Researchers at the University of California, Riverside, have been awarded more than 12,000 dollars to study a new way to process hemp for hempcrete. Hempcrete is a bio-composite made of the inner woody core of the hemp plant mixed with a lime-based binder. The hemp core or "Shiv" has a high silica content which allows it to bind well with lime. This property is unique to hemp among all natural fibers. The result is a lightweight cementitious insulating material weighing about a seventh or an eighth of the weight of concrete.
The students will experiment with a cleaner way to process hemp fibers to create pulp. Hemp is a promising, sustainable building material, but producing hemp pulp for hempcrete can leave behind some nasty pollutants. The most common way to produce industrial fibers from hemp-the Kraft pulping process-leaves behind roughly seven tons of runoff called "black liquor" for every one ton of usable pulp. Black liquor is a term from paper processing and refers to a stew of lignin residues, organic sulfides and other chemicals.
Charles Cai, an adjunct professor for chemical and environmental engineering and assistant research engineer at the Center for Environmental Research and Technology, is leading his team of chemical and environmental engineering students in finding a new way to process hemp for construction material. The California students want to try a one-step process to separate lignin from plant biomass at low temperatures, "to allow for much cleaner and faster pulping of hemp fibers without the production of black liquor."
"Our project goal is to produce hempcrete as a lighter, stronger and more environmentally friendly alternative to conventional fossil-based concrete. The students are trying out different compositions and processing conditions to create "a green chemistry" approach, Cai said.
A greener, more efficient process could help create more widespread use of hemp for other products like rope and textiles, he said. Following its legalization in California, he expects more demand, noting that they've already been in touch with businesses interested in their product.
"It's important for sustainable materials to have a broad range of applications," says Albert Fernandez, one member of the research team. "That's why we focus on industrial hemp, which already has applications in fuel, clothing, and construction."
