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Hemp has thousands of uses, many of which proponents believe have long-lasting environmental benefits. Harnessing hemp to make biofuels is one such path toward a greener future, though growers interested in entering this space might have to wait a little while longer.
“There’s not a market right now," says Dr. Robert Pearce, Ph.D., who’s leading a University of Kentucky (UK) study on hemp cultivars as a potential catalyst for biofuel and other bioproducts. “Right now it’s more of a research question as to how efficient we can be in the process.”
In a process called cellulolysis, harvested hemp plant material is shredded and chemically heated to release cellulose, Pearce says. Enzymes are used to break the cellulose into sugars, which in turn are fermented into ethanol. Finally, the ethanol is purified and distilled into viable biofuel products like biodiesel, which could be utilized to fuel an engine or even a biomass power plant.
Robert Pearce speaking at a UK Hemp Field Day event
Hempseed, fiber, leaves and any other above-ground part of the plant have potential to be sources of biofuel, according to UK and University of Connecticut (UConn) researchers. But to capitalize on this, North American hemp growers would benefit from a national biofuel-creation push that includes new regional infrastructure and an embrace of innovative technologies, say industry observers interviewed by Hemp Grower.
Pearce, extension professor in the College of Agriculture, Food and Environment at UK, says having a biofuel ecosystem in place would be an enormous step forward for farmers seeking entry into the marketplace.
“You need that infrastructure in place, because you’re dealing with bulky biomass material,” Pearce says. “Transportation is going to eat farmers up if they have to bring that material very far. We need regional centers where farms have a short distance to go for processing.”
In a lab setting, at least, hemp biofuel has shown promise: A decade ago, researchers at UConn found that industrial hempseeds can be used to create a sustainable diesel fuel.
Comprised primarily of hempseed oil, hemp biodiesel could theoretically power any conventional diesel engine. In the UConn study, 97% of the hemp oil was converted to biodiesel, proving it has “high efficiency of conversion,” according to UConn.
At UK, scientists recently studied dual-purpose cultivars with the best biofuel potential based on hempseed oil and fiber profiles. The cultivars included six that produced fiber only and five that generated both fiber and grain. Dual-purpose cultivars are thought to have higher projected economic returns than the fiber-only cultivars, with Bialobrzeskie from Poland and Colorado’s NWG 331—both dual-purpose—deemed the top-performing varieties for biofuel.
Dr. Jian Shi, Ph.D., an assistant professor in the Department of Biosystems and Agricultural Engineering at UK who is another leader on the study with Pearce, says Bialobrzeskie had estimated returns from grain sales and biofuel production of $1,564 per hectare. Meanwhile, NWG 331 had projected returns of $1,482 per hectare, along with the highest biomass yield and second highest grain yield of all cultivars.
In a previous study, Shi’s team learned that, for a given amount of biomass, hemp has biofuel-producing
Jian Shi in his lab at UK
potential comparable to other bioenergy crops such as kenaf, switchgrass and sorghum. Where the plant shines is in its higher yield per hectare—agronomy data suggest the per-hectare yield of hemp stems alone is at the same level as entire switchgrass and sorghum crops.
“For growers, hemp can be more profitable [than other bioenergy crops] because you have both the fiber and grain,” says Shi. “The fiber can also be used to make paper, clothing, building materials and more.”
Beyond hempseed oil, the plant has potential to produce ethanol and methanol, both forms of alcohol that can be used as fuel. Cellulolysis ferments and distills hemp biomass to extract ethanol. Methanol is generally produced from woody plant matter through the process of dry distillation.
The majority of biofuel currently comes from corn or sugarcane. Although their high sugar content is a robust source of ethanol, utilizing these plants for fuel production can cut into a farm’s food manufacturing profits, says Pearce. Conversely, the leaves and cellulose fibers from hemp are not valuable food sources.