Int. J. Renew. Energy Dev. 2024, 12 (4), 648-654 | 648 https://doi.org/10.14710/ijred.2023.52532 ISSN: 2252-4940/© 2023.The Author(s). Published by CBIORE Contents list available at IJRED website International Journal of Renewable Energy Development Journal homepage: https://ijred.undip.ac.id Investigating the potential of avocado seeds for bioethanol production: A study on boiled water delignification pretreatment Herliati Rahman * , Ayu Nehemia , Hadiatun Puji Astuti Department of Chemical Engineering, Faculty of Industrial Technology, University of Jayabaya, Indonesia Abstract. The increasing need for alternative fuels to replace fossil fuels has made bioethanol a promising option. Although numerous sources of sugar generation and agricultural wastes can be converted into ethanol, Avocado Seeds (AS) are particularly attractive as raw materials due to their abundance, high carbohydrate content, and lack of interactions with the food chain. Therefore, this study investigated the potential of AS for bioethanol production using several steps, including boiled water delignification pretreatment, catalytic hydrolysis, and fermentation with Saccharomyces cerevisiae. The delignification pretreatment of AS involved soaking in 4% (w/v) sodium hydroxide liquor for 24 hours. Then the mixture was heated to 80°C and stirred slowly for 2.5 hours and after that washing with boiled water at 100 o C for 1.5 hours and screening the mixture. Subsequently, catalytic hydrolysis and fermentation were carried out using two different concentrations of Saccharomyces cerevisiae as yeast, namely 10% (w/v) and 15% (w/v). Qualitative sample analysis was conducted using scanning electron microscopy (SEM) to observe the effect of delignification pretreatment, while FTIR analysis using Thermo Scientific Nicolet iS50 was used to test for glucose functional groups. Quantitative analysis was performed using gas chromatography 7890b mass spectrophotometry 5977A, Agilent DBVRX to determine hydrolysate fermentation. The results revealed that the highest ethanol yield was achieved through fermentation with 15% (w/v) yeast and 40% (v/v) catalyst, resulting in an ethanol yield of 83.755% of the theoretical maximum. Keywords: agricultural waste; enzyme; fermentation; hydrolysis @ The author(s). Published by CBIORE. This is an open access article under the CC BY-SA license (http://creativecommons.org/licenses/by-sa/4.0/). Received: 16 th Dec 2023; Revised: 14 th April 2023; Accepted: 20 th May 2023; Available online: 25 th May 2023 1. Introduction The global economy is in need of a transition towards more sustainable and environmentally friendly energy sources, as the reliance on fossil fuels remains high (Deby et al., 2014; Fadhil et al., 2017). Therefore, biofuels are being considered as potential replacements for traditional fuels such as petrol, diesel, and aerostatic fuels (Ahlgren et al., 2017; Rahman Herliati et al., 2018). Simulation studies of the world energy systems predict that biofuels could contribute significantly, ranging from 10% to 40% of the market, in the long term, indicating a substantial increase in their utilization (Acevedo-García et al., 2018). In Indonesia, the production of biofuels at a competitive price is being explored to support the economic and energy security of the country (Raza et al., 2021). Several studies have considered biomass as the most promising renewable carbon source for biofuels (Yu et al., 2020; Zhao et al., 2009). The National Research and Innovation Agency of Indonesia predicts that new renewable energy, including biomass, will increase power and heat generation by 2035 (Frankowski et al., 2022; Rahman et al., 2019; Sluiter et al., 2011). Bioethanol, derived from fruit waste biomass such as avocado seeds, is a viable biofuel option (Dong et al., 2019; Frankowski et al., 2022; Salehi et al., 2018). This biomass has several advantages, such as low cost, low dependence on the food chain, and colossal availability (Risyad et al., 2016; * Corresponding author Email: herliati@jayabaya.ac.id (H. Rahman) Muhammad et al., 2020; Mueansichai et al., 2022). According to the Central Bureau of Statistics Indonesia (BPS), 307.3 tons of avocados were produced in Indonesia in 2014 (Marlina et al., 2018; Sukaryo & Sri Subekti, 2017). The production rate continues to increase yearly, at a growth level of 24.48%, raising the number of avocado seeds (Sukaryo & Sri Subekti, 2017). Currently, avocado seeds are indiscriminately discharged into the environment, thereby leading to pollution (Risyad et al., 2016; Sluiter et al., 2011). However, there is growing interested in utilizing avocado seeds as a crucial biomass resource for bioethanol production, given their significant quantity and high cellulose content (Baruah et al., 2018; Paredes-Sánchez et al., 2021). According to the Food and Agriculture Organization (FAO), avocado (Persea Americana) is a tropical or subtropical fruit native to South America and widely grown in Asia (60%), including Indonesia (Hurtado-Fernández et al., 2018; Janice et al., 2018). The primary waste is avocado seeds, with a ratio of about 0.33 kg of seeds/kg of avocado (Acevedo-García et al., 2018; Ruiz et al., 2013). Due to its availability and high cellulose content (Baruah et al., 2018), [19], AS is regarded as an expected raw material for bioethanol. The first step in ethanol manufacturing is the generation of glucose or simple sugars from biomass and avocado seeds (Acevedo-García et al., 2018; Ruiz et al., 2013). Additionally, in 2004, Werby and Petersen stated that biomass can yield 12 Research Article