Rapid soil organic carbon stability analysis using HP-TGA-MS

Overview

This technology offers a faster, more accurate method for determining soil organic carbon (SOC) stability by using a High-Pressure Thermo-Gravimetric Analyzer hyphenated to a Mass Spectrometer (HP-TGA-MS). Current conventional techniques, such as dry combustion with elemental analysis, can quantify total organic carbon but cannot discretize between organic matter fractions of differing chemical stability. This limitation makes it difficult to assess which carbon pools are truly sequestered in stable forms versus those vulnerable to rapid decomposition.

The HP-TGA-MS approach addresses this gap by subjecting soil samples to controlled gasification reactions under varying conditions. Because different organic matter fractions (labile C, humus C, recalcitrant C) react differently under specific temperature, pressure, and oxidizer regimes, the resulting kinetics and gas products can be correlated back to the carbon species present. This enables quantitative classification of carbon pools by stability, supporting more reliable evaluation of soil carbon sequestration strategies and rewarding practices that store more stable carbon.

Technical specifications

Key capabilities:

• In-situ measurement of solids mass and gas composition during thermally-driven gas-solid reactions
• Variable reaction conditions ranging from mild to intense, with real-time monitoring
• Operates with multiple oxidizer types including air, steam, O2, and CO2
• Pressure range up to 30 bar
• Temperature regimes including constant, gradual, and step-wise profiles up to 1200 degrees Celsius
• Detection of gas products such as CO, H2, and CH4 to correlate with organic carbon fractions
• Tests conducted both with and without soil minerals to isolate mineral-carbon interactions

Advantages over conventional methods:

• Provides carbon fraction and stability data that traditional dry combustion and elemental analysis cannot deliver
• Faster and more facile compared to existing wet chemistry fractionation approaches
• Quantitative determination of labile, humus, and recalcitrant carbon pools

Technology readiness level

This research builds on extensive prior work in soil carbon sequestration conducted since 2018. Preliminary studies, including Haque et al. (2019), have established baseline methods for quantifying total organic carbon in soils (0.628 to 0.864 wt.%) using dry combustion and elemental analysis. The current phase focuses on developing and validating the HP-TGA-MS methodology by systematically testing how process conditions and gasification kinetics correlate to the speciation and stability of soil organic matter. Future work will evaluate data processing methods to ensure accurate correlation between reaction behavior and carbon stability classification. The technology is in an active research and method development stage.