WO2021161339A1

WO2021161339A1 - Systems and methods for treating organic waste

Info

Publication number: WO2021161339A1
Application number: PCT/IN2021/050131
Authority: WO
Inventors: Dileep Mathews PAUL; Rinu THOMAS; Nithin Thomas; Adarsh Johny KARIMTHURUTHEL
Original assignee: Dileep Mathews PAUL; Thomas Rinu; Nithin Thomas; Karimthuruthel Adarsh Johny
Priority date: 2020-02-12
Filing date: 2021-02-12
Publication date: 2021-08-19

Abstract

A system (100) and a method (200) for treating organic waste are disclosed. The system (100) includes a food crusher (2) for reducing particle size of the organic waste and a pre-treatment chamber (3) for pre-treating the crushed organic waste. The system further includes a hydrolysis chamber (7) operatively coupled to the pre-treatment chamber (3) to receive the pre-treated waste. A separator (22) for separating hydrolysed pre-treated waste from remaining unhydrolysed pre-treated waste is provided. The hydrolysed pre-treated waste is sent to a digester (9) to produce biogas and a digestate. The separator (22) is positioned between the hydrolysis chamber (7) and the digester (9).

Description

SYSTEMS AND METHODS FOR TREATING ORGANIC WASTE

TECHNICAL HELD:

[001] The present disclosure generally relates to systems and methods for treating organic waste, and more particularly relates to systems and methods for treating organic waste to produce biogas for domestic and commercial applications

BACKGROUND:

[002] Organic waste from houses and restaurants is the main source of municipal solid waste. Improper handling and disposal of the municipal waste is a major threat to the environment. The existing source level waste management systems have disadvantages such as big size, unhygienic conditions, and poor aesthetics, to name a few.

[003] There are different technologies that are used for source level organic waste treatment including, composting (aerobic digestion), big biogas systems and food crushers. Normal composting units that are generally available have bad odour and worm infestation. Existing anaerobic biogas systems that are available in the market are neither compact nor clean enough to be placed inside the house. Other systems like food crushers directly deposit the crushed food into the wastewater line and thereby wasting the energy content of the organic waste.

[004] Hence there is a need for a system that is compact and can be used indoors without producing any bad odour and conserves the energy of the organic waste.

SUMMARY:

[005] The summary is provided to introduce a selection of concepts in a simple manner that are further described in the detailed description of the disclosure. This summary is not intended to identify key or essential inventive concepts of the subject matter nor is it intended to determine the scope of the disclosure

[006] The disclosed device is a compact, automated, and user-friendly indoor waste management product. It changes the source level waste management system into a consumer appliance in all aspects, such as appearance, dimensions and functionality. The aesthetically pleasing unit is compact and can be positioned indoors, be it in a kitchen or in a restaurant. Automated systems

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SUBSTITUTE SHEETS (RULE 26) are incorporated to make it a ‘set and forget it' system. The product is hygienic and is free from bad odours.

[007] In one aspect, a method for treating an organic waste is disclosed. The method comprises mechanically treating the organic waste to reduce particle size of the organic waste, pre-treating the organic w¾ste in a pre-treatment chamber, hydrolysing the pre-treated waste in a hydrolysis chamber, separating the hydrolysed pre-treated waste fro remaining un-hydrolysed pre-treated waste in a separator, re-sending the un-hydrolysed pre-treated waste to the pre-treatment chamber and directing the hydrolysed pre-treated waste to a digester to produce biogas.

[008] In another aspect, a system for treating an organic waste is disclosed. The system comprises a food crasher for reducing particle size of the organic waste, a pre-treatment chamber for pre treating the crushed organic waste, a hydrolysis chamber operatively coupled to the pre-treatment chamber to receive the pre-treated waste, a separator for separating hydrolysed pre-treated waste from remaining un-hydrolysed pre-treated waste, and a digester for receiving the hydrolysed pre- treated waste to produce biogas

[009] Further advantages and other details of the present subject matter will be apparent from a reading of the following description and a review of the associated drawings. It is to be understood that the following description is explanatory only and is not restrictive of the present disclosure.

BRIEF DESCRIPTION OF THE FIGURES:

[0010] To further clarify the advantages and features of the disclosure, a more particular description of the disclosure will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the disclosure and are therefore not to be considered limiting of its scope. The disclosure will be described and explained with additional specificity and detail with the accompanying drawings in which:

[0011] Figure 1 is a schematic representation of a system for treating organic waste to produce biogas, in accordance with an embodiment of the present disclosure;

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SUBSTITUTE SHEETS (RULE 26) [0012] Figure 2 is a perspective view of a biogas system in accordance with an embodiment of the present disclosure;

[0013] Figure 3 is an exterior view of a biogas system in accordance with an embodiment of the present disclosure; and

[0014] Figure 4 is a flow chart illustrating a method for treating organic waste to produce biogas.

[0015] Further, persons skilled in the art to which this disclosure belongs will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the figures with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0016] Embodiments of the present disclosure will be described below in detail with reference to the accompanying figures.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS:

[0017] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications to the disclosure, and such further applications of the principles of the disclosure as described herein being contemplated as would normally occur to one skilled in the art to which the disclosure relates are deemed to be a part of this disclosure.

[0018] It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.

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SUBSTITUTE SHEETS (RULE 26) [0019] The organic waste disposed into the disclosed system undergoes a rapid anaerobic process which produces biogas and a liquid fertilizer as by-products. The waste is mechanically treated and crushed into a slurry using a food crusher. The food crusher is an arrangement like a domestic food waste dispenser. The waste in the form of the slurry' is then supplied to a pre-treatment chamber. In the pre-treatment chamber, the crushed organic waste undergoes a microwave and a chemical pre-treatment. Pre-treatment is done to speed up the anaerobic process. Further, the digester is designed as a two-stage process. This is done to closely control the process parameters of the hydrolysis step which is the rate limiting step of the anaerobic process. The un-hydrolysed waste is then separated and re-introduced into the pre-treatment chamber. The produced biogas then undergoes a three-stage filtration process to make it like natural gas. The gas is then compressed, stored and can later be used as cooking fuel.

[0020] Figure 1 is a schematic representation of a biogas system 100. Table 1 provides a list of the components of the system. In some embodiments, organic waste material is deposited into the biogas system (100) through a metallic/ceramic/plastic kitchen sink like arrangement (!) which is equipped with a lid. The waste is then crushed into a slurry using a food crusher (2). The food crusher (2) may be an arrangement like a domestic food waste dispenser. The waste in the form of the slurry' is then supplied to a pre-treatment chamber (3), where it is undergoes a three-stage pre treatment process. In the first stage (4), the waste in the form of the slurry is mixed thoroughly with enough water and NaOH (or similar additives) that is added from an automatic feeding system. The addition of NaOH is to maintain a proper pH and to speed up the anaerobic process. Thereafter the organic waste goes through the second step of pre-treatment, i.e., the microwave pre-treatment (5) In this step, a microwave radiation is generated and beamed through a guide into the pre-treatment chamber (3). In some embodiments, the organic waste is irradiated for up to 8 minutes. Microwave treatment (5) ensures the fast conversion of insoluble hydrocarbons into water-soluble hydrocarbons in the hydrolysis process. In the third stage (6) of pre-treatment, the organic waste is mixed with trace elements like selenium from an automatic feeding system. The trace element addition helps to reduce instabilities that are common with biogas digesters that run on the food waste.

[0021] In some embodiments, the pre-treated waste is then fed into a hydrolysis chamber (7), where it undergoes hydrolysis. In biogas production process, the favourable conditions (like pH,

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SUBSTITUTE SHEETS (RULE 26) temperature, bacteria) for hydrolysis are different from other following stages. Further, the hydrolysis is a rate determining step in the complete biogas production process. Hence for a faster digestion, the hydrolysis step is separated from other processes. The conditions in the hydrolysis chamber (7) are continuously monitored through a control unit (19), which senses pH, temperature, and other parameters. In some embodiments, the waste undergoes hydrolysis for about 5 -15 days.

[0022] The waste slurry' after hydrolysis is pumped using a slurry pump (8) into a separator (22). In an example embodiment, the separator may be a centrifugal separator. In another embodiment, the separator may be a hydro-cyclone filter. The pumping is performed after the completion of pre-treatment process in the pre-treatment chamber (3). In the separator (22), the w'aste separates into liquid digestate that has undergone the complete hydrolysis and insoluble solid particles which have not yet undergone the hydrolysis. In one embodiment, the w'aste may be partially separated into liquid digestate that has undergone the complete hydrolysis and insoluble solid particles. In some embodiments, the separation efficiency may be in a range of 60-100%. The liquid digestate is fed to the digester (9) where it undergoes the remaining steps of the anaerobic process, namely acetogenesis, acidogenesis and methanogenesis. The separated solid particles are re-introduced into the pre-treatment chamber (3) where it is mixed with the untreated food waste and again undergoes hydrolysis. This process ensures that most of the organic waste entering the digester (9) is hydrolysed, thereby improving the speed and quality of digestion.

[0023] The quantity of waste pumped into the digester (9) in any given day is equal to the quantity of waste deposited in the pre-treatment chamber (3) in the same day. The water level in the pre treatment chamber (3) is controlled by using a water level sensor (21) in the pre-treatment chamber (3). After emptying the pre-treatment chamber (3) to a predetermined level, water is partially filled in the pre-treatment chamber (3) to avoid any back flow of bad odour and to maintain the anaerobic conditions in the hydrolysis chamber (7). The digester (9) also has multiple monitoring devices

(19), which senses pH, temperature, and other parameters. It also contains a gas pressure sensor

(20) to control the quantity of gas to be pumped and compressed. Provisions are also made to add/remove additives in the digester (9) through additional plumbing (not shown in figure).

[0024] The digestate that is produced after the producti on of biogas is then fed to a post treatment chamber (10) where, the ammonia, hydrogen sulphide and other bad odour producing chemicals

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SUBSTITUTE SHEETS (RULE 26) are removed with the help of bacteria. The post treated digestate is converted into fertilizer that is then sent to a fertilizer storage tank (11). The fertilizer storage tank (11) is provided with an overflow system. The overflow system can be directly connected to the wastewater line of the house or any other commercial establishments.

[0025] The biogas produced in the digester (9) is sucked in and is purified using a multi-stage gas filter (13) where, most of the carbon dioxide, hydrogen sulphide and moisture content are removed. The gas is then compressed by using a gas compressor (14) and stored in a high-pressure gas cylinder (15). There is a non-return valve (12) in the gas line to prevent the back flow of gas into the digester (9). The compressed gas is then supplied to the gas stove through a pressure regulator (16). The high-pressure gas cylinder (15) is also equipped with a pressure sensor (20). The working of the gas compressor (14) is controlled by using the data from the pressure sensor (20) from digester (9) and high-pressure gas cylinder (15).

[0026] The working of food crusher (2), the pre-treatment chamber (3), the pump, the gas compressor (14), the pH adjustor, and the temperature controller are controlled by the control unit (18) using the readings from corresponding sensors. The above-mentioned components are arranged on a compact structure of beams (17) and panels that cover the device. The size, shape, material and design of this can be adapted according to the needs of the market.

[0027] The disclosed biogas system is compact in size and the system is designed as a consumer appliance which can be placed indoors. The reduction in size is achieved by reducing the total time taken for the anaerobic process. Further, the disclosed biogas system is fully automated and very' hygienic. The iterative pre-treatment-hydrolysis enables to achieve this. The proposed biogas system has a pre-treatment chamber (3), where the organic waste undergoes chemical, mechanical, and thermal/microwave pre-treatments. The pre-treatment ensures faster conversion of long chain hydrocarbons into short chain hydrocarbons and eventually result in a rapid hydrolysis. Furthermore, the multi-chamber design of the biogas system ensures that the hydrolysis happens in a separate chamber, where favourable conditions for hydrolysis like pH and temperature can be monitored and maintained. After the hydrolysis chamber (7) there is a separator, which filters the non-hydrolysed waste from the hydrolysed waste. The non-hydrolysed waste is then re-introduced into the pre-treatment chamber (3) and the hydrolysed waste is fed into the digester (9). This

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SUBSTITUTE SHEETS (RULE 26) ensures that there is near complete hydrolysis of the food waste and thereby significantly reduces the total time taken for the entire process. Additionally, the addition of trace elements and other additives into the process reduces the instabilities that creep into the anaerobic process.

[0028] Figure 2 is a perspective view of a biogas system in accordance with an embodiment of the present disclosure.

[0029] Figure 3 is an exterior view of a biogas system in accordance with an embodiment of the present disclosure.

[0030] Figure 4 is a flow chart illustrating a method for treating organic waste to produce biogas. The described method 200, may include block 202, “Mechanically treating the organic waste to reduce particle size of the organic waste block 204 “Pre-treating organic waste in a pre-treatment chamber”, block 206, “Hydrolysing pre-treated waste in a hydrolysis chamber”, block 208, “Separating hydrolysed pre-treated waste from remaining un-hydrolysed pre-treated waste in a separator”, block 210, “Re-sending un-hydrolysed pre-treated waste to the pre-treatment chamber”, block 212, “Directing hydrolysed pre-treated waste to a digester to produce biogas”, block 214, “Filtering biogas to remove impurities”, block 216, “Compressing and storing biogas”, and block 218, “Post treating digestate to produce a fertilizer”.

[0031] At block 202, the organic waste is mechanically treated to reduce the particle size of the organic waste and to make it into a slurry. The slurry is pre-treated in a pre-treatment chamber (3) in multiple stages at block 204. In the first stage (4), the waste in the form of the slurry is mixed thoroughly with enough water and NaOH to maintain a proper pH and to speed up the anaerobic process. In the second stage (5), the organic waste is subjected to the microwave pre-treatment. In this step, a microwave radiation is beamed through a guide into the pre-treatment chamber (3). In some embodiments, the organic waste is irradiated for up to 8 minutes to convert insoluble hydrocarbons into water-soluble hydrocarbons in the hydrolysis process. In the third stage (6), the organic waste is mixed with trace elements like selenium. The trace element addition helps to reduce instabilities that are common with biogas digesters that run on the organic/food waste.

[0032] At block 206, the pre-treated organic waste is fed into a hydrolysis chamber (7), where it

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SUBSTITUTE SHEETS (RULE 26) undergoes hydrolysis. In the hydrolysis chamber (7), pH and temperature are continuously monitored. In some embodiments, the waste undergoes hydrolysis for about 5 -15 days. The hydrolysed organic waste is sent to a separator (22) at block 208. In the separator (22), the waste partially or fully gets separated into liquid digestate that has undergone the complete hydrolysis and insoluble solid particles which have not yet undergone the hydrolysis. At block 210, the separated solid particles are re-introduced into the pre-treatment chamber (3) where it is mixed with the untreated food waste and again undergoes pre-treatment and hydrolysis. This process ensures that most of the organic waste entering the digester (9) is hydrolysed, thereby improving the speed and quality of digestion. At block 212, the liquid digestate is fed to the digester (9) where it undergoes the remaining steps of the anaerobic process, namely acetogenesis, acidogenesis and methanogenesis to produce biogas.

[0033] At block 214, the biogas produced is filtered using multi-stage gas filters (13) to remove impurities, where most of the carbon dioxide, hydrogen sulphide and moisture content are removed. At block 216, the biogas is compressed by using a gas compressor (14) and stored in a high-pressure gas cylinder (15). At block 218, the digestate that is produced after the production of the biogas is fed to a post treatment chamber (10) where, the ammonia, hydrogen sulphide and other bad odour producing chemicals are removed with the help of bacteria. The post treated digestate is converted into a fertilizer and sent to a fertilizer storage tank (11)

[0034] The following examples are intended as illustrative and non-limiting and represent specific embodiments of the present disclosure.

Example 1

[0035] To study the effect of presence of a separator between the hydrolysis chamber and the digester on the hydraulic retention time (HRT) of the anaerobic process, an experiment was conducted with two-chamber anaerobic digester, the first one being a hydrolysis chamber and the second one being a digester. An organic load of 2 kg kitchen waste per day was added to the system. The second chamber had a size of 120 litres which corresponded to an HRT of 30 days. A slurry pump was used to pump the waste into the second chamber. A separator was placed in this line and bypass to this separator was also provided. The experiment was conducted with and without the separator. The HRT in the second chamber was adjusted by changing the output height

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SUBSTITUTE SHEETS (RULE 26) of the exit from the second chamber. The output biogas was then weighed and measured. The results are presented in Table 2. It is evident from the results that having a separator between the two chambers decreased the FIR.T by around 25%.

[0036] The terms "comprises", "comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such a process or a method. Similarly, one or more devices or sub-systems or elements or structures or components preceded by "comprises... a" does not, without more constraints, preclude the existence of other devices, other sub-systems, other elements, other structures, other components, additional devices, additional sub-systems, additional elements, additional structures, or additional components. Appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Table 1: List of Components

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SUBSTITUTE SHEETS (RULE 26)

Table 2: Experimental results

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SUBSTITUTE SHEETS (RULE 26)

Claims

We Claim:

1. A method (200) for treating an organic waste, the method comprising: mechanically treating (202) the organic waste to reduce particle size of the organic waste; pre-treating (204) the mechanically treated organic waste in a pre-treatment chamber (3); hydrolysing (206) the pre-treated waste in a hydrolysis chamber (7); separating (208) the hydrolysed pre-treated waste from remaining un hydrolysed pre-treated waste in a separator (22); re-sending (210) the un-hydrolysed pre-treated waste to the pre-treatment chamber (3), and directing (212) the hydrolysed pre-treated waste to a digester (9) to produce biogas and a digestate.

2. The method (200) of claim 1, further comprising purifying (214) the biogas by using a multi-stage gas filter (13) to remove carbon dioxide, hydrogen sulphide and to reduce moisture content.

3. The method (200) of claim 2, further comprising compressing (216) the biogas and storing in a high-pressure gas cylinder (15).

4. The method (200) of claim 1, wherein pre-treating (204) the organic waste comprises a three-stage pre-treatment, wherein a first stage (4) comprises adding an alkali to the organic waste to maintain a pH in a range of 6-7, wherein a second stage (5) comprises subjecting the organic waste to a microwave radiation to ensure conversion of insoluble hydrocarbons present in the organic waste into water-soluble hydrocarbons, and wherein a third stage (6) comprises adding trace elements to reduce instabilities in the digester (9).

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SUBSTITUTE SHEETS (RULE 26)

5. The method (200) of claim 1, wherein the hydrolysed pre-treated waste comprises a liquid digestate that has undergone the complete hydrolysis, and wherein the un-hydrolysed pre-treated waste comprises insoluble solid particles.

6. The method (200) of claim I, wherein the hydrolysed pre-treated waste is fed to the digester (9), where it undergoes acetogenesis, acidogenesis and methanogenesis to produce the biogas and the digestate.

7. The method (200) of claim 1, wherein the un-hydrolysed pre-treated waste is resent into the pre-treatment chamber (3) where it is mixed with the organic waste, thereby ensuring the hydrolysed pre-treated waste enters the digester (9) to improve speed and quality of digestion

8. The method (200) of claim 1, wherein a quantity of the pre-treated organic waste sent to the digester (9) in any given day is equal to a quantity of the organic waste deposited in the pre-treatment chamber (3) in the same day.

9. The method (200) of claim 1, further comprising post treating the digestate, wherein the post treating removes ammonia, hydrogen sulphide, and any odour producing chemicals, and wherein the post treating converts the digestate into a fertilizer.

10. A system (100) for treating an organic waste, the system comprises: a food crusher (2) for reducing particle size of the organic waste; a pre-treatment chamber (3) for pre-treating the crashed organic waste; a hydrolysis chamber (7) operatively coupled to the pre-treatment chamber (3) to receive the pre-treated waste; a separator (22) for separating hydrolysed pre-treated waste from remaining un-hydrolysed pre-treated waste; and a digester (9) for receiving the hydrolysed pre-treated waste to produce biogas and a digestate, wherein the separator is positioned between the hydrolysis chamber (7) and the digester (9).

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SUBSTITUTE SHEETS (RULE 26)

11. The system (100) of claim 10, further comprising a multi-stage gas filter (13) for filtering the biogas to remove carbon dioxide, hydrogen sulphide and to reduce moisture content; a compressor (14) for compressing the biogas; and high-pressure gas cylinder (15) for storing the compressed biogas.

12. The system (100) of claim 10, wherein the pre-treatment chamber (3) is provided with a rvater level sensor (21).

13. The system (100) of claim 10, wherein the digester (9) is provided with a pH and temperature sensor (19), and a pressure sensor (20).

14. The system (100) of claim 10, further comprising a post treatment chamber (10) wherein the post treatment chamber is configured to remove ammonia, hydrogen sulphide, and any had odour producing chemicals using bacteria from the digestate and to convert the digestate to a fertilizer.

15. The system (100) of claim 14, further comprising a fertilizer storage tank (11) to store the fertilizer.

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SUBSTITUTE SHEETS (RULE 26)