By Deepak Kumar
[Deepak Kumar is a post-doctoral research associate in the Department of Agricultural and Biological Engineering.]
U.S. airlines consumed about 18 billion gallons of jet fuel in 2016. Globalization, increased population, and improved international trades have increased air travel, and subsequently energy use in the aviation sector.
Bio-jet fuel derived from oil crops or algae is a promising alternative to fossil jet fuel and considered to produce significantly less greenhouse gas emissions. Hydro-processing technologies to convert plant-derived oil to jet fuel are at an advanced stage of development, and the American Society for Testing and Materials has approved a 50:50 blend of petroleum-based jet fuel and hydro-processed renewable jet fuel use. However, high feedstock cost and challenges of low oil yields per land unit is a major obstacle in the growth of an industry producing biofuel derived from oil crops.
To address this issue, a multi-institutional team, led by University of Illinois researchers, has successfully engineered sugarcane, called lipid-cane, to produce large quantities of oil (up to 20 percent) in stem and leaves. Naturally, sugarcane contains only about 0.05 percent oil. As sugarcane is the most productive crop on the planet, this technology has opened the way to the production of far more industrial vegetable oil per land unit than previously possible.
A process technology to separate sugar and oil from lipid-cane has already been developed and patented by the University of Illinois. To understand the commercial viability of jet fuel production from this engineered sugarcane, we performed a comprehensive techno-economic analysis to establish a capital and operating cost profile of the process at commercial scale. We developed process models for a bio-refinery producing hydro-treated jet fuel (from lipids) and ethanol (from sugars) from lipid-cane, in SuperPro designer. The production cost of jet fuel for 20 percent lipid-cane was estimated at $2.59 per gallon of jet fuel, lower than most other oil crops and algae.
According to our analysis, lipid-cane with 20 percent lipids could produce 1,666 gallons of jet fuel per hectare of land, which is more than 15 times that from using soybean. Other than lower costs and high yields, use of lipid-cane instead of conventional oil crops provides an advantage of energy self-sustainability. The steam and electricity produced from the burning of cane bagasse (fiber left after juice extraction) were found sufficient to fulfill plant requirements. The surplus electricity could be sold back to the grid that displaces fossil electricity and provides environmental benefits.
Along with altering sugarcane metabolism to accumulate lipids, the project team is also trying to develop this crop with increased cold tolerance and high photosynthetic efficiency, which would allow additional biomass production and use of low-value land unsuited to most other crops.
In conclusion, lipid-cane is a promising new feedstock that can be used to produce economically competitive and large quantities of bio jet fuel to replace fossil fuels, enhance the nation’s energy security and reduce environmental impacts.
This project (PETROSS) was funded through the Department of Energy’s Advanced Research Projects Agency-Energy (ARPA‑E).