How Hemp Processing is Becoming More Efficient
July 31, 2020 
Traditional hempcrete made with untreated hemp hurds (left). Experimental hempcrete, made with CELF-treated hemp fibers (center) and agitated CELF-treated fibers (right). Photo: Charles Cai
Growers in states that have legalized recreational or medical cannabis are facing at least at least one key challenge: More than 90% of what they grow is considered refuse or plant waste, for which disposal is expensive. This dual situation has created a burgeoning industry to explore new methods for using the whole hemp plant and more sustainable ways to extract value from its stalk and hurd, the woody inner part of the stalk.
Charles Cai, a Research Engineer and Adjunct Professor at University of California, Riverside’s College of Engineering Center for Environmental Research and Technology, has developed and patented an improved pulping method that uses a naturally derived solvent, creates no toxic waste, emits no carbon dioxide, and converts nearly 100% of the hemp plant into usable components, such as cellulose fiber for use in textiles and construction, resinous lignin for use in bioplastics, sugars for use as sweeteners, and extractives for use in wellness products.
The method, called Co-solvent Enhanced Lignocellulosic Fractionation, or CELF, uses a renewable and highly recyclable solvent to perform pulping under mild conditions, saving process energy while generating zero harmful emissions. The only waste is a small amount of mineral ash that is filtered out of the process and can be used as a soil amendment. CELF was originally conceived to help convert plant waste into biofuels. However, its effectiveness at deconstructing plant matter makes it a Swiss Army knife for all plant processing. Its scientific merit was recently proven by one of the world’s fastest supercomputers.
Now, Cai is working with a team of undergraduate students to commercialize the hemp-processing technology through funding from the EPA’s People, Prosperity and the Planet Program, or EPA P3. Last year, the team demonstrated proof of concept for using the CELF pulping method, using it to make an improved type of hempcrete, a concrete-like, carbon sequestering building material made from hemp fibers.
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