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The Effect of CO2 Fixation for Microalgae based on CO2 Concentration and Flow Rate

이산화탄소 농도 및 유속에 따른 하천 내 미세조류의 이산화탄소 고정 효과

  • Park, Hyomin (Department of Environmental Science and Engineering, Ewha Womans University) ;
  • Lee, Sangdon (Department of Environmental Science and Engineering, Ewha Womans University)
  • 박효민 (이화여자대학교 환경공학과) ;
  • 이상돈 (이화여자대학교 환경공학과)
  • Received : 2018.06.18
  • Accepted : 2018.10.26
  • Published : 2018.11.30

Abstract

One of the recent environmental problems is climate change due to the increase of atmospheric $CO_2$, which causes ecological changes and various environmental problems. Therefore, various studies are being carried out to reduce $CO_2$ in the world in order to solve various environmental problems caused by increase of $CO_2$. The $CO_2$ reduction using microalgae is an environmentally friendly method by using photosynthesis reaction of microalgae. However, most studies using single species. There is no study on the $CO_2$ fixing efficiency of microalgae in natural rivers. Therefore, this study was to identify the microalgae in the Sum river and to analyze the growth characteristics of microalgae in the river to obtain optimal culture conditions. And the changes of biomass and chlorophyll-a of microalgae were analyzed according to $CO_2$ concentration and injection rate. The purpose of this study was to investigate the fixing efficiency of carbon dioxide in microalgae in natural rivers. Six kinds of dominant species were observed as a result of the identification of microalgae in Sum river(Ankistrodesmus falcatus, Scenedesmus intermedius, Selenodictyum sp., Xanthidium apiculatum var. laeve, Cosmarium pseudoquinarium, Dictyosphaerium pulchellum). All of these species were green algae. Biomass and chlorophyll-a increased with the increase of $CO_2$ concentration and biomass and chlorophyll-a increased faster flow rate at the same $CO_2$ concentration. Also, the quantity of $CO_2$ fixation on the microalgae tended to be higher when the flow rate of injected gas was faster. This study can be referred as being significant in the micro-algae in river. In addition, the optimal conditions for $CO_2$ fixation of microalgae in rivers and the quantification of the quantity of $CO_2$ fixation from microalgae in rivers can be used as basic data for future policy of $CO_2$ reduction.

최근 환경 문제로 대두되고 있는 것 중 하나는 대기 중 $CO_2$의 증가로 인한 기후변화이다. 이에 대한 영향으로 생태계가 변화하고 있으며, 다양한 환경문제가 발생되고 있다. 이로 인해 전 세계적으로 $CO_2$ 저감을 위한 다양한 연구들이 수행중이며, 이 중 미세조류를 이용한 $CO_2$ 저감 방안은 환경 친화적인 방법이라 할 수 있다. 그러나 미세조류를 이용한 $CO_2$ 저감 방안은 대부분 단일 종을 대상으로 하고 있으며, 자연 하천을 대상으로 한 미세조류의 $CO_2$ 고정 효율에 대한 연구는 전무한 실정이다. 그러므로 본 연구는 우리나라 하천 내 존재하는 미세조류들을 파악하고, 미세조류의 생장특성을 분석하여 최적의 배양조건을 도출 하였다. 그리고 $CO_2$ 농도와 주입 속도에 따른 미세조류의 biomass와 클로로필 a의 변화를 분석하여 자연 하천 내 존재하는 미세조류의 $CO_2$ 고정효율에 대해 연구하고자 하였다. 섬강 내 존재하는 미세조류를 배양하여 동정한 결과 6종의 우점종(Ankistrodesmus falcatus, Scenedesmus intermedius, Selenodictyum sp., Xanthidium apiculatum var. laeve, Cosmarium pseudoquinarium, Dictyosphaerium pulchellum)이 관찰되었으며, 이 종들은 모두 녹조류에 해당하였다. 한편 이산화탄소 농도 구배(5% $CO_2$, 10% $CO_2$, 15%$CO_2$, 대기조건의 가스 0.038% $CO_2$)와 유속(0.25, 0.5LPM)이 다른 가스를 주입하여 미세조류의 biomass와 클로로필 a의 변화를 살펴본 결과 이산화탄소의 농도가 증가할수록 biomass와 클로로필 a가 증가하였으며, 같은 이산화탄소 농도에서는 유속이 더 빠른 곳에서 미세조류의 biomass와 클로로필 a의 양이 더 증가하였다. 또한 미세조류에 고정화된 이산화탄소의 양은 주입되는 가스의 유속이 빠를수록 고정되는 이산화탄소의 양이 더 높아지는 경향을 보였다. 본 연구는 기존의 단일 종에서 행해지는 연구가 아닌 하천 전체의 미세조류를 대상으로 수행한 연구이며, 하천 내 존재하는 미세조류의 이산화탄소 고정을 위한 최적의 조건을 도출하고, 하천 내 존재하는 미세조류로부터 고정화된 이산화탄소의 양을 정량화하여 향후 이산화탄소 감축을 위한 정책을 위한 기초자료에 이용할 수 있다는 것에 큰 의의가 있다.

Keywords

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Fig. 1. Change of biomass over time with different CO2 concentration of air flows

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Fig. 2. Change of Chlorophyll-a over time with different CO2 concentration of air flows

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Fig. 3. CO2 fixation of microalgae according to CO2 concentration and flow rate (1 is 5% CO2 concentration and flow rate is 0.25 LPM, 2 is 5% CO2 concentration and flow rate is 0.5 LPM, 3 is 10% CO2 concentration and flow rate is 0.25 LPM, 4 is 10% CO2 concentration and flow rate is 0.5 LPM, 5 is 15% CO2 concentration and flow rate is 0.25 LPM, 6 is 15% CO2 concentration and flow rate is 0.5 LPM, 7 is air and flow rate is 0.25 LPM, 8 is 5% CO2 concentration and flow rate is 0.5 LPM)

Table 1. Culture conditions of microalgae cultured for 3 weeks

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Table 2. List of species observed after incubation

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