Method for producing medium-chain fatty acids

Abstract

The method for producing medium-chain fatty acids according to the present invention is a method (1) for producing medium-chain fatty acids (2) from organic waste (3), characterized in that it comprises a separation step (4) for separating the organic waste (3) into a solid fraction (5) and a liquid fraction (6), a step of fermenting the liquid fraction (6) during a post-fermentation step (7), a step of separating the at least partially fermented liquid fraction (11) into a low sludge effluent (14) and a high sludge effluent (13) by a biomass separation step (12), and an extraction step (15) for extracting the medium-chain fatty acids (2) from the low sludge effluent (14).

Description

[Technical field]

[0001] The present invention relates to a method for producing medium-chain fatty acids. More specifically, the present invention relates to a method for producing medium chain fatty acids from organic waste. [Background technology]

[0002] Traditionally, medium-chain fatty acids have been extracted from coconut oil or palm oil. A drawback of this conventional method is that it yields relatively low amounts of medium chain fatty acids. Another drawback is that coconut and palm oils are not sustainable sources for the production of medium chain fatty acids. SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a solution to one of the above mentioned drawbacks and other drawbacks. DISCLOSURE OF THEINVENTION

[0003] To this end, the present invention comprises: fermenting the organic waste in a primary fermentation to at least partially convert the organic waste into lactic acid; - separating the organic waste into a solid fraction and a liquid fraction; fermenting the liquid fraction during post-fermentation to convert at least a portion of the lactic acid into medium-chain fatty acids; - separating the at least partially fermented liquid fraction into a sludge-lean effluent and a sludge-rich effluent using a biomass separation process; and A process for extracting medium-chain fatty acids from effluent with little sludge The present invention relates to a method for producing medium-chain fatty acids from organic waste comprising the steps of: The advantage of this method is that it allows for the sustainable production of medium-chain fatty acids. Another advantage is that the process is a sustainable and ecological way of treating biological waste, resulting in biological products with high added value (compared to conventional waste treatment).

[0004] Another advantage of the present invention is that it is a method for in situ production of medium chain fatty acids, particularly using lactic acid as an intermediate product. This method allows for the processing of organic waste into medium-chain fatty acids without the need for exogenous additives or field ethanol production. Lactic acid is less harmful and / or toxic than ethanol and therefore does not require as rigorous safety precautions and testing.

[0005] The separation of the organic waste into solid and liquid fractions can be preceded by a mixing step in which the waste is mixed with the biomass. When mixing the organic waste with the biomass, microorganisms and / or additives, for example enzymes and / or specific nutrients such as trace elements and / or minerals and / or vitamins, can also be added. The advantage of this is that the additive may enhance the fermentation of waste materials. Preferably, the mixing step is followed by a primary fermentation in which the waste material is fermented. In the case of main and post-fermentation, a mixing step can be carried out between these fermentation steps, with process water being added to the fermentation mixture. This treated water may be obtained after separation of medium chain fatty acids from the lean sludge effluent. During post-fermentation and / or main fermentation, a process gas may be formed, said process gas preferably comprising hydrogen gas. The hydrogen gas can be used for the electrolytic production of protons. The advantage of this is that it provides the material needed to adjust the pH without the addition of exogenous acids and / or bases.

[0006] The fermentation mixture containing the medium chain fatty acids in solution can be filtered using one or more membrane filters, thereby retaining the biomass and leaving the medium chain fatty acids in a sludge-free effluent. The advantage of this is that the biomass can be reused, for example during mixing of the biomass with organic waste or during one or both fermentation steps. The methods described above are relatively simple to apply as they use existing equipment such as tanks, reactors, presses or centrifuges. The various steps of the method may have an intermittent operation, which allows alternating energy absorption steps, resulting in lower power consumption, which is both environmentally and economically advantageous. In a preferred embodiment, the method and the equipment that can be used for this method are powered using solar power and / or wind energy and / or biogas that can be obtained from the method. This amount of energy may also contribute to the electrolytic generation of protons and / or hydroxide ions, which may be used to adjust the pH. Additionally, preferably only limited amounts of chemicals, and / or water, and / or biomass etc. are supplied from outside. The method may be provided with various internal recycles allowing for example the reuse of chemicals, and / or compounds, and / or water, and / or biomass, and / or one or more combinations thereof. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 shows a schematic diagram of a continuous process according to the present invention. [Diagram 2] FIG. 2 illustrates an alternative method to that of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In order to better illustrate the features of the present invention, some preferred applications of the method for producing medium-chain fatty acids according to the present invention will now be described by way of non-limiting examples with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a continuous process according to the present invention. FIG. 2 illustrates an alternative method to that of FIG.

[0009] The method shown in FIG. 1 is intended to produce medium chain fatty acids 2 from organic waste 3 .

[0010] Medium chain fatty acids 2 refer to fatty acids with at least 6 C atoms, such as caproic acid, enanthic acid and octanoic acid.

[0011] As substrates for producing such medium-chain fatty acids 2, various waste streams 3 are suitable, such as, for example, kitchen waste (food waste), and / or food waste, and / or other selectively collected simply decomposable organic wastes 3, and / or other types of organic substrates with similar characteristics.

[0012] Such waste 3 may include both liquid and solid waste, or a combination thereof.

[0013] Thus, the organic waste 3 can be degraded by hydrolysis during the main fermentation process 21 and converted into lactic acid which acts as an intermediate product of the decomposition process and as a substrate for chain elongation.

[0014] During the main fermentation process 21, lactic acid may be partially converted into intermediate products of medium chain fatty acid production, such as short chain fatty acids, such as acetic acid and butyric acid, and may also be converted into end products, including medium chain fatty acids 2, including caproic acid.

[0015] The fermented organic waste 3 is separated into a solid fraction 5 and a liquid fraction 6 .

[0016] Such a liquid fraction 6 can be obtained by separating the waste material 3 using a sieve or a press, for example.

[0017] The liquid fraction 6 is then fermented during a post-fermentation step 7, whereby at least a portion of the lactic acid is converted into medium chain fatty acids 2 as the end product. The liquid fraction 6 still contains small organic particles, such as, for example, fibers, which are not retained during sieving and / or pressing of the organic waste 3 .

[0018] These organic particles are converted into lactic acid during a post-fermentation step 7, and then at least a portion of said lactic acid may be converted into medium chain fatty acids 2 during a post-fermentation step 7.

[0019] Therefore, more medium-chain fatty acid 2 can be obtained.

[0020] The solid fraction 5 may be converted into biogas 9 and / or compost 10 by an anaerobic digestion process 8 .

[0021] Preferably, the well known Dry Anaerobic Composting (DRANCO) system is used for this treatment.

[0022] Such a post-fermentation step 7 can be carried out in a continuous stirred tank reactor (CSTR), an upflow anaerobic sludge blanket reactor (UASB) or a packed bed reactor (PBR), among others.

[0023] After the post-fermentation step 7, the fermentation mixture 11 is separated by a biomass separation step 12, such as centrifugation and / or microfiltration, into a high sludge effluent 13, which mainly contains active microorganisms capable of catalyzing fermentation, and a low sludge effluent 14, which is rich in medium chain fatty acids 2.

[0024] Separating the fermentation mixture 11 is understood to mean separating the liquid fraction that has been at least partially fermented by the biomass separation step 12 .

[0025] The low sludge effluent 14 mentioned above may be free of sludge.

[0026] The low sludge effluent 14 is then used in a process 15 for extraction of medium chain fatty acids 2 from the low sludge effluent 14 .

[0027] This step can be carried out, for example, by fluid-fluid extraction or electrochemical extraction 15, with or without membrane filtration.

[0028] As shown in FIG. 2, preferably the waste material 3 is first subjected to a pre-treatment step 17 to protect the waste material 16 from unwanted impurities such as stones and plastics.

[0029] This pretreatment step 17 of the waste 3 may use, inter alia, sieves and / or drums, which may or may not rotate.

[0030] Furthermore, it is also possible to mechanically treat the waste 3 during the pretreatment step 17 in order to stimulate the release of organic compounds, for example by means of crushing and / or chopping and / or shredding.

[0031] Preferably, the organic waste 3 is mixed under anaerobic conditions with biomass 19 to form a mixture 20, said biomass 19 preferably coming from another stage of the production process.

[0032] The method may include various recycling steps so that the biomass 19 can be reused.

[0033] Thus, biomass 19 can be obtained from the main fermentation step 21 and / or after the separation step 4 of the solid fraction 5 and the liquid fraction 6 and / or after the biomass separation step 12, said obtained biomass 19 can be reused by adding it to the mixing step 18 of the waste 3 or the pretreated waste 31.

[0034] The biomass 19 may contain certain chain-elongating microorganisms, e.g., lactic acid forming bacteria such as Caproiciproducens sp and / or Ruminococcaceae sp and / or Clostridium kluyveri and / or Pseudoramibacter sp and / or Lactobacillus sp and / or Olsenella sp, etc., and thus contribute to the production of medium chain fatty acids 2.

[0035] After a mixing step 18 of the biomass 19 and the waste material 3 or pretreated waste material 31, the mixture 20 is subjected to a main fermentation step 21, whereby the mixture 20 is fermented under specific conditions.

[0036] During said main fermentation step 21, the organic waste 3 or pretreated waste 31 is at least partially fermented to lactic acid.

[0037] In a preferred embodiment, the lactic acid produced during the primary fermentation step 21 is at least partially converted into medium chain fatty acids 2 during the primary fermentation step 21.

[0038] Additionally, during the main fermentation step 21, a process gas 22 may be produced, which may be converted to methane.

[0039] Preferably, the treated gas 22 is discharged to the anaerobic digestion step 8 of the solid fraction.

[0040] The process gas 22 may contain hydrogen gas, which may be added to the main fermentation process 21 to stimulate microbial chain elongation.

[0041] Preferably, the hydrogen gas is also used for the electrolytic generation of protons and the method 1 may be provided with an internal acid supply.

[0042] During the main fermentation step 21 and / or the post-fermentation step 7, ethanol may also be produced.

[0043] Such in situ production of ethanol does not require the processing of biological waste to lactic acid, nor the chain extension of lactic acid to medium chain fatty acids, for example.

[0044] Furthermore, the method 1 is aimed at producing lactic acid which is converted to medium chain fatty acid 2 by microbial chain elongation.

[0045] In a preferred method, no significant amount of ethanol is produced and / or added during the main fermentation step 21 and / or the post-fermentation step 7.

[0046] After said main fermentation step 21, the fermented mixture 23 may be subjected to a mixing step 24 whereby process water 25 and / or still water 30 may be added to the mixture 23.

[0047] This treated water 25 comes from a later step of the method 1 and can be obtained after the biomass separation step 12 and / or after the extraction step 15.

[0048] The treated water 25 obtainable after the biomass separation step 12 via the extraction step 15 can be indirectly discharged to the mixing step 24, whereby the fermentation mixture 23 can be mixed with the discharged treated water 25 in the mixing step 24.

[0049] Between the biomass separation step 12 and the extraction step 15, a bypass 32 can be provided to allow said steps 12 and 15 to be operated independently of each other.

[0050] Preferably, the treated water 25 contains a relatively low concentration of medium chain fatty acids 2 .

[0051] Fresh water 30 can be added as necessary or desired to bring or maintain the concentrations of organic and inorganic compounds within the desired range.

[0052] Fresh water 30 may include tap water, rain water and / or ground water.

[0053] After mixing the treated water 25 with the fermentation mixture 23, the mixture 23 is preferably separated at least in a separation step 4 into the aforementioned liquid fraction 6 and solid fraction 5, and in this case too, the liquid fraction 6 is fed to a post-fermentation step 7.

[0054] It is also possible to separate the organic waste 3 and / or the pretreated waste 31 and / or the fermentation mixture 23 into a liquid fraction 6, a solid fraction 5 and a biomass-rich fraction 19.

[0055] The primary fermentation step 21 and / or the post-fermentation step 7 are controlled so that medium-chain fatty acids 2 containing caproic acid as a main component are formed by the chain elongation treatment of the microorganisms.

[0056] For this purpose, the organic waste 3 may be degraded by hydrolysis during the main fermentation process 21 and converted into lactic acid which acts as an intermediate product of the decomposition process and as a substrate for chain elongation.

[0057] During the primary fermentation process 21, lactic acid may be partially converted into intermediate products of medium chain fatty acid production, such as short chain fatty acids such as acetic acid and butyric acid, and end products medium chain fatty acids 2, including caproic acid.

[0058] During the production of lactic acid, the pH within the tank may decrease, countering the effect of microbial chain elongation which increases the pH, thereby keeping the pH within the tank in balance.

[0059] As a result, only minimal adjustment of the pH, for example by protons or hydroxide ions, and / or acid and / or base, is required.

[0060] During the post-fermentation step 7, the liquid fraction 6 is fermented and the conditions in the reactor or tank are controlled so that the lactic acid and / or acetic acid and / or butyric acid still present in the reactor are converted into medium chain fatty acids 2, such as caproic acid, as the most important end product.

[0061] Furthermore, during the post-fermentation step 7, a liquid waste 26, preferably rich in lactic acid, can be added directly to the reactor.

[0062] However, as shown in FIG. 2, it is possible to first separate said liquid waste 26 in a separation step 4, for example using a sieve, after which the liquid fraction can be used in a post-fermentation step 7.

[0063] The production of medium chain fatty acids occurs during one or more of the fermentation steps 7,21 described above, so long as the chain extension microorganisms are not inhibited by the substrate or the end product itself.

[0064] Said high sludge effluent 13 can serve as biomass 19 that can be mixed in a mixing step 18 with the waste 3 or pre-treated waste 31 prior to the main fermentation step 21 .

[0065] This high sludge effluent 13 can be circulated multiple times between the post-fermentation stage 7 and the biomass separation stage 12, thus allowing the residence time of the sludge 33 in the tank of the post-fermentation stage 7 to be controlled.

[0066] In this case, the low sludge effluent 14 contains a relatively large amount of fatty acids in solution.

[0067] Thus, in the low sludge effluent 14 there is a wide range of carbonic acids present, such as acetic acid, propionic acid, (iso)butyric acid, (iso)valeric acid, (iso)caproic acid, enanthic acid and / or caprylic acid.

[0068] A downstream extraction system 15 for the medium chain fatty acids 2 allows mainly caproic acid, enanthic acid and caprylic acid to be obtained as end products.

[0069] These medium chain fatty acids 2 may therefore be extracted in an extraction step 15 by means such as fluid-fluid extraction or electrochemical extraction, whereby said medium chain fatty acids 2 may also be extracted from the low sludge effluent 14.

[0070] By this extraction step 15, medium-chain fatty acids 2 such as caproic acid and an aqueous solution 27 containing little sludge and almost no medium-chain fatty acids 2 are obtained.

[0071] As shown in the embodiment of FIG. 2, during the mixing step 18 of the organic waste 3 and the biomass 19, it is also possible to add one or more additives 28, e.g. acids and / or bases and / or enzymes and / or one or more nutrients such as minerals, trace elements and vitamins.

[0072] Also, during the aforementioned mixing step 18, an exogenous cultured microbiome 29 can be added if the waste 3 / biomass 19 ratio needs to be adapted to add a higher proportion of microbial biomass 19 to the system, particularly if it is desirable to adjust the proportion of chain-elongating microorganisms.

[0073] Preferably, such a cultured microbiome 29 comprises bacteria such as Caproiciproducens sp and / or Ruminococcaceae sp and / or Clostridium kluyveri and / or Pseudoramibacter sp and / or Lactobacillus sp and / or Olsenella sp.

[0074] Depending on the reactor used, the residence times of the biomass and liquid fraction 6 during the post-fermentation step 7 can be set differently to prevent competitive reactions with slower growing microorganisms, such as methanogens.

[0075] During the biomass separation step 12, the fermentation mixture 11 can be filtered to remove components larger than 0.2-5 μm, thereby leaving the medium chain fatty acids 2 present in the filtered low sludge effluent 14.

[0076] For example, it is not excluded that the low sludge effluent 14 can be recycled several times to increase the yield of medium chain fatty acids 2 from the organic waste 2 .

[0077] Thus, after the medium chain fatty acid 2 extraction step 15, the short chain fatty acids in the low sludge effluent 14 can be returned to the post-fermentation step 7 by means of an aqueous solution 27 in order to convert said short chain fatty acids into medium chain fatty acids 2.

[0078] The biomass 19 can also be recycled after the biomass separation step 12, whereby the biomass 19 can be added to a tank for the post-fermentation step 7 or can be mixed with the organic waste 3 in a mixing step 18 before the main fermentation step 21.

[0079] In this manner, the influent waste 3 and / or pretreated waste 31 and / or mixture 20 and / or liquid fraction 6 can be inoculated with a substantial amount of active biomass 19 capable of catalyzing the fermentation steps 7 and 21.

[0080] In this biomass separation step 12 excess sludge 33 may be separated, said sludge 33 being added during the anaerobic digestion step 8 .

[0081] This sludge 33 contains, among other things, biomass 19, and excess biomass 19 may be removed from the tank and / or reactor.

[0082] During the post-fermentation stage 7 , a treated gas 22 may be formed, which may be fed to the main fermentation stage 7 and thus to the anaerobic digestion stage 8 .

[0083] Instead, the produced treated gas 22 is dumped directly from the tank of the post-fermentation step 7 to the anaerobic digestion step 8 of the solid fraction 5 .

[0084] During the separation step 4 of the waste material 3 or fermentation mixture 23 in a solid fraction 5 and a liquid fraction 6, interfering substances 34 may also be separated and removed from the system.

[0085] In a preferred embodiment, during the main fermentation step 21, the temperature in the tank varies between 25°C and 60°C, more preferably between 30°C and 50°C, and most preferably between 35°C and 45°C, thereby allowing the microorganisms to grow under optimal conditions.

[0086] Preferably, the pH value in the tank during the main fermentation step 21 is a low pH value between 4 and 6, and the dry matter content is preferably between 10 and 35%.

[0087] Typically, the main fermentation step 21 preferably takes from 1 to 10 days.

[0088] In a preferred embodiment, the post-fermentation step 7 is preferably carried out at a dry matter content of 1-15%, more preferably 2-10%, most preferably 4-8%, for a period of 6 hours to 10 days.

[0089] In a practical embodiment, the temperature in the tank varies during the post-fermentation step 7 between 22°C and 55°C, more preferably between 28°C and 45°C, most preferably between 30°C and 37°C, so that the microorganisms can grow under optimal conditions.

[0090] Depending on the tank used during said post-fermentation step 7, the residence time of the sludge 33 in the tank of the post-fermentation step 7 can be set and, if necessary, the sludge 33 can be vented to the anaerobic digestion step 8.

[0091] This has the advantage of suppressing competitive reactions with microorganisms such as methane bacteria.

[0092] Preferably, but not necessarily, the pH value in the tank is higher during the post-fermentation step 7 than during the main fermentation step; preferably, the pH value is between 5 and 7.

[0093] If necessary or desirable, the pH value in the tank can be adjusted both during the post-fermentation step 7 and during the main fermentation step 21.

[0094] In a preferred embodiment, the pH value is lowered by adding protons which can be obtained from the process gas 22 .

[0095] However, acid or base can be added to the tank or reactor as desired or necessary to bring the pH value into the desired range.

[0096] The invention is in no way limited to the embodiments described and illustrated by way of example, which method can be implemented according to different variants without departing from the scope of the invention.

Claims

1. A method (1) for producing medium-chain fatty acids (2) from organic waste (3) including kitchen waste and / or food waste and / or selectively collected simple decomposable organic waste, comprising: The method (1) - fermenting the organic waste in a main fermentation step (21) and at least partially converting the organic waste (3) into lactic acid; a separation step (4) for separating the organic waste (3) into a solid fraction (5) and a liquid fraction (6); - fermenting the liquid fraction (6) during a post-fermentation step (7), thereby converting at least a portion of the lactic acid into medium-chain fatty acids (2); - separating the at least partially fermented liquid fraction (11) into a low sludge effluent (14) and a high sludge effluent (13) by a biomass separation step (12); an extraction step (15) for extracting medium-chain fatty acids (2) from the low sludge effluent (14); have 2. A method for producing a medium-chain fatty acid comprising the steps of:

2. Before the main fermentation step (21), a mixing step (18) is carried out in which the organic waste (3), optionally subjected to a pretreatment step (17), is mixed with the biomass (19) to form a mixture (20).

2. The method of claim 1 .

3. During the mixing step (18) of mixing the organic waste (3) with the biomass (19), an additive (28) can be added to stimulate fermentation of the organic waste (3) in the fermentation step (7, 21).

3. The method of claim 2 .

4. The additives (28) include acids and / or bases and / or enzymes and / or one or more nutrients such as minerals, trace elements and vitamins.

4. The method according to claim 3 .

5. The main fermentation step (21) is carried out at a relatively high dry matter content between 10% and 35%.

2. The method of claim 1 .

6. The main fermentation step (21) is carried out at a temperature at which the microorganisms grow, between 25°C and 60°C, more preferably between 30°C and 50°C, and most preferably between 35°C and 45°C.

2. The method of claim 1 .

7. The pH value of the main fermentation step (21) is between 4 and 6 and can be adjusted by adding acid or base, or by adding protons and / or hydroxide ions.

2. The method of claim 1 .

8. The main fermentation step (21) is carried out for a minimum of 1 day and a maximum of 10 days.

2. The method of claim 1 .

9. The main fermentation step (21) is followed by a mixing step (24) to form an at least partially fermented mixture (23), and treated water (25) is added to the at least partially fermented mixture (23).

2. The method of claim 1 .

10. The post-fermentation process (7) is carried out for 6 hours to 10 days.

2. The method of claim 1 .

11. The pH value during the post-fermentation step (7) is between 5 and 7.

2. The method of claim 1 .

12. The post-fermentation step (7) is carried out at a dry matter content of 1-15%, more preferably 2-10%, most preferably 4-8%.

2. The method of claim 1 .

13. The post-fermentation step (7) is carried out at a temperature between 22°C and 55°C, more preferably between 28°C and 45°C, most preferably between 30°C and 37°C.

2. The method of claim 1 .

14. The extraction step (15) for extracting the medium chain fatty acids (2) from the low sludge effluent (14) comprises, for example, fluid-fluid extraction or electrochemical extraction.

2. The method of claim 1 .

15. The mixture (20) comprises lactic acid and / or a substrate that can be converted to lactic acid, and the lactic acid and / or the substrate can be converted during the main fermentation step (21) into intermediate products such as short chain fatty acids and into the final product, medium chain fatty acids (2).

3. The method of claim 2 .

16. The waste (3), optionally having undergone a pretreatment step (17) or a fermented mixture (23), contains lactic acid and / or short chain fatty acids, etc., which can be converted into medium chain fatty acids (2) as end products during the post-fermentation step (7).

2. The method of claim 1 .

17. Lactic acid and / or short chain fatty acids can be converted to medium chain fatty acids (2), including caproic acid, during the post-fermentation step (7) and / or the main fermentation step (21) by microbial chain elongation, thereby producing lactic acid and / or short chain fatty acids as intermediate products.

2. The method of claim 1 .

18. The solid fraction (5) is converted into compost (10) and / or biogas (9) by an anaerobic digestion process (8).

2. The method of claim 1 .

19. During the post-fermentation step (7) and / or the main fermentation step (21), a treated gas (22) is obtained, The treated gas (22) is discharged directly and / or indirectly to the anaerobic digestion process (8).

20. The method of claim 18 .

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