AU2017101295A4 - Process and apparatus for organic waste treatment - Google Patents

Abstract

A process for treating organic waste comprises the steps of: (a) blending organic waste in a blending vessel with a mineral mix having a vapour outlet and a solid outlet at a base of the blending vessel; (b) heating said organic waste to a temperature sufficient to eliminate pathogens and produce a vapour stream containing at least one nutrient to flow through said vapour outlet; (c) condensing said vapour stream as a nutrient rich liquid in a condenser; and (d) recovering a solid nutrient containing processed organic waste product from the solid outlet of the blending vessel following a controlled residence time of less than 8 hours. Apparatus for conducting the process is also disclosed.

Description

PROCESS AND APPARATUS FOR ORGANIC WASTE TREATMENT

[0001 ] This invention relates to a process and apparatus for organic waste treatment.

[0002] Organic waste applicable in this process includes manure from various farm animals, food waste and wasted food, slaughterhouse and market waste, waste paper as well as from any sources that handle food and excreta related matter. Organic waste contains elements required for plant growth, and those can improve the soil fertility. If treated through appropriate methods it can be hundred per cent recycled and can save the environment from pollution from landfilling and disposal of raw organic waste.

[0003] The commonly used treatment processes for organic waste are composting, vermicomposting and anaerobic digestion. They are biological processes, which require specific conditions that are depended on the moisture, carbon content, aeration or non- aeration and the optimum bacterial activities. Those processes in addition to the specificities, which are expensive and difficult to operate in a large scale, also result in losing valuable nutrients and carbon during operation. The main pathways through which nutrients get lost are dust, vapour, air, leachate and in general handling. All those forms end up as polluting factors and ultimately end up in expensive and unsustainable operation mainly on large scale.

[0004] It is an object of the present invention to provide a process and apparatus for organic waste treatment, which avoids problems such as those mentioned above and which, desirably, enables a high nutrient recovery in suitable forms for application to agricultural and horticultural land in a minimum time.

[0005] With this object in view, the present invention provides, in one aspect, a process for treating organic waste comprising the steps of: (a) blending organic waste with a mineral mix, preferably a mineral adsorbent mixture suitable for application to soils, in a blending vessel having a vapour outlet and a solid outlet at a base of the blending vessel; (b) heating said organic waste to a temperature sufficient to eliminate pathogens and produce a nutrient rich vapour stream containing at least one nutrient to flow through said vapour outlet; (c) condensing said vapour stream as a nutrient rich containing liquid in a condenser; and (d) recovering a solid nutrient containing processed organic waste product from the solid outlet of the blending vessel following a controlled residence time of less than 8 hours. The process is conveniently conducted as a batch wise process though can be conducted continuously, especially at larger scale.

[0006] Advantageously, the organic waste is segregated organic waste from which undesired non-decomposable materials such as glass, plastics, metals and so on are absent. Organic waste may include a range of materials including vegetable waste and animal waste such as manures. The organic waste may be shredded for size reduction, say below 10-15mm size, prior to delivery to the blending vessel.

[0007] Desirably, the organic waste is heated in the blending vessel to a temperature of 90-120aC. The temperature is controlled throughout the process distinguishing it from the temperature profile for a composting or fermentation process (which typically proceed at substantially lower temperatures). The process is completed in a residence time of less than 8 hours, desirably in 3 to 5 hours. Residence time depends on the initial moisture content of the organic waste. The higher the initial moisture content, the longer the required residence time. Decline in the rate of condensation may be used to control the residence time. When condensate production rate falls to less than a determined value, the process may be terminated.

[0008] Advantageously, the blending vessel is, while open, maintained under suction during the process to draw vapour stream from the blending vessel and towards the condenser and enhance recovery of nutrient rich liquid suitable as a liquid fertiliser. The nutrient rich liquid is sufficiently concentrated in plant nutrients, for example nitrogen and phosphorus, that dilution prior to application may be required. Due to the process, the nutrient rich liquid should also be sterile with no bacterial or fungal content on production. Salmonella sp, for example, should not be at detectable levels. With aseptic packaging, the nutrient rich liquid can be stored, transported and sold separately with good shelf life.

[0009] Preferably, the mineral adsorbent mixture may contain one or more minerals such as, but not limited to, zeolite, gypsum, bentonite, calcite, aragonite and dolomite, desirably naturally occurring minerals. In addition to this, essential nutrients for plant growth such as potassium, phosphorus and other trace elements for a target crop can be supplemented in the mixture. The mixture is blended into the organic material to enrich it for specific output. The adsorbent minerals remain in the final solid output helping to keep it odour free and pest free.

[0010] The blending vessel desirably includes a mixing means to mix the raw material for faster release of moisture and to enable mixing of mineral mix with the organic waste. To this end, the blending vessel conveniently includes mixing blades, for example spiral or paddle blades. The blending vessel may be rotated with speed regulated to the residence time required especially where the process is operated continuously.

[0011] The solid product is preferably left with moisture content of 10-20% by weight. Such moisture content would assist better activation of minerals and other components when applied to soil as a soil amendment. Such moisture content, making the solid product relatively dry, distinguishes the process from a fermentation process. Such moisture content also assists with packaging, soil application and prevents leaching of liquid from the final solid output product.

[0012] In another aspect, the present invention provides an apparatus for treating organic waste comprising: (a) a blending vessel for blending organic waste with a mineral mix, for example as described above, and having a vapour outlet; (b) a heating component for said blending vessel and heating said organic waste to a temperature sufficient to eliminate pathogens and produce a vapour stream containing at least one nutrient; (c) a condenser communicating with the vapour outlet for condensing said vapour stream as a sterile condensate liquid rich in plant nutrients; and (d) a solid outlet at a base of the blending vessel for recovering a solid nutrient containing processed organic waste output product.

[0013] A high recovery of inorganic and organic nutrients from the organic waste is desired. Accordingly, the blending vessel may be sealed to avoid loss of nutrient containing vapour stream. The blending vessel is desirably maintained under negative pressure by a pump, desirably a suction or vacuum pump to draw vapour stream from the blending vessel and towards the condenser. This helps to enhance speed of vapour extraction and reduce treatment time. The blending vessel should be maintained open during the process to avoid pressure build-up and to ensure safety. That is, the blending vessel is not subject to pressure vessel regulations.

[0014] The blending vessel may be a cylindrical vessel made of any suitable material such as stainless steel or carbon steel. The blending vessel should include a mixing means to mix the raw organic waste for faster release of moisture and to enable mixing of mineral mix with the organic waste. To this end, the blending vessel conveniently includes mixing blades. A convenient heater is a jacket heater. The energy source may be electric, hydrocarbon fuel or other energy sources such as solar power or hybrid power. The blending vessel may be rotated with speed regulated to the residence time required especially where the process and apparatus are operated continuously.

[0015] The apparatus may include a shredder where required to reduce size of organic waste matter greater than 10-15mm in size. The shredder may be separate from the blender and movable into a required position relative to a blender inlet only when required for size reduction.

[0016] The solid outlet conveniently includes a manually operable valve to enable recovery of nutrient rich solids at the end of the process.

[0017] The apparatus is conveniently mobile to enable movement to a convenient site. To that end the apparatus may be mounted on wheels or otherwise made mobile.

[0018] Capacity of the apparatus may be selected as desired. The apparatus is scalable and can be used for commercial, industrial or domestic purposes. The apparatus and process could be operated continuously, with the blending vessel being lengthened to the required capacity. Hotels, for example, may find the process and apparatus particularly convenient.

[0019] The process and apparatus for organic waste treatment may be more fully understood from the accompanying drawings in which:

Fig. 1 is a schematic diagram of an apparatus for treating organic waste in accordance with one embodiment of the present invention.

[0020] Referring now to Fig. 1, there is shown an apparatus 10 for treating organic waste comprising a blending vessel 13 for blending organic waste with mineral mix having a vapour outlet 14a; a heater H for the blending vessel 13; and a condenser 16 communicating with the vapour outlet 14a through a vapour line 14. Condenser 16 condenses the vapour stream as a nutrient rich condensate liquid recoverable in liquid tank 18. Tank 18 includes a spigot 18a for delivering the nutrient rich liquid to containers such as container 20. A solid outlet 13b is located at the base 130 of the blending vessel 13 for recovering a solid nutrient containing processed organic waste output product. Apparatus 10 is mobile and can be moved to convenient locations on wheels 23, 24 and 26. The components of the apparatus, as above described, may readily be assembled and disassembled to enable ready movement.

[0021] Blending vessel 13 is a cylindrical vessel, for example of stainless steel or carbon steel. Blending vessel 13 includes mixing blades 13c, for example spiral or paddle blades operated by an electric motor (not shown), to mix the organic waste and assist the blending process while also assisting moisture release and nutrient liquid recovery. Blending is improved if the organic waste is segregated organic waste free of non decomposable contaminants such as plastics, paper and metals. The organic waste could be an animal waste product such as horse, cow or elephant manure from farms and zoos. Food and vegetable wastes from any food preparation, serving and processing facilities can be treated. Solid outlet 13b is conveniently a simple manually operable valve.

[0022] As shown, a shredder 12 with cutting blades 12a is deployed on a gantry 12b above the feed inlet 13aa to reduce organic waste size to a size of 10-15mm for better performance of the organic waste treatment process. The shredder 12 is movable into position on wheels 23. The gantry 12b may be height adjustable to enable use of the shredder 12 for blending vessels 13 of different capacity to that shown. Here, the blending vessel 13 has a capacity of from 100kg up to about 1 tonne.

[0023] Heater H is conveniently a jacket heater which may be fuelled in any desired manner, for example by electricity or other energy sources as described above. The jacket heater H may be heated by steam generated by heating of water by the energy source or direct electric heating coil. Desired temperature in blending vessel 13 is in the range 90-120SC, sufficient temperature to destroy pathogens and produce a nutrient rich vapour stream recoverable through condensation as a sterile plant nutrient rich liquid.

[0024] Organic waste treatment apparatus 10 includes a suction pump 15 to maintain a negative pressure and draw vapour from the blending vessel 13 and through condenser 16. The suction pump 15 may be controlled to enhance speed of vapour extraction but without causing very low pressure in the blender. Condenser 16 is conveniently water cooled and needs only to be connected to a water supply through ports 16a. Cooling water can be recycled following chilling if desired. As cooling water may be 40 to 50eC following a condensation step, there is a source of hot water for washing or other purposes.

[0025] The organic waste treatment proceeds in batch wise mode as follows. Segregated shredded organic waste with known moisture content is delivered from shredder 12, through feed inlet 13aa and into blending vessel 13. A mineral adsorbent mixture, such as a mixture of activated carbon and zeolite supplemented or enriched if necessary with phosphorus, potassium, or other trace elements is added to both minimise odour and supplement the nutrient value of the solid output product as a soil amendment for enhancing crop growth. Vacuum pump 16 is switched on and water supply is connected to condenser 16 through ports 16a.

[0026] Jacket heater H is switched on and the blending vessel 13 is heated to 90 to 120SC. This temperature range is maintained throughout the process. The waste is mixed in the blending vessel 13 and the mixing blades 13c turn the organic waste. At the same time, a nutrient rich vapour evolves from the organic waste and is drawn through vapour outlet 14a and vapour line 14 and towards condenser 16.

[0027] Sterile nutrient rich condensate liquid forms and collects in liquid fertiliser tank 18, which is desirably maintained sterile. The process is continued for some time before liquid fertiliser is distributed to containers 20, again under sterile packaging conditions if longer shelf life is required.

[0028] Initial moisture content of the organic waste, usually 60-80%, indicated a residence time of organic waste in blending vessel 13 of 3 to 8 hours. At the end of this time, condensate flow slows and the process can be terminated. Outlet 13b is opened and a treated solid organic product containing 10-20 wt% moisture content can be recovered. This product is suitable as a soil amendment.

[0029] As a guide, 45 to 65% of the original organic waste is converted to a solid output product and 35-55% is available as sterile nutrient rich liquid product. The nutrient rich liquid product, suitable for use as a liquid fertiliser, may - for example and following treatment of vegetable waste- have the following analysis.

Ammonium Nitrogen (mg/L) 6.55

Nitrate Nitrogen (mg/L) <0.10

Boron (mg/L) 0.05

Calcium (mg/L) 5.37

Iron (mg/L) 0.12

Magnesium (mg/L) 0.28

Manganese (mg/L) < 0.05

Phosphorus (mg/L) 0.09

Potassium (mg/L) 0.38

Sodium (mg/L) 0.67

Sulphur (mg/L) 37.42

Zinc (mg/L) 0.27

Conductivity (dS/m) 0.143 pH 4.2

In this example too, the nutrient rich liquid may be sterile with expected thermotolerant coliforms below 3 MPN/g for food waste and non-detectable levels of Salmonella sp.

[0030] The process and apparatus for organic waste treatment enables faster treatment, high nutrient recovery and a low energy, potentially low footprint process, which can be adapted to various applications. The process should also eliminate all the pollution effects related to the particular type of organic waste treated (for example food and manure related).

[0031] Modifications to the process and apparatus for waste treatment as described herein may be apparent to the skilled reader of this disclosure. For example, the process and apparatus could be operated continuously. Such modifications and variations are deemed within the scope of the present invention.

Claims (9)

1. CLAIMS:

   1. A process for treating organic waste comprising the steps of: (a) blending organic waste in a blending vessel with a mineral mix having a vapour outlet and a solid outlet at a base of the blending vessel; (b) heating said organic waste to a temperature sufficient to eliminate pathogens and produce a vapour stream containing at least one nutrient to flow through said vapour outlet; (c) condensing said vapour stream as a nutrient rich liquid in a condenser; and (d) recovering a solid nutrient containing processed organic waste product from the solid outlet of the blending vessel following a controlled residence time of less than 8 hours.
2. 2. The process of claim 1 wherein said organic waste is segregated organic waste from which non decomposable materials are absent and said segregated organic waste has particle size below 10-15mm size.
3. 3. The process of claim 2 wherein said organic waste is shredded to particle size below 10-15mm size.
4. 4. The process of claim 2 wherein said organic waste is heated in the blending vessel to a temperature of 90-120aC and the process is completed in a residence time of less than 8 hours depending on an initial moisture content of the organic waste.
5. 5. The process of claim 4 wherein pressure of the blending vessel is controlled to draw vapour stream from the blending vessel and towards the condenser and enhance speed of extraction of nutrient rich liquid suitable as a liquid fertiliser.
6. 6. The process of claim 5 wherein said solid product has a moisture content of 10-20% by weight.
7. 7. An apparatus for treating organic waste comprising: (a) a blending vessel for blending organic waste with a mineral mix having a vapour outlet; (b) a heater for said blending vessel and heating said organic waste to a temperature sufficient to eliminate pathogens and produce a vapour stream containing at least one nutrient; (c) a condenser communicating with the vapour outlet for condensing said vapour stream as a nitrogen rich nutrient containing condensate liquid; and (d) a solid outlet at a base of the blending vessel for recovering a solid nutrient containing processed organic waste product.
8. 8. The apparatus of claim 7 including a shredder for reducing organic waste size to below 10 to 15mm.
9. 9. The apparatus of claim 7 or 8 being mobile to enable movement to a convenient site.