POTENTIAL GREEN HOUSE GAS REDUCTION IN SODA CAUSTIC INDUSTRY

Kata kunci: Indonesia memiliki kapasitas industri kaustik soda yang besar di Asia Tenggara. Untuk mengetahui potensi pengurangan Gas Rumah kaca (GRK) pada industri kasutik soda di Indonesia. Pada makalah ini dengan menggunakan metodologi SA_AM001 tentang Pengenalan Efisiensi Tinggi Elektroli di Pabrik Pengolahan Soda kaustik, dihitung potensi pengurangan emisi gas rumah kaca dari konsumsi energi elektrolizer. Metodologi ini telah diterapkan di Kerajaan Arab Saudi, dan dengan menggunakan beberapa asumsi diimplementasikan di Republik Indonesia.


INTRODUCTION
Green House Gas (hereinafter is referred to as GHG) reduction activity for tackling global warming have been starting by a force since 2005 when Clean Development Mechanism started. Through CDM many projects related to the GHG reduction had started by developed countries in the developing countries area. However, since the economic crisis in Europe in 2008, the carbon market price was falling down and finally, reached the lowest price in 2013. In that time, almost all CDM project activities in the world were stopped or postponed. In Indonesia as a developing country, the CDM project activity in that year became fewer and in the following year, the CDM project was none.
In exchange for GHG reduction activity, in 2011, Japanese government through the bilateral cooperation with Asian countries build the new mechanism to reduce GHG emission, which named by Joint Crediting Mechanism (hereinafter referred to as JCM) (Jun, Tae Yong et al, 2016;Sugino, M., et al, 2017;Muhammad Djindan, 2016). In each country which had has the bilateral cooperation with Japanese Government to implement JCM project, Secretariat of the Joint Committee for the Joint Crediting Mechanism (JCM) between both country was established. The joint committee has a role to organize and to monitor the project implementation including the methodology proposed to calculate GHG emission for each project which proposed to be implemented in that country. A less than half of the investment cost of the JCM project can be subsidized by Japanese Government through Japanese Ministry of Environment or Ministry of Economy, Trade, and Industry. In addition, the technology proposed in the JCM project should be the first implementation in the proposed sector in that country.
In this paper by using a comparison with the JCM project which already implemented in the soda-caustic industry in the Kingdom Arab Saudi, the potential of GHG emission reduction in the soda caustic industry in Indonesia is discussed. In soda caustic industry, the electrolyzers are the main contributor to GHG emission because consumes the highest energy. The GHG reduction is conducted by a replacement of the existing elements of ion exchange membranes bipolar electrolyzers with the latest model of ion exchange membranes.

Electrolytic Process
Three kinds of electrolysis process by brine electrolysis widely used in soda caustic industry are diaphragm cells, mercury cells, and membrane cells. In recent years, however, there have been fewer plants using the mercury method and the ionexchange membrane method has become increasingly common. This trend seems to reflect (1) the introduction of an energy-saving process (ion-exchange membrane method/IEM), (2) consideration of the impact of mercury on health and the environment, and (3) reaction to regulations laid down by the Minamata Convention on Mercury in 2013.
In addition, the ion-exchange membrane method has an advantage of power consumption (consumption rate) per production volume of caustic soda or chlorine is generally 24% to 36% less than the mercury and diaphragm methods. This advantage can be utilized to reduce GHG emission from the electricity consumption of the electrolyzers. The basic technology of membrane cell was established in Japan in the 1970s and has been developed and improved to date. Since 1999, all caustic soda production in Japan has been producing by ion-exchange membrane technology.
An ion-exchange membrane is a membrane used for separating anode and cathode chambers, and a fluorine-based cation-exchange membrane is generally used. In brine electrolysis, an oxidation reaction occurs in the anode chamber and reduction reaction occurs in the cathode chamber, which means the mixture and isolation of substances generated in both chambers must be controlled. The ion-exchange membrane used here is the cation-exchange membrane. Na+ (the sodium ion) in the anode chamber migrates to the cathode chamber through the membrane while Cl-(chlorine ion) generated in the anode chamber remains, as it cannot pass the membrane. On the other hand, water molecules are reduced to hydrogen and OH-(hydroxide ion) in the cathode chamber but most of the OH-cannot pass the membrane, which means NaOH (caustic soda) is generated in the cathode chamber by Na+ migrating from the anode chamber and OH-. At this time, the anode chamber becomes strongly oxidized due to chlorine ions while the cathode chamber is strongly alkaline. In addition, liquid temperature increases during the brine electrolysis, both the chemical durability and the separation are required for the ion-exchange membrane. Therefore, a fluoro-based ionexchange membrane composed of a polymer equipped with a perfluorocarbon backbone and a cation-exchange ability is applied. The latest kind and high efficiency of ion exchange membrane is F-8080 type. This kind o membrane has a higher durability against impurities, high stability of current efficiency and lowest and stable current voltage (Asahi Glass Co. Ltd, 2016). This type of ion exchange membrane is proposed in the JCM project. Figure 1 shows the typical of ion-exchange membrane method electrolyzer.

Soda Caustic Industries in Indonesia
In 2006, about 84% of the total world soda caustic was produced electrolytically using diaphragm and membrane cells, while about 13% was made using mercury cell . In Indonesia the biggest soda-caustic Indonesia, Asahi Chemical which has the same group with the sodacaustic biggest producer in the World. Table 1 shows the soda caustic industry in Indonesia. Except for Asahi Chemical and PT Sulfindo Adiusaha, the others soda caustic producer uses their soda caustic production to their paper industry. Therefore, the potential GHG reduction is calculated for only two biggest soda caustic producers, which is Asahi Chemical and PT. Sulfindo Adiusaha below. Both companies use ion exchange membrane provided by Asahi Kasei Corporation. The SEC is assumed to be a same with a SEC value in the Kingdom of Saudi Arabia of 2,088 kWh (DC)/t-NaOH. The total capacity production is 1,020,000 t-NaOH/yr, which consist of 8 units of electrolyzer. For one electrolyzer,