Reducing Emissions of Persistent Organic Pollutants from a Diesel Engine by Fueling with Water-Containing Butanol Diesel Blends Yu-Cheng Chang, † Wen-Jhy Lee,* ,† Hsi-Hsien Yang, ‡ Lin-Chi Wang,* ,§ Jau-Huai Lu, ⊥ Ying I. Tsai, ∥ Man-Ting Cheng, # Li-Hao Young, ⊗ and Chia-Jui Chiang ∇ † Department of Environmental Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan ‡ Department of Environmental Engineering and Management, Chaoyang University of Technology, 168 Jifeng E. Road, Taichung 41349, Taiwan § Department of Civil Engineering and Geomatics, Cheng Shiu University, 840 Chengching Road, Kaohsiung 83347, Taiwan ⊥ Department of Mechanical Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 40254, Taiwan ∥ Department of Environmental Resources Management, Chia Nan University of Pharmacy and Science, 60 Erh-Jen Road Sec. 1, Tainan 71710, Taiwan # Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 40254, Taiwan ⊗ Department of Occupational Safety and Health, China Medical University, 91 Hsueh-Shih Road, Taichung 40402, Taiwan ∇ Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road Sec. 4, Taipei 10607, Taiwan *S Supporting Information ABSTRACT: The manufacture of water-containing butanol diesel blends requires no excess dehydration and surfactant addition. Therefore, compared with the manufacture of conventional bio-alcohols, the energy consumption for the manufacture of water-containing butanol diesel blends is reduced, and the costs are lowered. In this study, we verified that using water-containing butanol diesel blends not only solves the tradeoff problem between nitrogen oxides (NO x ) and particulate matter emissions from diesel engines, but it also reduces the emissions of persistent organic pollutants (POPs), including polycyclic aromatic hydrocarbons, polychlori- nated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls, polychlori- nated diphenyl ethers, polybrominated dibenzo-p-dioxins and dibenzofurans, polybrominated biphenyls and polybrominated diphenyl ethers. After using blends of B2 with 10% and 20% water-containing butanol, the POP emission factors were decreased by amounts in the range of 22.6%−42.3% and 38.0%−65.5% on a mass basis, as well as 18.7%−78.1% and 51.0%−84.9% on a toxicity basis. The addition of water-containing butanol introduced a lower content of aromatic compounds and most importantly, lead to more complete combustion, thus resulting in a great reduction in the POP emissions. Not only did the self-provided oxygen of butanol promote complete oxidation but also the water content in butanol diesel blends could cause a microexplosion mechanism, which provided a better turbulence and well-mixed environment for complete combustion. ■ INTRODUCTION An increasing energy demand and environmental pollution has motivated a search for bio-fuels, such as bio-diesels 1,2 and bio- alcohols, 3,4 that can be used as alternative fuels for diesel engines. In general, both bio-diesel and bio-alcohols, such as ethanol and butanol, have the advantages of higher brake thermal efficiency (BTE) and lower emissions of particulate matter (PM), carbon monoxide (CO) and hydrocarbons (HC). 5−7 However, bio-diesel produces greater amounts of nitrogen oxides (NO x ) emissions than fossil diesel, 6,8 whereas bio-alcohol has a greater potential to decrease NO x output because of its high vaporization heat. 3,9 Butanol is preferable to ethanol for adoption in diesel engines because of its good solubility in diesel, its greater heating value, its higher cetane number and miscibility and its lower vapor pressure. 10−12 However, butanol is produced by the fermentation of biomass and has a high water content, which requires extra energy to dehydrate it for practical use. Furthermore, the energy demand for the dehydration process increases with the purity of the fuel. For example, in the production of bio-ethanol, increasing the purity of ethanol from 95% to 99.9% requires approximately 40% more energy than the total energy demand. 13 Therefore, from the perspective of Received: November 26, 2013 Revised: February 24, 2014 Accepted: April 16, 2014 Published: April 16, 2014 Article pubs.acs.org/est © 2014 American Chemical Society 6010 dx.doi.org/10.1021/es405278w | Environ. Sci. Technol. 2014, 48, 6010−6018