Electrochemical Extraction of Methanol and Hydrogen from Biomass Under Mild Conditions and Estimation of Their Potential Abundance By Semantic Segmentation
Authors: Morimoto Yuto , Yamazaki Taiga , Nakamura Yuto , Nagao Masahiro , Hibino Takashi 
Published: December 2024

This study proposes a new electrochemical method for extracting methanol and hydrogen from unused or discarded lignocellulosic biomass. Although some lignocellulosic biomass is being used as solid fuels such as wood chips and pellets, a large amount of lignocellulosic biomass is discarded. A need therefore exists to develop effective methods to recover resources and energy from these waste materials.1,2

We have developed a method of using a graphite sponge anode to generate reactive oxygen species under relatively mild conditions of 75°C and ambient pressure in the process of extracting methanol from lignosulfonic acid. Compared with the conventional method that uses Pt anodes, the new method significantly improves the methanol yield. The use of graphite sponges enhances the demethylation of methoxy groups in lignin and inhibits the peroxidation of methanol to CO2, thereby increasing the methanol yield and expanding the surface area and capacity of the electrode to increase lignin utilization. In addition, hydrogen is produced at the cathode in this method and the electrolysis residue can be reused as a fuel for fuel cells, contributing to energy recovery and the efficient use of resources. The hydrogen evolution reaction proceeds in proportion to the current density at the cathode and is not affected by the type of reactants at the anode, imparting the system with flexibility to process various biomass wastes.
An important aspect of this research is the ability to efficiently convert lignocellulosic biomass waste into chemicals, fuels, and electricity. In particular, the process can be run using only renewable energy while minimizing energy consumption, thus reducing environmental impact. In addition, for this research to be practical, estimating the amount of biomass produced annually in each region and the amount disposed of without being utilized, as well as the amount of methanol and hydrogen that could be produced using this technology, is important. We therefore used semantic segmentation to recognize forested areas in satellite images and calculated the forest area per region. Under the assumption of a model forest, we estimated the lignin content from the forest area and calculated the potential methanol and hydrogen contents. These estimates are expected to be useful in discussing the economics of methanol and hydrogen production from waste biomass.
In conclusion, this study provides a sustainable recycling and estimation method for lignocellulosic biomass waste. In addition to the extraction of methanol and hydrogen, the electrolysis residue can be effectively used as a fuel to increase the overall efficiency of biomass utilization. This technology is expected to contribute to the reduction of waste, the recovery of resources, and the promotion of the use of renewable energy and is an important step toward the realization of a recycling-oriented society.

Acknowledgment

This research was partially supported by JSPS KAKENHI Grant Number 22K12474.

REFERENCES

[1] T. Hibino, K. Kobayashi, M. Nagao, D.W. Zhou, S.Y. Chen, Y. Yamamoto, ACS Catal. 2023, 13, 8890-8901.
[2] T. Hibino, K. Kobayashi, D.W. Zhou, S.Y. Chen, A. Zinchenko, S. Teranishi, A. Miyawaki, Y. Sawada, Appl. Catal. B Environ. 2024, 341, 123328.