Field trials underway to study sugarcane production for jet fuel

Researchers are investigating the feasibility of growing substantial amounts of “energycane” biomass as a source for jet fuel—a win for farmers, the state’s sustainability goals, and the economy.

By Kiaria Zoi Nakamura.

Jake Rodrique stands next to stand of sugarcane, holding seed cane in one hand and a cutting knife in the other.
Jake Rodrique, academic support specialist at the UH Hilo Agricultural Farm Laboratory, harvests seed cane for study on growing sugarcane for jet fuel. Courtesy photo.
Bruce Mathews
Bruce Mathews

A groundbreaking study investigating the growth of certain cultivars of sugarcane for conversion into high-performance jet fuel is underway at the University of Hawai‘i at Hilo. Utilizing advanced technologies in agronomics and bioeconomy, the researchers are ultimately looking to improve the island’s environmental sustainability, build a stronger economy for and through local farmers, and create educational opportunities for students.

The project is a collaborative one between the UH Hilo College of Agriculture, Forestry, and Natural Resource Management and the Joint BioEnergy Institute (JBEI), one of four U.S. Department of Energy-funded Bioenergy Research Centers based in California.

Bruce Mathews, dean of the Hilo college, where the research is underway, is principal investigator of the project.

“The aviation industry recognizes that bio-based, or sustainable aviation fuels are essential to the future of aviation,” says Mathews. “Fully one-half of the industry’s greenhouse gas reduction goals for 2050 can only be achieved via sustainable jet fuels. Electric airplanes are only feasible for small planes on short-distance flights and the only electric airplane under development that has substantial range is a hybrid that still requires liquid fuel.”

Peter Matlock
Peter Matlock

Working on the project with Mathews is Peter Matlock of JBEI. Matlock is JBEI’s strategic advisor for aviation fuels now also serving as the Hilo college’s bioeconomy research and commercialization specialist. The duality of his roles has proven beneficial for both institutions as the sugarcane research progresses.

The term “biomass” is another way of saying “plant material” and Matlock says that sugarcane was selected as the crop of focus because it is a tremendously prolific biomass producer.

Traditionally, commercial industry has accessed only the sucrose from the plant, which has and continues to serve as a foundation for the world’s sugar industry.

But when growing sugarcane solely for sugar, the rest of the crop, specifically major plant biomass components known as lignian, cellulose, and hemicellulose, normally go to waste. The popular practice of burning sugarcane prior to harvest is to eliminate extra biomass material that previously had no value, and residual biomass left over after sucrose extraction (bagasse) is typically burned to make power. Yet, converting this biomass into high-valued products generates more revenue from the same plant material and eliminates incentives to burn crops—reducing air pollution as a bonus.

“The interesting thing is if we can take the rest of the plant and break it apart, we’d also have yummy digestible bits that can be fed into microbes to make our end products,” Matlock explains, meaning the conversion of sugarcane into biofuel for aviation use. This fermentation process is much more ideal than traditional chemical synthesis, which often involves high heat and high pressure to force a reaction.

“The beauty of biology is that evolution created enzymes, which typically operate at room temperature,” says Matlock. Fermentation takes advantage of these natural, biological processes and lessens reliance on fossil fuels, whose use emits carbon dioxide into the atmosphere. “We get more productivity, much better economics, much better feasibility, and better environmental benefits this way.”

The field trials

Field trials growing different cultivars of sugarcane began earlier this year at the UH Hilo Agricultural Farm Laboratory in Pana‘ewa with support from the U.S. Department of Agriculture’s Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center located in Hilo.

Mathews, an expert in agronomic crop production in the tropics, formulated the project’s methodology for growing. The first test crops were planted at the farm in February, and the current phase of the study includes evaluating two different cultivars at two fertilizer input levels and two harvesting schedules, one-year versus two-year.

Nick Krueger
Nick Krueger

Taking the lead on coordinating the planting of the field trials is Nick Krueger, an instructor of integrated crop livestock systems at UH Hilo. His major responsibilities on the sugarcane study include field implementation and management, and data collection and analysis.

“We have installed both a pot and a field trial to look at how things, such as fertilization regime and harvest interval, affect total yield of energycane,” says Krueger. Energycane is a term used for sugarcane cultivars that are high in fiber and generally low in sugar.

“In addition to total yield, we’ll also be analyzing quality components such as the amounts of various fiber fractions and quality of sugar. This research is exciting because although it may appear to be beating the dead horse of old sugar in Hawai‘i, there are many additional uses for energycane other than raw sugar production.”

Pots of cane seedlings newly sprouted on two racks out in a field.
Pot studies of energycane cultivars are being done at the U.S. Department of Agriculture’s Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center located in Hilo. March 25, 2021. Photo by Bruce Mathews.

Krueger says almost all of the South Pacific relies on imported petroleum products, and this research could help alleviate that issue by identifying a crop that could produce fuel, while also supporting farmers in Hawai‘i. Further, he says, the cultivars of energycane used in the study were developed shortly before the fall of sugar in Hawai‘i, and the best agronomic practices for their most productive growth have not yet been identified.

Jake Rodrique
Jake Rodrique

Assisting with the field work is Jake Rodrique, the farm’s academic support specialist.

The study includes interspecific hybrids of Saccharum officinarum L. and primarily Saccharum spontaneum L. Unlike the two modern commercial cultivars under evaluation in the field study, the researchers are also conducting a pot study of an early 1900s S. officinarum hybrid containing a lower percentage of S. spontaneum genetics and is being compared to the modern cultivars.

There will be no tilling or plowing during the trials, thus minimizing the amount of carbon dioxide emitted into the atmosphere and reducing financial costs. The goal is to minimize subsequent fertilizer applications even with multiple harvests. Researchers also will be measuring carbon storage in the soil. One of the cultivars has a particularly vigorous root system which should help in this regard while also improving nutrient use efficiency parameters under the high rainfall environment.

“The objective is to show that we can grow substantial amounts of cane biomass under these environmentally-friendly conditions with carbon storage in the soil,” explains Matlock. Hopefully, with emerging and future carbon credit markets, this component would help provide additional revenue source for farmers.

Three-tier plan

The initial field trials are the first level of a three-tier plan. The initial stage also involves sharing information gained through the trials via trainings and hands-on demonstrations within the community.

The second level has more to do with educational tourism, a way of attracting students from all over the world to work on such biotech projects taking place exclusively in Hawai‘i. The vision is to attract international students and give them opportunities to build networks amongst Hawai‘i students and themselves that would serve them for the rest of their careers.

The third level, envisioned for the future, deals with actual production in the islands, which Matlock says will involve state policy.

“We know the science is sound and the fundamental assumptions are reasonable,” says Matlock. “This is a good thing to do for the island and the world.”

 

Story by Kiaria Zoi Nakamura, who is earning a bachelor of arts in English with a minor in performing arts and a certificate in educational studies at UH Hilo.

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