Fuel 286 (2021) 119467 Available online 21 October 2020 0016-2361/© 2020 Elsevier Ltd. All rights reserved. Full Length Article Physico-chemical properties of Acetone-Butanol-Ethanol (ABE)-diesel blends: Blending strategies and mathematical correlations Ibham Veza , Muhammad Faizullizam Roslan , Mohd Farid Muhamad Said * , Zulkarnain Abdul Latiff , Mohd Azman Abas Automotive Development Centre, School of Mechanical Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Malaysia A R T I C L E INFO Keywords: Acetone-Butanol-Ethanol (ABE) Physico-chemical Fuel property Mathematical correlation Diesel engine Biofuel ABSTRACT Butanol offers more promising results compared to lower carbon alcohol. Yet, it has not been commercially produced as a biofuel due to its expensive recovery process from Acetone-Butanol-Ethanol (ABE) fermentation. If ABE is used directly as a biofuel, the process will be more straightforward, thus eliminating its energy and cost- intensive purifcation process. Study on ABE as a biofuel has become a growing feld for the last fve years. Several preliminary studies have reported convincing results of using ABE-diesel blends in diesel engines. However, many of the studies on ABE lacks clarity regarding its fuel properties. In fact, no previous study has investigated the fuel properties of ABE. Therefore, this study aims to quantify some critical physico-chemical properties of ABE-diesel blends. Several important fuel properties were investigated in this study; calorifc value, density, kinematic viscosity, distillation characteristics and cetane index. In terms of blending strategy, results from this study indicate that ABE(3 6 1) can be added up to 42% to diesel fuel, while ABE(6 3 1) and ABE (1 3 6) can only be added up to 22% and 23%, respectively. Also, the mathematical correlations to estimate ABE’s fuel properties are presented. The equations developed in this study gave have high coeffcient of determination values. They can serve as prediction models for future studies. Considering its relatively low-cost production and satisfying physico-chemical properties, ABE has the potential to become a promising alternative biofuel. 1. Introduction Traditionally, ABE is a major area of interest within the feld of biotechnology. Today, research on ABE has received increased attention across several disciplines, from applied microbiology to mechanical engineering. ABE has been the subject of several engine research both in gasoline and diesel engine. A recent study by Veza et al. [1] has high- lighted the important fndings of ABE addition in internal combustion engines. Butanol is typically produced with a ratio of 3:6:1 and 2.9:1 through the conventional ABE and BA fermentation process. Algayyim et al., for instance, used BA(2.9:1) in their studies [2,3] following the results by Li et al. [4] that found butanol/acetone ratio of 2.9:1 was successfully produced using cassava through an in-situ extractive fermentation by C. acetobutylicum. However, other ABE volumetric ratios aside from 3:6:1 or BA(2.9:1) have shown promising results in numerous studies, both in gasoline and diesel engines, such as 1:8:1 [5], 1:6:3 [6] 6:3:1 [6–14], 5:4:1 [5] and 5:14:1 [8,10,15,16]. In regards to ABE ratio with 6:3:1, Wu et al. [11] found that the use of ABE(6 3 1)-diesel blends gave very similar premixed combustion with pure diesel and far stronger than that of ABE(3 6 1). With the increase of acetone ratio in ABE(6 3 1), it was also found that the combustion duration shortened, which is considered as an advantage to improve fuel effciency in diesel engine. Furthermore, shorter combustion duration also led to a narrow plateau of space integrated natural luminosity, thus reducing soot emissions. This fndings are in line with other studies [12–14] indicating the potential of ABE(6 3 1) to enhance the combus- tion characteristics of ABE-diesel blends. As for ABE(1 3 6), it was investigated to represent the dominant role of ethanol in ABE. There- fore, the effect of increased acetone, butanol and ethanol can be compared and were well-represented in ABE(6 3 1), ABE(3 6 1) and ABE (1 3 6), respectively. It is not safe using higher percentage of ABE(3 6 1) due to acetone’s high fammability. However, numerous studies have attempted to add more than 30% of ABE(3 6 1) into diesel fuel and even used ABE(6 3 1) despite its higher acetone content. Chang et al [15] and Ma et al. [17] * Corresponding author. E-mail address: mdfarid@utm.my (M. Farid Muhamad Said). Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel https://doi.org/10.1016/j.fuel.2020.119467 Received 15 May 2020; Received in revised form 20 September 2020; Accepted 7 October 2020