KR20050081766A - Continuous photo bioreactor for carbon dioxide removal and mass production of microalgae - Google Patents

Abstract

The present invention according to the first aspect is a semi-continuous or continuous photoreactor for the growth of microalgae, the medium supply unit for supplying the medium for the growth of microalgae into the reactor, the reactor to induce the flow of the flow of the medium Reduction of carbon dioxide and mass production of microalgae, characterized in that it comprises a plurality of partitions installed inside, an acid base unit for supplying carbon dioxide into the reactor, a light source installed inside or outside the reactor to provide light in the reactor Provide a photoreactor.

In addition, the present invention according to the second aspect is a continuous or semi-continuous photoreactor for the growth of microalgae, medium supply unit for supplying a medium for the growth of microalgae into the reactor, the reactor is divided into spots and cows And an internal circulation device for alternately circulating the medium in the reactor to one of the spots or cows, an acid base unit for supplying carbon dioxide into the reactors, and a light source for providing light into the reactors from inside or outside the reactors. It provides a photoreactor for reducing carbon dioxide and mass production of microalgae, characterized in that it comprises a.

Description

Continuous Photo Bioreactor for Carbon Dioxide Removal and Mass Production of Microalgae

The present invention relates to a photoreactor capable of culturing microalgae, and more particularly, to a continuous photoreactor capable of culturing microalgae in large quantities while effectively removing carbon dioxide, which is a cause of global warming.

The interest of the global village is increasing about side effects such as damage to the natural environment caused by the rapid development of science. In particular, much attention has been paid to global warming, which raises the global average temperature, causing sea level rise and increasing the occurrence of abnormal climates such as EL-Nino. Global warming is known to be caused by the Greenhouse effect gas in the atmosphere. Representative greenhouse gases include CO ₂ , N ₂ O, and CH ₄ . It is known that carbon dioxide has the greatest influence (more than 55% of the total). On the other hand, since the "FRAME WORK CONVENTION on CLIMATE CHANGE" came into force in March 1994, international discussions on carbon dioxide emission reduction have been under way, and the development of technology to efficiently control and remove the carbon dioxide emitted. There is an active research on. In Korea, fossil fuel dependence is close to 90% of the total fuel consumption, and greenhouse gas emissions are steadily increasing as 1.8% of the world's emissions (11th in the world in 1997). Is expected to increase, and as a member of the OECD, it is inevitable to implement national and broader measures to reduce carbon dioxide emissions.

Physical and chemical control methods, biological immobilization methods, and marine storage methods are used to control carbon dioxide without disturbing industrial activities. Since the mid-1990s, active research has been conducted in Japan and Europe. In particular, this method has the advantage that photosynthetic efficiency is superior to higher plants and that the reaction proceeds at room temperature and atmospheric pressure. However, problems such as high concentration and mass cultivation difficulties, necessity of extensive site, deterioration of immobilization efficiency due to scale-up of reactor, disposal of produced biomass have been pointed out as problems. In order to solve this problem, it is necessary to develop a semi-continuous or continuous culture system capable of high concentration and large-scale cultivation, and to develop a process for preventing carbon deterioration of efficiency and fixing carbon dioxide continuously for a long time. Appropriate recycling of the produced biomass should prevent other waste from being produced. Important environmental factors of photo-bioreactor for mass cultivation of microalgae are nutrients such as light intensity, temperature, pH, CO ₂ concentration, nitrogen and phosphorus, among which the importance of light intensity is higher than other environmental factors. Recognizing this, various studies have been conducted to properly supply the light required by microalgae.

In Japan, which has climate conditions similar to those of our country, we have carried out a project called "The Green Planet Project", which has led to the reduction of global CO ₂ emissions by 200 billion tons per year since 1989 under the Ministry of International Trade and Industry. Aim. Detailed research contents include collecting information on environmental industries and technologies around the globe, immobilizing CO ₂ , developing environmental pollution measuring sensors, and developing biodegradable plastics, but the most important areas are CO ₂ through bacteria and algae culture. It can be said that the immobilization method of. Overseas, basic research on biological carbon dioxide immobilization has been actively conducted by many researchers in Japan since the early 1990s. On the other hand, the development of the biological carbon dioxide immobilization technology using the photoreactor of our country is about 10 years behind the United States, Japan and the like. On the other hand, if a large-scale cultivation using a large site, such as Israel and Thailand, advanced technology is not required, but it is considered to be an unsuitable method when the available land area is limited like our country. Table 1 below shows the site area required to remove the same amount of carbon dioxide according to the type of biomass. Referring to this, it is considered that the carbon dioxide immobilization method using the microalgae can remove the carbon dioxide efficiently using a lot of sites (Tokyo Electric Company, Japan, 1994).

<Table 1> Various CO2 Immobilization Efficiency in Nature

Biomass Area required (km ² ) Pine tree 2,100  Macroalgae 900  Rainforest 600 sugar cane 400 Microalgae 140

※ Estimation criteria: 90% of CO2 emitted from 100MW coal-fired power plant

Therefore, the most important research direction in the biological carbon dioxide immobilization process for our country is the establishment of high concentration and mass technology of microalgae to immobilize carbon dioxide through photosynthesis. Table 2 below compares the different types of biological carbon dioxide immobilization processes (Ministry of Environment, "Chemical and Biological Immobilization Techniques of Carbon Dioxide", 1997). As can be seen here, the use of an optical fiber reactor is the best carbon dioxide immobilization efficiency, but the required cost is difficult to install, and in the case of a pond type reactor, the installation cost is low, but a large site is required and the immobilization efficiency is low. Therefore, most of the research since the 1990s was carried out using a tubular reactor with a low cost, a lot of land, and a high immobilization efficiency, and a result of culturing microalgae at a high concentration using some optical fiber reactors was reported, but the installation cost and operation Costs are high, and large-scale installation has a problem that has not been practical yet.

As a result, the culture technologies developed so far have problems such as difficulty in efficient light supply into the reactor when the microorganisms are high in concentration and efficiency decrease due to scale up of the reactor. In addition, the typical method for culturing photosynthetic microorganisms is batch and continuous culture. In the case of batch culture, when the algae passes the growth phase, the growth of algae is a stationary phase. ), Almost no immobilization of carbon dioxide by algae after the growth phase. On the other hand, in the case of continuous, semi-continuous culture that can compensate for these disadvantages, not only long-term operation is possible, but also substantial mass culture is possible. On the other hand, the microalgae immobilized and grown carbon dioxide is generated as another waste if not properly recycled will adversely affect the environment. Therefore, studies are being actively conducted on the use of biofuel or animal and animal feed in foreign countries. However, many studies have been conducted in the development of photoreactor and operation technology for the cultivation of high concentration microalgae, focusing on the immobilization of carbon dioxide in Korea, and the research and treatment of the produced microalgae is insufficient.

<Table 2> Efficiency Comparison of Carbon Dioxide Immobilization Methods

Reactor mode CO ₂ fixation rate (g CO ₂ / m ² / day) Site Installation cost Operation cost  Pond 40 Large-scale Almost none lowness  Tubular 80 Narrow space lowness height  Optical fiber 160 Narrow space height Very high

The present invention has been made to solve the problems of the prior art, the main object of the present invention is to directly fix the carbon dioxide generated in the industry using fossil fuel in a continuous, high-quality nutrients and high calories The present invention provides a photoreactor capable of providing a microalgae (euglena, etc.) biomass that can be contained and used as feed for animals or fry.

The present invention according to the first aspect for solving the technical problem is a continuous or semi-continuous photoreactor for the growth of microalgae, the medium supply unit for supplying the medium for the growth of microalgae into the reactor, the medium of Reduction and reduction of carbon dioxide, characterized in that it comprises a plurality of partitions installed inside the reactor to induce the flow of the flow, an acid base unit for supplying carbon dioxide into the reactor, a light source installed inside or outside the reactor to provide light in the reactor and It provides a photoreactor for mass production of microalgae.

In addition, the present invention according to the second aspect is a continuous or semi-continuous photoreactor for the growth of microalgae, medium supply unit for supplying a medium for the growth of microalgae into the reactor, the reactor is divided into spots and cows And an internal circulation device for alternately circulating the medium in the reactor to one of the spots or cows, an acid base unit for supplying carbon dioxide into the reactors, and a light source for providing light into the reactors from inside or outside the reactors. It provides a photoreactor for reducing carbon dioxide and mass production of microalgae, characterized in that it comprises a.

The present invention according to the second aspect preferably provides a photoreactor wherein the internal circulation device is a chain scraper.

The present invention according to the first and second aspects preferably provides a photoreactor with a concentration of 0.035 to 15% (V / V) of carbon dioxide supplied from the acid group.

The present invention according to the first and second aspects preferably provides a photoreactor in which the hydraulic residence time in the reactor is determined to be 3-10 days.

The present invention according to the first and second aspects preferably provides a photoreactor in which the acid groups are installed at the bottom of the reactor.

Hereinafter, the content of the present invention will be described in detail with reference to the drawings.

1 is a block diagram of a photoreactor according to a first aspect of the present invention, which is presented as a preferred embodiment of the present invention, wherein the photoreactor 11 includes a light source 12, an diffuser 13, a partition 14, and a gas mixer 15. ), A humidifier 16, and a medium supply pump 17, which is a medium supply means.

The microalgae to be cultured contain high-quality nutrients and high calories, and thus do not require any special limitation as long as they are species that can be used as feed for animals or fry, but preferably euglena.

The light source 12 is sufficient to be able to transmit light into the photoreactor 11 and does not need to be placed in a specific position. Therefore, it may be provided at any position inside or outside the photoreactor 11. In addition, the light source may be a natural light source or an artificial light source, but an artificial light source is more suitable for the reactor, and an example thereof is a fluorescent lamp for plant cultivation.

The acidizer 13 is a portion for supplying a gas containing carbon dioxide that has passed through the humidifier 16 into the reactor, and is preferably installed under the photoreactor 11 to prevent the microalgae from being precipitated. . The reason why the humidifier 16 is provided is that it is possible to prevent evaporation of the medium when the entrained air is saturated to 100% humidity and fed to the photoreactor.

The partition wall 14 is installed at a predetermined interval inside the photoreactor 11, and the medium supplied from the medium pump 17 induces a smooth plug flow in the inside of the photoreactor.

The operation of the photoreactor will be described with reference to FIG. 1. The medium is introduced into the reactor from the medium supply pump 17, and the flow of the medium is guided by the partition 14 to smoothly flow inside the reactor. At this time, the flow rate of the medium is preferably adjusted so that the hydraulic residence time (HRT) in which the microalgae stays in the photoreactor is in the range of 3 to 10 days.

The composition of the medium may differ depending on the specific microalgae provided to the culture. According to the present invention, when Euglena gracilis Z is used as the microalgae, the modified Cramer-Myers medium of Table 3 was selected as the optimum medium composition.

<Table 3> Badge Composition

ingredient Concentration (g / ℓ) Minerals and vitamins Concentration (mg / ℓ) (NH ₄ ) ₂ SO ₄ 1.0 Fe ₂ (SO ₄ ) ₃ ㆍ 7H ₂ O 3.0 KH ₂ PO ₄ 1.0 MnCl ₂ 4H ₂ O 1.8 MGSO ₄ 7H ₂ O 0.2 CoSO ₄ 7H ₂ O 1.5 CaCl ₂ 2H ₂ O 0.02 ZnSO ₄ ㆍ 7H ₂ O 0.4 EDTA-3Na.2H ₂ O 0.8 Na ₂ MoO 4 .2H ₂ O 0.2 - - CuSO ₄ ㆍ 5H ₂ O 0.02 - - Vitamin B ₁ 0.1 - - Vitamin B ₁₂ 0.0005

Inoculation of the initial microalgae does not require any particular limitation, but in the present invention, it was incubated for 2 weeks in a preliminary culture tank prepared separately and planted at 3 to 5% of the total medium volume in the photoreactor.

Carbon dioxide is delivered into the photoreactor through the acid unit 13. If carbon dioxide is intended only for the cultivation of microalgae, pure carbon dioxide may be supplied, and carbon dioxide (CO ₂ ) contained in the exhaust gas may be used when accompanied with the purpose of treating carbon dioxide in the exhaust gas.

Carbon dioxide and air are supplied to the gas mixer 15 via each flow meter, and the mixed gas is supplied to the humidifier 16 via the flow meter. The concentration of carbon dioxide supplied from the humidifier 16 is preferably adjusted in the flowmeter or / and the gas mixer so as to be in the range of 0.035 to 15% (V / V), more preferably 8 to 12% (V / V). Can be.

The brightness required at the time of culturing the microalgae may vary depending on the specific microalgae used. Suitable luminosity for most microalgae has already been published in the literature, such as "Chemical and Biological Immobilization Techniques of Carbon Dioxide" (Ministry of Environment, 1997). In the present invention, a fluorescent lamp was used as a case of culturing euglena, and the luminance was set to 480 μmol / m 2 / s, but is not necessarily limited thereto.

Euglena grows during the hydraulic retention time (HRT) in the photoreactor 11 by supplying carbon dioxide, which is a medium and carbon source, into the photoreactor. Separately served as feed for animals or fry.

2 is a block diagram of a photoreactor according to a second aspect of the present invention, which is presented as a preferred embodiment of the present invention, wherein the photoreactor 21 includes a light source 22, an diffuser unit 23, an internal circulation device 24, and a compressor ( 25), and a medium supply pump 26, wherein the reactor 21 is divided into a spot 27 where light is provided and a cow 28 that is a light blocked portion.

The light source 22 is sufficient to be able to transmit light to the sights 27 of the photoreactor, and does not need to be placed in a specific location. Therefore, it may be provided at any position inside or outside the photoreactor 11. The light source may be a natural light or an artificial light source, but a natural light source is more suitable in the reactor.

The diffuser 23 is a portion for supplying a gas containing carbon dioxide supplied from the compressor 25 into the reactor, and is preferably installed in the lower portion of the photoreactor 21 to float the microalgae to precipitate in the lower portion of the reactor. To prevent them. At this time, the gas containing carbon dioxide may be used as the exhaust gas resulting from the combustion of light oil in a boiler or the like.

The photoreactor 21 is divided into a spot 27 and a cow 28, and a light source is supplied only to the spot 27. The attraction is equipped with an internal circulation device 24 for circulating the medium. A typical example of the internal circulation device is a chain scraper, and each scraper circulates the medium while circulating. Microalgae, which are supplied with light energy from the spot, grow mainly in cows, and are cultured in the photoreactor until the saturation concentration is reached in the photoreactor since the initial inoculation. Microalgae grow rapidly as they cycle through sights and cows during the HRT.

When culturing the microalgae using the photoreactor according to the present invention, it can be seen that the culture efficiency of about 20 to 40% is increased under the same conditions as compared to the conventional batch culture (see Fig. 5).

Hereinafter, the content of the present invention will be described in more detail with reference to Examples. However, these examples are only presented to understand the content of the present invention, and the scope of the present invention should not be construed as being limited to these embodiments.

Example 1 Derivation of Optimal Culture Conditions of Microalgae

The microalgae strain used in this experiment is Euglena gracilis Z, which must be supplied with energy for growth through light and supply carbon source from the outside. The temperature was maintained at 27 ° C. using Cramer-Myers medium (see Table 3), and carbon dioxide was supplied at a concentration of 10% (V / V) to incubate purely.

First, in order to examine the changes in the properties of the microalgae according to the change in the carbon dioxide concentration supplied, other environmental conditions were fixed, and the carbon dioxide was mixed with air to adjust the concentration within the range of 0.035% to 15%, and the batch culture was performed. As a result, as shown in FIG. 3, the concentration of carbon dioxide for optimum culture was found to be 10%.

Example 2 Evaluation of Efficiency of Continuous Photoreactor

In the case where the partition wall was installed inside the photoreactor (see FIG. 1), the light intensity was maintained at 480 μmol / m2 / s using an artificial light source (plant cultivation fluorescent lamp), and the carbon dioxide concentration was fixed at 10% and the hydraulic residence time When the culture was continuously changed from 3 to 10 days, the concentration of microalgae increased as the hydraulic retention time increased up to 6 days as shown in FIG. 4, but the hydraulic retention time was more than 8 days The difference in microalgae concentration was not large.

On the other hand, natural light source (sun) is used when an internal circulator is added to improve the light reactor so that the light and dark areas are more clearly distinguished so that the microalgae grow in the light and dark areas. The brightness was maintained at an average of 450 μmol / ㎡ / s, and was continuously cultured by changing the hydraulic retention time from 3 to 10 days. At this time, emission gas emitted from a boiler using diesel oil was used as a carbon dioxide source, and this exhaust gas was composed of 11% of CO ₂ , 26 ppm of NOx, and 5 ppm of SOx. . As a result, as the hydraulic residence time increases as shown in Figure 5 it was observed that the concentration of microalgae continues to increase.

When comparing the results of the continuous culture with the results of the conventional batch culture, as shown in Table 4 below, the microalgal concentration in the case of the photoreactor in which the inner partition is installed is compared with the microalgal concentration in the batch culture under the same culture conditions. It was increased by 23%, and the increase of 35% in the case of the photoreactor divided into light and dark areas.

<Table 4> Improvement of microalgae cultivation efficiency by new concept photoreactor

Culture method Photoreactor mode Driving period HRT Final microalgal concentration Batch General tubular 6 days - 0.60 ± 0.1 g / L Continuous Bulkhead installation (100L) 24 days 6 days 0.74 ± 0.1 g / L Continuous Light and dark cross (1,000L) 24 days 6 days 0.81 ± 0.2 g / L

Example 3 Evaluation of the utility of the produced microalgal biomass

Meanwhile, as a result of performing elemental analysis by drying the euglena grown for 6 days through continuous culture, it was found that about 65% of the total dry weight was composed of carbon as shown in Table 5 below. Since the carbon source was grown from carbon dioxide supplied to the mixed air, about 0.42 g of new microalgae were synthesized from 1 g of carbon dioxide gas during the growth period.

In addition, various components and calories of the cultured microalgae were investigated and shown in Table 6 below. As a result, it was found that it contains about 47% protein and 15% fat component, and the apparent metabolizable energy is about 4,700 cal / g, which can be utilized as feed for animals and fry. It was judged that.

Table 5 Cell Components of Euglena Microalgae Cultured Continuously

Component Average value C 64.8% H 7.7% O 13.7% N 13.8% Molecular formula C _6.28 H _8.95 ON _1.15

Table 6 Nutritional Value of Continuously Cultured Eugleza Microalgae

Component Average value Crude protein 46.75% Crude fat 15.19% Crude fiber 0.33% View minutes 4.96% moisture 3.49% Metabolic energy 4,676 cal / g

According to the present invention, while effectively removing carbon dioxide, microalgae can be cultured in large quantities. Therefore, the photoreactor according to the present invention can directly fix carbon dioxide generated in an industry using fossil fuel in a continuous manner, thereby reducing carbon dioxide, which is a global warming gas, and being produced as a byproduct. Algal (euglena, etc.) biomes contain high-quality nutrients and high calories and can be used as feed for animals or fry.

1 is a block diagram of a photoreactor presented as a preferred embodiment of the present invention according to the first aspect

2 is a block diagram of a photoreactor presented as a preferred embodiment of the present invention according to a second aspect

3 is a growth observation of the microalgae according to the change in carbon dioxide concentration

Figure 4 is a result of measuring the microalgae culture efficiency performed in the photoreactor according to the first aspect of the present invention

5 is a graph showing the result of measuring the microalgae culture efficiency performed on the photoreactor according to the second aspect of the present invention

<Code Description of Main Parts of Drawing>

11,21: photoreactor 12,22: light source

13,23: footnote 14: bulkhead

15: Gas Mixer 16: Humidifier

17, 26: medium supply pump 24: internal circulation device

25: air compressor

Claims (6)

In the continuous or semi-continuous photoreactor for the growth of microalgae, a medium supply for supplying a medium for the growth of microalgae into the reactor, a plurality of partitions installed inside the reactor to induce the flow of the flow of the medium, Photoreactor for reducing carbon dioxide and mass production of microalgae including an acid base unit for supplying carbon dioxide into the reactor, a light source installed inside or outside the reactor to provide light in the reactor In the continuous or semi-continuous photoreactor for the growth of microalgae, a medium supply unit for supplying a medium for the growth of microalgae into the reactor, the reactor is divided into a spot and a cow, the reactor in one of the spot or cow Reduction of microalgae and microalgae, including an internal circulation device for circulating the medium alternately between the spot and the cow, an acid base unit for supplying carbon dioxide into the reactor, and a light source for providing light into the reactor from inside or outside the reactor. Photoreactor for Mass Production The photoreactor of claim 2, wherein the internal circulation device is a chain scraper. The photoreactor according to claim 1 or 2, wherein the concentration of carbon dioxide supplied from the acidifier is set at 0.035 to 15% (V / V). The photoreactor according to claim 1 or 2, wherein the hydraulic retention time in the reactor is set to 3 to 10 days. The photoreactor according to claim 1 or 2, wherein the acid group is installed at the bottom of the reactor.