Biochar Aging: Mechanisms, Physicochemical Changes, Assessment, And Implications for Field Applications

TLDR

Biochar is a highly porous, carbon‑rich material sought for carbon sequestration, pollutant immobilization, and soil fertility, but its performance changes over time due to temperature, precipitation, microbial activity, and fragmentation, necessitating study of its aging mechanisms. The study evaluates biochar aging science, summarizes property changes, and proposes a state‑of‑the‑art for artificial aging simulation, while considering implications for soil amendment development, advocating quantitative approaches and engineered pre‑aging for sustainable applications. The authors assess biochar aging through long‑term field monitoring and artificial aging techniques—including chemical oxidation, wet–dry cycling, and mineral modification—to emulate natural aging processes and evaluate property changes.

Abstract

Biochar has triggered a black gold rush in environmental studies as a carbon-rich material with well-developed porous structure and tunable functionality. While much attention has been placed on its apparent ability to store carbon in the ground, immobilize soil pollutants, and improve soil fertility, its temporally evolving in situ performance in these roles must not be overlooked. After field application, various environmental factors, such as temperature variations, precipitation events and microbial activities, can lead to its fragmentation, dissolution, and oxidation, thus causing drastic changes to the physicochemical properties. Direct monitoring of biochar-amended soils can provide good evidence of its temporal evolution, but this requires long-term field trials. Various artificial aging methods, such as chemical oxidation, wet–dry cycling and mineral modification, have therefore been designed to mimic natural aging mechanisms. Here we evaluate the science of biochar aging, critically summarize aging-induced changes to biochar properties, and offer a state-of-the-art for artificial aging simulation approaches. In addition, the implications of biochar aging are also considered regarding its potential development and deployment as a soil amendment. We suggest that for improved simulation and prediction, artificial aging methods must shift from qualitative to quantitative approaches. Furthermore, artificial preaging may serve to synthesize engineered biochars for green and sustainable environmental applications.