Current State-of-the-Art

Much of our transportation of goods and people currently relies on fossil fuels and, in 2020, transportation contributed to nearly 30% of greenhouse gas emissions in the United States.¹EPA. (2015). Sources of Greenhouse Gas Emissions [Overviews and Factsheets]. View Publication. Recent actions by the Biden Administration in the U.S. federal government have highlighted the issue and put forth recommendations and commitments towards advancing sustainable aviation fuels.²The White House. (2021). FACT SHEET: Biden Administration Advances the Future of Sustainable Fuels in American Aviation [Press Release]. View Publication.

There are several examples of energy dense molecules produced by engineered microbes that could be used as sustainable biofuels for aviation, marine, or heavy duty transportation, including isoprenoids farnesene or bisabolene,³Liu, C.-L., Tian, T., Alonso-Gutierrez, J., Garabedian, B., Wang, S., Baidoo, E. E. K., Benites, V., Chen, Y., Petzold, C. J., Adams, P. D., Keasling, J. D., Tan, T., & Lee, T. S. (2018). Renewable production of high density jet fuel precursor sesquiterpenes from Escherichia coli. Biotechnology for Biofuels, 11(1), 285. View Publication. isobutene,⁴Van Leeuwen, B. N. M., van der Wulp, A. M., Duijnstee, I., van Maris, A. J. A., & Straathof, A. J. J. (2012). Fermentative production of isobutene. Applied Microbiology and Biotechnology, 93(4), 1377–1387. View Publication. methyl ketones,⁵Goh, E.-B., Baidoo, E. E. K., Keasling, J. D., & Beller, H. R. (2012). Engineering of Bacterial Methyl Ketone Synthesis for Biofuels. Applied and Environmental Microbiology, 78(1), 70–80. View Publication. or polycyclopropanated fuels.⁶Cruz-Morales, P., Yin, K., Landera, A., Cort, J. R., Young, R. P., Kyle, J. E., Bertrand, R., Iavarone, A. T., Acharya, S., Cowan, A., Chen, Y., Gin, J. W., Scown, C. D., Petzold, C. J., Araujo-Barcelos, C., Sundstrom, E., George, A., Liu, Y., Klass, S., … Keasling, J. D. (2022). Biosynthesis of polycyclopropanated high energy biofuels. Joule, 6(7), 1590–1605. View Publication. There have been a few reported successful tests of marine biofuels, but the design of marine engines has limited this expansion.⁷Tanzer, S. E., Posada, J., Geraedts, S., & Ramírez, A. (2019). Lignocellulosic marine biofuel: Technoeconomic and environmental assessment for production in Brazil and Sweden. Journal of Cleaner Production, 239, 117845. View Publication. Tests that have been conducted on lignocellulosic biofuels include a soy biodiesel used by the Great Lakes Environmental Research Laboratory,⁸Great Lakes Environmental Research Laboratory (2017). Lake Michigan Field Station. View Publication. a blended fuel that includes a sugar-based biodiesel provided by Amyris and tested by the US Maritime Administration,⁹Risley, & Saccani. (2013). Renewable Diesel For Marine Application | MARAD. View Publication. and a wood residue-derived biofuel.¹⁰UPM Biofuels. (2016). GoodFuels Marine and Boskalis have successfully tested UPM’s sustainable wood-based biofuel for marine fleet. GoodFuels Marine and Boskalis Have Successfully Tested UPM’s Sustainable Wood-Based Biofuel for Marine Fleet | UPM Biofuels. View Publication.

More research is needed to improve carbon utilization from feedstocks (e.g., sugars, carbon dioxide, organic acids). For example, research should be undertaken to develop engineering biology approaches to more efficiently degrade lignocellulose, to improve carbon utilization and decrease processing time. Engineered ecological succession – creating a microbiome that progresses through different feedstocks – could help capture all available carbon in a system; such a system might include microbes that fix or degrade carbon dioxide or lignocellulose to sugars, combined with microbes that can ferment acids produced into other valuable compounds. Mixotrophic systems that co-consume sugars and gas have been shown to increase the carbon yield,¹¹Jones, S. W., Fast, A. G., Carlson, E. D., Wiedel, C. A., Au, J., Antoniewicz, M. R., Papoutsakis, E. T., & Tracy, B. P. (2016). CO₂ fixation by anaerobic non-photosynthetic mixotrophy for improved carbon conversion. Nature Communications, 7(1), 12800. View Publication. and integrated bioprocesses have been shown to couple CO₂ conversion to acetate with acetate conversion to higher density molecules such as lipids or isoprenoids.¹²Hu, P., Chakraborty, S., Kumar, A., Woolston, B., Liu, H., Emerson, D., & Stephanopoulos, G. (2016). Integrated bioprocess for conversion of gaseous substrates to liquids. Proceedings of the National Academy of Sciences, 113(14), 3773–3778. View Publication.

Making transportation vehicles travel more efficiently is another way to lower emissions from the shipping and transportation sector. This could be achieved in part by reducing dynamic friction on vehicle surfaces. Biomaterials, such as biofilms or biomolecular/cell-free biocoatings, could be used to cover surfaces and reduce friction or shear stress, and even provide a level of protection (efforts are already underway to achieve such technologies, see for example the DARPA Arcadia program). These biomaterials could be developed to contain antimicrobial compounds (e.g., antimicrobial peptides, antibiotics, anti-quorum sensing) to prevent fouling (e.g., barnacles on ships), physically modify surfaces to decrease bacterial attachment sites and prevent bacterial adhesion,¹³Dang, & Lovell. (2015). Microbial Surface Colonization and Biofilm Development in Marine Environments | Microbiology and Molecular Biology Reviews. View Publication. or to degrade bacterial holdfast structures to prevent “primary surface colonizers” from attaching and starting the biofilm formation process.

Breakthrough Capabilities & Milestones

Enable the production of energy-dense biofuels from renewable feedstocks.

Enable the production of bio-coatings and biomaterials to improve transportation efficiency.

Footnotes

1. EPA. (2015). Sources of Greenhouse Gas Emissions [Overviews and Factsheets]. https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions
2. The White House. (2021). FACT SHEET: Biden Administration Advances the Future of Sustainable Fuels in American Aviation [Press Release]. https://www.whitehouse.gov/briefing-room/statements-releases/2021/09/09/fact-sheet-biden-administration-advances-the-future-of-sustainable-fuels-in-american-aviation/
3. Liu, C.-L., Tian, T., Alonso-Gutierrez, J., Garabedian, B., Wang, S., Baidoo, E. E. K., Benites, V., Chen, Y., Petzold, C. J., Adams, P. D., Keasling, J. D., Tan, T., & Lee, T. S. (2018). Renewable production of high density jet fuel precursor sesquiterpenes from Escherichia coli. Biotechnology for Biofuels, 11(1), 285. https://doi.org/10.1186/s13068-018-1272-z
4. Van Leeuwen, B. N. M., van der Wulp, A. M., Duijnstee, I., van Maris, A. J. A., & Straathof, A. J. J. (2012). Fermentative production of isobutene. Applied Microbiology and Biotechnology, 93(4), 1377–1387. https://doi.org/10.1007/s00253-011-3853-7
5. Goh, E.-B., Baidoo, E. E. K., Keasling, J. D., & Beller, H. R. (2012). Engineering of Bacterial Methyl Ketone Synthesis for Biofuels. Applied and Environmental Microbiology, 78(1), 70–80. https://doi.org/10.1128/AEM.06785-11
6. Cruz-Morales, P., Yin, K., Landera, A., Cort, J. R., Young, R. P., Kyle, J. E., Bertrand, R., Iavarone, A. T., Acharya, S., Cowan, A., Chen, Y., Gin, J. W., Scown, C. D., Petzold, C. J., Araujo-Barcelos, C., Sundstrom, E., George, A., Liu, Y., Klass, S., … Keasling, J. D. (2022). Biosynthesis of polycyclopropanated high energy biofuels. Joule, 6(7), 1590–1605. https://doi.org/10.1016/j.joule.2022.05.011
7. Tanzer, S. E., Posada, J., Geraedts, S., & Ramírez, A. (2019). Lignocellulosic marine biofuel: Technoeconomic and environmental assessment for production in Brazil and Sweden. Journal of Cleaner Production, 239, 117845. https://doi.org/10.1016/j.jclepro.2019.117845
8. Great Lakes Environmental Research Laboratory (2017). Lake Michigan Field Station. Retrieved July 26, 2022, from https://www.glerl.noaa.gov/lmfs/index.html#greenShips
9. Risley, & Saccani. (2013). Renewable Diesel For Marine Application | MARAD. https://www.maritime.dot.gov/innovation/meta/renewable-diesel-marine-application
10. UPM Biofuels. (2016). GoodFuels Marine and Boskalis have successfully tested UPM’s sustainable wood-based biofuel for marine fleet. GoodFuels Marine and Boskalis Have Successfully Tested UPM’s Sustainable Wood-Based Biofuel for Marine Fleet | UPM Biofuels. https://www.upmbiofuels.com/whats-new/news/2016/09/goodfuels-marine-and-boskalis-have-successfully-tested-upms-sustainable-wood-based-biofuel-for-marine-fleet/
11. Jones, S. W., Fast, A. G., Carlson, E. D., Wiedel, C. A., Au, J., Antoniewicz, M. R., Papoutsakis, E. T., & Tracy, B. P. (2016). CO₂ fixation by anaerobic non-photosynthetic mixotrophy for improved carbon conversion. Nature Communications, 7(1), 12800. https://doi.org/10.1038/ncomms12800
12. Hu, P., Chakraborty, S., Kumar, A., Woolston, B., Liu, H., Emerson, D., & Stephanopoulos, G. (2016). Integrated bioprocess for conversion of gaseous substrates to liquids. Proceedings of the National Academy of Sciences, 113(14), 3773–3778. https://doi.org/10.1073/pnas.1516867113
13. Dang, H. & Lovell, C.R. (2015). Microbial Surface Colonization and Biofilm Development in Marine Environments | Microbiology and Molecular Biology Reviews. Retrieved August 26, 2022, from https://doi.org/10.1128/MMBR.00037-15