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Biofuels as an alternative to traditional transportation fuels: Chemist's Perspective Ole John Nielsen and Vibeke Friis Andersen Department of Chemistry, University of Copenhagen Copenhagen June 10th 2011
Acknowledgements • Tim Wallington (FORD) • Sherry Mueller (FORD) • Jim Anderson (FORD) • Mads Andersen (NASA) • The CCAR group • $$$: Danish Natural Science Research Council • $$$: Villum Kahn Rasmussen Foundation • $$$: EUROCHAMP2
What features do we desire in a vehicle fuel? • Cheap, either already abundant in nature, or easy to make • Fuel and spent fuel should be easy and safe to handle (i.e., liquid or gas [not solid] over “typical” temperature operation range of -20 to +40 oC and no reaction with air or water under ambient conditions) • For a chemical fuel we need at least two reactants. Inefficient to carry more than one reactant on vehicle/plane, best to use atmosphere as second reactant. Atmosphere is 78% N2, 21% O2, 1% Ar. N2 is poor reactant (N≡ N bond too strong), Ar is unreactive, leaves O2 • Fuel should have highly exothermic reaction with O2 but not at ambient temperature (kinetics and thermochemistry) • High energy density. • Environmentally benign, renewable and the oxide(s) should be benign
Periodic Table Exclude elements that: (i) have solid oxides
Periodic Table Exclude elements that: (i) have solid oxides, (ii) do not have highly exothermic reaction with oxygen
Periodic Table Exclude elements that: (i) have solid oxides, (ii) do not have highly exothermic reaction with oxygen, (iii) have toxic oxides
Periodic Table Conclusion: hydrogen and carbon are likely to be the two most important elements in transportation fuels.
Periodic Table Conclusion: hydrogen and carbon are likely to be the two most important elements in transportation fuels and oxygen will do no harm
Sustainabilty: Economic, Environmental Social sustainability Biofuels address: Energy security Climate Change Support for rural communities 2. Motivation for biofuels - Sustainability Proven oil reserves. Source: BP
3. Biofuel History- Biofuels are not new 1908 – Ford Model T introduced Around 1915 - First Flexible Fuel Model T Vehicle - (low compression engine, adjustable carburetor, and spark advance allowed use of gasoline, ethanol, or blends) Ford’s vision was to “build a vehicle affordable to the working family and powered by a fuel that would boost the rural farm economy.” 1916 -"All the world is waiting for a substitute for petrol. The day is not far distant when, for every one of those barrels of petrol, a barrel of ethanol must be substituted.” – Henry Ford
1970s World energy crisis; Leaded gas phased-out; US subsidies for ethanol blends 1978MTBE became oxygenate of choice; 1980sExcess oil capacity caused drop in crude oil price Vehicle Ethanol: Rise and Fall 1920s Gasoline was motor fuel of choice; 6-12% ethanol added for anti-knock 1920sTetraethyl lead added for anti-knock 1937Ford supported ethanol for fuel. Ethanol blends account for 25% of sales in Midwest 1940sLow-priced, Middle-East oil www.jgi.doe.gov 2000sMTBE phased-out due to environmental concerns; Crude oil price more than doubled (~$30/bbl to $80+/bbl) 2005U.S. oil imports accounted for 70% of consumption, U.S. Energy Policy Act mandated 7.5 billion gallons of renewable fuel use by 2012 2007President Bush announced 35 billion gallons alternative fuel goal (2017). Ethanol production capacity was 10-12 billion gallons by 2010.
Biofuel are many different things first, second and third generation… / butanols
Says 27% in 2050 (a ref – but no ref….) 4. Will biofuels survive this time? • 2005: 0.8 EJ (1% of the total road transportation fuel) • 2010: 2-3% of rtf • 2050: 20 EJ from first generation biofuels (11% rtf)a • 2050: 23 EJ from second generation biofuels (12% rtf)a aOECD-SG/SD/RT(2007)3
Global biomass supply potential converted into biofuel could satisfy approximately 20-30% of projected global transportation energy needs in 2050 360 Mha (Tot land 1.9 Gha) 140 Mha (Tot land 0.3 Gha) 520 Mha (Tot land 2 Gha) 730 Mha (Tot land 1.6 Gha) 1290 Mha (Tot land 3.4 Gha) 620 Mha (Tot land 1 Gha) • Assumptions: • 100 EJ from energy crops (0.5 Gha, 10 t/ha, 20 GJ/t) • 100 EJ from waste material (e.g. straw, sawdust, manure, MSW) 730 Mha (Tot land 2 Gha) 460 Mha (Tot land 0.8 Gha) Global total land ~13 Gha Global arable and pasture land ~4.85 Gha Source: Maria Grahn, Chalmers University (2007)
5. The Atmospheric Chemistry • One example: iso-butanol • Reaction with OH radicals is the most important atmospheric reaction • Determine the OH rate constant and the degradation products V. F. Andersen, T. J. Wallington,O. J. Nielsen: “Atmospheric Chemistry of i-butanol”, J. Phys. Chem. A 114, 12462-12469 (2010)
Experimental TechniquesSmog chamber with FTIR1.Cl2+hν→2Cl2.CH3ONO+hν CH3O + NO CH3O + O2 HCHO + HO2 HO2 + NO OH + NO2
OH radical kinetics • OH + (CH3)2CHCH2OH → products (9) • OH + C3H6 → products (10) • OH + C2H4 → products (11) • Linear least squares analysis gives • k9/k10 = 0.41±0.04 and k9/k11= 1.41±0.10. • Using k10= 2.63 x 10-11 and k11 = 8.52 x 10-12 • gives k9 = (1.08 ± 0.11) x 10-11 and(1.20 ± 0.09) x 10-11 cm3 molecule-1 s-1. • Hence k9 = (1.14±017) x 10-11 • Reaction with OH radicals is the major atmospheric loss process for (CH3)2CHCH2OH • Combined with [OH]=1x106 • Gives lifetime ~ 1 day
OH radical kinetics Oxidation kinetics of i-butanol are well established.
OH radical oxidation products OH radical initiated oxidation gives CH3C(O)CH3 in a molar yield of 61 ±4%. Experimental data are indistinguishable from the result (57%) predicted using structure activity relationships and assumed in atmospheric models.
61% SAR: 4% 57% 37% Results are consistent with model assumptions
Conclusions • Biofuels can address climate change and energy security. • Biofuels not a wonder solution, but could make an important 10-30% contribution to the transportation sector. • Incorporating biofuels into transportation fuels requires adherence to fuel specifications. • Implementing a biofuels strategy requires the consideration of vehicle compatibility for optimal performance • Provide support for rural communities (i.e. social benefit) • Second and “third” generation biofuels needed. • Many ways to make biofuels, good ways and bad ways, encourage the good ways (certification perhaps?) • Modern biofuel science in its infancy – future contribution of biofuels to transportation fuel pool is unclear • Environmental impacts (atm chem) of potential biofuels must be quantified/investigated • Food vs Fuel issues? • Need to address CO2 from all sectors
Transportation biofuels present interesting questions - It’s a great time to be an atmospheric chemist We have a lot to roar about Thank you for your attention
Externalities of biomass growth and biofuel production will be magnified as scale increases. • Many factors must be considered for scale-up of first generation and development of second generation. • Economics • Feedstock price and transport • Processing • Land use changes • Food prices • Natural habitat, biodiversity • Environmental properties (LCA) • Petroleum reduction • Greenhouse gas reduction • Other resources • Properties as fuels
On-road light-duty car and trucks contribute about 20% of US, 17% of EU-15, and 11% of global fossil fuel CO2 emissions. Need to address CO2 in all sectors. T. J. Wallington, J. L. Sullivan, and M. D. Hurley, Emissions of CO2, CO, NOx, HC, PM, HFC-134a, N2O and CH4 from the Global Light Duty Vehicle Fleet, Meteorol. Z., 17, 109 (2008)
Energy content MJ/kg • Gasoline 43.4 • Diesel 42.8 • Methanol 20.1 • Ethanol 27.0 • 1-Butanol 33.1 • Propane 46.3 • Methane 55.6 • DME 28.4 • Hydrogen 121.5 • Biodiesel (FAME) 37.5
140 L Pyrex chamber black-lamps 296 K 1-760 Torr FTIR-detection FTIR SMOG CHAMBERS 100 L Quartz chamber UVA, UVA and sunlamps 245-325 K 1-760 Torr FTIR-detection
UV irradiation of: • compound X/reference/CH3ONO/NO/air • (reference = C2H2 or C2H4) • CH3ONO + hν CH3O + NO • CH3O + O2 HCHO + HO2 • HO2 + NO OH + NO2 • OH + compound X products • OH + reference products
Biodiesel model compound • CH3(CH2)7CH=CH(CH2)7C(O)OCH3 from oleic acid, C15H31C(O)OCH3 from palmitic acid • Energy density • Biodiesel is composed of esters of fatty acids (typically methyl esters) and is made via a relatively simple trans-esterification process from tri-acyl-glycerides. Esters because of cold flow properties. • Prior to the use of such acylated glyercine derivatives, information on their atmospheric chemistry and hence environmental impact is required. • CH3C(O)O(CH2)2OC(O)CH3,ethylene glycol diacetate, as a model compound for such acylated glycerine molecules.
Linear least squares analysis gives k4/k5 = 0.28 ± 0.03 and k4/k6 = 2.8 ± 0.3. Using k5 = 8.7 x 10-12 and k6 = 8.45 x 10-13, we derive k4 = (2.4 ± 0.3) x 10-12 cm3molecule-1s-1. Atmospheric lifetime of approx. 5 days OH + CH3C(O)O(CH2)2OC(O)CH3 → products (4) OH + C2H4 → products (5) OH + C2H2 → products (6)
Closed symbols: 5 Torr O2 Open symbols: 700 Torr O2 CH3C(O)OC(O)H CH3C(O)OH CH3C(O)OC(O)CH2OC(O)CH3 CH3C(O)OH Mechanism?
UV irradiation of: • CH3CH2CHOHCH2CH3/reference/CH3ONO/NO/air • (reference = C2H2 or C2H4) • CH3ONO + hν CH3O + NO • CH3O + O2 HCHO + HO2 • HO2 + NO OH + NO2 • OH + CH3CH2CHOHCH2CH3 products (4) • OH + reference products (5/6)
Previously published value k = (1.2 ± 0.3) × 10‑11 cm3molecule‑1s‑1. Structure activity relationship (SAR) prediction of 1.13 x 10-11 cm3molecule-1s-1 with 90% of the predicted reactivity is on the central carbon atom. No product studies have been reported. OH + CH3CH2CHOHCH2CH3 → products (4) OH + C2H4 → products (5) OH + C3H6 → products (6) Linear least squares analyses give k4/k5 = 1.6 ± 0.05 and k4/k6 = 0.46 ± 0.03 Using k5 = 8.52 x 10-12 and k6 = 2.68 x 10-11, we derive k4 = (1.3 ± 0.1) x 10-11 cm3molecule-1s-1. Gives an atmospheric lifetime for 3-pentanol of around 1 day.
As in the case of OH, a significant fraction of the Cl reactivity is expected to take place at the central C atom: CH3CH2CHOHCH2CH3 + Cl → α(CH3CH2C.OHCH2CH3) + HCl (1) CH3CH2C.OHCH2CH3 + O2 → CH3CH2C(O)CH2CH3 + HO2 (100%) We expect to observe a significant yield of 3-pentanone as one of the products in the reaction of 3-pentanol with Cl atoms in the presence of O2. 3-pentanone also reacts with Cl atoms, kCl=8.1x10-11 cm3molecule-1s-1. The corresponding rate equation can be solved analytically to relate the concentration of 3-pentanone to the conversion of 3-pentanol. The curve through the data is a fit of the expression above to the data which gives α = 42%. There is some fundamentals to be learned!
Biofuel – future • 2005: 0.8 EJ (1% of the total road transportation fuel) • 2050: 20 EJ from first generation biofuels (11% rtf) • 2050: 23 EJ from second generation biofuels (12% rtf)
Biofuel – future • Energy security/availability • US consuming and importing more energy than ever before • Shrinking petroleum reserves • Political unrest in oil-producing regions • High (and unstable) petroleum prices
First-Generation Biofuel: Corn Ethanol 20% of the US corn harvest in 2006 was used to produce ethanol, but that ethanol replaced only 2.4% of gasoline consumption (equivalent to an average blend of E3.6). Second-generation biofuels are needed.
Displacement of substantial fraction of petroleum requires development of second generation biofuels. Biofuels are not likely to replace petroleum entirely, but they could displace 10, 20, or 30% of U.S. gasoline use in next few decades through use of B5, E10, and E85. Biofuels are generally more expensive than fossil fuels. Mandates/subsidies will probably be required.
All biofuels are not created equal Solar energy Use in vehicle Biomass growth Biofuel production Land use changes Food prices Resource use (energy, water, chemicals) Biodiversity Biofuels close the carbon cycle by recycling atmospheric CO2. Degree of closure depends on fuel and process (lifecycle analysis).
Proven oil reserves at end 2004 Source: 2005 BP Energy review
Population Growth to 10 - 11 Billion People in 2050 Per Capita GDP Growth at 1.6% yr-1 Energy consumption per Unit of GDP declines at 1.0% yr -1
Total Primary Power vs Year 2005: 14 TW 2050: 28 TW
Prerequisites The stone age did not end for the lack of stone And the oil age will end long before we run out of oil • Transportation biofuels are going to be around – for what ever reasons • What are transportation biofuels going to be ? -(if you read the papers) Bioethanol and biodiesel ? • But look at what plants are made of ? Biorefinery at College Station, Texas makes mixed alcohols from biomass