skip to main content

View PDF Download fulltext

Analysis of pine resin potential as an additive on the physical and combustion characteristics of coconut shell bio-briquettes

1Department of Chemical Engineering, Brawijaya University, Jl. Mayjen Haryono 167 Malang, 65145, Indonesia

2Department of Agroindustrial Technology, University of Trunojoyo Madura, Bangkalan, East Java 69162, Indonesia

Received: 11 Nov 2025; Revised: 18 Apr 2026; Accepted: 10 May 2026; Available online: 18 May 2026; Published: 1 Jul 2026.
Editor(s): Editor Office
Open Access Copyright (c) 2026 The Author(s). Published by Centre of Biomass and Renewable Energy (CBIORE)
Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Citation Format:
Abstract

Indonesia is still heavily reliant on fossil fuels; however, the growth of renewable energy sources, such as biomass, offers a promising alternative energy source. Because of its high calorific value (6,500–7,600 kcal/kg) and widespread availability, coconut shell was selected for this investigation as bio-briquette. This study aimed to analyse how the properties of coconut shell bio-briquettes were affected by the carbonization time and the concentration of pine resin added as an additive. This study investigates the production and characterization of coconut shell bio-briquettes as a sustainable solid fuel. Coconut shell charcoal was carbonized at 600°C for 120, 180, and 240 min, then ground and sieved to a particle size of –60+80 mesh. Tapioca starch (5%) was used as a binder, and pine resin, derived from Pinus merkusii, was applied externally as an ignition-enhancing additive at concentrations of 2%, 4%, 6%, 8%, and 10%. The resulting bio-briquettes were analyzed for proximate parameters (moisture, ash, volatile matter, and fixed carbon) and combustion characteristics (calorific value, ignition time, and burning rate) following SNI 01-6235-2000 standards.  At a carbonisation time of 240 min and a concentration of 8% pine resin, the best results were obtained in terms of moisture content (3.87%), ash (3%), volatile matter (10.80%), fixed carbon (82.33%), calorific value (7,761.21 cal/g), ignition time (63 s), and burning rate (0.1093 g/min). These findings demonstrate that pine resin can effectively enhance ignition performance without compromising the combustion stability. Coconut shell biobriquettes with the addition of pine resin show high potential as an environmentally friendly alternative fuel because they produce a high calorific value, low moisture and ash content, and fixed carbon content that meets SNI 01-6235-2000 standards and ISO 17225 for solid biofuel. These characteristic indicate that bio-briquettes can be used as a renewable energy source to replace fossil fuels for household needs and small-scale industries.

Keywords: biobriquettes; carbonization time; coconut shells; pine resin additives; tapioca binder

Article Metrics:

  1. Abdel Aal, A. M. K., Ibrahim, O. H. M., Al-Farga, A., & El Saeidy, E. A. (2023). Impact of Biomass Moisture Content on the Physical Properties of Briquettes Produced from Recycled Ficus nitida Pruning Residuals. Sustainability (Switzerland), 15(15). https://doi.org/10.3390/su151511762
  2. Adam, S. N. F. S., Aiman, J. H. M., Zainuddin, F., & Hamdan, Y. (2021). Processing and Characterisation of Charcoal Briquettes Made from Waste Rice Straw as A Renewable Energy Alternative. Journal of Physics: Conference Series, 2080(1). https://doi.org/10.1088/1742-6596/2080/1/012014
  3. Adeleke, A. A., Nzerem, P., Salihu, A., Anosike-Francis, E. N., Olosho, A. I., Obasesam, E. E., Abubakar, S. S., Yerima, D. J., & Jakada, K. (2023). A Review on Biomass Briquettes as Alternative and Renewable Fuels. 2023 2nd International Conference on Multidisciplinary Engineering and Applied Science, ICMEAS 2023, 1–7. https://doi.org/10.1109/ICMEAS58693.2023.10429785
  4. Agussalim, A., Khairana, A., Rajab, M., Rezky, M., & Dwiyanti, U. (2022). Mutu dan karakteristik penyalaan briket arang tempurung kelapa dengan aplikasi lapisan arang sengon pada permukaannya. Jurnal Rekayasa Proses, 16(1), 49. https://doi.org/10.22146/jrekpros.70277
  5. Ajimotokan, H. A., Ehindero, A. O., Ajao, K. S., Adeleke, A. A., Ikubanni, P. P., & Shuaib-Babata, Y. L. (2019). Combustion characteristics of fuel briquettes made from charcoal particles and sawdust agglomerates. Scientific African, 6. https://doi.org/10.1016/j.sciaf.2019.e00202
  6. Alabi, O., Adeyi, T., & Ekun, S. (2023). Analyzing Energy Performance and Assessing Dry Moisture Content of Briquettes through Numerical Investigations. Engineering and Technology Journal, 0(0), 1–10. https://doi.org/10.30684/etj.2023.143782.1608
  7. Aljarwi, M. A., Pangga, D., & Ahzan, S. (2020). Uji Laju Pembakaran Dan Nilai Kalor Briket Wafer Sekam Padi Dengan Variasi Tekanan. ORBITA: Jurnal Kajian, Inovasi Dan Aplikasi Pendidikan Fisika, 6(2), 200. https://doi.org/10.31764/orbita.v6i2.2645
  8. Almu, M. A., Syahrul, & Padang, Y. A. (2014). Analisa Nilai Kalor Dan Laju Pembakaran Pada Briket. Dinamika Teknik Mesin, 4(2), 117–122
  9. Angın, N., Ertas, M., Aras, O., & Genc, M. (2025). A Novel Approach to the Development of Natural Based Biopolymer in the Presence of a Reusable Catalyst : Characterization and Modeling of Material Properties. Journal of Polymer Science, 63, 164–177. https://doi.org/10.1002/pol.20240576
  10. Anisa, D., Wati, R., & Supriyono, T. (2025). Analisis kandungan volatile matter pada briket batok kelapa dengan metode gravimetri untuk optimasi kualitas pembakaran. Kolecer, 01(1), 37–44
  11. Ashraful, A. M., Masjuki, H. H., Kalam, M. A., Rizwanul Fattah, I. M., Imtenan, S., Shahir, S. A., & Mobarak, H. M. (2014). Production and comparison of fuel properties, engine performance, and emission characteristics of biodiesel from various non-edible vegetable oils: A review. Energy Conversion and Management, 80, 202–228. https://doi.org/10.1016/j.enconman.2014.01.037
  12. Asri, S. (2013). Efisiensi Konsentrasi Perekat Tepung Tapioka Terhadap Nilai Kalor Pembakaran pada Biobriket Batang Jagung (Zea mays L.). Jurnal Teknosains, 7, 78–89
  13. Bot, B. V., Sosso, O. T., Tamba, J. G., Lekane, E., Bikai, J., & Ndame, M. K. (2023). Preparation and characterization of biomass briquettes made from banana peels, sugarcane bagasse, coconut shells and rattan waste. Biomass Conversion and Biorefinery, 13(9), 7937–7946. https://doi.org/10.1007/s13399-021-01762-w
  14. Cholilie, I. A., & Zuari, L. (2021). Pengaruh Variasi Jenis Perekat terhadap Kualitas Biobriket Berbahan Serabut dan Tandan Buah Lontar (Borassus flabellifer L.). Agro Bali : Agricultural Journal, 4(3), 391–402. https://doi.org/10.37637/ab.v4i3.774
  15. Dai, L., Wang, Y., Liu, Y., Ruan, R., He, C., Yu, Z., Jiang, L., Zeng, Z., & Tian, X. (2019). Integrated process of lignocellulosic biomass torrefaction and pyrolysis for upgrading bio-oil production: A state-of-the-art review. Renewable and Sustainable Energy Reviews, 107(January), 20–36. https://doi.org/10.1016/j.rser.2019.02.015
  16. Dinesha, P., Kumar, S., & Rosen, M. A. (2019). Biomass Briquettes as an Alternative Fuel: A Comprehensive Review. Energy Technology, 7(5). https://doi.org/10.1002/ente.201801011
  17. Ditjenbun. (2023). Statistik Perkebunan Jilid I 2022-2024. Sekretariat Direktorat Jenderal Perkebunan
  18. Erwin, J., Julham, P. P., & Netti, H. (2015). Pengaruh Suhu dan Waktu Karbonisasi Terhadap Nilai Kalor dan Karakteristik Pada Pembuatan Bioarang Berbahan Baku Pelepah Aren (Arenga Pinnata). Jurnal Teknik Kimia USU, 4(2), 46–52. https://doi.org/10.32734/jtk.v4i2.1470
  19. Esmar, B. (2011). Tinjauan proses pembentukan dan penggunaan arang tempurung kelapa. Jurnal Penelitian Sains, 14(4), 25–29. http://ejurnal.mipa.unsri.ac.id/index.php/jps/issue/view/18
  20. Espina, R. U., Barroca, R. B., & Abundo, M. L. S. (2022). The Optimal High Heating Value of the Torrefied Coconut Shells. Engineering, Technology and Applied Science Research, 12(3), 8605–8610. https://doi.org/10.48084/etasr.4931
  21. Fadlurrahman, M. D., Widiyanti, L., & Rusnadi, I. (2024). Pengaruh Variasi Massa Tempurung Kelapa dan Waktu Karbonisasi Terhadap Kualitas Arang. 9, 205–212
  22. Fansyuri, M., Nurkholis, -, Mikhratunnisa, -, Rizaldi, L. H., & Ariskanopitasari, -. (2023). Karakteristik briket ampas tebu (bagasse) dari bahan perekat tepung beras ketan. Jurnal Agrotek Ummat, 10(1), 1. https://doi.org/10.31764/jau.v10i1.12266
  23. Gale, M., Nguyen, T., Moreno, M., & Gilliard-AbdulAziz, K. L. (2021). Physiochemical Properties of Biochar and Activated Carbon from Biomass Residue: Influence of Process Conditions to Adsorbent Properties. ACS Omega, 6(15), 10224–10233. https://doi.org/10.1021/acsomega.1c00530
  24. Gobel, A. P., & Arief, A. T. (2022). Pengaruh Karbonisasi Terhadap Karakteristik Tempurung Kelapa Berdasarkan Uji Proksimat Dan Nilai Kalor. Jurnal Mineral, Energi, Dan Lingkungan, 5(1), 48. https://doi.org/10.31315/jmel.v5i1.5370
  25. Handayani, H. E., Ningsih, Y. B., & Meriansyah, M. S. (2019). Effects of carbonization duration on the characteristics of bio-coal briquettes (coal and cane waste). IOP Conference Series: Materials Science and Engineering, 478(1). https://doi.org/10.1088/1757-899X/478/1/012027
  26. Hasibuan, R., & Pardede, H. M. (2023). Pengaruh Suhu dan Waktu Pirolisis terhadap Karakteristik Arang dari Tempurung Kelapa. Jurnal Teknik Kimia USU, 12(1), 46–53. https://doi.org/10.32734/jtk.v12i1.8534
  27. Heliani, K. R., Rahmawati, F., & Wijayanta, A. T. (2024). Screen printed carbon electrode from coconut shell char for lead ions detection. International Journal of Renewable Energy Development, 13(1), 19–30
  28. Herjunata, R., Noviandini, S. R., & Kholisoh, S. D. (2020). Pengaruh Variasi Perekat pada Briket Berbahan Limbah Tempurung Kelapa. Prosiding Seminar Nasional Teknik Kimia “Kejuangan,” J(11), 1–5
  29. Ibitoye, S. E., Mahamood, R. M., Jen, T. C., & Akinlabi, E. T. (2022). Combustion, Physical, and Mechanical Characterization of Composites Fuel Briquettes from Carbonized Banana Stalk and Corncob. International Journal of Renewable Energy Development, 11(2), 435–447. https://doi.org/10.14710/ijred.2022.41290
  30. IEA. (2024). Bioenergy. https://www.iea.org/energy-system/renewables/bioenergy
  31. Ifa, L., Yani, S., Nurjannah, N., Darnengsih, D., Rusnaenah, A., Mel, M., Mahfud, M., & Kusuma, H. S. (2020). Techno-economic analysis of bio-briquette from cashew nut shell waste. Heliyon, 6(9). https://doi.org/10.1016/j.heliyon.2020.e05009
  32. Ikhtiarbakti, A., & Gareso, P. L. (2018). Characterization Of Active Carbon Prepared From Coconuts Shells Using FTIR, XRD And SEM Techniques. Jurnal Ilmiah Pendidika Fisika Al-Biruni, 07(April), 33–39. https://doi.org/10.24042/jipfalbiruni.v7i1.2459
  33. Jamilatun, S. (2008). Sifat-Sifat Penyalaan dan Pembakaran Briket Biomassa, Briket Batubara dan Arang Kayu. Rekayasa Proses, 2(2), 37–40. https://doi.org/10.22146/jrekpros.554
  34. Jimenez, R. R., & Ladha, J. K. (2008). Communications in Soil Science and Plant Analysis Automated elemental analysis : A rapid and reliable but expensive measurement of total carbon and nitrogen in plant and soil samples. Communications in SOil Science and Plant Analysis, July 2012, 1897–1924
  35. Junary, E., Pane, J. P., & Herlina, N. (2015). Pengaruh Suhu dan Waktu Karbonisasi Terhadap Nilai Kalor dan Karakteristik pada Pembuatan Bioarang Berbahan Baku Pelepah Aren (Arenga pinnata). Jurnal Teknik Kimia USU, 4(2), 46–52
  36. Junginger, H. M., Mai-Moulin, T., Daioglou, V., Fritsche, U., Guisson, R., Hennig, C., Thrän, D., Heinimö, J., Hess, J. R., Lamers, P., Li, C., Kwant, K., Olsson, O., Proskurina, S., Ranta, T., Schipfer, F., & Wild, M. (2019). The future of biomass and bioenergy deployment and trade: a synthesis of 15 years IEA Bioenergy Task 40 on sustainable bioenergy trade. Biofuels, Bioproducts and Biorefining, 13(2), 247–266. https://doi.org/10.1002/bbb.1993
  37. Kalak, T. (2023). Potential Use of Industrial Biomass Waste as a Sustainable Energy Source in teh Future. Energies, 16, 1–25. https://doi.org/10.3390/en16041783
  38. Kebede, T., Berhe, D. T., & Zergaw, Y. (2022). Combustion Characteristics of Briquette Fuel Produced from Biomass Residues and Binding Materials. Journal of Energy, 2022, 1–10. https://doi.org/10.1155/2022/4222205
  39. Kipngetich, P., Kiplimo, R., Tanui, J. K., & Chisale, P. (2023). Effects of carbonization on the combustion of rice husks briquettes in a fixed bed. Cleaner Engineering and Technology, 13(December 2022), 100608. https://doi.org/10.1016/j.clet.2023.100608
  40. Kongprasert, N., Wangphanich, P., & Jutilarptavorn, A. (2019). Charcoal briquettes from Madan wood waste as an alternative energy in Thailand. Procedia Manufacturing, 30, 128–135. https://doi.org/10.1016/j.promfg.2019.02.019
  41. Kpalo, S. Y., Zainuddin, M. F., Manaf, L. A., & Roslan, A. M. (2020). A review of technical and economic aspects of biomass briquetting. Sustainability (Switzerland), 12(11). https://doi.org/10.3390/su12114609
  42. Kumar, J. A., Kumar, K. V., Petchimuthu, M., Iyahraja, S., & Kumar, D. V. (2021). Comparative analysis of briquettes obtained from biomass and charcoal. Materials Today: Proceedings, 45(xxxx), 857–861. https://doi.org/10.1016/j.matpr.2020.02.918
  43. Kuspradini, H., Rosamah, E., Sukaton, E., Arung, E. T., & Kusuma, I. W. (2018). Pengenalan Jenis Getah Gum - Lateks - Resin (Kiswanto (ed.); Issue 4). Mulawarman University Press
  44. Lazim, Z. M., & Hadibarata, T. (2015). Adsorption Characteristics of Bisphenol A onto Low-Cost Modified Phyto-Waste Material in Aqueous Solution. Water Air Soil Pollut, 226, 34–45. https://doi.org/10.1007/s11270-015-2318-5
  45. Martins, G. I., Secco, D., Rosa, H. A., Bariccatti, R. A., Dolci, B. D., Melegari De Souza, S. N., Santos, R. F., Benetoli Da Silva, T. R., & Gurgacz, F. (2015). Physical and chemical properties of fish oil biodiesel produced in Brazil. Renewable and Sustainable Energy Reviews, 42, 154–157. https://doi.org/10.1016/j.rser.2014.10.024
  46. Mohammed, T., & Olugbade, T. (2015). Burning Rate of Briquettes Produced from Rice Bran and Palm Kernel Shells International Journal of Material Science Burning Rate of Briquettes Produced from Rice Bran and Palm Kernel Shells. International Journal of Material Science Innovations, 03(02), 68–73
  47. Ningsih, A. (2019). Analisis kualitas briket arang tempurung kelapa dengan bahan perekat tepung kanji dan tepung sagu sebagai bahan bakar alternatif. JTT (Jurnal Teknologi Terpadu), 7(2), 101–110. https://doi.org/10.32487/jtt.v7i2.708
  48. Ningsih, L. A., Setiawan, I., Syarif, T., Nurdjannah, N., Ifa, L., Afiah, I. N., & Kusuma, H. S. (2023). Pine-to-Bioenergy: Potential of pine sap as adhesive and pine flower biomass waste in the production of biobriquettes. Fuel, 350(May), 128872. https://doi.org/10.1016/j.fuel.2023.128872
  49. Novalinda, A., Fernianti, D., & Atikah. (2022). Pengaruh Rasio Campuran Dan Waktu Terhadap Mutu Biobriket Dari Pelepah Kelapa Sawit Dan Ampas Tebu. Distilasi, 7(2), 1–8
  50. Obi, O. F., Pecenka, R., & Clifford, M. J. (2022). A Review of Biomass Briquette Binders and Quality Parameters. Energies, 15(7), 1–22. https://doi.org/10.3390/en15072426
  51. Palanisamy, E., Velusamy, S., Al-Zaqri, N., & Boshaala, A. (2023). Characterization and energy evaluation analysis of agro biomass briquettes produced from Gloriosa superba wastes and turmeric leave wastes using cassava starch as binder. Biomass Conversion and Biorefinery, 13(12), 11321–11337. https://doi.org/10.1007/s13399-023-04543-9
  52. Pari, G., Efiyanti, L., Darmawan, S., Saputra, N. A., Hendra, D., Adam, J., Inkriwang, A., & Effendi, R. (2023). Initial Ignition Time and Calorific Value Enhancement of Briquette with Added Pine Resin. Journal of the Korean Wood Science and Technology, 51(3), 207–221. https://doi.org/10.5658/WOOD.2023.51.3.207
  53. Pratama, A. R., & Praswanto, D. H. (2022). Analisa Laju Pembakaran pada Briket Ampas Kopi dan Serbuk Kayu dengan Campuran Minyak Sawit. Prosiding SENIATI, 6(2), 250–258. https://doi.org/10.36040/seniati.v6i2.4986
  54. Putu, S., Gunawan, G., Ngurah, I. G., & Santhiarsa, N. (2024). Utilization of Coconus Shell Activated Carbon to Generate Electrical Energy Using Sodium CHloride Electrolyte. EUREKA, 4, 28–39. https://doi.org/10.21303/2461-4262.2024.003281
  55. Rampe, M. J., Santoso, I. R. S., Rampe, H. L., Tiwow, V. A., & Apita, A. (2021). Infrared Spectra Patterns of Coconut Shell Charcoal as Result of Pyrolysis and Acid Activation Origin of Sulawesi , Indonesia. ICST, 8008, 3–6
  56. Rodhiyah, Rahmatulloh, A., & Firdaus, R. C. (2024). Perbandingan Analisis Parameter Moisture Content Flavour Powder Menggunakan Moisture Analyzer Dan Oven. DISTILAT: Jurnal Teknologi Separasi, 10(1), 287–295. https://doi.org/10.33795/distilat.v10i1.4877
  57. Saputra, D. A., Margianto, & Raharjo, A. (2023). Pengolahan Briket Bonggol Jagung Dengan Perekat Tepung Tapioka dan Getah Pohon Pinus. Jurnal Teknik Mesin, 19(1), 17–25
  58. Saputro, D. D., Widayat, W., Saptoadi, H., & Fauzun. (2013). KARAKTERISTIK PEMBAKARAN BRIKET LIMBAH. Sainteknol : Jurnal Sains Dan Teknologi, 11(2), 113–122
  59. Sarker, T. R., Nanda, S., Meda, V., & Dalai, A. K. (2023). Densification of waste biomass for manufacturing solid biofuel pellets: a review. In Environmental Chemistry Letters (Vol. 21, Issue 1). Springer International Publishing. https://doi.org/10.1007/s10311-022-01510-0
  60. Sarria-Villa, R. A., Gallo-Corredor, J. A., & Benítez-Benítez, R. (2021). Characterization and determination of the quality of rosins and turpentines extracted from Pinus oocarpa and Pinus patula resin. Heliyon, 7(8). https://doi.org/10.1016/j.heliyon.2021.e07834
  61. Shafiyya, J. V. A., Kusumasari, H. S., Praharsiwi, I. M., & Mujiburohman, M. (2022). Pengaruh Kondisi Operasi dan Jenis Perekat Terhadap Karakteristik Briket Ampas Teh. Jurnal Energi Baru Dan Terbarukan, 3(3), 249–258. https://doi.org/10.14710/jebt.2022.14930
  62. Siahaan, S., Hutapea, M., & Hasibuan, R. (2013). Penentuan kondisi optimum suhu dan waktu karbonisasi pada pembuatan arang dari sekam padi. Jurnal Teknik Kimia USU, 2(1), 26–30
  63. Singla, M. K., Gupta, J., Safaraliev, M., Nijhawan, P., Oberoi, A. S., & Menaem, A. A. (2024). Characterization of an activated carbon electrode made from coconut shell precursor for hydrogen storage applications. International Journal of Hydrogen Energy, 61, 1417–1428. https://doi.org/https://doi.org/10.1016/j.ijhydene.2024.02.341
  64. Siswati, N. D., Guntoro, H. K., & Pratama, N. W. (2019). Kajian Penambahan Oksidator Terhadap Sifat Penyalaan Briket Arang Tempurung Kelapa. Jurnal Teknik Kimia, 14(1), 5–9. https://doi.org/10.33005/jurnal_tekkim.v14i1.1648
  65. Slade, R., Bauen, A., & Gross, R. (2014). Global bioenergy resources. Nature Climate Change, 4(2), 99–105. https://doi.org/10.1038/nclimate2097
  66. Tabasso, S., Grillo, G., Fransesco, M., & Cravotto, G. (2020). Biomass burning in sub-saharan africa: Chemical issues and action outreach. In Biomass Burning in Sub-Saharan Africa: Chemical Issues and Action Outreach. Springer Netherlands. https://doi.org/10.1007/978-94-007-0808-2
  67. Tesfaye, A., Workie, F., & Kumar, V. S. (2022). Production and Characterization of Coffee Husk Fuel Briquettes as an Alternative Energy Source. Advances in Materials Science and Engineering, 2022. https://doi.org/10.1155/2022/9139766
  68. Tomen, W. T., Diboma, B. S., Bot, B. V., & Tamba, J. G. (2023). Physical and Combustion properties investigation of hybrid briquettes from tropical Sawdust: Case study of Iroko (Milicia excelsa) and Padouk (Pterocarpus soyauxii). Energy Reports, 9, 3177–3191. https://doi.org/10.1016/j.egyr.2023.02.006
  69. Trubetskaya, A., Leahy, J. J., Yazhenskikh, E., Müller, M., Layden, P., Johnson, R., Ståhl, K., & Monaghan, R. F. D. (2019). Characterization of woodstove briquettes from torrefied biomass and coal. Energy, 171, 853–865. https://doi.org/10.1016/j.energy.2019.01.064
  70. Ungureanu, N., Vladut, V., Voicu, G., Dinca, M. N., & Zabava, B. S. (2018). Influence of biomass moisture content on pellet properties - Review. Engineering for Rural Development, 17, 1876–1883. https://doi.org/10.22616/ERDev2018.17.N449
  71. Vallinayagam, R., Vedharaj, S., Yang, W. M., Lee, P. S., Chua, K. J. E., & Chou, S. K. (2013). Combustion performance and emission characteristics study of pine oil in a diesel engine. Energy, 57, 344–351. https://doi.org/10.1016/j.energy.2013.05.061
  72. Zaenul Amin, A., Pramono, & Sunyoto. (2017). Pengaruh Variasi Jumlah Perekat Tepung Tapioka Terhadap Karakteristik Briket Arang Tempurung Kelapa. Sainteknol : Jurnal Sains Dan Teknologi, 15(2), 111–118. https://doi.org/10.15294/sainteknol.v15i2.11693

Last update:

No citation recorded.

Last update: 2026-05-21 16:25:18

No citation recorded.