• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Methane production procedure by anaerobic alperujo-microalgae co-digestion. The present invention is part of the sector of the use of by-products of the food industry. In particular, the object of the present invention is an improved process for the production of methane from the anaerobic codigestion of alperujo, the main by-product generated in the production of olive oil, with the microalgae Dunaliella salina. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2837496A1
    申请号:ES201931156
    申请日:2019-12-26
    公开日:2021-06-30
    发明作者:Llorente Barbara Maria Rincon；Rodriguez Maria Jose Fernandez；La Lama Calvente David De；Padilla Rafael Borja；Antonia Jimenez-Rodriguez
    申请人:Consejo Superior de Investigaciones Cientificas CSIC；Universidad Pablo de Olavide；
    IPC主号:
    专利说明:

    [0004] The present invention is part of the sector of the use of by-products of the food industry. In particular, the object of the present invention is an improved process for the production of methane from the anaerobic codigestion of alperujo, the main by-product generated in the production of olive oil, by means of the production system by centrifugation in two phases, with the microalgae Dunaliella salina.
    [0006] BACKGROUND OF THE INVENTION
    [0008] The alperujo is the main by-product resulting from the extraction of olive oil in the oil mills, and shows a high water content (56%), an acid pH (5.4) and a high content of organic matter (91%), much of it lignin in nature (35%). In addition, alperujo has a high fat content (3-4%) and also water-soluble polyphenols (0.9%), fractions that give it phytotoxic properties. The content of potassium (K) is relatively low, also showing low content of phosphorus (P), micronutrients and heavy metals. In addition, alperujo is deficient in nitrogen, therefore, the anaerobic digestion process of it is associated with a nitrogen deficiency that is reflected in the metabolism of microorganisms and therefore in the yields of biogas and methane production. In conclusion, alperujo is very problematic both for its characteristics (low pH, high organic load, high content of reducing sugars, etc.) and for the quantities in which it is generated (from 2,000,000-4,000,000 t / year) and its treatment is very necessary.
    [0010] Among the methods used for the recovery of this by-product is its anaerobic digestion, obtaining methane of high calorific value, which makes it useful for different applications such as its use in cogeneration engines to produce heat and electricity.
    [0012] On the other hand, anaerobic co-digestion of alperujo with a co-substrate that complements this nitrogen deficiency can improve methane yields. end. In this sense, the anaerobic co-digestion of different percentages of mixture between different species of microalgae and alperujo has been studied. Anaerobic co-digestion processes of alperujo with different microalgae such as Scenedesmus quadricauda, Chlamydomonas reinhardtii 6145, Chlamydomonas reinhardti cw15, and Dunaliella salina are known.
    [0014] The results of the co-digestion of the alperujo with these microalgae in the percentages studied do not always give good results, which gives rise to a growing interest in the development of processes that allow a better use of products such as the alperujo for the production of methane. with better results in terms of performance and kinetics.
    [0016] DESCRIPTION OF THE INVENTION
    [0018] The alperujo, as mentioned above, is deficient in nitrogen, therefore, its anaerobic digestion process is associated with a nitrogen deficiency that is reflected in the metabolism of microorganisms and therefore in the yields of biogas production and methane. The anaerobic co-digestion of alperujo with a co-substrate that complements this nitrogen deficiency improves the final methane yields. That is why in the present invention the anaerobic codigestion of different percentages of mixture between Dunaliella salina and alperujo has been studied, which will allow the olive industry to treat its by-products through anaerobic co-digestion obtaining an extra energy benefit in the form of methane that could be used in the oil mill itself and would save on energy costs.
    [0020] Therefore, in a first aspect, the present invention refers to a method for obtaining methane from alperujo or solid oil mill waste (OMSW), by anaerobic co-digestion of a substrate comprising alperujo with microalgae, characterized by that the microalgae is Dunaliella salina and that it is based on a proportion of alperujo: microalgae that is between 85: 15 and 95: 5.
    [0022] In a preferred embodiment the substrate comprises a mixture of alperujo and Dunaliella salina in a ratio between 90:10 and 95: 5 in volatile solids, and more preferably where the substrate consists of a mixture of alperujo and Dunaliella salina 95: 5 in volatile solids.
    [0024] In another more preferred embodiment, the above procedure comprises the following steps:
    [0025] (a) adding a substrate consisting of a mixture of alperujo and Dunaliella salina to the digestion reactor;
    [0026] (b) addition of microbial inoculum to the digestion reactor in proportion of volatile inoculum solids: substrate between 3.0 and 0.5;
    [0027] (c) adding a trace element solution to the inoculum: substrate mixture from step (b);
    [0028] (d) closure of the digestion reactor and displacement with inert gas, preferably nitrogen gas, of the headspace air;
    [0029] (e) digestion for a period between 30 and 50 days at a mesophilic temperature between 20 and 390C, and at a stirring speed between 200 and 500 rpm.
    [0031] The anaerobic digestion of a substrate of a lignocellulosic nature, such as alperujo, can be limited in the first stage or hydrolysis-acidogenesis stage by the presence of the complex structures of hemicellulose, cellulose and lignin. The use of some pretreatment prior to anaerobic digestion, such as thermal pretreatment, ultrasound, or microwaves, could favor the breakdown of these complex structures, allowing better results in methane yields and production kinetics obtained.
    [0033] On the other hand, the use of a suitable microbial inoculum in step (b) of the procedure is essential for the proper development of these anaerobic digestion processes. In a preferred embodiment, the inoculum from step (b) is selected from anaerobic sludge from wastewater treatment plants or stations (WWTP), or mature microbial inoculums from agri-food industry reactors.
    [0035] In a more preferred embodiment the volatile solids ratio of inoculum: substrate is 2: 1. This proportion of volatile solids is calculated based on the volatile solids contained in both the inoculum and the starting substrate or substrates (alperujo and / or Dunaliella salina microalgae or both), according to Example 1 herein invention.
    [0037] On the other hand, depending on the origin of the microbial inoculum used in step (b), it may still contain undigested remains of the substrate fed into the reactor of origin. This is the case of inocula from industrial reactors or WWTPs. If not previously removed, these remains could alter the results of anaerobic digestion of a new substrate to be treated by anaerobic digestion. Therefore, in a preferred embodiment, a time interval of between 36 to 48 hours should be allowed to pass from when the inoculum is harvested until the inoculum is added in step (b) of the process of the invention.
    [0039] The various microorganisms that make up the microbial inoculum, preferably bacteria and Achaeans, and that participate in the anaerobic digestion process, have nutritional requirements of macro and micro nutrients for the maintenance of their metabolism and their reproduction. On some occasions the composition of the substrate fed to the anaerobic reactors can cover these essential needs. However, to ensure the proper beginning and development of anaerobic digestion, initially at the time of inoculation of the anaerobic reactors with microorganisms, a certain amount of trace elements can be added to ensure that there is no lack of them and that there is a good start-up of the process by activating the microbial enzyme systems. These trace elements play a crucial role in the growth and metabolism of anaerobic microorganisms, being essential for many biochemical and physiological processes. Some trace elements such as Nickel, Cobalt or Molybdenum act as co-factors in enzymes involved in the methane formation process. On the other hand, the bio-accessibility of the trace elements in the metabolic routes of anaerobic microorganisms is related in most cases, not with the total amount of these metals, but with the fraction found in solution. Other factors such as the pH of the medium or the temperature can cause the precipitation and / or chelation of these trace metals, thus reducing their bio-accessibility. Therefore, the main objective of adding the trace elements at the start of the digesters is to promote the metabolism and the activity of the microorganisms involved in the process.
    [0041] This is why, in another preferred embodiment, the trace element solution of step (c) comprises salts of metallic elements selected from among iron, copper, zinc, cobalt, manganese, molybdenum, nickel, aluminum, selenium, and any mixtures thereof. In a more preferred embodiment the metal salts of the trace element solution are selected from Fe2 +, Cu2 +, Zn2 +, Co2 +, Mn2 +, Ni2 +, Al3 +, Se4 + Mo6 +; and any of its mixtures; and in an even more preferred embodiment the solution of trace elements comprises at least two salts that are selected from among FeCl2-4H20, C0CI26 H2O, MnCl2-4H20, AICI36H2O, (NH4) 6M or 702-4H20, H3BO3, ZnCl2, CuCl2- 2H20, N¡CI2-6H20, Na2Se03-5H20, and EDTA.
    [0043] In an even more preferred embodiment, the trace element solution from step (c) comprises FeCl2-4H20, CoCl2-6H20, MnCl2-4H20, AICI3-6H20, (NFDeMorCMFhO, H3B03, ZnCl2, C or CI2-2H20, N¡ CI2-6H20, Na2Se03-5H20 and EDTA.
    [0045] Finally, it is interesting to mention that the agitation speed of the digesters in step (e) of the process of the invention must be carefully selected since very slow speeds could give rise to a low interaction or transfer of the inoculum-substrate and therefore give rise to to obtaining low methane yields, while, on the other hand, very high stirring speeds could lead to breakage of the flocs formed by anaerobic microorganisms in the digesters, also leading to low methane yields. Choosing a suitable stirring speed is essential for the smooth running of the process.
    [0047] In conclusion, by means of the procedure of the invention, for the alperujo-microalga codigestion mixture with the Dunaliella salina microalgae ( D. salina) and the mixture percentage 95% alperujo-5% of D. salina, working under mesophilic conditions of operation (35 ° C), the following have been achieved:
    [0048] • Improvements in the methane production yield, since the methane yields obtained were 491 ± 1 mL CH4 / g SV added (SV: volatile solids), this value represents an increase of 29.2% in the production of methane compared to that obtained in the anaerobic digestion process of alperujo alone, 380 ± 1 mL CH4 / g SV added- • Increase in methane production kinetics by 35%, in terms of mL of methane produced / g SVday. Going from obtaining 40.6 mL of methane / g SVday for the digestion of the alperujo by itself, to obtaining 54.7 mL of methane / g SV day in the indicated co-digestion mixture. In the percentage of alperujo- D.salina mixture that is presented, there is an improvement in the kinetics. There is, therefore, for this percentage of mixture both an improvement in the amount of methane obtained, or yield, as in the speed at which it is produced, or kinetics.
    [0050] In the present invention, volatile solids (SV) are understood as the portion of organic matter that can be removed or volatilized when organic matter is burned in a muffle furnace at a temperature between 400 ° C to 900 ° C. In particular, the inoculum: substrate ratio is expressed in SV as a measure of the organic matter content of the substrate / s regardless of the humidity they have. The water content of alperujo, for example, can reach between 65 and 90% by weight.
    [0052] Throughout the description and claims the word "comprise" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and characteristics of the invention will emerge in part from the description and in part from the practice of the invention. The following examples and figures are provided by way of illustration, and are not intended to be limiting of the present invention.
    [0054] BRIEF DESCRIPTION OF THE FIGURES
    [0056] Figure 1: Evolution of the chemical soluble oxygen demand (CODs) in the anaerobic digestion experiments of solid residues from oil mills or alperujo (RSA), RSA that have been hydrothermally pretreated under mild conditions (RSA PHS) and co-digestion of a mixture of RSA: Dunaliella salina 95: 5 in volatile solids.
    [0058] Figure 2: Methane yield obtained in batch anaerobic digestion experiments of solid oil mill waste obtained by the two-phase centrifugation production system (RSA), RSA with mild hydrothermal pretreatment (RSA PHS) and co-digestion of a mixture of RSA: Dunaliella salina 95: 5 in volatile solids.
    [0060] EXAMPLES
    [0062] The invention will be illustrated below by means of tests carried out by the inventors, which show the effectiveness of the product of the invention.
    [0063] Analytical methods
    [0065] All analyzes were performed according to the Standard Methods of the American Public Health Association (APHA-AWWA-WPCF, 1998. Standard Methods for the Examination of Water and Wastewater, 20th Edition, American Public Health Association, American Water Works Association and Water Environmental Federation, Washington DC). The following parameters were measured: total chemical oxygen demand (COD), soluble chemical oxygen demand (CODs), total solids (ST), volatile solids (SV), total alkalinity (AT), pH, total nitrogen Kjeldahl (NTK) and volatile fatty acids (VFA). The soluble parameters were determined after centrifugation (Eppendorf, 10,000 rpm, 10 min) and filtration (47 mm glass fiber filter) of the sample.
    [0067] ST and SV were determined according to standard methods 2540B and 2540E, respectively (APHA, 1998); COD was determined using the method described in detail elsewhere (Raposo, F., de la Rubia, MA, Borja, R. and Alaiz, M., 2008. Assessment of a modified and optimized method for determining Chemical oxygen demand of solid substrates and Solutions with high suspended solid content. Talanta 76 (2), 448-453), while CODs was determined using closed digestion and the 5220D colorimetric standard method (APHA, 1998). The pH was determined using a model Crison 20 Basic pH meter. AT was determined by titration to pH 4.3 (APHA, 1998). C and N were determined by means of a LECO CHNS-932 Elemental Analyzer (Leco Corporation, St Joseph, MI, USA). The NTK was determined using a method based on the 4500-Norg B of Standard Methods (APHA, 1998).
    [0069] Individual volatile fatty acids (VFAs) from C2 to C7, including iso-C4, iso-C5 and iso-C6, were analyzed using a gas chromatograph (Shimadzu GC 2010) equipped with a flame ionization detector (FID) and a capillary column filled with Nukol (nitroterephthalic acid modified polyethylene glycol). Before injection, 900 pL of the sample was mixed with 150 pL of H3PO4 (1: 2, vol: vol) to adjust the pH below 2.0 and 150 pL of a crotonic acid solution (2000 mg / L ) as an internal standard. This mixture was centrifuged to remove solids and transferred to a 1500 pL gas chromatography vial; the sample injection volume was 1 pL. The injector and detector temperatures were maintained at 200 ° C and 250 ° C, respectively, while the column temperature increased from 120 to 160 ° C. at an increasing rate of 10 ° C / min.
    [0071] Determination of volatile solids
    [0073] Total solids and volatile solids are determined by methods 2540 B and 2540 E of the Standard Methods (APHA, AWWA, WPCF, 1989), respectively. They are based on the evaporation of a sample of known volume in a tared porcelain capsule after being dried in an oven at 103-105 ° C for 1 hour. After evaporation at 103-105 ° C, the increase in weight over that of the empty capsule represents total solids (TS), which includes both dissolved solids and suspended solids.
    [0075] Subsequently, the residue obtained in the capsule is incinerated at a temperature of 550 ± 500C for 1h. After this time, the weight loss represents the volatile solids (SV) and the solids that still remain in the capsule constitute the mineral solids (SM).
    [0077] Example 1. Calculation of the quantities to obtain the proportion in volatile solids of inoculum: substrate and alperujo: microalgae desired
    [0079] In the first place, the volatile solids of the inoculum, the alperujo and the Dunaliella salina microalgae are determined and, based on these volatile solids, we proceed to look for an inoculum-substrate ratio of 2 between them, which does not exceed the capacity of the reactor or digester to be used in anaerobic digestion and leaving at least 20% headspace in the anaerobic reactor.
    [0081] For the concrete example of a ratio of 2: 1 inoculum: substrate, if the determination of SV of the inoculum is 0.0209 g SV¡nocuio / g of inoculum and the SV of alperujo are 0.2018 g SVaiperujo / g alperujo, and considering a 250 mL reactor, a 50 mL headspace would have to be left in the reactor. If 190.15 g of inoculum are taken, it is equivalent to 3.97 g SVinoc (that is, 190.15 g inoculum X 0.0209 g SVinoc / g inoculum = 3.97 g SVmochium). For an inoculum: substrate ratio of 2: 1, it would be necessary to add half the volatile solids of alperujo, that is, 3.97 / 2 = 1.99 g SVaiperujo and since alperujo has a volatile solids content of 0.2018 g SVaiperujo / g alperujo a total of 9.85 g of alperujo should be added (1.99g SV alperujo / 0.2018 g SVaiperujo / g alperujo = 9.85 g of alperujo). Therefore, for an inoculum: substrate ratio of 2: 1, it is necessary to put 190.15 g of inoculum and 9.85 g of alperujo that in total add 200.
    [0083] Table 1. Example of calculations for an inoculum: substrate 2: 1 ratio. When the volatile solids content (SV) is 0.0209 g SVinoc / g inoculum for the inoculum and 0.2018 g SVaiperujo / g alperujo for the alperujo and considering a 250 mL reactor,
    [0085] inoculum to add SV Total inoculum (g)
    [0086] SV Alperujo (g) Alperujo a
    [0087] (g) (g) add (g)
    [0088] 190.15
    [0090] On the other hand, to calculate the alperujo: microalgae proportions, the same procedure would be followed, starting from a volatile solids content for the inoculum and alperujo similar to the previous one and a volatile solid content for the Dunaliella salina microalgae of 0.4723 g SVDunaiieiia / g Dunaliella salina.
    [0092] To maintain an inoculum: substrate ratio of 2: 1, in a 250 mL reactor leaving a 20% head space, an estimate is made of the amount of inoculum necessary so that the total content is 200 g. 190.5 g of inoculum are taken, that is, 3.98 g of SV inocium, and 3.98 / 2 = 1.99 g of SV substrate. As it is a co-digestion and a 95: 5 ratio is wanted alperujo: Dunaliella salina, of those 1.99 g of substrate SV , 1.89 g SVaiperujo (1.99x 0.95) will be of alperujo and 0.10 g SVDunaliella salina (1.99x0.05) will be made of microalgae D. salina. As the SV content of the alperujo and the microalgae are known, the amount of each substrate to be added is found below: 1.89 g SVaiperujo / 0.2018 g SVaiperujo / g alperujo = 9.372 g of alperujo and 0 , 10 g SV Dunaliella salma / 0.4723 g SVDunaiieiia / g Dunaliella salina = 0.211 g of the alga Dunaliella salina.
    [0094] Table 2. Example of calculations for a co-digestion percentage of 95% alperujo-5% Dunaliella salina microalgae, maintaining the inoculum: substrate ratio 2: 1. When the content of volatile solids (SV) is 0.0209 g SVinoc / g of inoculum for the inoculum and 0.2018 g SVaiperujo / g alperujo for the alperujo and that of the Dunaliella salina microalgae 0.4723 g SV d . saline / g D. saline considering a 250 mL reactor.
    [0095] 95% Alperujo 5% D. salina
    [0096] Inoculum to sv SV D.
    [0097] SV alperujo Alperujo to SV D. salina salina to add inoculum substrate * add such (g) (g) (g) (g) add (g) To (g)
    [0098] (g) (g)
    [0100] * g SV substrate = of both substrates in total, both alperujo and D. salina
    [0102] Example 2. Comparative study between co-digestion under conditions of alperujo ratio: D. saline is 95: 5 with other mixtures known in the state of the art 5
    [0104] Different combinations of alperujo ID were tested. saline : 100%. alperujo; 75% alperujo-25% D. salina ; 50% alperujo-50% D. salina ; and 25%. alperujo-75% D. salina.
    [0106] 0 The tests of the biochemical potential of methane (PBM) were carried out in a system of multi-batch reactors; the effective volume of the reactors was 250 mL, in continuous stirring by magnetic bars at 500 rpm and in a thermostatic water bath at mesophilic temperature (35 ± 20C).
    [0108] 5 The inoculum: substrate ratio was 2: 1 (expressed in volatile solids). For each reactor containing 239 mL of inoculum, the amount of substrate necessary to obtain the required ratio between inoculum and substrate was added, along with 239 pL of trace element solution.
    [0110] 0 The composition of the trace element solution is: FeCI2-4H20, 2000 mg / L;
    [0111] C0CI26 H2O, 2000 mg / L; MnCl2'4H20, 500 mg / L; AICI36H2O, 90 mg / L; (NH4) 6M or 7024-4H20, 50 mg / L; H3BO3, 50 mg / L; ZnCl2, 50 mg / L; CuCI2-2H20, 38 mg / L, NÍCI26H2O, 50 mg / L, Na2Se03-5H20 194 mg / L and EDTA 1000 mg / L.
    [0112] Table 3. Comparison of methane yield and methane production rate for different alperujo: microalgae proportions
    [0114]
    [0116] *% by weight on the inoculum: substrate ratio of 2: 1
    [0118] Example 3. Substrates and inoculum
    [0120] Three different substrates were used: (i) RSA, (ii) RSA, pretreated with a mild hydrothermal pretreatment at 121 ° C, 30 minutes and 1.1 bar (110 kPa) (RSA PHS) and (iii) the mixture of co -digestion of the RSA: Dunaliella salina 95: 5 mixture in volatile solids. The pretreatment at 121 ° C and 1.1 bar (110 kPa) for 30 min was chosen based on the previous results obtained from different mild hydrothermal pretreatments carried out in RSA. 500 g of RSA was introduced into a 1 liter autoclavable bottle and then autoclaved under the selected conditions. The sample was then cooled to room temperature and stored at 4 ° C for less than 24 h until use. Table 4 shows the main characteristics of the substrates and the inoculum used during the experiments. The RSA was collected from the experimental olive oil mill located at the Instituto de la Grasa (CSIC), Seville (Spain). The olive pit pieces were removed using a 2 mm mesh. Dunaliella salina ( D. salina) was provided as lyophilized biomass by the University of Huelva, Huelva (Spain). The main characteristics of D. salina are presented in Table 4. The anaerobic reactors were inoculated with biomass obtained from an industrial upflow reactor of anaerobic sludge for wastewater from a brewery located in Seville (Spain).
    [0121] Table 4. Main characteristics of the substrates and the inoculum used during the experiments
    [0122] Inoculum values RSA values * D. salina values ** Parameters
    [0123] ST (g / kg) 27.7 ± 1.8 231.5 ± 2.3 887.9 ± 7.3
    [0124] SV (g / kg) 20.9 ± 1.7 201.8 ± 2.6 472.3 ± 8.1
    [0125] COD (g of 02 / kg) nd 325.1 ± 0.4 272 ± 8
    [0126] CODs (g of 02 / kg) na 144.4 ± 4.1 na
    [0127] NTK (g / kg) na na 7.9 ± 0.7
    [0128] PH 7.1 ± 0.2 4.7 ± 0.1 8.22 ± 0.2 (1:20) *** AT (g CaC03 / kg) nd 2.7 ± 0.0 nd
    [0129] * Concentrations expressed as: weight / weight of wet sample.
    [0130] ** Concentrations expressed as: weight / weight of lyophilized sample.
    [0131] *** (p: v) using distilled water.
    [0132] ST: total solids
    [0133] SV: volatile solids
    [0134] COD: total chemical oxygen demand
    [0135] CODs: soluble chemical oxygen demand
    [0136] NTK: total nitrogen Kjeldahl
    [0137] AT: total alkalinity
    [0139] Example 4. Tests of the biochemical potential of methane (PBM)
    [0141] The tests were carried out batchwise in a multiple reactor system with an effective volume of 200 mL. The reactors were continuously stirred by magnetic bars at 440 rpm and placed in a thermostatic water bath at mesophilic temperature (35 ± 2 ° C).
    [0143] The inoculum: substrate ratio was 2: 1 (based on SV). Each reactor contained 150 mL of inoculum, the amount of substrate necessary to provide the required inoculum to substrate ratio, and finally 150 µl of trace element solution were added.
    [0145] The composition of the trace element solution was: FeCl2-4H20, 2000 mg / L; C0CI26 H2O, 2000 mg / L; MnCl2-4H20, 500 mg / L; AICI36H2O, 90 mg / L; (NH4) 6M or 702-4H20, 50 mg / L; H3BO3, 50 mg / L; ZnCl2, 50 mg / L; CuCl2-2H20, 38 mg / L, NÍCI26H2O, 50 mg / L, Na2Se03-5H20 194 mg / L and EDTA 1000 mg / L. Reactors with inoculum solution and trace elements, but without addition of substrate, were used as controls.
    [0147] The reactors were sealed by previously displacing the air contained in the headspace with nitrogen at the beginning of the test. The biogas produced was passed through a 3N NaOH solution to capture CO2; the remaining gas was assumed to be methane. The biogas volume was expressed under standard conditions of pressure and temperature (273 K, 1 bar (100 kPa). Anaerobic digestion experiments were performed for a period of approximately 34 days until the accumulated gas production remained essentially unchanged. 10 reactors of each experiment were placed and 7 of them were sacrificed to evaluate the evolution of the different parameters by means of different analyzes.
    [0149] Example 5. Evolution of pH
    [0151] Table 5 shows the evolution of the pH, the variation of the AT and the AGV throughout the time of the three experiments.
    [0153] Table 5. Evolution of individual volatile fatty acids, total volatile fatty acids (total VFA), pH and total alkalinity (AT) in batch anaerobic digestion experiments of solid oil mill waste (RSA), RSA pretreated by mild hydrothermal pretreatment ( RSA PHS) and co-digestion of the mixture RSA: Dunaliella salina 95: 5 in SV.
    [0155]
    [0156]
    [0158] * N E: not found
    [0160] The pH trend did not show relevant fluctuations in any of the experiments. During the anaerobic digestion (DA) of RSA, the minimum pH value was 7.6 at the beginning of the experiment and the maximum value, 8.1, was reached at the end of the experiment. When RSA PHS DA and co-digestion were performed, the pH values were between 7.5 and 8. These values remained relatively constant in all experiments within the range described as optimal for the growth of methanogenic archaea.
    [0162] The evolution of AT values throughout the RSA experiment ranged from 4349 ± 66 mg of CaCOs / L to 5551 ± 62 mg of CaCOs / L, during the RSA PHS experiment the AT values varied from 3341 ± 74 mg CaCOs / L at 5534 ± 67 mg CaCOs / L and 4182 ± 68 mg CaCO3 / L to 5693 ± 82 mg CaCO3 / L for the codigestion experiment. In all three cases, the increase in alkalinity in the system was progressive, reaching the highest AT value at the end of the experiment. This increase in AT values coincides with the accumulation of ammonia in the system due to the degradation and stabilization of the organic matter that is hydrolyzed. During the hydrolysis stage of the DA process, complex organic matter was degraded into simpler soluble molecules that can be used as substrates for microbial metabolism by hydrolysis and acidogenesis. Subsequently, the substrates were consumed in the acetogenesis and methanogenesis phases. Throughout the three experiments, the final concentration of ammonia was below the limit established as toxic for the evolution of the DA process. The AT values were also relatively stable, and within the optimal range for the DA process, indicating good process stability and self-buffering capacity during the three experiments carried out.
    [0164] The AGV content is one of the most used parameters to control the stability of the DA process. AGV concentration is the main factor affecting intermediate alkalinity. The variation in AGV over time is summarized in Table 5. Throughout the RSA PHS experiment, the AGV concentration was highest on day 4. The concentration of isobutyric acid, butyric acid, valeric acid and caproic acid in the RSA PHS experiment it reached values of 625 mg / L, 477 mg / L, 466 mg / L and 484 mg / L, respectively. The total AGV concentration reached on day 4 was 2052 mg / L. Pretreatment accelerated the solubilization (hydrolysis) of RSA and reduced the particle size so that a shortened hydrolytic step could be observed. The total AGV concentrations observed during RSA DA were significantly higher than those obtained for the RSA PHS experiments. RSA AGV accumulation started on day 2 and reached its highest level on day 6. Then, the AGV concentration decreased to 0 on day 8. The maximum AGV peak was observed two days later than that observed during the DA from RSA from SHP. The highest accumulation of VFA during RSA AD was on day 6 and consisted mainly of acetic acid (1710 mg / L), isobutyric acid (825 mg / L), valeric acid (448 mg / L), and caproic acid (251 mg / L), reaching a total VFA concentration of 3226 mg / L. Hydrolytic bacteria took longer to break down raw or untreated RSA into simpler substances, and a large accumulation of VFA was observed on the sixth day of the experiment, indicating that the DA process is not as straightforward as in the case of pretreatment. . Both the RSA PHS and the RSA DA produced a VFA accumulation above the limit established by Siegert and Banks (Siegert, I, Banks, CJ, 2005. The effect of volatile fatty acid additions on the anaerobic digestion of cellulose and glucose in batch reactors. Process Biochemistry, 40 (11), 3412-3418). Siegert and Banks (2005) reported the inhibition of cellulolytic activity and, therefore, in the rate of cellulose hydrolysis when the AGV concentration was equal to or greater than 2 g / l, regardless of the pH of the system.
    [0166] During the co-digestion experiment, although most of the organic matter came from the RSAs, the contribution of the microalgae helped to smooth the hydrolytic stage, making it more evenly spaced over time, thus improving the DA process. The AGV accumulation decreased compared to that obtained for RSA. The main VFA concentrations were caproic acid (747 mg / L), isobutyric acid (578 mg / L) and valeric acid (421 mg / L) on day 6, but similar values were reached on day 8 (isobutyric acid = 460 mg / L and caproic acid = 747 mg / L). The accumulation of AGV began on day 2 and was observed until day 8, but the maximum concentration of total AGV was lower than that observed during the RSA and RSA PHS experiments and did not exceed the limit established by Siegert and Banks (2005) as toxic.
    [0168] Figure 1 shows the evolution of the CODs throughout the trials. The solubilization of organic matter was quite different throughout the three experiments. In the co-digestion experiment, a constant concentration of soluble organic matter was observed. The contribution of the microalgae to the system added an organic matter more easily biodegradable than the lignocellulosic RSA, keeping the COD values almost constant around 5000 mg of O2 / I. A decrease in the concentration of soluble organic matter was only observed between days 8 and 10, in which COD values of 3864 mg of O2 / I and 4328 mg of O2 / I were reached, respectively (Figure 1). This constant concentration of dissolved organic matter led to a synergy between the nutrients and the bacteria involved in the anaerobic digestion process. The COD concentration observed during co-digestion was higher than that observed in the RSA PHS and RSA DA experiments. The concentration of the CODs in the RSA and RSA PHS experiments often fluctuates considerably. The initial COD value in the RSA experiment was 2203 mg O2 / I and 2771 mg O2 / I for the RSA PHS experiment. This small difference is due to the effect of the thermal pretreatment on the substrate, which helped to break down the lignocellulose fibers and the solubilized organic matter. The effect was also observed of thermal pretreatment with time, since in the RSA PHS experiment two maximum peaks of solubilization of organic matter were observed, the first on day 2 and the second on day 14 after the start of the experiment. On the other hand, during the AD of RSA, only a maximum peak of solubilization of organic matter was observed and it was delayed in time, since it was observed on day 8. These fluctuations in the solubilization of organic matter did not allow a synergy between nutrients and the bacterial community. During the DA of RSA, hydrolysis was observed to be the rate limiting step. The hydrolysis step is the main bottleneck during AD of substrates with a high content of lignocellulose due to the low biodegradability of the substrate. Thermal pretreatment helped break down cellulose, hemicellulose, and lignin fibers (Rincón et al., "Biochemical methane potential of two-phase olive mill solid waste: Influence of thermal pretreatment on the process kinetics." Bioresource Technology, 140, 249 -255, 2013) .However, co-digestion produced an improvement in the hydrolysis stage, observing the positive synergistic effect of the codigestion mixture to balance the nutrients in the process, showing the increase in methane yield produced by the microorganisms.
    [0170] The effect of pretreatment (RSA PHS) and anaerobic co-digestion of RSA and D. salina microalgae were investigated in a mixing ratio of 95 and 5%, respectively, compared to the DA of raw RSA. The methane yields for the three experiments are shown in Figure 2. After 34 days of DA, the cumulative methane production showed the same trend of variation in each experiment. Methane production throughout the test grew exponentially in the first 8 days and then stabilized. Despite being a difficult biodegradable substrate, methane production was immediate in each of the three experiments, possibly because the bacteria used an internal fraction that was easily degradable, and therefore the hydrolysis step could have started with this fraction more available. In all three cases, the methane yield stabilized from day 22 after the start of the experiment. Finally, higher methane productions were observed for co-digestion than, for the individual substrates, RSA and RSA PHS. Final values of 380 ± 1 mL of CH4 / g of S added for the RSA, 424 ± 2 mL of CH4 / g of S added for the RSA PHS and 491 ± 1 mL of CH4 / g of S added for the mixture of co were determined. -digestion. A 29.2 and 4% increase in methane yield was achieved for co-digestion and RSA PHS compared to untreated RSA, respectively. Increased performance of Methane obtained in the RSA PHS compared to the crude RSA (4%) was similar to that reported by Rincón et al. (2013) for PBM testing of heat pretreated RSA compared to raw RSA (5%). Rincon et al. (2013) reported a methane yield of 373 ± 4 mL of CH4 / g of S added for the PBM test of raw RSA and of 392 ± 14 mL of CH4 / g of S added for the test of PBM of RSA pretreated at 120 ° C for 180 min.
    [0172] The maximum daily methane production of 48 ± 8 μL of CH4 / g of S added was achieved on the seventh day for the PBM test of RSA and of 58 ± 2 and 76 ± 5 mL of CH4 / g of S added on day 5 for the RSA PHS and the co-digestion mix, respectively. Fernández-Rodríguez et al. (2014) (Fernández-Rodríguez et al. "Assessment of two-phase olive mili solid waste and microalgae co-digestion to improve methane production and process kinetics." Bioresource Technology, 157, 263-269, 2014) also obtained an improvement in production of methane through the co-digestion of RSA-microalgae Dunaliella salina. However, a lower methane yield was achieved with the mixture of 75% RSA-25% D. salina (330 mL CH4 / g added S), improving methane production from RSA by only 2 , 8%.
    [0174] Example 6. Estimation of the model parameters by kinetic modeling
    [0176] First order kinetic model
    [0178] To study the kinetics of the process and estimate the performance of the process in the DA and the co-digestion of the three cases studied, the following first order kinetic model was used:
    [0180] G = G m [1 -exp (-kt)] (1)
    [0182] where G is the cumulative specific methane production (mL of CH4 / g of S added), Gm is the final methane production (mL of CH4 / g of S added), k is the specific rate constant (days- 1) and t is the digestion time (days). This kinetic model is normally applied to evaluate the kinetics of discontinuous DA processes for different types of biodegradable substrates. This model is based on the assumption that methane production is proportional to the amount of substrate and is not limited by microbial cell mass.
    [0183] Table 6 summarizes the kinetic parameters obtained from Equation (1) for the co-digestion mixture and the two substrates studied alone. The values after ± represent the standard deviation of each parameter. As can be seen, deviations were obtained between the experimental values of Gm (Figure 2) and the theoretical (Table 6) lower than 7.7% for all the cases studied. Furthermore, the low values of the standard deviations and the high values of the coefficients of determination demonstrate the appropriate fit of the experimental results to the proposed model.
    [0185] As can be seen in Table 6, final methane production increased by 8.5% and 24% when RSA was thermally pretreated and co-digested with D. salina (95% RSA-5% D. salina ) respectively, compared to the value obtained for the untreated RSA. PBM tests of selected source mixtures of FORSM (Municipal Solid Waste Organic Fraction) and sewage sludge were reported to show an increase in methane production from 18% to 47% compared to DA of single sewage sludge (Cabbai, V., Ballico, M., Aneggi, E., Goi, D., 2013. BMP tests of source selected OFMSW to evalúate anaerobic co-digestion with sewage sludge. Waste Management 33, 1626-1632). The kinetic constant, k, increased by 12% when RSA was co-digested with D. salina (95% RSA-5% D. salina) compared to the values achieved for untreated RSA and heat pretreated RSA ( 0.17 days'1 in both cases).
    [0187] Table 6. Kinetic parameters obtained from the first order kinetic model in the experiments of batch anaerobic digestion of RSA, mild hydrothermal pretreatment (RSA PHS) and co-digestion of the mixture RSA: Dunaliella salina 95: 5 in SV.
    [0191] * R2: coefficient of determination ** E.E.E .: Standard error of estimation; *** The error was defined as the difference between the measured and predicted methane yield values.
    [0193] Modified Gompertz kinetic model
    [0195] On the other hand, the modified Gompertz kinetic model is a sigmoid function that is considered as a kind of mathematical model for a time series. Therefore, it can be one of the best functions to predict biogas production in a batch DA process. Many researchers have studied the application of different kinetic models and found that the modified Gompertz model has one of the best fits for biogas or methane production data as a function of time in anaerobic processes performed in batch mode.
    [0197] In the modified Gompertz model, the cumulative methane production is related to the digestion time through the following equation:
    [0199] B = B m * exp [-exp [(R m * e / B m ) * (X - 1) 1]] (2)
    [0201] where B is the cumulative methane production at time t (mL of CHVg of S added); Bm is the maximum methane production or potential methane yield (mL of CHVg of S added); Rm is the maximum methane production rate (mL of CH4 / g of S added ■ d); X is the delay time (d); t is the digestion time (d) in which the cumulative methane production is calculated; and finally, e is exp (1) = 2.7183. The parameters Bm, Rm and X were calculated for each of the experiments studied using the non-linear regression approach with SigmaPlot 11.0 software. Table 7 shows the values for the model parameters obtained from the modified Gompertz model for the three substrates analyzed. In a similar way to what happened with the experimental values of maximum methane production, the theoretical maximum methane production was 8 and 23% higher when the RSA was heat pretreated and when it was codified with D. salina compared to the value Obtained for untreated RSA. Therefore, a considerable increase in the Biodegradability of the substrate when RSA was pretreated or thermally encoded with D. salina, especially in the latter case, compared to crude RSA.
    [0203] Furthermore, the differences between the measured and predicted methane yields were found to be only 6,7,10,1 and 12,1% for the untreated RSA, the thermally pretreated RSA and the D. salina co-digested RSA, respectively. . The high values for the coefficients of determination (R2) and the low values of the standard errors of the estimates (Table 7) again show the excellent fit of the experimental results to the modified Gompertz Model.
    [0205] Table 7. Parameters of the modified Gompertz model for the three substrates studied: solid oil mill waste (RSA), RSA mild hydrothermal pretreatment (RSA PHS) and co-digestion of the RSA: Dunaliella salina 95: 5 mixture in volatile solids.
    [0207]
    [0209] * R2: coefficient of determination ** E.E.E .: Standard error of estimation; *** The error was defined as the difference between the measured and predicted methane yield values.
    [0211] The maximum rate of methane production, Rm, for the co-digestion of 95% RSA-5% of D. salina and thermally pretreated RSA increased by 34.7 and 10.3% compared to the values obtained for the raw RSA. Therefore, the Thermal pretreatment and co-digestion of this substrate with D. salina improved the speed of the RSA DA process, accelerating the rate of methane production.
    权利要求:
    Claims (8)
    [1]
    1. Procedure for obtaining methane from alperujo by anaerobic co-digestion of a substrate comprising alperujo with microalgae, characterized in that the microalgae is Dunaliella salina and that the proportion of alperujo: microalgae is between 85: 15 and 95: 5 in volatile solids.
    [2]
    2. Process according to claim 1 where the ratio of alperujo: microalgae is 95: 5 in volatile solids.
    [3]
    3. Method according to any of the preceding claims, characterized in that it comprises the following steps:
    (a) adding a substrate consisting of a mixture of alperujo and Dunaliella salina to the digestion reactor;
    (b) addition of inoculum to the digestion reactor in proportion of volatile solids inoculum: substrate of step (a) comprised between 3.0 and 0.5;
    (c) adding a trace element solution to the inoculum: substrate mixture from step (b);
    (d) closing the digestion reactor and moving the headspace air with inert gas; Y
    (e) digestion for a period between 30 and 50 days at a mesophilic temperature between 20 and 390C, and at a stirring speed between 200 and 500 rpm.
    [4]
    4. Process according to claim 3, wherein the volatile solids ratio of inoculum: substrate in step (b) is 2: 1.
    [5]
    5. Process according to any of claims 3 to 4, wherein the trace element solution of step (c) comprises salts of metallic elements selected from among iron, copper, zinc, cobalt, manganese, molybdenum, nickel, aluminum, selenium, and any of its mixtures.
    [6]
    6. Process according to claim 5, wherein the metal salts of the solution of trace elements are selected from Fe2 +, Cu2 +, Zn2 +, Co2 +, Mn2 +, Ni2 +, Al3 +, Se4 + Mo6 +; and any of its mixtures.
    [7]
    7. Process according to any of claims 5 to 6 wherein the solution of trace elements comprises at least two salts selected from FeCl2-4H20, C or CI2-6H20, MnCl2-4H20, AICI3-6H20, (NH4) 6Mo702- 4H20, H3B03, ZnCl2, C or CI2-2H20, N í CI2-6H20, Na2Se03-5H20, and EDTA.
    [8]
    8. Process according to claim 7, wherein the trace element solution of step (c) comprises FeCl2-4H20, CoCl2-6H20, MnCl2-4H20, AICI3-6H20, (NH4) 6M or 702-4H20, H3B03, ZnCl2, CuCl2-2H20, NiCl2-6H20, Na2Se03-5H20 and EDTA.
    类似技术:
    公开号 | 公开日 | 专利标题
    Li et al.2019|Enhancement of methane production in anaerobic digestion process: A review
    Yang et al.2010|Enhanced efficiency of biological excess sludge hydrolysis under anaerobic digestion by additional enzymes
    Ho et al.2012|Mitigating ammonia inhibition of thermophilic anaerobic treatment of digested piggery wastewater: use of pH reduction, zeolite, biomass and humic acid
    Zhang et al.2014|Anaerobic digestion of food waste stabilized by lime mud from papermaking process
    Veluchamy et al.2017|Biochemical methane potential test for pulp and paper mill sludge with different food/microorganisms ratios and its kinetics
    Ryue et al.2020|A critical review of conventional and emerging methods for improving process stability in thermophilic anaerobic digestion
    Yao et al.2017|Simultaneous ammonia stripping and anaerobic digestion for efficient thermophilic conversion of dairy manure at high solids concentration
    Yu et al.2017|Hydrolysis and acidification of agricultural waste in a non-airtight system: Effect of solid content, temperature, and mixing mode
    Ramos-Suárez et al.2014|Benefits of combining anaerobic digestion and amino acid extraction from microalgae
    Fu et al.2018|Improved methane production of corn straw by the stimulation of calcium peroxide
    Wu et al.2020|Enhanced biohydrogen and biomethane production from Chlorella sp. with hydrothermal treatment
    Zhang et al.2017|Synergistic effects of anaerobic digestion from sewage sludge with lime mud
    Du et al.2019|Synergistic methane production from the anaerobic co-digestion of Spirulina platensis with food waste and sewage sludge at high solid concentrations
    Zhang et al.2015|Influencing mechanism of high solid concentration on anaerobic mono-digestion of sewage sludge without agitation
    Yuan et al.2019|Enhancing methane production of excess sludge and dewatered sludge with combined low frequency CaO-ultrasonic pretreatment
    Linyi et al.2020|Enhancing degradation and biogas production during anaerobic digestion of food waste using alkali pretreatment
    Sun et al.2020|Improved anaerobic digestion efficiency of high-solid sewage sludge by enhanced direct interspecies electron transfer with activated carbon mediator
    Zhang et al.2018|Enhancement of solubility and biohydrogen production from sewage sludge with lime mud filtrate
    Saragih et al.2019|The effectiveness of anaerobic digestion process by thermal pre-treatment on food waste as a substrate
    Bolzonella et al.2020|Biological thermophilic post hydrolysis of digestate enhances the biogas production in the anaerobic digestion of agro-waste
    Grübel et al.2019|Microwave-assisted sustainable co-digestion of sewage sludge and rapeseed cakes
    ES2837496B2|2022-02-23|METHANE PRODUCTION PROCEDURE THROUGH ALPERUJO-MICROALGA ANAEROBIC CO-DIGESTION
    Tyagi et al.2021|Microbial community dynamics in anaerobic digesters treating organic fraction of municipal solid waste
    Thanos et al.2021|Enhanced biogas production in pilot digesters treating a mixture of olive mill wastewater and agro-industrial or agro-livestock by-products in Greece
    Ma et al.2020|Calcium ions affect sludge digestion performance via changing extracellular polymeric substances in anaerobic bioreactor
    同族专利:
    公开号 | 公开日
    WO2021130396A1|2021-07-01|
    ES2837496B2|2022-02-23|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2021-06-30| BA2A| Patent application published|Ref document number: 2837496 Country of ref document: ES Kind code of ref document: A1 Effective date: 20210630 |
    2022-02-23| FG2A| Definitive protection|Ref document number: 2837496 Country of ref document: ES Kind code of ref document: B2 Effective date: 20220223 |
    优先权:
    申请号 | 申请日 | 专利标题
    ES201931156A|ES2837496B2|2019-12-26|2019-12-26|METHANE PRODUCTION PROCEDURE THROUGH ALPERUJO-MICROALGA ANAEROBIC CO-DIGESTION|ES201931156A| ES2837496B2|2019-12-26|2019-12-26|METHANE PRODUCTION PROCEDURE THROUGH ALPERUJO-MICROALGA ANAEROBIC CO-DIGESTION|
    PCT/ES2020/070775| WO2021130396A1|2019-12-26|2020-12-09|Method for producing methane by means of anaerobic codigestion of alperujoand a microalga|
    [返回顶部]