim 1 which can maintain the moisture level of between 40 and 80% by interval sludge addition from the external source.

4. The novel composter as claimed in claim 1 which has a vertical and cylindrical type vessel (100) which requires less installation area compared to horizontal drum design.

5. The composter as claimed in claim 4 which has a vertical and cylindrical type vessel (100) which can provide more effective working volume compared to horizontal drum design.

6. The novel composter as claimed in claim 4 which has a vertical and cylindrical type vessel (100) which can eliminate the possiblity of dead zone mixing problems.

7. The novel composter as claimed in claim 4 which has a top loading feeding (1) system of the composter is taking full advantages of the gravitational force in distributing the raw materials inside the vessel.

8. The novel composter as claimed in claim 4 in which the compost product will be discharged through the outlet (3) located at the bottom of the vessel by gravity force without any additional removal mechanism.

9. The novel composter as claimed in claim 4 which is equipped with a vertical helical screw impeller (12) and scrapers, installed at the centre position of the vessel which is operated by an electrical motor and a reduction gear (5).

10. The novel composter as claimed in claim 9 in which the unique helical screw impeller (12) design will generate a good axial mixing pattern by conveying the composting materials from bottom to the top (21) and free drop to the side (20) by the gravitational force to complete the mixing process.

11. This novel composter as claimed in claim 9 in which a unique helical screw impeller (12) design will also create less friction by reducing the mixing load to the impeller compared to conventional mixing paddle and will reduce wearing of components that will ensure lower maintenance cost and provide longer lasting of material.

12. The novel composter as claimed in claims 5 to 7 which contributes to the high efficiency of the system and consequently contribute to the power saving of the composter as a results of smaller load, less friction, small electrical motor and axial mixing pattern with vertical position of the vessel.

13. The novel composter as claimed in claims 5 to 7 which has an efficient aeration method in the vessel in which is achieved by introducing the air by the air blower controlled by the O₂ meter through the nozzles (14) at different position attached at the internal wall of the vessel and simultaneous air and material mixing by the impeller.

14. The novel composter as claimed in claims 5 to 7 wherein for the enhancement of the composting process, accumulation of CO₂ will be removed from the vessel by centrifugal exhaust fan controlled by CO₂ meter that will discharge 16 m above the ground.

15. The novel composter as claimed in claims 5 to 7 wherein the vertical installation and conical bottom shape of the vessel (100) will facilitate the effective collection of the leachate run off in which accumulated leachate will be either recycled to the vessel or sent to the storage tank using a pump.

16. The novel composter as claimed in claims 5 to 7 wherein the equipment operating conditions such as optimum temperature, moisture content, O₂ and removal of excess CO₂ is controlled by PLC controller to ensure the high rate decomposition process will take place.

17. The novel composter as claimed in claim 16 in which safely switches are also installed at all openings and motorised equipment to prevent accidental occurrence during operation and maintenance of the composter system.

18. The novel composter as claimed in claim 16 in which also applicable for bigger capacity by means of expansion of up to 5 tonnes per day of compost product using the same size of impeller, gear box and motor.

19. The novel composter as claimed in claim 16 in which also applicable for bigger capacity by means of expansion of up to 10 tonnes per day of compost product using the various sizes of vessel, impeller, gear box and motor.

20. The novel composter as claimed in claim 16 in which also applicable for bigger capacity by means of expansion of up to 50 tonnes per day or higher of compost product using the duplicate module with various sizes of impeller, gear box and motor.