Butanol fuel: Wikis

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Butanol may be used as a fuel in an internal combustion engine. Because its longer hydrocarbon chain causes it to be fairly non-polar, it is more similar to gasoline than it is to ethanol. Butanol has been demonstrated to work in vehicles designed for use with gasoline without modification.[1] It can be produced from biomass (as "biobutanol") as well as fossil fuels (as "petrobutanol"); but biobutanol and petrobutanol have the same chemical properties.

Contents

Production of biobutanol

Butanol from biomass is called biobutanol [2]. It can be used in unmodified gasoline engines [3].

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Technologies

Biobutanol can be produced by fermentation of biomass by the A.B.E. process. The process uses the bacterium Clostridium acetobutylicum, also known as the Weizmann organism. It was Chaim Weizmann who first used this bacteria for the production of acetone from starch (with the main use of acetone being the making of Cordite) in 1916. The butanol was a by-product of this fermentation (twice as much butanol was produced). The process also creates a recoverable amount of H2 and a number of other by-products: acetic, lactic and propionic acids, acetone, isopropanol and ethanol.

The difference from ethanol production is primarily in the fermentation of the feedstock and minor changes in distillation. The feedstocks are the same as for ethanol: energy crops such as sugar beets, sugar cane, corn grain, wheat and cassava as well as agricultural byproducts such as straw and corn stalks.[4] According to DuPont, existing bioethanol plants can cost-effectively be retrofitted to biobutanol production.[5]

Algae butanol

Biobutanol can be made entirely with solar energy, from algae (called Solalgal Fuel) or diatoms.[6]

Producers

ButylFuel, LLC used a U.S. Department of Energy Small Business Technology Transfer [7]grant to develop a process aimed at making biobutanol production economically competitive with petrochemical production processes.

DuPont and BP plan to make biobutanol the first product of their joint effort to develop, produce, and market next-generation biofuels. In Europe the Swiss company Butalco[8] is developing genetically modified yeasts for the production of biobutanol from cellulosic materials.

Distribution

Butanol better tolerates water contamination and is less corrosive than ethanol and more suitable for distribution through existing pipelines for gasoline.[5] In blends with diesel or gasoline, butanol is less likely to separate from this fuel than ethanol if the fuel is contaminated with water.[5] There is also a vapor pressure co-blend synergy with butanol and gasoline containing ethanol, which facilitates ethanol blending. This facilitates storage and distribution of blended fuels.[5][9][10]

Properties of common fuels

[citation needed]

Fuel Energy
density
Air-fuel
ratio
Specific
energy
Heat of
vaporization
RON MON
Gasoline and biogasoline 32 MJ/L 14.6 2.9 MJ/kg air 0.36 MJ/kg   91–99   81–89
Butanol fuel 29.2 MJ/L 11.1 3.2 MJ/kg air 0.43 MJ/kg   96   78
Ethanol fuel 19.6 MJ/L   9.0 3.0 MJ/kg air 0.92 MJ/kg 107   89
Methanol 16 MJ/L   6.4 3.1 MJ/kg air 1.2 MJ/kg 106 92

Energy content and effects on fuel economy

Switching a gasoline engine over to butanol would in theory result in a fuel consumption penalty of about 10%[12] but butanol's effect on mileage is yet to be determined by a scientific study. While the energy density for any mixture of gasoline and butanol can be calculated, tests with other alcohol fuels have demonstrated that the effect on fuel economy is not proportional to the change in energy density.[13]

Octane rating

The octane rating of n-butanol is similar to that of gasoline but lower than that of ethanol and methanol. n-Butanol has a RON (Research Octane number) of 96 and a MON (Motor octane number) of 78 while t-butanol has octane ratings of 105 RON and 89 MON.[14] t-Butanol is used as an additive in gasoline but cannot be used as a fuel in its pure form because its relatively high melting point of 25.5 °C causes it to gel and freeze near room temperature.

A fuel with a higher octane rating is less prone to knocking (extremely rapid and spontaneous combustion by compression) and the control system of any modern car engine can take advantage of this by adjusting the ignition timing. This will improve energy efficiency, leading to a better fuel economy than the comparisons of energy content different fuels indicate. By increasing the compression ratio, further gains in fuel economy, power and torque can be achieved. Conversely, a fuel with lower octane rating is more prone to knocking and will lower efficiency. Knocking can also cause engine damage.[15]

Air-fuel ratio

Alcohol fuels, including butanol and ethanol, are partially oxidized and therefore need to run at richer mixtures than gasoline. Standard gasoline engines in cars can adjust the air-fuel ratio to accommodate variations in the fuel, but only within certain limits depending on model. If the limit is exceeded by running the engine on pure butanol or a gasoline blend with a high percentage of butanol, the engine will run lean, something which can critically damage components. Compared to ethanol, butanol can be mixed in higher ratios with gasoline for use in existing cars without the need for retrofit as the air-fuel ratio and energy content are closer to that of gasoline.[9][10]

Specific energy

Alcohol fuels have less energy per unit weight and unit volume than gasoline. To make it possible to compare the net energy released per cycle a measure called the fuels specific energy is sometimes used. It is defined as the energy released per air fuel ratio. The net energy released per cycle is higher for butanol than ethanol or methanol and about 10% higher than for gasoline.[16]

Viscosity

Substance Kinematic
viscosity
at 20°C
Butanol 3.64 cSt
Ethanol 1.52 cSt
Methanol 0.64 cSt
Gasoline 0.4–0.8 cSt
Diesel >3 cSt
Water 1.0 cSt

The viscosity of alcohols increase with longer carbon chains. For this reason, butanol is used as an alternative to shorter alcohols when a more viscous solvent is desired. The kinematic viscosity of butanol is several times higher than that of gasoline and about as viscous as high quality diesel fuel.[17]

Heat of vaporization

The fuel in an engine has to be vaporized before it will burn. Insufficient vaporization is a known problem with alcohol fuels during cold starts in cold weather. As the heat of vaporization of butanol is less than half of that of ethanol, an engine running on butanol should be easier to start in cold weather than one running on ethanol or methanol.[9]

Potential problems with the use of butanol fuel

The potential problems with the use of butanol are similar to those of ethanol:

  • To match the combustion characteristics of gasoline, the utilization of butanol fuel as a substitute for gasoline requires fuel-flow increases (though butanol has only slightly less energy than gasoline, so the fuel-flow increase required is only minimal, maybe 10%, compared to 40% for ethanol.)
  • Alcohol-based fuels are not compatible with some fuel system components.
  • Alcohol fuels may cause erroneous gas gauge readings in vehicles with capacitance fuel level gauging.
  • While ethanol and methanol have lower energy densities than butanol, their higher octane number allows for greater compression ratio and efficiency. Higher combustion engine efficiency allows for lesser greenhouse gas emissions per unit motive energy extracted.

As an advantage, butanol production from biomass could be more efficient (i.e. unit engine motive power delivered per unit solar energy consumed) than ethanol or methanol routes. Also, some bacteria that produce butanol are able to digest cellulose, not just starch and sugars.[18]

Possible butanol fuel mixtures

Standards for the blending of ethanol and methanol in gasoline exist in many countries, including the EU, the US and Brazil. Approximate equivalent butanol blends can be calculated from the relations between the stochiometric fuel-air ratio of butanol, ethanol and gasoline. Common ethanol fuel mixtures for fuel sold as gasoline currently range from 5% to 10%. The share of butanol can be 60% greater than the equivalent ethanol share, which gives a range from 8% to 16%. "Equivalent" in this case refers only to the vehicle's ability to adjust to the fuel. Other properties such as energy density, viscosity and heat of vaporisation will vary and may further limit the percentage of butanol that can be blended with gasoline.[citation needed] Consumer acceptance may be limited due to the offensive smell of butanol.[citation needed]

Current use of butanol in vehicles

Currently no production vehicle is known to be approved by the manufacturer for use with 100% butanol. As of early 2009, only few vehicles are approved for even using E85 fuel (i.e. 85% ethanol + 15% gasoline). BP and Dupont, engaged in a joint venture to produce and promote butanol fuel, claim[19] that "biobutanol can be blended up to 10%v/v in European gasoline and 11.5%v/v in US gasoline". [20]

David Ramey drove from Blacklick, Ohio to San Diego, California using butanol in an unmodified 1992 Buick Park Avenue.[1][21]

In the 2009 Petit Le Mans race, the No. 16 Lola B09/86 - Mazda MZR-R of Dyson Racing ran on a mixture of biobutanol and ethanol developed by team technology partner BP.

Research

The Swiss company Butalco GmbH uses a special technology to modify yeasts in order to produce butanol instead of ethanol. Yeasts as production organisms for butanol have decisive advantages compared to bacteria.[22] The company Gevo in Pasadena, Ca, is developing a biotechnology process to mass-produce iso-butanol from renewable resources [23].

See also

References

  1. ^ a b "ButylFuel, LLC". http://www.butanol.com. Retrieved 2008-01-29. 
  2. ^ Alternative Fuels and Advanced Vehicles Data Center: Biobutanol
  3. ^ http://www.cobaltbiofuels.com/advancing-biofuels/biobutanol/
  4. ^ http://www.ars.usda.gov/research/publications/Publications.htm?seq_no_115=151101
  5. ^ a b c d BP DuPont Fact Sheet Biobutanol (PDF).
  6. ^ Fossil Freedom - Home Page
  7. ^ Small Business Innovation Research
  8. ^ http://www.butalco.com
  9. ^ a b c J.L. Smith; J.P. Workman (December 20, 2007). "Alcohol for Motor Fuels". Colorado State University. http://www.ext.colostate.edu/PUBS/FARMMGT/05010.html. Retrieved 2008-01-29. 
  10. ^ a b Randall Chase (2006-06-23). ""DuPont, BP join to make butanol; they say it outperforms ethanol as a fuel additive"". Associated Press. http://www.usatoday.com/money/industries/energy/2006-06-20-butanol_x.htm?csp=34. Retrieved 2008-01-29. 
  11. ^ Internal Combustion Engines, Edward F. Obert, 1973
  12. ^ Calculated from the difference in energy densities listed above
  13. ^ ACE Fuel Economy Study (PDF).
  14. ^ UNEP.org-Properties of oxygenates (PDF).
  15. ^ "DICTIONARY OF AUTOMOTIVE TERMS - "En" (scroll way down to "engine knock")~~~~". http://www.motorera.com/dictionary/EN.HTM. Retrieved 2008-03-21. 
  16. ^ http://www.oilgae.com/energy/sou/ae/re/be/alc/but/but.html
  17. ^ Engineering Toolbox
  18. ^ http://www.sciencedaily.com/releases/2008/01/080123153142.htm
  19. ^ http://www.bp.com/liveassets/bp_internet/globalbp/STAGING/global_assets/downloads/B/Bio_biobutanol_fact_sheet_jun06.pdf
  20. ^ http://www.google.com/url?sa=t&source=web&ct=res&cd=3&ved=0CA8QFjAC&url=http%3A%2F%2Fwww.bp.com%2Fliveassets%2Fbp_internet%2Fglobalbp%2FSTAGING%2Fglobal_assets%2Fdownloads%2FB%2FBio_bp_dupont_fact_sheet_jun06.pdf&ei=rNcjS4L9FYfYsQP7kujgDg&usg=AFQjCNGWFtTSr2l3tJtMVoSj5IB8YDrfUQ
  21. ^ "Boosting Biomass-to...Butanol?". Green Car Congress. 20 July 2005. http://www.greencarcongress.com/2005/07/boosting_biomas.html. Retrieved 2008-01-29. 
  22. ^ "BUTALCO: Bio-based Innovations". Butalco GmbH. 2007. http://www.butalco.com. Retrieved 2008-01-29. 
  23. ^ "GEVO: Catalysts of Change". Gevo Inc.. 2008. http://www.gevo.com/about.php. Retrieved 2009-05-03. 
  • Continuous two-stage ABE fermentation using Clostridium beijerinckii NRLL B592 operating with a growth rate in the first stage vessel close to its maximal value, J Mol Microbiol Biotechnol. 2000 Jan;2(1):101-5.
  • As Gas Prices Climb, Butanol Research Reaches Exciting Stage
  • The Economics of Acetone-Butanol Fermentation: Theoretical and Market Considerations, J.R. Gapes, J Mol Microbiol Biotechnol. 2000 Jan;2(1):27-32.

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