Grantee Research Project Results
2023 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, 2022 through June 30,2023
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 pulp industrial hemp to prepare it for high performance hempcrete 2.0 manufacturing. The project objectives are:
- Compare chemical composition of CELF-pulped (or modified) hemp with traditional decorticated hemp
- Compare thermal and structural performance of hempcrete 2.0 (made with CELF-pulped hemp) against traditional hempcrete
- Ferment CELF-pulped hemp into fuel ethanol
- Disseminate results to project collaborators and publish findings
Progress Summary:
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 sticks, as shown in Table 1. As hemp sticks are unprocessed and undecorticated, it contains both the hurd and bast fibers, instead of just the decorticated hemp hurd. The higher content of glucan present in CELF pulped hemp should allow us to achieve QAPP targets for both Objective 2 and 3.
Table 1: Chemical and component compositional analysis of raw and CELF pulped hemp solids
# | Sample (ID) | Glucan (%) | Xylan (%) | Lignin (%) | Other Sugars (%) | Extractives (%) | Ash (%) |
---|---|---|---|---|---|---|---|
1 | Decorticated hurd (raw) | 46.6 | 17.9 | 16.5 | 4.3 | 12.7 | 2.0 |
2 | CELF-pulped decorticated hurd | 87.2 | 2.1 | 9.1 | 0 | 0.6 | 1.0 |
3 | Hemp sticks (raw) | 42.2 | 17.6 | 21.2 | 3.5 | 11.5 | 4.0 |
4 | CELF-pulped hemp sticks | 85.5 | 2.3 | 11.0 | 0.5 | 0.5 | 0.2 |
Objective 2: We have optimized formulation of hempcrete 2.0 using CELF-pulped hemp stalk and have produced repeatable and consistent 2”x2” briquettes similar to the hempcrete briquettes we produced during Phase 1 of the project (please refer to our previous Annual Report I for images). Thermal conductivity testing was performed on briquettes containing increasing lime binder content: 1:3:3 (biomass:binder:water), 1:1.5:3, and 1:1:3 briquettes (Figure 1) to obtain their relative thermal conductivities. We observed improved binding with the CELF-pulped hemp and lime; thus, we can reduce the amount of lime incorporated into the samples in to reduce lime consumption and improve thermal conductivity.
Figure 1. CELF-pulped hempcrete briquets with the following biomass:binder:water ratios: 1:1:3 (left), 1:1.5:3 (middle), 1:3:3 (right).
As outlined in Table 2, all modified hempcrete briquettes managed a thermal conductivity of 0.05 W/(m*K) or less, resulting in a satisfactory R-value of 20 or higher. This thermal performance surpassed traditional hempcrete performance. Although we were unable to produce large enough briquettes for a tensile strength test, we can anticipate that the strength of the material exceeds that of traditional hempcrete based on the specific densities of the modified hempcrete briquettes as listed in Table 2.
Sample ID | Thermal Conductivity (W/m*K) | R-value | Specific Density (kg/m3) |
1:1:3 traditional hempcrete | 0.06 | 16.67 | 278 |
1:1:3 modified briquet (CELF) | 0.042 | 23.8 | 488 |
1:1.5:3 modified briquet (CELF) | 0.043 | 23.2 | 414 |
1:3:3 modified briquet (CELF) | 0.049 | 20.4 | 383 |
Objective 3: For this objective, we carried out high-solids simultaneous saccharification and fermentation (SSF) fermentation of CELF-pulped hemp sticks using Saccharomyces cerevisiae D5A at a hemp solids loading of 13 wt% and Cellic® Ctec2 enzyme dosage of 30FPU. The resulting SSF ethanol concentrations over 14 days of culture are shown in Figure 2.
Figure 2. Resulting ethanol concentrations from SSF of CELF-pulped hemp sticks over culture time. Project target of 30 g/L, shown as the red line, was far exceeded due to the high digestibility of CELF-pulped hemp sticks.
Supplemental Keywords:
hemp; industrial hemp; hemp pulping; CELF, hempcrete; ethanolProgress 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.