The invention relates to a device and to a method for sequestering atmospheric carbon dioxide using an air capture module in functional conjunction with a bioreactor equipped with autotrophic microorganisms.
The need to quantitatively sequester carbon dioxide (CO2) from the atmosphere is viewed as a global problem. In addition to significantly reducing the use of fossil fuels, a direct sequestration of CO2 from the atmosphere is considered to be necessary to be able to achieve the worldwide climate targets. These consist in a maximum permissible temperature increase of less than 2° C. compared to when record-keeping began. Other measures, such as geoengineering, for example by iron fertilization of the ocean or the introduction of sulfur compounds into the atmosphere so as to enhance the reflection of solar radiation, are rated as very risky, with ecological consequences.
According to the findings of climate researchers, an average global temperature rise of more than 2° C. results in irreversible disruptions of the climate systems. Another global problem is the decarbonization of industry, which often accompanies the phase-out of the use of fossil fuels and energy sources. This means that carbon sources other than fossil sources have to be found for chemical processes.
Technology describes the direct sequestration of carbon dioxide from the atmosphere using bioenergy with carbon capture and storage (BECCS). This involves using cultivated crops for energy purposes (biomass and gas-fired power plants) and storing the arising CO2 in geological strata. BECCS, however, has the following drawbacks: 1.) CO2 injection into geological strata, which is associated with risks and only possible in few regions of the earth. 2.) Competition with agriculture since the high land requirement for BECCS results in a shortage of cultivation space for food production.
The use of photobioreactors, which contain autotrophically growing microorganisms and produce biomass, is considered to be a promising option of carbon dioxide sequestration. For example, it is easy to use microalgae. This biomass has a variety of uses, such as 1.) biogas generation for energy production, 2.) recovery of carbon compounds for the chemical industry, 3.) biofuels, and 4.) food additives, which can be contained especially in algae, 5.) other valuable substances such as pharmaceutically acting substances and cosmetics, 6.) organic fertilizer made of biomass (biofertilizer).
In the prior art, WO 1998/045409 A1 and EP 2 568 038 A1 describe laminar photobioreactors for the production of microalgae, wherein the following problems are discussed:
a.) A suitable microorganism has to be used, which is easy and inexpensive to cultivate and has a high biomass production.
b.) A continuous CO2 supply must be ensured since the atmospheric CO2 concentration in the amount of 400 ppm (0.04%) does not allow optimal growth of microalgae, for example. It was found that, at optimal CO2 concentrations, microalgae create biomass approximately 10 to 50 times more efficiently than crops. The technical teaching describes that microalgae such as Chlorella, Scenedesmus, Spirulina, Nannochloropsis, Nostoc and Chlorococcus are able to grow very well in the range of 1 to 20% CO2 (that is approximately 25 to 500 times higher than in the atmosphere), and have an accordingly high biomass productivity (see also Appl. Biochem. Biotechnology, 2016 179:1248-1261 and the literature cited therein). Previously, the problem was solved by using chemically pure CO2 (technical CO2). Of course, this does not solve the problem of carbon sequestration since this CO2 is obtained in a highly energy-consuming process as a by-product in the chemical industry. A variety of working groups have already attempted to use alternatives in the form of waste gas flows from power plants. Even though this would allow the CO2 arising during the combustion of fossil energy sources to be sequestered, it would not ensure a direct removal of CO2 from the atmosphere. Moreover, it is known that waste gas flows from power plants contain impurities such as sulfur, nitrogen oxides, carbon monoxide and heavy metals, which can drastically inhibit the growth of microorganisms. Removing harmful impurities from these waste gas flows is a very cost-intensive process. In contrast, a direct introduction of atmospheric air into photobioreactors would have the drawbacks that, first, too little CO2 is present for optimal growth and, secondly, that algae predators such as protozoa and zooplankton may be present on small dust particles in the air. These organisms subsist on algae and can thus heavily disrupt the bioreactor operation.
c.) For microalgae to grow optimally, it is necessary that the oxygen that develops during the light reaction is removed since it can have a toxic effect, and moreover also triggers the process of photorespiration, wherein CO2 is formed again.
d.) Another problem is that an efficient bioreactor should allow a continuous operation, that is, the supply of nutrient solution and removal of biomass take place constantly, without having to stop the reactor. Moreover, a bioreactor should be configured so flexibly that different types of microalgae, and even prokaryotic chemolithotrophic CO2 fixers, can be cultivated.
e.) The photobioreactor has to maintain optimal growth conditions of the microorganism, such as temperature, pH value, nutrients and the like.
The prior art, however, does not describe a suitable device and method for sequestering atmospheric carbon dioxide using a bioreactor, and in particular a photobioreactor.
It is therefore the object of the invention to provide a suitable device or a method for sequestering atmospheric carbon dioxide by producing biomass.
To achieve this object, the invention thus relates to a device for sequestering atmospheric carbon dioxide, wherein at least one module comprising a capture unit binds atmospheric carbon dioxide by way of an adsorber material and, after treatment by way of heat or a vacuum, the atmospheric carbon dioxide is kept available, and the module is connected to at least one bioreactor, wherein atmospheric carbon dioxide is continuously supplied to autotrophic microorganisms in at least one bioreactor.
In another preferred embodiment, the invention relates to a device for sequestering atmospheric carbon dioxide, wherein at least one module comprising a capture unit binds atmospheric carbon dioxide by way of an adsorber material and, after treatment by way of heat or a vacuum, the atmospheric carbon dioxide is kept available in a container, in particular a pressurized container, wherein atmospheric carbon dioxide is continuously supplied to autotrophic microorganisms in at least one bioreactor.
In another embodiment, the invention relates to a device for sequestering atmospheric carbon dioxide, comprising a module comprising a capture unit, wherein atmospheric carbon dioxide is bound by way of an adsorber material and, after treatment by way of heat or a vacuum, the atmospheric carbon dioxide is kept available in a pressurized container, and at least one bioreactor containing autotrophic microorganisms.
A pressure reducer can be assigned to such a pressurized container, so that a continuous CO2 stream can be provided, if necessary using measuring and control technology.
In another preferred embodiment, atmospheric carbon dioxide can be supplied to autotrophic microorganisms in at least one bioreactor together with air. Ratios of 5:95 vol. % CO2/air, and in particular from 1:99 vol. % CO2/air to 10:90 vol. % CO2/air, are preferred.
To achieve this object, the invention thus likewise relates to a method for sequestering atmospheric carbon dioxide, wherein at least one module comprising a capture unit binds atmospheric carbon dioxide by way of an adsorber material and, after treatment by way of heat or a vacuum, the atmospheric carbon dioxide is kept available, and the module is connected to at least one bioreactor, wherein atmospheric carbon dioxide is continuously supplied to autotrophic microorganisms in at least one bioreactor.
The prior art describes the sequestration of CO2 from industrial waste gases by way of a bioreactor, which, however, is entirely different, since such waste gases are of a different quality and, air contains other harmful substances and has an insufficient CO2 concentration.
In a preferred embodiment, the device according to the invention includes such features according to
Preferably, bioreactor modules that run parallel and are connected to one another are used (1a-1n,
The company Climeworks in Switzerland (http://www.climeworks.com/) produces functional air capture modules, for example, which can be connected to the bioreactor in accordance with the invention. Atmospheric CO2 is bound by way of these air capture modules (10,
A measuring and control unit (5,
On the other hand, this is preferably a continuous bioreactor, which can operate in a circuit. The algae are conducted across a vapor-liquid separator (also: gas-liquid separator) (8,
The invention thus relates to such a device according to the invention which additionally comprises a gas-liquid separator, so that a continuous circulatory process can advantageously be achieved, and arising oxygen can be removed.
In another preferred embodiment, 5 to 50% of the culture medium or nutrient solution is replaced within a day. The device comprises a measuring unit (7,
The installation can likewise be operated with chemo(litho)autotrophic bacteria, such as Archaea bacteria, which likewise receive CO2 via the air capture module. A light reaction is not required, but an energy source in the form of H2 (molecular hydrogen) is.
Within the meaning of the present invention, the expression “autotrophic microorganisms” thus encompasses those microorganisms that utilize light as an energy source (photoautotrophic microorganisms) or a chemical energy source (such as hydrogen) (chemoautotrophic microorganisms). Autotrophic microorganisms are able to carry out carbon dioxide fixation and create biomass in this way.
Within the meaning of the present invention, a “bioreactor” can synonymously be referred to as a fermenter and is used to cultivate the autotrophic microorganisms for producing biomass, wherein according to the invention a continuous operation of the bioreactor is preferred. A person skilled in the art is able to set appropriate operating parameters, for example, for algae, among other things microorganisms, by way of a measuring and control system (temperature, pH value of the culture solution and the like), and to provide culture media. A photobioreactor as described in WO 1998/045409 A1 and EP 2 568 038 A1 is furthermore preferred.
Monosaccharides and/or polysaccharides, and more particularly glucose, can be added in a concentration of 0.3 to 10 g/L culture medium as another advantageous carbon source in a culture medium.
Within the meaning of the present invention, an “air capture module” is able to capture atmospheric CO2 by way of a capture unit according to the invention, having a large surface, wherein the CO2 is chemically or physically bound by way of an adsorber or filter, such as sodium hydroxide, amines or cellulose. By way of heating (for example, to 50 to 120 degrees Celsius) and/or a vacuum, the CO2 can be brought into the gas phase again by the reusable capture unit or filter, so as to be conducted in a concentrated form into a bioreactor in accordance with the invention, preferably by way of a first container, and in particular a pressurized container. An “air capture module” thus relates to a first device, wherein a capture unit (or container) chemically or physically binds atmospheric CO2 using an adsorber material and keeps it available in a container, in particular a pressurized container, after the treatment by way of heat and/or a vacuum.
The company Climeworks AG, Switzerland, specializes in the air capture technology. The chemical fixation capacity per module is approximately 35 kg/CO2 per hour, and can be increased to a scale of tons/hour by utilizing multiple modules. This allows the provision of large amounts of CO2 for the gasification of the autotrophic microorganisms for CO2 fixation in a bioreactor, likewise in a continuous operation.
Such an air capture module is used to recover carbon dioxide from the ambient air and, if needed, likewise provides condensation water from the ambient air for further material use. Preferably, a carbon dioxide recovery installation is selected which initially binds carbon dioxide from the air current using an adsorption operation and, thereafter, releases the carbon dioxide for further use by way of a temperature and/or vacuum process.
The aforementioned device can likewise be described as a method and can also encompass the use of this device for sequestering atmospheric carbon dioxide.
The biomass that is obtained and produced can be used for the usual applications, such as the production of biofuel, chemical substances, energy use and the like (supra).
The following examples are provided to describe the invention, however without limiting the subject matter of the invention.
Adsorption Operation:
Ambient air is taken in by a container (capture unit) filled with adsorber material using a fan. The ambient air usually contains 0.04 vol. % carbon dioxide and, depending on climate, a certain amount of water vapor. The carbon dioxide accumulates to a high degree at the surface of the adsorber material, which contains sodium hydroxide, amines or cellulose. Moreover, water accumulates at the surface of the adsorption material, wherein usually at least 2 moles of water per 1 mole of carbon dioxide, however, at least 1 mole per 1 mole of carbon dioxide, is adsorbed.
Regeneration is required when the surface of the adsorber material is saturated or enriched with carbon dioxide. This can take place by way of heat and/or a vacuum, wherein the physically or chemically bound CO2 (or carbonate) is converted into the form of a gas again and is collected in a container and, if necessary, buffered and, if necessary, compressed. The temporary buffering of the carbon dioxide in a short-term storage device and in a long-term storage device connected in parallel thereto can take place at increased pressure. After cooling, the adsorber material can be reused.
Flat Plate Photobioreactor Example:
A flat plate photobioreactor from the company IGV (Potsdam, Germany) is used. It is composed of planar chambers that are connected to tubes and vertically positioned in series. The chambers are rectangular and have an edge length of 1 m and a depth of 2 cm. This results in a volume of 20 liters each. Five chambers connected in series result in a total volume of 100 liters. The flow is driven by way of the system pump, as shown in
The photobioreactor is exposed to light by way of LEDs from the company Valoya Oy (Helsinki, Finland). The LEDs used are the BX90 series (88 W) having the spectra AP67 and NS1. This covers the majority of the visible light spectrum. Each plate module of the photobioreactor is exposed separately to LED lighting. The arrangement is advantageously selected in such a way that an input photon flux density of approximately 110 μmol/m2s is achieved, which is excellently suited for spirulina, for example.
Production of Algae Biomass using a Flat Plate Photobioreactor:
Sterile culture medium having the following composition is added into the installation (Aiba, S. and Ogawa T. 1976, Assessment of Growth Yield of a Blue-green Alga, Spirulina platensis, in Axenic and Continuous Culture. Journal of General Microbiology 102, 179-182):
NaHCO3 (4.05×10−2 M) , Na2CO3 (9.50×10−3 M) , K2HPO4 (7.17×10−4 M) , NaNO3 (7.35×10−3 M) , K2SO4 (1.43×10−3 M) , NaCl (4.27×10−3 M) , MgSO4×7H2O (4.15×10−4 M) , CaCl2×2H2O (9.01×10−5 M), FeSO4×7 H2O (1.64×10−5 M), EDTA=Titriplex III (0.04 g/L)+2.5 ml/L micro nutrient medium (2.2 mg/L ZnSO4×7 H2O, 25 mg/L MnSO4×4 H2O, 28 mg/L H3BO3, 2 mg/L Co [NO3]2×6 H2O, 0.21 mg/L Na2 MoO4×2H2O, 0.79 mg/L CuSO4×5 H2O)+1 ml/L Vitamin B12 (1.5 g/L) . The pH value is 9.3.
Initially, a sterile starter culture (1 L) is inoculated with Spirulina platensis (Culture Collection of Algae Gottingen, SAG) in the above-described nutrient solution in a shake flask (shake frequency of 100 to 120 rpm) and cultivated in the batch for 3 to 4 days. The photon flux density (PFD) is set to 100 to 150 μmol/m2s. The gasification is carried out by way of a cotton stopper and diffusion.
The flat plate photobioreactor is inoculated with this starter culture, and the entire system (see
The installation is designed so as to be operable in a batch process, that is, the biomass is only harvested once at the end of the experiment. In this case, the bioreactor is operated for 5 to 8 days. The highest productivity, however, is preferably achieved during continuous or semi-continuous operation. A defined proportion of the reactor volume is replaced with fresh culture medium or nutrient medium in the process (see devices 4 and 7 in
Algae biomass using open pond bioreactor (Appl Microbiol Biotechnol (2007) 74:1163-1174)):
Instead of the flat plate photobioreactor, an open system is used, which has a volume of 500 L. The nutrient medium (see above) is continuously circulated using a flow rate of 0.2 to 0.5 m s−1 by way of electrically operated bucket wheel-like paddles. The open pond system is operated in a batch process or in a semi-continuous process. After inoculation with 10 liters of spirulina starter culture (see above), the cultivation is carried out in a batch process up to 7 days. In the semi-continuous process, a certain proportion (for example 10%) of the medium in which the microalgae have multiplied is harvested every day, and replaced with new medium. The open pond system is illuminated in a closed space from above using LEDs of the BX180 series (Valoya, Finland). The open pond system is gasified with a 2.5% CO2/air mixture. The CO2 is provided by way of an air capture module. The room temperature is 24° C. After seven days, the biomass is harvested or the bioreactor is run on a semi-continuous basis. The concentration of the biomass is approximately 5 g/L.
Example of carbon sequestration by way of humus formation: One of the following microalgae capable of nitrogen fixation is inoculated in the closed photobioreactor or in the open pond system with CO2 supply (mixture of 2.5% CO2 and air): Nostoc, Anabaena, Aulosira, Tolypothrix, Nodularia, Cylindrospermum, Scytonema, Aphanothece, Calothrix, Anabaenopsis, Mastigocladus, Fischerella, Stigonema, Haplosiphon, Chlorogloeopsis, Camptylonema, Gloeotrichia, Nostochopsis, Rivularia, Schytonematopsis, Westiella, Westiellopsis, Wollea, Plectonema, Chlorogloea. Nostoc muscorum is well-suited for the open pond system and grows in liquid medium in a manner similar to spirulina. Nostoc muscorum is cultivated for 14 days and then harvested as a batch. As an alternative, a semi-continuous cultivation is carried out, wherein every day approximately 10% of the resultant biomass is harvested, and the withdrawn medium is replaced with fresh culture medium. During the cultivation phase, atmospheric nitrogen is fixed by the algae. The algae biomass is dried. The batch process results in a yield of 700 mg biomass/L.
The dry biomass is pressed to form granules, which are distributed in the soil as biofertilizer. This algae biomass is largely composed of carbon (>50%), which stems from the CO2 fixation in the case of autotrophic growth. The inoculation of a suitable soil substrate with Nostoc also results in an improvement in the supply of nitrogen. The biomass has a ratio of carbon to nitrogen of 10 to 15:1.
The biofertilizer made of algae biomass improves the growth of plants, such as trees, whereby further CO2 sequestration is enabled.
Legend for
1: bioreactor modules that run parallel and are connected to one another, 2: air capture module (optionally including gas buffer module), 3: central cultivation tank, 4: nutrient solution from outside, 5: measuring and control unit for CO2, pH value, temperature, 6: (system) pump, 7: measuring unit for biomass concentration and control unit for deliberate delivery of culture medium, 8: vapor-liquid separator for separating gas and liquid, 9: illumination in the case of photobioreactor, 10: entry and binding of atmospheric CO2, 11: exit of atmospheric oxygen or nitrogen.
Legend for
1: bioreactor modules that run parallel and are connected to one another, 2: air capture module, 3: central cultivation tank, 4: nutrient solution from outside, 5: measuring and control unit for CO2, pH value, temperature, 6: (system) pump, 7: measuring unit for biomass concentration and control unit for deliberate delivery of culture medium, 8: CO2 pressurized container, 9: illumination in the case of photobioreactor, 10: entry and binding of atmospheric CO2, 11: exit of atmospheric oxygen or nitrogen, 12: compressed air, together with CO2 a constant ratio of 5% CO2 and 95% air is conducted by way of a gas mixing station into the bioreactor.
Number | Date | Country | Kind |
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17200037.4 | Nov 2017 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2018/080134 | 11/5/2018 | WO | 00 |