# Lignin Derivatives in Chestnut Wood Hydrochar: Mild Solvolysis and Characterization

## TL;DR

This study explores how hydrothermal treatment of chestnut wood can produce lignin derivatives, which may be useful for industrial applications.

## Contribution

The paper evaluates lignin preservation in hydrochar from chestnut wood, offering insights into its valorization potential.

## Key findings

- Lignin is present in certain hydrochar fractions, indicating potential for high-value applications.
- Hydrothermal treatment leads to structural changes in lignin, as shown by FTIR and NMR analyses.
- Detannized wood shows different lignin characteristics compared to virgin wood.

## Abstract

Castanea sativa plays a significant role in the Italian forestry sector, covering 7.5 % of Italy's land. This biomass resource includes significant volumes of wood processing residues: in recent years, its exploitation has shifted from fuel production to high‐value applications, focusing on lignocellulosic biomass fractionation to obtain biopolymers. Lignin, the most abundant aromatic biopolymer, has gained attention due to its potential for various industrial uses. Amid chemical treatments, hydrothermal treatment offers a sustainable approach to generate energy and chemicals simultaneously.

As depicted in Figure 1, the goal of this study is to evaluate the hydrochar from the hydrothermal treatment of chestnuts to determine the presence of lignin or resulting derivatives which can be isolated for high‐value applications. Virgin wood and detannized wood were processed in a hydrothermal reactor at 200 °C. The resulting hydrochar was characterized using FTIR and 2D NMR for functional group analysis, SEM for char morphology, HPSEC for molecular weight determination, TGA for thermal properties and the Folin Test to confirm the preservation of lignin structure post‐treatment. Preliminary results indicate lignin is present in certain fractions, suggesting the potentiality of this biomass for lignin production.

This research investigates the effects of hydrothermal treatment on hydrochar derived from virgin wood and detannized wood, focusing on the preservation of lignin content. Results from Fourier Transformed Infrared Spectroscopy, solubility tests, scanning electron microscopy (SEM), Folin‐Ciocalteau analysis and High Performance Size Exclusion Chromatography (HPSEC) highlight significant structural changes and the potential for lignin valorization.