SOLARGAS SYSTEM OPERATED IN MULTIPLE MODES

Abstract

The invention relates to a method and a device for producing biogas in a combined fermenter, in the first section (2) of which organic material is produced by phototrophic microorganisms (1) using atmospheric carbon dioxide and oxygen, said organic material being used to produce biomethane by means of methanogens (5) in a second section (4). The fermenter is operated in multiple modes and using special gassing and degassing methods such that an optimal gas supply corresponding to the requirements of the respective microorganisms and preferably also the absorption or the use of atmospheric carbon dioxide is ensured.

Claims

1. A method for producing biogas in a combined fermenter, in which phototrophic microorganisms (1) in a first section (2) produce organic material, in particular glycolic acid from carbon dioxide and oxygen, and secrete it into a medium (3) (production mode) which is fed into a second section (4) in which methanogens (5) produce biomethane and carbon dioxide therefrom under anoxic conditions, characterized in that the medium (3) is degassed to remove oxygen during the transition from the first section (2) to the second section (4) and is regassed with oxygen during return (exchange mode).

2. The method according to claim 1, characterized in that, while contact to the second section (4) is interrupted, the medium (3) is degassed to remove oxygen and is gassed with air from the environment during return; the air is then used by the phototrophic microorganisms (1) for carbon assimilation (regeneration mode); the medium (3) is then degassed to remove air and gassed with oxygen during return.

3. The method according to claim 1 or 2, characterized in that the ratio of carbon dioxide to oxygen in the medium (3) located in the first section (2) is low, preferably 1:800 to 1:3000, in the production mode.

4. The method according to any one of the preceding claims, characterized in that, in the exchange mode, the medium (3) is gassed with a substitute gas, in particular with carbon dioxide or nitrogen, after the oxygen degassing during the transition from the first section (2) to the second section (4), and is degassed to remove the substitute gas during return before the oxygen gassing.

5. The method according to any one of the preceding claims, characterized in that the carbon dioxide is separated from the biogas produced in the second section (4) and is used for carbon dioxide gassing according to claim 4.

6. The method according to any one of the preceding claims, characterized in that filters, in particular hollow fiber contactors, are used for the gassing and degassing, the pore size being less than 0.1 m, preferably less than 0.04 m.

7. The method according to any one of the preceding claims, characterized in that cyanobacteria, preferably biofilm-forming and preferably metabolizing the produced organic material minimally, more preferably less than 10% thereof, in particular Gloeothece 6909, Plectonema boryanum, Anabaena sp. and Nostoc sp., are present as the phototrophic microorganisms (1) in the first section (2).

8. The method according to any one of the preceding claims, characterized in that the methanogens (5) in the second section (4) are a mixture of acetotrophic and hydrogenotrophic archaea, wherein the acetotrophic archaea, in particular Methanosarcina or Synthrophobotulus, split the organic material from the first section (2) into carbon dioxide and hydrogen which is used by hydrogenotrophic archaea, in particular Methanocella paludicola, Methanocella arvoryzae or Methanopyrus kandleri, for biomethane production, and/or are mixed cultures obtained by selection from sediments of lakes and oceans, bovine rumen, intestines of termites and other animals, rice fields, marshes or biogas systems.

9. The method according to any one of the preceding claims, characterized in that inhibitors of intracellular degradation of the organic material and/or intracellular carbon dioxide storage are present in the first section (2).

10. The method according to any one of the preceding claims, characterized in that, in the phototrophic microorganisms (1), the expression and/or the activity of glycolic acid dehydrogenase and/or glycolic acid oxidase are or are being suppressed; carbon dioxide accumulation by carboxysomes and pyrenoids is inhibited; ribulose-1,5-bisphosphate carboxylase/oxygenase and/or glycolic acid phosphate phosphatase are overexpressed; ribulose-1,5-bisphosphate carboxylase/oxygenase type II is expressed; the excretion of organic material, especially of glycolic acid, through the cell membrane is enhanced.

11. A device for producing biogas in a combined fermenter, comprising the following components: a first section (2), which is partially transparent, with phototrophic microorganisms (1) located in a medium (3); a second section (4), which is opaque, with methanogens (5) located in the medium (3) which is exchanged in exchange mode with the first section (2), the oxygen content being reduced; a connecting system (6) between the first section (2) and the second section (4); filters in the connecting system (6) for gassing and degassing the medium (3) which are connected to gas feeds and gas discharges, a biogas discharge (7) from the second section (4); pumps and valves for distributing liquid and gas streams.

12. The device according to claim 11, characterized in that the connecting system (6) comprises a first connecting pipe (8) and a second connecting pipe (9); the connecting system (6) comprises a first cross-connecting pipe (10), interconnecting the first connecting pipe (8) and the second connecting pipe (9); a first filter (11) is a part of the first connecting pipe (8) between the first section (2) and the first cross-connecting pipe (10); a second filter (12) is a part of the second connecting pipe (9) between the first section (2) and the first cross-connecting pipe (10); a third filter (13) is a part of the first connecting pipe (8) between the second section (4) and the first cross-connecting pipe (10); a fourth filter (14) is a part of the second connecting pipe (9) between the second section (4) and the first cross-connecting pipe (10); a second cross-connecting pipe (15) connecting the first section (2) and the first cross-connecting pipe (10); a fifth filter (16) is a part of the second cross-connecting pipe (15) and is connected to an air line (17) with an air filter (18), preferably with a pore size of 0.2 m or less; an oxygen discharge (19), an oxygen feed (20), a substitute gas feed (21) and a substitute gas discharge (22) are present; a substitute gas storage (23) and an oxygen storage (24) are present; a biogas filter (25) is provided as a part of the biogas discharge (7) with a downstream biomethane storage tank (26); the substitute gas storage (23) is connected to the biogas filter (25); a first pump (27) is present as a part of the first cross-connecting pipe (8) between the first section (2) and the first filter (11) and a second pump (28) is present as a part of the second connecting pipe (9) between the first cross-connecting pipe (10) and the second filter (12).

13. The device according to any one of the preceding claims, characterized in that the first section (2) is protected from excessive solar irradiation, in particular that the transparent region (29) of the first section (2) can be gradually darkened.

14. The device according to any one of the preceding claims, characterized in that the phototrophic microorganisms (1) are preferably immobilized on cellulose or a mobile carrier material, in particular gas-permeable gel capsules, and the methanogens (5) are preferably immobilized on activated carbon or a mobile carrier material, in particular gas-permeable gel capsules.

15. The device according to any one of the preceding claims, characterized in that the filters are configured as hollow fiber contactors, in particular having a gas pump (30), a permeate space (31), partitions (32), hollow fibers (33), an inlet space (34) and an outlet space (35).

Description

DESCRIPTION OF THE DRAWINGS

[0042] FIG. 1 shows a two-dimensional view of a device according to the invention for carrying out the method, wherein dashed parts represent a level transition.

[0043] FIGS. 2-6 show views of the fermenter shown in FIG. 1 in multiple modes.

[0044] FIG. 7 shows the layout of a hollow fiber contactor preferably used as a filter.

[0045] FIG. 8 schematically shows the sequence of the Calvin cycle in phototrophic microorganisms under carbon-dioxide-rich conditions (left side) and under oxygen-rich conditions (right side).

[0046] FIG. 9 shows the reactions catalyzed by RuBisCO with the molecules involved indicated as structural formulas.

[0047] FIG. 10 shows the oxygenase reaction of RuBisCO and the further metabolization of the phosphoglycolic acid thus produced with the molecules involved indicated as structural formulas and the enzymes.

[0048] FIG. 11 shows a diagram on the production of glycolic acid in mol per mg of chlorophyll a by Gloeothece 6909 at different oxygen/carbon dioxide ratios and different irradiances.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0049] In the production mode shown in FIG. 2, the phototrophic microorganisms (1) Gloeothece 6909, previously captured and immobilized on a surface, produce glycolic acid under oxic conditions and solar irradiation, which is secreted into the medium (3) (FIGS. 9 and 11). In this mode, all valves of the first section (2) and the second section (4) towards the connecting system (6) are closed. With direct solar irradiation in the middle of summer, the duration of the production mode is one hour. A controlling clock terminates the production mode correspondingly.

[0050] In the exchange mode shown in FIG. 3, the valves towards the first connecting pipe (8) and the second connecting pipe (9) are opened, while the valves towards the first cross-connecting pipe (10) and the second cross-connecting pipe (15) are closed. The first pump (27) and the second pump (28), designed as peristaltic pumps, then pump the medium (3) from the first section (2) into the second section (4). On its way, the medium passes through the first filter (11), which, like the other filters, is designed as a hollow fiber contactor in this embodiment (FIG. 7). A gas pump (30) in the form of a vacuum pump creates a vacuum in the permeate space (31) between the partitions (32) and the hollow fibers (33) which are traversed by the medium (3) from the inlet space (34) to the outlet space (35). The oxygen molecules exit the liquid and penetrate through the hollow fibers and into the permeate space (31). From there, they are extracted by the gas pump (30) and transported through a pipe to the oxygen storage (24) and from there to the second filter (12). Meanwhile, the degassed medium exits the first filter (11) and reaches the third filter (13) through the first connecting pipe (8), where a gas pump (30) creates positive pressure of carbon dioxide in the permeate space. This way, the carbon dioxide molecules exit the substitute gas storage (23) through the hollow fibers into the medium (3). The medium (3) then flows into the second section (4). There, methanogens (5), previously selected for glycolic acid utilization and immobilized, consume the glycolic acid and convert it into a gaseous mixture consisting of biomethane and carbon dioxide in a ratio of 3 to 5 um which bubbles to the top. A biogas discharge (7) collects the gas stream and passes it through a biogas filter (25), a hollow fiber contactor for separating gases in which the carbon dioxide is separated and passed into the substitute gas storage (23). The purified biomethane, on the other hand, is stored in the biomethane storage tank (26). The medium (3) exits the second section (4) and is degassed in the fourth filter (14) to remove carbon dioxide which is, in turn, provided for gassing by the third filter (13) or stored in the substitute gas storage (23). The second filter (12) again gasses the medium (3) with oxygen originating from the degassing by the first filter (11). The now re-oxygenized medium (3) returns to the first section (2). As soon as the medium (3) has been exchanged between the sections, a new production mode starts. After at least two passages of the production and exchange mode, the transition to the regeneration mode begins.

[0051] In the transition to the regeneration mode, the valves from the second section (4), a part of the first connecting pipe (8), from the second connecting part (9) and a part of the first cross-connecting pipe (10) are closed according to FIG. 4. The first pump (27) pumps the medium (3) into a cycle through the first part of the first connecting pipe (8), the upper part of the first cross-connecting pipe (10) and the second cross-connecting pipe (15). On its way, the medium (3) first passes the first filter (11) in which it is degassed to remove oxygen which is intermediately stored in the oxygen storage (24). Afterwards, the medium (3) flows through the fifth filter (16) where it is gassed with ambient air drawn in through an air line (17) and an air filter (18). The medium finally returns to the first section (2).

[0052] In the regeneration mode, the valves of the sections towards the connecting system (6), as shown in FIG. 5, are closed. Upon solar irradiation, carbon (FIG. 8) and nitrogen are assimilated by the PTMs from the air dissolved in the medium (3). The duration of the regeneration mode depends on the duration of a passage of the production mode.

[0053] In the transition to the production mode, the vales from the second section (4), the first connecting pipe (8), a part of the second connecting pipe (9) and a part of the first cross-connecting pipe (1) are closed according to FIG. 6. The second pump (28) pumps the medium (3) into a cycle through the first part of the second connecting pipe (9), the lower part of the first cross-connecting pipe (10) and the second cross-connecting pipe (15). On its way, the medium (3) first passes the fifth filter (16) in which it is degassed to remove the remaining air which is discharged through the air line (17) and through the air filter (18) to the environment. Afterwards, the medium (3) flows through the second filter (12) where it is gassed with the oxygen previously stored in the oxygen storage (24). It finally returns to the first section (2). The valves of the first section (2) are closed. The production mode starts upon solar irradiation detected by a solar detector.

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