001.docx CHEMICAL ENGINEERING TRANSACTIONS VOL. 83, 2021 A publication of The Italian Association of Chemical Engineering Online at www.cetjournal.it Guest Editors: Jeng Shiun Lim, Nor Alafiza Yunus, Jiří Jaromír Klemeš Copyright © 2021, AIDIC Servizi S.r.l. ISBN 978-88-95608-81-5; ISSN 2283-9216 Life Cycle Based Carbon Footprint Assessment of Indonesia’s Geothermal Energy Exploration Project Joni S. Adiansyaha,*, Wahidul Biswasb, Nawshad Haquec aDepartment of Mine Engineering, Universitas Muhammadiyah Mataram, Indonesia bSustainable Engineering, Curtin University, WA, Australia aCSIRO Energy, Clayton, VIC, Australia joni.adiansyah@ummat.ac.id Indonesia is committed to increase the contribution of renewable energy to at least 23 % of the total Indonesian energy mix by 2025. The geothermal energy resource of Indonesia could potentially help achieve this target, but there are environmental challenges associated with geothermal energy exploration. This study is aimed to estimate the carbon footprint of the geothermal exploration project using a life cycle assessment (LCA) approach. Literature published to date did not consider the use of LCA to specifically assess the environmental impacts of geothermal energy exploration. A geothermal energy exploration project in West Java, Indonesia, has been taken as a case study to conduct an LCA considering four main activities, namely land clearing, access road improvement, slim-hole well pad, and standard-hole well pad construction. ReCiPe impact assessment analysis was used to convert inputs and outputs of these activities to carbon footprints of 1 m2 of area of geothermal energy exploration. The result showed that the total carbon footprint of geothermal energy exploration stages was 53.2 kg CO2-eq/m2/y. The two most significant contributors to carbon footprints were the construction of a standard-hole well pad (56 %) and a slim-hole well pad (43 %). Diesel fuel and chemicals were two main carbon footprint sources of geothermal energy exploration project. In terms of inputs, the utilization of caustic soda for neutralization during the drilling activity contributed 64.5 % of the total carbon footprint, followed by diesel fuel consumption (27 %), bentonite (4.04 %) and barium sulphate (4.43 %) for the high carbon footprint for standard-hole well pad construction. The effective utilization of caustic soda and diesel by preparing standard operational procedure (SOP) and implementing ISO quality and environmental management systems (ISO 90001 and 14001) could increase the environmental performance of geothermal energy exploration. 1. Introduction Energy consumption is one of the indicators for the increase of the greenhouse gas (GHG) concentration in the atmosphere, which is responsible for climate change. There exists a reasonable correlation between energy consumption and environmental impacts, including resource degradation (Kwakwa et al., 2020), climate change (Akhmat et al., 2014), greenhouse gas emission in copper mine (Adiansyah, 2019), carbon footprint in mine disposal management (Adiansyah, 2020), and correlation of energy consumption and trade (Shahzad et al., 2017). Fossil fuels, including coal, petroleum, and other liquids, account for the major share (44 %-55 %) of global energy consumption (Ismail et al., 2020), while the growth of renewable energy is expected to increase significantly during 2018-2050 (EIA, 2019). One renewable energy source is geothermal that distributed into more than 30 countries worldwide (Geoenergy, 2020) with the total current installed capacity in 2020 is approximately 15.9 GWe (Huttrer, 2020). Ten countries that recorded as the highest geothermal installed capacity are the United States of America, Indonesia, Philippines, Turkey, Kenya, Mexico, New Zealand, Italy, Japan, and Iceland (Huttrer, 2020). The Government of Indonesia (GOI) has already committed to increase the share of renewable energy in the energy mix to 23 % and 31 % by 2025 and 2050. The total renewable energy potential recorded by The Indonesian National Energy Council is equivalent to 442 GWe, and geothermal energy is listed as one of the five most significant renewable energy potentials in Indonesia (DEN, 2019). Other studies confirm that DOI: 10.3303/CET2183011 Paper Received: 21/06/2020; Revised: 05/09/2020; Accepted: 11/09/2020 Please cite this article as: Adiansyah J.S., Biswas W., Haque H., 2021, Life Cycle Based Carbon Footprint Assessment of Indonesia’s Geothermal Energy Exploration Project, Chemical Engineering Transactions, 83, 61-66 DOI:10.3303/CET2183011 61 Indonesia’s geothermal potential is the largest resource worldwide with a total of 29 GWe from more than 300 geothermal sites (Huttrer, 2020). The potential sites are mainly located in Java, Sumatera, Sulawesi, and East Nusa Tenggara. The huge untapped potential of this resource has convinced the GOI to make an ambitous target of expanding the capacity of geothermal power plant to around 6,000 MW by 2020 (ADB and WB, 2015). Whilst this target has been failed, the GOI further made a target of 7,000 MWe by 2025 (Huttrer, 2020). Despite geothermal power could potentially strengthen nation’s energy security, it is not entirely environmentally benign as environmental impacts are occuring during the life cycle stages of this plant. The environmental impacts include land disturbance, solid and liquid waste disposal, disturbance of flora and fauna, and the depletion of ecological resources. There are social impacts during exploration, construction, operation, and post-operation stages of geothermal electricity generation (Bošnjaković et al., 2019). Boron contaminated the irrigation water and soil (Yilmaz and Ali Kaptan, 2017), hydrogen sulphide and CO2 emissions can occur (Huang and Tian, 2006). The environmental impact assessment is required to evaluate the potential impact of the geothermal project to device strategies for generating electricity with reduced environment impact. Life Cycle Assessment (LCA) could be used as a tool for assessing the environmental impact of a project or activity. Various studies associated with LCA in geothermal power sector are found including dry steam geothermal (Buonocore et al., 2015), review on geothermal technologies (Tomasini-Montenegro et al., 2017), low-temperature geothermal (Ruzzenenti et al., 2014), geothermal plant (Martínez-Corona et al., 2017). In addition, one recent study compares the environmental impact of three types of renewable energy sources, namely geothermal, solar, and wind (Basosi et al., 2020). Those studies were focused on the operational stage of a geothermal power plant by evaluating the technology applied. None of the current studies discussed the LCA of geothermal exploration projects in Indonesia. Given the nation has the world’s largest reservoir of geothermal energy and the electricity generation from it is expected to increse significantly, it is becomes inevetable to carry out an LCA of Indonesia’s geothermal development particulalry including its’ exploration stage. On the other hand, Indonesia has a target for reducing the Greenhouse Gas (GHG) emission from energy sector about 14 % by 2030 (DEN, 2019). One of the abvious strategies is by increasing the share of renewable energy in the Indonesia’s energy mix. In addition, more than 50 % of the electricity production in Indonesia is supplied by coal-fired power plant where the coal combustion would generate sulphur dioxide (SO2), nitrogen oxides (NOx), and particulate matters that contribute to enviromental and health problems (EIA, 2020). This study is important to estimate the contribution of geothermal energy exploration project on Indonesia’s carbon footprint. In addition, the environmental hotspots that contribute to the environmental impact would also be presented. 2. Methods The LCA approach was followed to assess the carbon footprint of geothermal exploration project in Indonesia. ReCiPe in SimaPro (Version 9.0) LCA software (Mark et al., 2016) was used for estimating the carbon footprint of geothermal exploration due to absence of local method. The database used ecoinvent database that provided by SimaPro. The LCA consists of four main steps of ISO 14040:2006, namely goal and scope definition, inventory analysis, life cycle impact analysis, and interpretation (ISO, 2006) (ISO, 2006). The first two steps were discussed in Section 2.1 and 2.2, where the impact analysis and interpretation stage were presented in the results and discussion section. A case study of a geothermal exploration project was taken to calculate the carbon footprint generated from the life cycle assessment perspective. The project that is located at Serang Regency, Banten Province, Indonesia. It has a distance of approximately 3.8 km from Palka main road. Geothermal working area of Banten Lake Caldera is located in the North-West of Banten Province with a total concession area of about 104.2 km2. In addition, this project is predicted to be able to generate electric power of 2 x 55 MW. 2.1 Goal and scope definitions The goal of this study was to estimate the carbon footprint of the geothermal exploration project in Indonesia. The scope of this study is presented in Figure 1 that consists of four stages, namely land clearing, access road construction, slim-hole well pad construction, and standard-hole well pad construction. The functional unit was the carbon footprint generated per square meter land utilised per year. 2.2 Inventory analysis A life cycle inventory is a critical step in the life cycle assessment, where each input and output data for the geothermal exploration life cycle are collected. These data, as presented in Table 1 and Table 2, include equipment, fuel consumption, chemical usage, waste generated, and water consumption are used to calculate 62 the carbon footprint associated with the life cycle of the geothermal exploration project where manufacturing process of machineries was excluded. Figure 1: Geothermal energy exploration boundary Table 1: Data inventory for equipment and fuel consumption Activity Sub-activity Equipment Fuel usage (L/h) Work hours (h) Work Days (d) Total fuel Consumption (L) Land Clearing Tree Chipper Excavator 33.71 8 10 2,696.8 Removal of green waste Dump truck 27.73 8 5 1,109.2 Land grading Excavator 33.71 8 20 5,393.6 Loader 20.66 8 20 3,305.6 Dump truck 27.73 8 15 3,327.6 Work supervision LV 4 x 4 41.96 8 30 10,070.4 Access Road Base course Dump truck 27.73 8 20 4,436.8 Dozer 52.61 8 90 37,879.2 Excavator 33.71 8 90 24,271.2 Grading Grader 39.83 8 90 28,677.6 Loader 20.66 8 40 6,611.2 Dump truck 27.73 8 20 4,436.8 Soil removal Loader 20.66 8 20 3,305.6 Dump truck 27.73 8 20 4,436.8 Work supervision LV 4 x 4 41.96 8 90 30,211.2 Slim-hole well pad Construction Crane 49.20 8 90 35,424 Forklift 18.96 8 150 22,752 Electricity Generator 17.89 8 150 21,468 Excavator 33.71 8 150 40,452 Dozer 52.61 8 150 63,132 Drilling truck 72.80 18 60 78,624 Grading Grader 39.83 8 150 47,796 Loader 20.66 8 90 14,875.2 Work supervision LV 4 x 4 41.96 8 150 50,352 Standard- hole well pad Construction Crane 49.20 8 60 23,616 Forklift 18.96 8 90 13,651.2 Electricity Generator 17.89 8 90 12,880.8 Excavator 33.71 8 90 24,271.2 Dozer 52.61 8 90 37,879.2 Drilling rig 170.42 18 35 107,364.6 Grading Grader 39.83 8 90 28,677.6 Loader 20.66 8 60 9,916.8 Work supervision LV 4 x 4 41.96 8 90 30,211.2 Table 2 concludes that three chemical types are required by the standard-hole construction stage, namely bentonite, barium sulphate, and caustic soda with total usage of approximately 380,000 kg. The wastes, both solid and liquid, are mainly generated by employee activities. The total solid waste and wastewater generated during the geothermal exploration project were 12,411 kg and 1,702 m3 (Table 2). Based on the SimaPro guideline, solid/domestic waste and drilling mud were classified as final waste flow, and the wastewater was 63 categorized as emission to water. In addition, the land CO2 sequestration due to land use (24.2 Ha) was sourced from Widhanarto et al. (2016) for use in the carbon footprint analysis. Table 2: Data inventory for materials and land use change Material Activity Quantity Unit Chemical usage Bentonite Well pad operation in standard-hole 80,000 kg Barium sulphate Well pad operation in standard-hole 45,000 kg Caustic soda Well pad operation in slim-hole 63,000 L Well pad operation in standard-hole 255,000 L Waste generated Domestic/solid waste Land clearing 399 kg Access road 1,260 kg Slim-hole well pad 6,720 kg Standard-hole well pad 4,032 kg Wastewater Land clearing 54,720 L Access road 172,800 L Slim-hole well pad 921,600 L Standard-hole well pad 552,960 L Drilling mud Slim-hole well pad 125 m3 Standard-hole well pad 840 m3 Water consumption Water Land clearing 68,400 L Access road 216,000 L Slim-hole well pad 1,152,000 L Standard-hole well pad 691,200 L Land sequestration (Widhanarto et al., 2016) Land clearing 362.14 t CO2/Ha/y 2.3 Limitation The lack of a local database library for materials such as bentonite, barium sulphate, and caustic soda has created less reliability and accuracy result of the life cycle impact assessment. In addition, the current public availability report of geothermal exploration does not describe the type of equipment usage and mileage. Equipment fuel consumption was estimated based on the equipment horsepower (HP) approach. 3. Results and discussion The results and discussion section presented the carbon footprint analysis and environmental hotspot of the geothermal exploration project. The carbon footprint of each activity was described in Section 3.1, and the hotspot analysis of carbon footprint was discussed in Section 3.2. 3.1 Carbon footprint analysis The carbon footprint of the geothermal exploration project ranged from 0.11 kg CO2-eq/m2/y to 29 kg CO2- eq/m2/y, as presented in Table 3. The highest carbon footprint was recorded by standard-hole well pad construction where total workdays for completing this activity were 90 d. The carbon footprint contribution of standard-hole well pad activity was approximately 56 % of the total carbon footprint. In addition, two main inputs that resulted in the high carbon footprint for standard-hole well pad construction were chemicals usage (73 %), and fuel consumption (27 %). These chemicals usages have a specific function in well pad drilling activity. The specific function of each material is as follows: bentonite is commonly used for increasing mud viscosity, barium sulphate is aimed to increase density, and caustic soda would maintain the pH and alkalinity of drilling mud. The wastes associated with the use of these chemicals during drilling and mud-cutting were considered as a non-hazardous waste by the Indonesian Ministry of Energy and Mineral Resources (ESDM, 2017). Based on the inventory analysis, as discussed in Section 2.2 showed the slim-hole well pad construction consumed higher amount of diesel fuel (374,875 L) than standard-hole well pad construction (288,469 L). The latter required higher amount of caustic soda (192,000 L) than the former, resulting a higher carbon footprint impact of chemical compared to diesel fuel. In addition, the carbon footprint that generated from carbon sequestration loss due to land clearing was 14.97 t CO2/Ha/y or equivalent with 1.50 kg CO2-eq/m2/y. Total carbon footprint emitted by the geothermal energy exploration were kg CO2-eq/m2/y. 64 Table 3: Carbon footprint for geothermal energy exploration Activity Global Warming (GW) Unit Land clearing 0.11 kg CO2-eq/m2/y Access road 0.28 kg CO2-eq/m2/y Slim-hole well pad 22.31 kg CO2-eq/m2/y Standard-hole well pad 29.00 kg CO2-eq/m2/y 3.2 Carbon footprint hotspot The hotspot analysis is aimed to identify the inputs causing the most carbon footprint. SimaPro provides the network analysis option for identifying carbon footprint hotspots (Figure 2). Three main hotspots in the life cycle impact of geothermal exploration projects were caustic soda, diesel fuel, and barium sulphate. The utilization of caustic soda as a neutralization agent during the drilling activity contributed 64.5 % of the total carbon footprint and followed by diesel fuel consumption with 27 % of the overall carbon footprint. The other two contributors were bentonite (4.04 %) and barium sulfate (4.43 %). These four materials have also identified as the main inputs in the inventory stage (see Table 1 and Table 2). In sum, the life cycles of these materials production have contributed significantly to greenhouse gas emissions that requiring Indonesian companies to source these chemicals from manufacturers producing them with reduced level of GHG emissions. Indication of environmental hotspots could be used as an initial information on how to reduce the carbon footprint from the geothermal energy exploration project. The effective utilization of diesel fuel and chemicals by preparing standard operational procedure (SOP) should be considered by the project to manage the environmental hotspots. In addition, one possible strategy that might be applied to increase the effectiveness of material utilization could be to implement good management principles of well pad construction by adopting the ISO management system concept (ISO, 2015). Figure 2: Environmental hotspot using networking analysis 4. Conclusions This research paper conducted the life cycle assessment to calculate the carbon footprint of geothermal exploration in Indonesia, which has not been done yet. The carbon footprint of geothermal exploration was estimated to be 53.2 kgCO2-eq/m2/y and diesel fuel and chemical consumption for drilling and mud cutting were identified as the hotspots. 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