PROCEEDINGS, Thirty-Fourth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, February 1-3, 2010 SGP-TR-188 GEOTHERMAL CO 2 BIO-MITIGATION TECHNIQUES BY UTILIZING MICROALGAE AT THE BLUE LAGOON, ICELAND Indra Suryata 1,2 , Halldor G. Svavarsson 1,2 , Sigurbjörn Einarsson 1 , Ása Brynjólfsdóttir 1 and Grzegorz Maliga 3 1. Blue Lagoon R&D, Grindavik, Iceland 2. Reykjavik University, Reykjavik, Iceland 3. Wroclaw University of Technology, Wroclaw, Poland e-mail: indra08@ru.is ABSTRACT This paper describes the techniques used to sequester the CO 2 from geothermal power plant’s flue gas by means of photosynthetic microalgae. Some fundamental parameters of microalgae growth (pH- level, CO 2 feed rate, temperature and illumination conditions) were analyzed in the process of optimizing its growth. A unique microalgae species that thrives in the geothermal area of the Blue Lagoon at the Reykjanes peninsula was investigated. The preliminary results published here provide additional alternatives for managing CO 2 greenhouse gas emission from geothermal power plant and also provide additional value for the microalgae biomass production. It is demonstrated that geothermal flue gas can be efficiently used as a feedstock for microalgae cultivation. INTRODUCTION Compared to conventional power plants, burning fossil fuel, geothermal energy is generally considered to be a benign energy source in regard to environmental impact. Geothermal power plants does, however, release considerable amount of the greenhouse gas, CO 2 , to the atmosphere. The geothermal power plant HS Orka Ltd. in Svartsengi (Figure 1), which is currently producing 75 MW of electricity and 150 MW of thermal water, emits approximately 181 g CO 2 /kWh (power production only) to the atmosphere [Armannsson, 2003]. For the last few years, extensive research and experiments has been conducted and shown the feasibility to reduce the CO 2 gas emission by utilizing the concept of microalgae CO 2 sequestration. The geothermal area The high-temperature geothermal areas in Iceland are found inside the spreading zone of the two tectonic plates which Iceland straddles, the American and the Eurasian plate, closely associated with the country's active volcanic systems. Cold ingresses fluid geothermal seawater, a mixture of sea water and ground water, comes into contact with cooling magmatic intrusions at great depth, is rapidly heated and ascends towards the surface. The HS Orka power plant in Svartsengi, located at the Reykjanes peninsula in south western of Iceland, extracts the geothermal reservoir fluid from wells drilled into the reservoir. The wells are as deep as 2,000 meters and the fluid attains temperature of 240°C. This geothermal fluid is then used to heat freshwater for central heating purposes and to produce electricity. After dissipating most of its heat away, a part of the geothermal reservoir fluid is led directly to the surrounding lava where it creates the lagoon, Blue Lagoon. Figure 1. The geothermal power plant of HS Orka in Svartsengi, Iceland. The lagoon is a dynamic ecosystem, which is mainly characterized by two organisms: firstly, the photoautotrophic Cyanobacterium (blue-green microalgae), which represents the primary producers, using light as the energy source, gradually dominating the ecosystem as the brightness increases during the summer and creating organic matter for the consumers. Secondly, S. lacuscaerulensis [Petursdottir et. al., 2009], the heterotrophic alphaproteobacterium, which is dominant during