Key Takeaways & Executive Findings
- •• Biochar and hydrochar are carbon-rich materials derived from biomass via pyrolysis and hydrothermal carbonization, respectively, with distinct physicochemical properties. • Biochar exhibits high porosity, aromaticity, and thermal stability, making it suitable for CO2 capture, energy storage, catalysis, and soil improvement. • Hydrochar retains more surface functional groups and heteroatoms, offering advantages in aqueous-phase catalysis, pollutant adsorption, and bioremediation. • Comprehensive characterization using techniques like N2 adsorption, SEM, XRD, XPS, Raman, FTIR, Boehm titration, and TGA is essential for optimizing performance in diverse applications.
Abstract
The conversion of biomass into carbon-rich materials, biochar and hydrochar, has emerged as a promising strategy to solve pressing environmental challenges while supporting sustainable industrial development. A comprehensive analysis of recent advances in the characterization and application of these materials is provided, emphasizing their distinct production methods, physicochemical properties, and functional versatility. Biochar, typically obtained by pyrolysis at high temperatures, has a high porosity, aromaticity, and thermal stability, making it well-suited for applications such as CO2 capture, electrochemical energy storage, catalysis, and soil improvement. In contrast, hydrochar, produced by hydrothermal carbonization in aqueous media at moderate temperatures, retains a higher number of surface functional groups and heteroatoms, offering advantages in aqueous-phase catalysis, pollutant adsorption, and bioremediation. The critical role of physicochemical characterization in optimizing material performance is outlined, and analytical techniques including liquid nitrogen adsorption, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, infrared spectroscopy, Boehm titration, and thermogravimetric analysis are discussed. These show how physical-chemical characteristics such as surface area, functional group chemistry, and degree of graphitization govern the materials’ suitability for specific applications. Emerging uses in wastewater treatment, biofuel production, animal feed, and advanced oxidation processes are examined, alongside their relevance to multiple UN Sustainable Development Goals, particularly in climate action, clean energy, and responsible production. The materials are versatile and can be produced on a large scale. Their performance can be fine-tuned using different production and post-treatment processes, making them key enablers in the transition to a circular, carbon-conscious economy.
1. Introduction
The innovative conversion of waste biomass (including agricultural, forestry, and industrial residues) into biochar and hydrochar creates versatile, carbon-rich materials with significant potential to address environmental concerns and enhance energy security. These materials are crucial for soil amendment, pollution remediation, carbon sequestration, and advanced applications like electrochemical energy storage and catalysis. This valorization process directly supports multiple United Nations Sustainable Development Goals (SDGs) by promoting SDG 12 (Responsible Consumption) through waste utilization, contributing to SDG 13 (Climate Action) by greenhouse gas reduction, and fostering a circular bioeconomy that aligns with SDG 7 (Clean Energy) and SDG 9 (Innovation). This multifaceted contribution positions biochar and hydrochar as pivotal components in the global pursuit of a more sustainable and resilient future.
Biochar and hydrochar are both derived from biomass, but differ significantly in their production processes, structure and functional properties. Biochar is typically produced through pyrolysis under limited oxygen conditions at high temperatures (>400 °C), resulting in a highly aromatic, porous structure with a large specific surface area and well-developed micro- and mesoporosity. Hydrochar, on the other hand, is produced through hydrothermal carbonization (HTC) at lower temperatures (180–250 °C) in aqueous environments, leading to a more functionalized surface rich in oxygen-containing groups and often higher heteroatom content.
The performances of these high-carbon materials in diverse applications are strongly dependent on their physicochemical properties, necessitating comprehensive characterization using techniques that assess chemical composition, morphology, degree of graphitization, and thermal and structural stability. The global biochar market reflects the growing industry and research interest in carbon-rich materials. The global biochar market is projected to grow significantly, from an estimated USD 877.15 million in 2024 to approximately USD 3111.96 million by 2034.
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Bruna Rijo, Ana Paula Soares Dias (2025). Recent advances in the characterization and applications of biochar and hydrochar. SinoTechIntel Verified Research. https://doi.org/10.1016/S1872-5805(NCM2026-41-02-02)
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Frequently Asked Questions
What is the difference between biochar and hydrochar?
Biochar is produced by pyrolysis at high temperatures (>400°C) under limited oxygen, resulting in high porosity, aromaticity, and thermal stability. Hydrochar is produced by hydrothermal carbonization at lower temperatures (180-250°C) in aqueous media, retaining more surface functional groups and heteroatoms.
What are the main applications of biochar?
Biochar is used for CO2 capture, electrochemical energy storage, catalysis, soil improvement, and wastewater treatment due to its high surface area and porosity.
What are the main applications of hydrochar?
Hydrochar is advantageous in aqueous-phase catalysis, pollutant adsorption, and bioremediation due to its higher content of surface functional groups.
Why is characterization important for biochar and hydrochar?
Characterization techniques such as N2 adsorption, SEM, XRD, XPS, Raman, FTIR, Boehm titration, and TGA help determine surface area, functional groups, and graphitization degree, which are critical for optimizing performance in specific applications.
How do biochar and hydrochar contribute to sustainability?
They support UN Sustainable Development Goals by promoting responsible consumption (SDG 12), climate action (SDG 13), clean energy (SDG 7), and innovation (SDG 9) through waste valorization and carbon sequestration.
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