Center for Environmental Research and Technology

Abstract

A novel green chemistry pulping method, called Co-solvent Enhanced Lignocellulosic Fractionation (CELF), is applied to rapidly process industrial hemp into separate streams including 1) pulped fiber, 2) lignin, 3) extractives, and 4) sugars, enabling their seamless application to sustainable building materials, bioplastics, wellness products, and foods, respectively. The “one-pot” CELF reaction has been optimized in Phase I work to simultaneously perform both physical separation of fibers as well as chemical fractionation of lignin, sugars, and extractives from raw undecorticated hemp and other industrial hemp varieties. Furthermore, CELF emits zero gaseous emissions and zero toxic waste products. The three main objectives of this project are:

1. Design a pilot-scale reactor tailored to process both raw hemp and hemp hurd.
2. Perform characterization of hemp pulped fibers, hemp lignin, and hemp extractives.
3. Expand the range of commercial building products from hemp processed by CELF.

Approach:

In Phase 1, the research team successfully demonstrated lab-scale operation of CELF to perform chemical decortication, delignification, and extraction of various hemp varieties. The objective in Phase 1 was to use the pulped hemp fibers to produce an advanced hempcrete construction material that demonstrated improved structural properties, moisture absorption properties, and thermal insulation properties over conventional hempcrete. In addition, researchers were able to extract valuable hemp lignin in a highly pure form suitable as a precursor for bioplastics, adhesive resins, and specialty carbon products. The team has partnered with Hempire USA, Match Patch Pro, and The Hurd Co to explore adoption into commercial products. In Phase 2, the research team aims to produce larger hempcrete blocks to perform field trials. To do this, researchers will execute the buildout of a pilot-scale CELF reactor specifically designed for processing larger quantities of hemp with lower energy consumption. Researchers will then optimize the reaction at larger scale to tune the properties resulting fiber and lignin products. Chemical and structural characterization will allow demonstration of an expanded range of potential sustainable and recyclable construction materials. Finally, researchers aim to perform a techoeconomic and life cycle assessment of the process to address potential technical risks.

Expected Results:

• Improved Thermal Properties
  • The team expects to increase conventional hempcrete’s thermal resistance (R-value) to beyond 4.5, and target thermal conductivity of 0.06 W/mK to 0.09 W/mK. This will allow hempcrete to compete with current products.
• Better Structural Performance
  • CELF-pumped hemp fibers have shown significant improvements in its association with lime binder and water. We will evaluate compressive strength and structural rigidity of different hemp composite materials.
• Diversified Final Products
  • CELF extracts purified lignin, sugars, organics away from the plant fiber, enabling a diverse range of co-products. We aim create recyclable resins and plastics from hemp lignin, and to find alternative uses for the fiber such as light-weight composites.

CELF uses a renewable and recyclable solvent to perform pulping under mild conditions, saving process energy and while generating zero process emissions. By utilizing the entire plant, CELF promises to generate virtually no solid waste as even the remaining ash minerals are clean enough to be used for soil amendment. Hempcrete is also known to sequester CO₂ further reducing the carbon footprint of building projects.