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Diesel engines are widely employed in both heavy-duty vehicles and generators,due to its high thermal efficiency,high power output and low emissions of regulated pollutants,such as carbon monoxide (CO) and hydrocarbon (HC).However,the International Agency for Research on Cancer (IARC) has classified diesel engine exhaust as carcinogenic to humans (Group 1),and research has shown that there is a significantly increased risk of mortality from lung cancer with increased exposure to diesel exhaust.1 Cleaner and more efficient diesel engines have been developed over the past few decades.For example,the exhaust gas recirculation (EGR) process was developed to reduce NOx emissions.However,due to the trade-off relationship between NOx and PM,the EGR is not effective for simultaneously removing NOx and PM 2,3.Now the focus of pollutant reduction techniques is mainly on cleaner alternative fuels.4 Numerous studies have investigated the emission and energy performance of diesel engines that are fueled with biodiesel5-11.Their findings show that the related particulate matter (PM),carbon monoxide (CO),total hydrocarbons,sulfur dioxide,and polycyclic aromatic hydrocarbon (PAH) emissions are lower than those of regular diesel.In addition,these fuels improved the engine performance.However,many of these studies also indicated that the use of biodiesel and related diesel blends lead to higher NOx emissions,which are strictly controlled by emissions standards in many countries 12-14.Thus,NOx emissions are a critical barrier for the adoption of biodiesel.Alcohol additives,such as ethanol and butanol can reduce NOx formation,while reducing PM and CO emissions and improving energy performance.These types of alcohol could be produced by fermenting biomass feedstocks; however,high water content in the fermentation products make it difficult to use without dehydration.The removal of water during product fermentation will require additional energy and increase production costs.Recently,several studies have reported that water-containing alcohol-diesel blends improve the energy efficiency of diesel engines and reduce pollutant emissions (NOx,PM,Total-PAHs and Total-BaPeq) 8,15,16.The addition of water-containing alcohol-diesel blends is beneficial in terms of saving energy and reducing pollution.The high oxygen concentrations of the alcohol-diesel blends could result in more complete combustion,which would increase energy efficiency and lower PM,CO and PAH emissions.In addition,the oxygenated additives and the small amount of water could result in a cooling effect that reduces the combustion temperature.This process would also reduce the NOx emissions.However,previous studies have only considered individual oxygenated fuels rather than the typical compounds that are produced from the biomass feedstock fermentation process.These compounds include acetone,butanol and ethanol at volume percentages of approximately 22-33,62-74 and 1-6%,respectively17-19.Here,a water-containing acetone-butanol-ethanol (ABE) solution,which simulates products that are produced from biomass fermentation without dehydration processing,was investigated as a biodiesel-diesel blend additive to lower NOx emissions from diesel engines.Although biodiesel had a greater NOx emission,the blends that contained 25% of the water containing ABE solution had significantly lower NOx (4.30-30.7 %),PM (10.9-63.1 %),and PAH emissions (26.7-67.6 %) than the biodiesel-diesel blends and regular diesel,respectively.In addition,the thermal energy efficiency of this new blend was 0.372-7.88 % higher with respect to both the biodiesel-diesel blends and regular diesel.Because dehydration and surfactant additions are not necessary,the application of water containing ABE-biodiesel-diesel blends can simplify fuel production processes,reduce energy consumption,and lower pollutant emissions.Thus,the water containing ABE-biodiesel-diesel blend is a highly potential green fuel in the future.