Visiting Fellow Viewpoint

 From the Desk of Professor Toru Nakajima

Carbon (C) credit, a system that assigns a monetary value to farmers for enhancing soil organic carbon (SOC) stock through agricultural practices (e.g., Regenerative Agriculture), serves as a powerful tool for climate change mitigation and adaptation strategy, soil health improvement, and ecosystem services. C sequestration value must be processed and evaluated through measurement, reporting, and verification (MRV) protocol to ensure the trustworthiness of the C credit system in agricultural lands. However, the major challenges associated with C sequestration measurement are cost and precision. In general, collecting more soil samples and C measurements can lead to more precise results. On the other hand, it increases the cost of measurement. In addition, we, soil scientists, know that soil’s 

physical, chemical, and biological properties have a huge variability in a field, due to the nature of nature. Therefore, it is very important to understand and develop how to measure C sequestration with reasonable cost and precision in order to meet MRV protocol requirements. One way to measure C sequestration is direct measurement, including field soil sampling and laboratory analysis of the combustion method. The direct measurement is the gold standard, and we all have experience using this measurement. However, this measurement is labor intensive, taking a long time, and costly. Also, we need to deal with field variability, especially on-farm sites, which are, in most cases, the target areas for C credit. Soil C sensors (e.g., Mid-infrared, Spectrometer, and WIFI signal) are a game changer for C sequestration measurement. It is low-cost and easy to measure and will be the future method of C sequestration. Soil C sensors need to be developed and evaluated. And, we still have to deal with field variability and field labor work. In addition, remote sensing for C sequestration (e.g., UAV and Satellites) and soil C models (e.g., RothC model, DNDC, SWAT, and CENTURY) are one of the ways to estimate C sequestration.

There are various methods to measure C sequestration, each with its advantages and disadvantages. Remain unresolved issues of each C sequestration method need to be addressed for C credit. I will keep working on that!


Toru Nakajima signature

Toru Nakajima
Associate Professor
Tokyo University of Agriculture