Pyrogenic carbon, a carbon rich material produced when biomass burns or is converted into biochar, is widely found in soils, sediments, and aquatic environments around the world. Scientists have long known that this material can influence environmental chemical reactions by transferring electrons, but how its properties change as it ages in nature has remained unclear.
A new study published in the journal Biochar reveals that aging significantly alters the way pyrogenic carbon conducts and exchanges electrons. The findings suggest that these changes may influence nutrient cycling, pollutant degradation, and microbial processes in environmental systems.
Researchers investigated pyrogenic carbon produced from several biomass sources at two different temperatures, 350 °C and 750 °C. They then simulated environmental aging using chemical oxidation, freeze thaw cycles, and natural aging over one year. The results showed that aging can fundamentally reshape the electrochemical behavior of the material.
“We found that aging does not affect all pyrogenic carbon in the same way,” said the study’s corresponding author. “Its electron transfer properties depend strongly on the temperature at which the material was produced.”
For pyrogenic carbon produced at lower temperatures such as 350 °C, aging dramatically increased electrical conductivity. In some cases conductivity increased by more than three orders of magnitude. The researchers found that this improvement was linked to the formation of oxygen containing functional groups on the carbon surface. These chemical groups, such as quinones and carbonyls, act as redox active sites that help shuttle electrons.
In contrast, aging had the opposite effect on high temperature pyrogenic carbon produced at 750 °C. Instead of increasing conductivity, aging damaged the polyaromatic carbon structures that enable efficient electron transport. As a result the electrical conductivity of these materials decreased over time.
The study also examined how aging influences the ability of pyrogenic carbon to donate or accept electrons. Aging generally reduced the electron donating capacity of the material while increasing its electron accepting capacity. This shift occurred because aging transformed electron donating hydroxyl groups into more oxidized groups such as carboxyl and carbonyl groups.
“These transformations mean that aged pyrogenic carbon tends to accept electrons more readily but donate them less easily,” the researchers explained. “Such changes can reshape how the material participates in environmental redox reactions.”
These altered electrochemical properties may have important implications for agriculture and environmental management. In soils, aged pyrogenic carbon with stronger electron accepting ability may promote nitrification and influence nitrogen availability for plants. It may also help immobilize certain contaminants by facilitating redox reactions with pollutants or metals.
However the researchers note that these benefits may come with trade offs. Changes in electron transfer properties could also affect microbial respiration pathways or alter greenhouse gas emissions depending on environmental conditions.
The findings highlight the importance of considering how biochar and other forms of pyrogenic carbon evolve over time after they are introduced into soils or ecosystems.
“Pyrogenic carbon can persist in the environment for hundreds to thousands of years,” the authors noted. “Understanding how its properties change during aging is essential for predicting its long term environmental effects.”
The study provides new insight into the mechanisms controlling electron transfer in pyrogenic carbon and offers guidance for designing biochar materials tailored for environmental remediation, nutrient management, and sustainable agriculture.
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Journal Reference: Cao, M., Ren, H., Zhu, P. et al. Pyrolysis temperature determines aging effects on the electron transfer and exchange properties of pyrogenic carbon. Biochar 8 , 29 (2026).
https://doi.org/10.1007/s42773-025-00546-z
About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
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Pyrolysis temperature determines aging effects on the electron transfer and exchange properties of pyrogenic carbon
18-Feb-2026