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Diesel engines for additized ethanol

One option to use ethanol is the compression ignition engine. The properties of ethanol resemble gasoline, not diesel fuel and if ethanol is going to be used in compression ignition engine, either the engine or the fuel has to be modified, the latter option requiring fuel additives. Ethanol differs significantly from conventional diesel fuel regarding cetane number, heating value, self-ignition temperature, vaporization characteristics, and boiling point. Cetane number of neat ethanol is less than 12, whereas today the requirement for diesel in Europe is higher than or equal to 51 (ethanolproperties). Neat ethanol as such will not ignite in conventional diesel engine. Also the lubricity of ethanol is unacceptable for high-pressure injection pumps in diesel engines. The low boiling point of ethanol increases the risk of cavitation, and the high conductivity the risk of corrosion (Peckham 2001, McCormick 2001). 

Ethanol engines

In the past Detroit Diesel manufactured glow-plug equipped heavy-duty engines for using methanol or ethanol. However, many problems like engine wear, and glow-plug failures and excessive fuel consumption were encountered. Thus the production of these engines was discontinued. In Sweden another approach was selected: adding ignition improver and lubricity additive to ethanol to enable the usage of the conventional diesel combustion process. In some cities in Sweden buses manufactured by Scania run on additive treated ethanol. The first ethanol bus started service in 1985, and in 2000 there were 407 buses running in Sweden. Now more than 600 buses have been supplied by Scania. Today ethanol buses are running also in other countries, for example, in Mexico, Australia, and Denmark. 

The modifications of diesel engines for ethanol-use include e.g. increased compression ratio, a special fuel injection system and a special catalyst to control aldehyde emissions. Scania's current 3rd generation ethanol engine is an adaptation of Scania's latest 9-litre diesel engine with air-to-air charge cooling and exhaust gas recirculation, EGR. The ethanol version features, among other things, elevated compression ratio (28:1) to facilitate ignition, higher fuel delivery to compensate lower energy density of the fuel, and special materials for the fuel system. The engine is available with Euro V and EEV emission certification (Scania 2007, Nylund 2011). 

Etamax D fuel

The fuel used in ethanol buses in Sweden is called Etamax D. It contains 92 % m/m of hydrated ethanol (grade 95%), 5.0 % m/m ignition improver (poly-ethylene-glycol derivative from Akzo Nobel, Beraid 3540), 2.8 % m/m denaturants (2.3 % m/m MTBE and 0.5% m/m isobutanol) and corrosion inhibitor additive. Etamx DTM fuel contains 6.4 % m/m water. (SEKAB brochure, Westman 2008). In Sweden, standard SS 15 54 37 is specification for alcohols for high-speed diesel engines (Table 1). The standard does not include denaturants, ignition improvers or colorants.

Table 1. Selected properties of SEKAB's specification for Etamax DTM and Swedish SS 15 54 37 standard for ethanol used in high-speed diesel engines. Complete requirements are available from respective organizations.

Exhaust emissions

Earlier generations of Scania's ethanol buses showed exhaust emissions similar to advanced diesel buses equipped with an oxidation catalyst or particle filters, but higher emissions than those of sophisticated CNG buses (NOx). The smoke emission from ethanol buses was almost negligible (likewise buses on gaseous fuels). Acetaldehyde emissions were high for ethanol buses, but the cancer risk index low (similar EPA factors used as for E85). (Ahlvik 2001). 

Nylund et al. (2011) reported of tests with Scania's new generation ethanol vehicles: two trucks and one bus; all with the 8.9-litre 270 hp ethanol engine. As reference, three diesel trucks (Euro V), three diesel buses and two CNG buses (stoichiometric and lean-burn) were tested. In general, NOx emissions from ethanol vehicles were average, but PM emissions lower (buses) or significantly lower (trucks) compared to diesel vehicles without particulate filters (even 75% reduction in PM). The stoichiometric CNG bus showed lowest, whereas the lean-burn CNG bus the highest NOx values. PM emissions were higher for ethanol than for CNG average (Figure 1). Energy consumption of the ethanol bus was some 8% higher, and for ethanol trucks marginally lower, than the average diesel. It was noticeable that for the CNG buses energy increase was close to 40%, respectively. The conclusions seems to be quite similar with the new and older generation of ethanol vehicles: exhaust emissions from ethanol vehicles are close to clean diesel vehicles equipped with NOx and PM reducing technologies, whereas the sophisticated stoichiometric CNG vehicles are the cleanest. 

Figure 1. NOx vs. PM emissions for buses. The results with ethanol bus is marked with red star. (Nylund et al. 2011).


Aakko, P. and Nylund, N.-O. (2003) Particle emissions at moderate and cold temperatures using different fuels. Warrendale: Society of Automotive Engineers. SAE Paper 2003-01-3285.

Aakko-Saksa, P., Rantanen-Kolehmainen, L., Koponen, P., Engman, A. and Kihlman, J. (2011) Biogasoline options – Possibilities for achieving high bio-share and compatibility with conventional cars. SAE International Journal of Fuels and Lubricants, 4:298–317 (also SAE Technical Paper 2011 24-0111). Full technical report: http://www.vtt.fi/inf/pdf/workingpapers/2011/W187.pdf

Ahlvik, P. (2001) Swedish Experiences from Low-Emission City Buses: Impact on Health and Environment. DEER´01, August 5-9, 2001. 

Chiba, F., Ichinose, H., Morita, K., Yoshioka, M., Noguchi, Y. and Tsugagoshi, T. High Concentration Ethanol Effect on SI Engine Emissions (2010) SAE Technical Paper 2010-01-1268.

CRFA (2003) Canadian Renewable Fuels Association Website. http://www.greenfuels.org.

De Serves, C. (2005) Emissions from Flexible Fuel Vehicles with different ethanol blends. AVL MTC AB, Sweden. Report No AVL MTC 5509. Online http://www.senternovem.nl/mmfiles/Emissions%20from%20flexible%20fuel%20vehicles_tcm24 280163.pdf

E85 Handbook (2010) Handbook for Handling, Storing, and Dispensing E85. US Department of Energy. DOE/GO-102010-3073. 

Graham, L., Belisle, S. and Baas, C.-L. (2008) Emissions from light duty gasoline vehicles oper-ating on low blend ethanol gasoline and E85. Atmospheric Environment 42(2008) 4498–4516.

Haskew, H. and Liberty, T. (2006) Fuel permeation from automotive systems: E0, E6, E10, E20 and E85. Final report. CRC Project No. E-65-3.

Jacobson, M. (2007) Effects of Ethanol (E85) versus Gasoline Vehicles on Cancer and Mortality in the United States. Environ. Sci. Technol. 2007, 41, 4150–4157.

Karlsson, H., Gåste, J. and Åsman, P. (2008) Regulated and non-regulated emissions from Euro 4 alternative fuel vehicles. Society of Automotive Engineers. Warrendale. Tech-nical Paper 2008-01-1770.

Kassel, R. (2006) An Environmental Perspective: EPA’s RFS Proposal. Presentation in the meet-ing of Mobile Sources Technical Review Subcommittee (MSTRS), October 4, 2006.

Larsen, U., Johansen, T. and Schramm, J. (2009) Ethanol as a fuel for road transportation. IEA Advanced Motor Fuels Agreement. Annex XXXV. http://virtual.vtt.fi/virtual/amf/pdf/annex35report_final.pdf

McCormick, R.L. and Parish, R. (2001) Technical Barriers to the Use of Ethanol in Diesel Fuel. National Renewable Energy Laboratory. Colorado 2001 (report NREL/MP-540-32674). 

Nylund, N.-O., Laurikko, J., Laine, P., Suominen, J., Anttonen, M. P. (2011) Benchmarking HD Ethanol Vehicles Against Diesel and CNG Vehicles. XIX International Symposium on Alcohol Fuels ISAF, Verona, Italy. October 10th - 14th, 2011.

Peckham, J. (editorial) (2001) Ethanol-diesel raises safety, performance, health concerns: Autos. Diesel Fuel News, 12 November 2001 (11/2001). p. 9–10. 

Petterson, L. (1994) Alcohol Fuels for Internal Combustion Engines. Dissertation. Kungliga Tekniska Högskolan. Stockholm, Sweden. 

Scania (2007) Scania continues renewable fuel drive. New highly efficient diesel-ethanol engine - ready to cut fossil CO2 emissions by 90%. Press info 21.5.2007.

Stahl, W. and Stevens, R. (1992) Fuel-alcohol permeation rates of fluoroelastomers fluoroplastics, and other fuel resistant materials. SAE Technical Paper 920163. Referred to in Kassel (2006) An Environmental Perspective: EPA’s RFS Proposal.

Westerholm, R., Ahlvik, P. and Karlsson, H.L. (2008) An exhaust characterization study based on regulated and unregulated tailpipe and evaporative emissions from bi-fuel and flexi-fuel light-duty passenger cars fuelled by petrol (E5), bioethanol (E70, E85) and biogas tested at ambient temperatures of +22 °C and 7 °C. Final Report to the Swedish Road Administration, March 2008.

Westman, B. (2008) Ethanol fuel in diesel engines for energy efficiency. BAFF – Bioalcohol fuel foundation. Conference on sustainable ethanol. Gothenburg, Sweden. 26 May 2008.

West, B., López, A., Theiss, T., Graves, R., Storey, J. and Lewis, S. (2007) Fuel economy and emissions of the ethanol-optimized Saab 9-5 biopower. SAE Technical Paper 2007-01-3994.

Yanowitz, J. and McCormic, R. (2009) Effect of E85 on tailpipe emissions from light-duty vehicles. J. Air & Waste Manage. Assoc. 59(2009)172–182.