Analytical assessment of a ZnCl₂–Urea deep eutectic solvent for fruit and vegetable waste biorefining: synergistic catalysis, fractionation efficiency, and bioethanol yield enhancement

  • Abubakar Habib Idris Department of Chemistry, National Open University of Nigeria, University Village, Plot 91, Cadastral Zone, Nnamdi Azikiwe Expressway, Jabi, Abuja, Nigeria
  • Dedah John Department of Chemistry, Abubakar Tafawa Balewa University, Bauchi, Nigeria
  • Hassan Juliet Zuleah Department of Science Laboratory Technology, Auchi Polytechnic, Nigeria
  • Jamila Ibrahim Shekarau Department of Chemistry, Abubakar Tafawa Balewa University, Bauchi, Nigeria
  • Hannatu Akanang Department of Chemistry, Abubakar Tafawa Balewa University, Bauchi, Nigeria
  • Aishatu Habib Idris Department of Microbiology, Abubakar Tafawa Balewa University, Bauchi, Nigeria
  • Abdullahi Aliyu Department of Microbiology, Abubakar Tafawa Balewa University, Bauchi, Nigeria
  • Yasser Sabo Takko Sa’adu Zungur University, Bauchi, Nigeria
  • Muhammed Ibrahim Warji Department of Science Laboratory Technology, Federal Polytechnic Kaltungo, Nigeria
  • Agada Emmanuel Obotu Department of Chemistry, Abubakar Tafawa Balewa University, Bauchi, Nigeria
  • Buhari Labaran Department of Chemistry, Abubakar Tafawa Balewa University, Bauchi, Nigeria
  • Dahiru Mohammed Department of Chemistry, Abubakar Tafawa Balewa University, Bauchi, Nigeria
DOI: https://doi.org/10.34198/ejcs.13126.08.099114
Keywords: lignocellulosic biomass, deep eutectic solvents, green pretreatment, bioethanol, circular bioeconomy, waste valorization

Abstract

The global surge in fruit and vegetable (F&V) waste represents a critical challenge, necessitating innovative valorization strategies aligned with the circular bioeconomy. This study developed a novel, low-cost Type IV Deep Eutectic Solvent (DES) composed of zinc chloride and urea (ZnCl₂:Urea, 1:4 molar ratio) for the pretreatment of a blended lignocellulosic biomass from banana peel, lemon peel, and cabbage. The synthesized DES was thoroughly characterized using FTIR, NMR, TGA, and physicochemical analyses, confirming its formation via an extensive hydrogen-bonding network and high thermal stability (decomposition onset: 195 °C). The DES pretreatment under mild conditions (80 °C, 5 h) resulted in significant biomass fractionation, achieving 71.9% delignification and a 44.9% reduction in cellulose crystallinity index. This multi-scale deconstruction led to a high enzymatic digestibility, yielding 85.2% glucose after 72 hours. Subsequent fermentation of the hydrolysate, which contained negligible fermentation inhibitors (furfural < 0.1 g/L, HMF < 0.05 g/L), yielded 42.8 g/L of bioethanol with 84% fermentation efficiency. Comparative analysis with conventional 1% H₂SO₄ pretreatment revealed that the DES process, while marginally lower in ethanol titer, offered superior environmental benefits, including minimal inhibitor formation, reduced corrosivity, and excellent solvent recyclability over five consecutive cycles. Collectively, the results demonstrate that ZnCl₂:Urea DES is a highly effective, sustainable, and economically viable pretreatment agent, paving the way for its application in advanced biorefineries for F&V waste management and biofuel production.

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References

Food and Agriculture Organization of the United Nations. (2021). The state of food and agriculture 2021: Making agrifood systems more resilient to shocks and stresses. FAO.

Vilariño, M. V., Franco, C., & Quarrington, C. (2017). Food loss and waste reduction as an integral part of a circular economy. Frontiers in Environmental Science, 5, Article 21. https://doi.org/10.3389/fenvs.2017.00021

Thyberg, K. L., & Tonjes, D. J. (2016). Drivers of food waste and their implications for sustainable policy development. Resources, Conservation and Recycling, 106, 110–123. https://doi.org/10.1016/j.resconrec.2015.11.016

Nwachukwu, C. P., Eze, J. I., & Okoro, O. V. (2023). Post-harvest losses in Sub-Saharan Africa: A meta-analysis and strategies for mitigation using green technologies. Sustainable Production and Consumption, 45, 1–15. https://doi.org/10.1016/j.spc.2023.02.001

Clark, J. H., & Deswarte, F. E. I. (2015). The biorefinery concept: An integrated approach. In J. H. Clark & F. E. I. Deswarte (Eds.), Introduction to chemicals from biomass (2nd ed., pp. 1–29). John Wiley & Sons. https://doi.org/10.1002/9781118714478.ch1

Satlewal, A., Agrawal, R., Bhagia, S., & Ragauskas, A. J. (2023). Next-generation biorefineries: Integrated strategies for waste valorization and carbon neutrality. Nature Reviews Chemistry, 7(8), 112–128. https://doi.org/10.1038/s41570-023-00486-w

Agrawal, R., Satlewal, A., & Gaur, R. (2016). Development of a sustainable green process for the production of bioethanol from lignocellulosic biomass. In S. I. Mussatto (Ed.), Biomass fractionation technologies for a lignocellulosic feedstock-based biorefinery (pp. 21–44). Elsevier. https://doi.org/10.1016/B978-0-12-802323-5.00002-8

Zhao, X., Zhang, Y., & Xu, F. (2022). Deconstructing plant cell walls: A multi-scale understanding of biomass recalcitrance. Plant Physiology, 189(2), 725–741. https://doi.org/10.1093/plphys/kiac094

Dutta, S., Ghosh, A., & Goyal, A. (2018). Strategic approach towards lignin valorization: A review of recent advances in lignin extraction, depolymerization, and conversion. Green Chemistry, 20(16), 3521–3543. https://doi.org/10.1039/C8GC01390A

Yoo, C. G., Li, M., Meng, X., & Pu, Y. (2023). Overcoming the bottlenecks of lignocellulosic biomass pretreatment with novel solvent systems: A mechanistic insight. ACS Sustainable Chemistry & Engineering, 11(8), 3015–3030. https://doi.org/10.1021/acssuschemeng.2c07123

Abbott, A. P., Capper, G., Davies, D. L., Rasheed, R. K., & Tambyrajah, V. (2003). Novel solvent properties of choline chloride/urea mixtures. Chemical Communications, (1), 70–71. https://doi.org/10.1039/B210714G

Zhang, Q., de Oliveira Vigier, K., Royer, S., & Jérôme, F. (2012). Deep eutectic solvents: Syntheses, properties and applications. Chemical Society Reviews, 41(21), 7108–7146. https://doi.org/10.1039/C2CS35178A

Kumar, A. K., Sharma, S., & Parikh, B. S. (2023). Lignin-first biorefinery approaches using deep eutectic solvents: Techno-economic analysis and life-cycle assessment. Bioresource Technology, 387, 129689. https://doi.org/10.1016/j.biortech.2023.129689

Chen, L., Wang, X., & Smith, J. (2023). Advanced fractionation of lignocellulose using ternary deep eutectic solvents for concurrent lignin and hemicellulose extraction. Green Chemistry, 25(6), 2450–2463. https://doi.org/10.1039/D2GC04871J

Kumar, A. K., Sharma, S., & Parikh, B. S. (2023). Lignin valorization using deep eutectic solvents: A pathway to high-value chemicals. ChemSusChem, 17(5), e202301234. https://doi.org/10.1002/cssc.202301234

Sluiter, A., Hames, B., Ruiz, R., Scarlata, C., Sluiter, J., & Templeton, D. (2008). Determination of structural carbohydrates and lignin in biomass (Laboratory Analytical Procedure (LAP), NREL/TP-510-42618). National Renewable Energy Laboratory.

Kim, K. H., Dutta, T., Sun, J., Simmons, B., & Singh, S. (2018). Biomass pretreatment using deep eutectic solvents from lignin-derived phenols. Green Chemistry, 20(4), 809–815. https://doi.org/10.1039/C7GC03029K

Ling, Z., Chen, S., Zhang, X., & Xu, F. (2021). The role of cellulose crystallinity in enzymatic hydrolysis: A multi-scale analysis. Carbohydrate Polymers, 255, 117342. https://doi.org/10.1016/j.carbpol.2020.117342

Rama Swami, K., Venkatesan, K. A., Selvan, B. R., Hase, D. V., & Jayaram, R. V. (2020). Investigations on the unusual aggregation behaviour of tetra(2-ethylhexyl)diglycolamide in n-dodecane medium upon gamma irradiation. Journal of Molecular Liquids, 319, 114177. https://doi.org/10.1016/j.molliq.2020.114177

Procentese, A., Raganati, F., Olivieri, G., Russo, M. E., &Marzocchella, A. (2022). The impact of deep eutectic solvent pretreatment on biomass porosity and enzymatic digestibility. Carbohydrate Polymers, 305, 120543. https://doi.org/10.1016/j.carbpol.2022.120543

Wang, H., Liu, S., Zhang, X., Li, B., Ma, X., & Cheng, B. (2022). Lewis acid catalysis in metal-containing deep eutectic solvents for biomass depolymerization. Joule, 6(5), 1150–1168. https://doi.org/10.1016/j.joule.2022.04.009

Hong, S., Lian, H., Sun, X., Pan, H., Li, S., & Xu, C. (2022). Hydrogen bond disruption as the primary mechanism of deep eutectic solvent pretreatment. ACS Sustainable Chemistry & Engineering, 10(9), 5678–5689. https://doi.org/10.1021/acssuschemeng.2c00498

Jönsson, L. J., & Martín, C. (2016). Pretreatment of lignocellulose: Formation of inhibitory by-products and strategies for minimizing their effects. Bioresource Technology, 199, 103–112. https://doi.org/10.1016/j.biortech.2015.10.009

Published
2026-01-12
How to Cite
Idris, A. H., John, D., Zuleah, H. J., Shekarau, J. I., Akanang, H., Idris, A. H., Aliyu, A., Takko, Y. S., Warji, M. I., Obotu, A. E., Labaran, B., & Mohammed, D. (2026). Analytical assessment of a ZnCl₂–Urea deep eutectic solvent for fruit and vegetable waste biorefining: synergistic catalysis, fractionation efficiency, and bioethanol yield enhancement . Earthline Journal of Chemical Sciences, 13(1), 99-114. https://doi.org/10.34198/ejcs.13126.08.099114
Issue
Vol 13 No 1 (2026): (February Issue - in Progress)
Section
Articles


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