# Quantitative characterization of pore structure of several biochars with 3D imaging

## TL;DR

This study uses 3D imaging to analyze the pore structures of various biochars, revealing how raw material and processing influence porosity and water retention properties crucial for soil amendment.

## Contribution

It provides a detailed quantitative characterization of biochar pore structures using X-ray microtomography and image analysis, linking raw material to pore properties.

## Key findings

- Pores relevant to water retention are present in biochar volume.
- Porosity and pore size depend on biochar type.
- Raw material significantly affects micrometre-scale pore characteristics.

## Abstract

Pore space characteristics of biochars may vary depending on the used raw material and processing technology. Pore structure has significant effects on the water retention properties of biochar amended soils. In this work, several biochars were characterized with three-dimensional imaging and image analysis. X-ray computed microtomography was used to image biochars at resolution of 1.14 $\mu$m and the obtained images were analysed for porosity, pore-size distribution, specific surface area and structural anisotropy. In addition, random walk simulations were used to relate structural anisotropy to diffusive transport. Image analysis showed that considerable part of the biochar volume consist of pores in size range relevant to hydrological processes and storage of plant available water. Porosity and pore-size distribution were found to depend on the biochar type and the structural anisotopy analysis showed that used raw material considerably affects the pore characteristics at micrometre scale. Therefore attention should be paid to raw material selection and quality in applications requiring optimized pore structure.