The impact of low to high waste cooking oil-based biodiesel blends on toxic organic pollutant emissions from heavy-duty diesel engines Nicholas Kiprotich Cheruiyot a , Wen-Che Hou a, ** , Lin-Chi Wang b, c, d, * , Chia-Yang Chen a a Department of Environmental Engineering, National Cheng Kung University,1 University Road, Tainan, 70101, Taiwan b Department of Civil Engineering and Geomatics, Cheng Shiu University, 840 Cheng-Ching Road, Kaohsiung City, 83347, Taiwan c Center for Environmental Toxin and Emerging-Contaminant Research, Cheng Shiu University, 840 Cheng-Ching Road, Kaohsiung City, 83347, Taiwan d Super Micro Mass Research and Technology Center, Cheng Shiu University, 840 Cheng-Ching Road, Kaohsiung City, 83347, Taiwan highlights  Using biodiesel improved combustion and resulted in PAH and POP reductions.  PAHs and POPs decreasing trend was observed till B60 in the EURO IV engine.  Poor combustion due to high viscosity increased PAHs and POPs in B80 and B100.  Biodiesel effect on PCDD/F emissions was more pronounced in the EURO III engine.  Biodiesel reduce PAHs and POPs from diesel engines with the appropriate blending ratio. article info Article history: Received 29 December 2018 Received in revised form 11 June 2019 Accepted 30 June 2019 Available online 1 July 2019 Handling Editor: Andreas Sjodin Keywords: Heavy-duty diesel engines WCO-Based biodiesel PM PAHs POPs abstract As yet, the effect of biodiesels on the emissions of polycyclic aromatic hydrocarbons (PAHs) and poly- chlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from heavy-duty diesel engines (HDDEs) has only been studied using limited fuel blend ratios. To clarify the influence of using higher fractions of biodiesel on the emissions of toxic organic pollutants from diesel engines, in this research, the emissions of PM, PAHs, and persistent organic pollutants (POPs) from EURO IV and EURO III HDDEs fueled by low to high waste cooking oil (WCO)-based biodiesel-petrodiesel fuel blends were studied, including D100 (0% biodiesel), B20 (20%), B40 (40%), B60 (60%), B80 (80%), and B100 (100%). The engines were tested ac- cording to the US FTP-75 test procedure. The results for the EURO IV diesel engine showed that the PM and toxic organic pollutant emissions were reduced with increases in the blending ratio up until the B60 scenario when compared to the D100 scenario. This is because biodiesel has higher oxygen content and no or lower aromatic content than petrodiesel. Nevertheless, during the B80 and B100 scenarios, the PM and toxic organic pollutant emissions increased due to the high viscosity property of biodiesel, which negatively affected the combustion process. The biodiesel effect on the emissions from EURO III engine was more pronounced because of its lower combustion efficiency, and therefore the improvement in combustion using biodiesel resulted in greater PCDD/F reductions. © 2019 Published by Elsevier Ltd. 1. Introduction Besides traditional pollutants, diesel engines emit various toxic organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) (Chang et al., 2014b; Cheruiyot et al., 2015; Chen et al., 2017b) and persistent organic pollutants (POPs) (Chang et al., 2014b; Mwangi et al., 2015; Cheruiyot et al., 2016; Chen et al., 2017b; Redfern et al., 2017a), including polychlorinated dibenzo-p-dioxins and di- benzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), poly- brominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), polybrominated biphenyls (PBBs), and polybrominated diphenyl ethers (PBDEs). Although the environmentally ubiquitous PBDEs are thought to be from using daily products indoors that contain brominated flame retardants (BFRs) (Prevedouros et al., 2004; * Corresponding author. Department of Civil Engineering and Geomatics, Cheng Shiu University, 840 Cheng-Ching Road, Kaohsiung City, 83347, Taiwan. ** Corresponding author. E-mail addresses: whou@mail.ncku.edu.tw (W.-C. Hou), lcwang@csu.edu.tw (L.-C. Wang). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere https://doi.org/10.1016/j.chemosphere.2019.06.233 0045-6535/© 2019 Published by Elsevier Ltd. Chemosphere 235 (2019) 726e733