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Synthetic Fuels

There are several pathways for producing hydrocarbon fuels from non-petroleum sources, such as electricity. However, we find that electrofuels, or synthetic fuels from electricity, are cost prohibitive at this time.

Environmental Impacts of Synfuel

The following compares greenhouse gas emissions from several methods of producing complex hydrocarbons.

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Sources: Lattanzio 1, Steele et al. 2, Tu et al. 3, EPA 4. Electrofuels, also known as power-to-fuel, are hydrocarbons that are produced from electrolyzed hydrogen. For these, the emissions intensity of electricity is taken from Schlömer et al. 5 and a conversion efficiency of 40-50% is applied, as estimated by Malins 6. No emissions other than those from electricity are assumed, though additional emissions should be attributed if the CO₂ source is from a flue gas and would otherwise be sequestered 6. Carbon capture and sequestration might also reduce emissions from coal- and gas-to-liquids 7.

Despite the low efficiency of electrofuel production, corn ethanol requires far more land per unit energy.

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The land use estimate of algal biodiesel is estimated from Atabani et al. 8. Yeh et al. 9 report land use from oil production. Data from Building Energy Codes Program 10 is used to estimate the primary energy behind electricity, Malins 6 gives the conversion efficiency, and Ong et al. 11 give the land use of solar power. Efficiency on gas-to-liquids is from Steynberg and Dry 12, and for coal-to-liquids from Höök and Aleklett 13. Additional land use estimates are taken from General Electric 14, Stevens et al. 15, World Energy Council 16.

Environmental Impacts of Synthetic Gas

Following are estimates of the greenhouse gas impacts of three methane production pathways.

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Biomethane and natural gas are reported by the Union of Concerned Scientists 17, and electromethane, or methane produced from electrolyzed hydrogen, from Malins 6. Electromethane reduces emissions relative to natural gas only if the electricity comes from a low carbon source.

About two megajoules of electricity are needed to create one megajoule of electromethane 6.

The environmental benefits of biomethane are greatest when captured methane, a potent greenhouse gas, is prevented from being released into the atmosphere.

Energy Requirements

As an energy carrier, liquid fuels require more primary energy input to produce than energy they contain. The conversion efficiency of primary energy into usable fuel varies by production method.

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Sources: Höök and Aleklett 13 for coal-to-liquids and Steynberg and Dry 12 for gas-to-liquids. The low efficiency of electrofuels stem from two conversion processes: from a primary energy source into electricity, with efficiency about 32% (Building Energy Codes Program 10); and then from electricity into hydrocarbons, with efficiency 40-50% (Malins 6).

In cars, electrofuels are a less efficient use of electricity than hydrogen and much less efficient than direct use in an electric vehicle.

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Source: Malins 6. The low efficiency of electrofuels stems from additional losses from the internal combustion engine, which has an efficiency of about 30% in modern cars (fueleconomy.gov 18).

Economics of Synthetic Fuels

With the exception of sugarcane ethanol, most alternatives to petroleum-based gasoline are more expensive and not widely used without policy support.

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Sources: Biofuels and Emerging Technologies Team 19 for gas-to-liquids, Brynolf et al. 20 for electrofuels, Mantripragada and Rubin 21 for coal-to-liquids, Moyo et al. 22 for biofuels, and the EIA 23 for wholesale gasoline as of June 2019. Electrofuels are especially expensive due to energy losses in the production processes. Prices are highly dependent on the price of feedstock.

The conversion of coal and natural gas into liquid fuels carry heavy greenhouse gas and other environmental costs, and they are not likely to ever be economically attractive options 24, 25. Aside from sugarcane, biofuels are also unlikely to be economically sound, and they carry major land use impacts. Electrofuels can be an acceptable option only with a low-cost and low-impact electricity source, and even then their use is likely to be confined to sectors that are difficult to electrify directly, such as aviation and long-distance trucking 6.

Carbon abatement costs of electrofuels are as follows.

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Cost of synthetic fuels, with a carbon cost of $50/ton, and estimated carbon abatement cost. A plant size of 50,000 barrels per day is assumed, as per the Industrial Environmental Research Laboratory 26.

With such high carbon abatement costs, it does not make sense for a private developer to build a synfuel plant.

Problem:
Emissions From Aviation
Solution:
Electrofuels for Aviation

Syngas Economics

Due to the current low price of natural gas in the United States, alternative methods of producing methane are not cost competitive.

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Price of methane from several pathways. Sources: Jalalzadeh-Azar 27 for biomethane, Malins 6 for electromethane, and Nasdaq 28 for natural gas as of September 2019.

Following are estimates of the cost and the cost of carbon abatement for two types of synthetic methane plants in the United States. Due to the low price of natural gas, the economics of such plants are very challenging.

The image: "methane_cost.svg" cannot be found!

Cost of biomethane and electromethane plants relative to natural gas and cost of carbon abatement. These calculations are based on a plant that produces 54 billion cubic feet of natural gas each year, as does the Great Plains Synfuels Plant 29.

Biomethane

Biomethane is produced primarily from waste products: wastewater, landfills, manure, and other organic wastes; additional production would be possible from dedicated crops but would be more expensive. World potential is estimated as follows.

The image: "biomethane_potential.svg" cannot be found!

Biomethane production potential, compared to world natural gas. Source: IEA 30, with total natural gas production from BP 31.

From waste products, the biomethane potential in the United States is almost 8 million tons per year 32, less than 1% of total natural gas production 33.

Problem:
Global Warming From Methane
Solution:
Methane Capture From Waste

Coal-to-Gas

There is a single coal-to-gas plant, the Great Plains Synfuels Plant, operating in the United States. In addition to synthetic natural gas, the plant produces CO₂ for enhanced oil recovery and gas-derived products. Although the plant operates profitably, another probably would not be built due to the low cost of natural gas 29.

In East Asia, where natural gas is more expensive, gasifiers are of increasing popularity. Coal is most common syngas feedstock, comprising about half of the world's 70 gigawatts (thermal) of syngas capacity as of 2010 34.

Methane as Shipping Fuel

Liquified natural gas (LNG) comprises a small but growing share of the shipping fuel market 35. LNG eliminates most SOx, NOx, and particulate pollution relative to diesel fuels 36, but it may have higher life cycle greenhouse gas emissions.

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LNG has higher lifecycle greenhouse gas emissions, or at best slightly lower emissions, than more common diesel fuels when methane leakage is taken into account. The standard scenario assumes a leakage rate of 1.4%, and the high leakage scenario assumes a rate of 2.3%. Several other studies give somewhat lower emissions for LNG but do not take leakage into account or do so to a smaller degree 37. Source: 38.

References

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  2. Steele, P., Puettmann, M., Penmetsa, V., Cooper, J. "Life-Cycle Assessment of Pyrolysis Bio-Oil Production". Forest Products Journal 62(4), pp. 326-334. 2012. ↩

  3. Tu, Q., Eckelman, M., Zimmerman, J. "Harmonized algal biofuel life cycle assessment studies enable direct process train comparison". Applied Energy 224, pp. 494-509. August 2018. ↩

  4. U.S. Environmental Protection Agency. "Lifecycle Greenhouse Gas Results". Accessed June 11, 2019. ↩

  5. Schlömer S., T. Bruckner, L. Fulton, E. Hertwich, A. McKinnon, D. Perczyk, J. Roy, R. Schaeffer, R. Sims, P. Smith, and R. Wiser. Annex III: Technology-specific cost and performance parameters. In Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C. Minx (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 2014. ↩

  6. Malins, C. "What role for electromethane and electroammonia technologies in European transport’s low carbon future?". Cerulogy, Addendum to What role for electrofuel technologies in European transport’s low carbon future?. June 2018. ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9

  7. Jaramillo, P., Griffin, M., Matthews, S. "Comparative Analysis of the Production Costs and Life-Cycle GHG Emissions of FT Liquid Fuels from Coal and Natural Gas". Environmental Science & Technology 42(20), pp. 7559-7565. 2008. ↩

  8. Atabani, A., Silitonga, A., Badruddin, I., Mahlia, T., Masjuki, H., Mekhilef, H. "A comprehensive review on biodiesel as an alternative energy resource and its characteristic". Renewable and Sustainable Energy Reviews 16(4), pp. 2070-2093. May 2012. ↩

  9. Yeh, S., Jordaan, S., Brandt, A., Turetsky, M., Spatari, S., Keith, D. "Land Use Greenhouse Gas Emissions from Conventional Oil Production and Oil Sands". Environmental Science & Technology 44(22), pp. 8766-8772. October 2010. ↩

  10. Building Energy Codes Program. "Prototype Building Models High-rise Apartment". Building Technologies Office, Office of Energy Efficiency and Renewable Energy, U. S. Department of Energy. April 2011. ↩ ↩2

  11. Ong, S., Campbell, C., Denholm, P., Margolis R., Heath, G. "Land-Use Requirements for Solar Power Plants in the United States". June 2013. ↩

  12. Steynberg, A., Dry, M. Fischer-Tropsch Technology. Elsevier Science, Volume 152, 1st Edition, Hardcover ISBN: 9780444513540, eBook ISBN: 9780080472799. October 2004. ↩ ↩2

  13. Höök, M., Aleklett, K. "A review on coal to liquid fuels and its coal consumption". International Journal of Energy Research 34(10), pp. 848-864. October 2010. ↩ ↩2

  14. General Electric. "GE Global Power Plant Efficiency Analysis". Accessed June 22, 2019. ↩

  15. Stevens, L., Anderson, B., Cowan, C., Colton, K., Johnson, D. "The Footprint of Energy: Land Use of U.S. Electricity Production". Strata. June 2017. ↩

  16. World Energy Council. "Energy Efficiency Indicators". Accessed June 22, 2019. ↩

  17. Union of Concerned Scientists. "The Promises and Limits of Biomethane as a Transportation Fuel (2017)". 2017. ↩

  18. fueleconomy.gov. "Where the Energy Goes: Gasoline Vehicles". Office of Energy Efficiency and Renewable Energy, U.S. Environmental Protection Agency. Accessed September 3, 2019. ↩

  19. Biofuels and Emerging Technologies Team. "Gas-To-Liquid (GTL) Technology Assessment in support of AEO2013". Energy Information Administration, U.S. Department of Energy. January 2013. ↩

  20. Brynolf, S., Taljegard, M., Grahn, M,. Hansson, J. "Electrofuels for the transport sector: A review of production costs". Renewable and Sustainable Energy Systems 81(2), pp. 1887-1905. January 2018. ↩

  21. Mantripragada, H., Rubin, E. "Performance, cost and emissions of coal-to-liquids (CTLs) plants using low-quality coals under carbon constraints". Fuel 103, pp. 805-813. October 2012. ↩

  22. Moyo, P., Moyo, M., Dube, D., Rusinga, O. "Biofuel Policy as a Key Driver for Sustainable Development in the Biofuel Sector: The Missing Ingredient in Zimbabwe’s Biofuel Pursuit". Modern Applied Science 8(1), pp. 36-58. December 2013. ↩

  23. U.S. Energy Information Administration. "Daily Prices". Accessed June 29, 2019. ↩

  24. Höök, M., Fantazzini, D., Angelantoni, A., Snowden, S. "Hydrocarbon liquefaction: viability as a peak oil mitigation strategy". Philosophical Transactions. Series A: Mathematical, physical, and engineering science, 372(2006). January 2014. ↩

  25. Ramberg, D., Chen, Y., Paltsev, S., Parsons, J. "The economic viability of gas-to-liquids technology and the crude oil–natural gas price relationship". Energy Economics 63, pp. 13-21. March 2017. ↩

  26. Industrial Environmental Research Laboratory. "Environmental Aspects of Synfuel Utilization". March 1981. ↩

  27. Jalalzadeh-Azar, A. "A Technoeconomic Analysis of Biomethane Production from Biogas and Pipeline Delivery". National Renewable Energy Laboratory, Renewable Resources for Fuel Cells Workshop San Antonio, TX. October 2010. ↩

  28. Nasdaq. "NG:NMX Natural Gas". Accessed September 13, 2019. ↩

  29. National Energy Technologies Lab. "Great Plains Synfuel Plant". U.S. Department of Energy. Accessed December 11, 2020. ↩ ↩2

  30. International Energy Agency. "Outlook for biogas and biomethane: Prospects for organic growth". March 2020. ↩

  31. BP. "Statistical Review of World Energy 2019". 2019. ↩

  32. National Renewable Energy Laboratory. "Biogas Potential in the United States". October 2013. ↩

  33. U.S. Energy Informatin Administration. "The U.S. leads global petroleum and natural gas production with record growth in 2018". August 2019. ↩

  34. Floridi, D., Libera, D., Pallone, L. "Gasification & biofuels: circular economy in Milan waste collection system". Energy and Emissions in Transportation Systems. December 2022. ↩

  35. DNV GL. "Energy Transition Outlook 2019: Maritime Forecast to 2050". September 2019. ↩

  36. Sphera. "Life Cycle GHG Emission Study on the Use of LNG as Marine Fuel". January 2020. ↩

  37. Lindstad, E., Rialland, A. "LNG and Cruise Ships, an Easy Way to Fulfil Regulations—Versus the Need for Reducing GHG Emissions". Sustainability 12(5). March 2020. ↩

  38. Pavlenko, N., Comer, B., Zhou, Y., Clark, N., Rutherford, D. "The climate implications of using LNG as a marine fuel". International Council on Clean Transportation, Working Paper 2020-02. January 2020. ↩