Grantee Research Project Results
2021 Progress Report: A Green Chemistry Approach to Pulping Hemp as an Industrially Relevant Renewable Fiber for Construction
EPA Grant Number: SV840036Title: A Green Chemistry Approach to Pulping Hemp as an Industrially Relevant Renewable Fiber for Construction
Investigators: Cai, Dr.Charles
Institution: University of California - Riverside
EPA Project Officer: Aja, Hayley
Phase: II
Project Period: July 1, 2020 through June 30, 2022 (Extended to December 31, 2023)
Project Period Covered by this Report: July 1, 2020 through June 30,2021
Project Amount: $74,882
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2020) Recipients Lists
Research Category: P3 Awards
Objective:
The purpose of this project is to develop a more environmentally sustainable pulping and fractionation approach called CELF (co-solvent enhanced lignocellulosic fractionation) to process newly-legalized industrial hemp in the US. Processing raw hemp stalks using CELF can potentially utilize the entire hemp plant without decortication while producing purer hemp intermediates for new applications in green construction and green manufacturing. For Phase 2 of this EPA P3 project, we proposed the following four objectives:
- Compare chemical composition of CELF pulped hemp with traditional decorticated hemp. Achieve at least 80% cellulose content in pulped hemp fiber.
- Compare thermal and structural performance of hempcrete produced from CELF-pulped hemp stalks against traditional hempcrete produced from mechanically decorticated hemp hurd.
- Perform fermentation of hemp-based sugars from CELF pulping to produce ethanol at concentrations exceeding 30 g/L.
- Disseminate results to project collaborators and publish findings
Progress Summary:
We have partially completed objective 1, 2 and 3 during year 1: while successfully achieving QAPP targets for objectives 1 and 3. Following NREL protocol TP-510-42620, the following compositions have been analyzed for raw hemp hurd, raw hemp stalk, and CELF pulped hemp hurd and stalk, as shown in Table 1:
| # | Sample (ID) | Glucan | Xylan | Lignin | Other Sugars | Extractives | Ash |
| 1 | Raw decorticated hurd | 46.6% | 17.9 | 16.5% | 4.3% | 12.7% | 2.0% |
| 2 | CELF pulped hurd | 87.2% | 2.1% | 7.1% | 0% | 0.6% | 3.0% |
| 3 | Raw hemp stalk | TBD | TBD | TBD | TBD | TBD | TBD |
| 4 | CELF pulped hemp stalk* | 69.4% | 7.3% | 18.8% | 0.5% | 0.5% | 3.5% |
*Sample 4 needs to be re-run due to material change from raw hurd (decorticated) to raw stalk (undecorticated) mid-way through project.
We have further optimized formulation of “enhanced” hempcrete using CELF-pulped hemp stalk and have produced repeatable and consistent 2”x2” sample briquettes, shown in Figure 1. We found that the enhanced hempcrete briquettes produced from CELF pulping was noticeably denser, stronger, less friable, and more shape conforming than conventional hempcrete produced directly from decorticated hemp hurd. Hempcrete briquettes were made with a composition of biomass:binder:water ratio of 1:1:3.
Figure 1. Hempcrete made from raw decorticated hemp hurd (left) and CELF-pulped hemp stalk (right).
We then carried out ethanol fermentation using Saccharomyces cerevisiae D5A at a glucan-from-solids loading of 10wt% using Sample 4 in Table 1. All cultures were performed in duplicate using 125mL shake flasks that were incubated at 37℃. YPD extract was supplemented to promote cell viability. The enzyme used in this study was Cellic® Ctec2 generously supplied by Novozymes Inc. and the strain used was S. cerevisiae D5A. Results shown in Figure 2.
Figure 2. Resulting ethanol concentrations from SSF of CELF hemp over culture time. QAPP target of 30 g/L is shown as a red line.
As not all the hemp that undergoes processing could be used for green construction materials, we illustrated a potential use-case for the production ethanol. CELF is a lower-temperature chemical pulping process that has demonstrated high reliability when scaled up; ideal for processing large quantities of underutilized industrial hemp resources. At larger scales, the feasibility for producing renewable 2nd generation fuel ethanol from CELF pulped hemp is an important feature to reduce waste generation and greenhouse gas emissions.
Future Activities:
Performance testing of hempcrete briquettes. Re-run analysis on hemp stalk.
Supplemental Keywords:
hempcrete, hemp, CELF, green chemistry, green manufacturingProgress and Final Reports:
Original AbstractP3 Phase I:
A Green Chemistry Approach to Pulping Hemp as anIndustriallyRelevantRenewable Fiber for Construction | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.