Technology Developed to Highly Accurately Estimate Carbon Storage in Soil Using Optical Measurement and Carbon Cycle Model

Comparison with Conventional Technology

Mitsubishi Electric Corporation has developed a technology to highly accurately estimate carbon storage in agricultural soil by combining image analysis and optical measurement technology with a carbon cycle model composed of a plant 'root biomass model (*1)' and a microorganism-based 'organic matter decomposition model (*2)'. This technology eliminates the need for large-scale soil sampling and soil analysis using chemical methods, which were previously necessary to grasp carbon fluctuations in the soil, thereby realizing more efficient and lower-cost wide-area soil monitoring. This will support the evaluation of carbon storage originating from farmland, which can be applied to the GX-ETS (*3) scheduled to be fully operational from FY2026, and contribute to improving agricultural productivity and reducing greenhouse gases.

As initiatives such as the Green Transformation (GX) promotion policy and emission reduction plans by companies and local governments accelerate toward the realization of the government's 2050 carbon neutral goal, agricultural soil is attracting attention as a carbon sink. Carbon storage in agricultural soil not only reduces greenhouse gases but also contributes to improving the water retention and fertility of the soil, thereby enhancing the growing environment for crops. However, the amount of carbon in the soil is greatly influenced by biological and chemical processes that are difficult to observe directly, such as the speed of organic matter decomposition by microorganisms and the growth of crop roots. Therefore, large-scale soil sampling and chemical analysis were essential to grasp it.

This time, our company has established a technology that dynamically reproduces the carbon cycle in the soil by inputting remote sensing images taken from the sky and optical measurement data acquired on the ground into a simulation model that shows the growth of crop roots and soil metabolism. In an initial demonstration experiment in Toyotomi-cho, Hokkaido, we confirmed that this technology can evaluate carbon storage over a wide area at a low cost while significantly improving accuracy compared to conventional methods. This technology will provide data that can be used as objective evidence for third-party verification in the MRV (Monitoring, Reporting, and Verification) required by GX-ETS, and will support the creation of various reports. In the future, we will proceed with additional demonstrations on diverse farmlands both in Japan and overseas, and contribute to improving agricultural productivity and reducing greenhouse gases.

Features of the Development

1. Reduction of man-hours and costs for initial carbon measurement through optical soil measurement

・Established a method to measure the initial carbon amount (*5) inexpensively and in a short period by eliminating the soil sampling and analysis processes of the collected soil through high-precision ground-based spectral measurement (*4) (optical measurement) performed at specific points on the farmland.

2. High-precision estimation of carbon increase/decrease in soil by integrating 'root biomass model' and 'organic matter decomposition model' into a 'carbon cycle model'

・Developed a 'root biomass model' that estimates the amount of unseen roots from surface data (vegetation index, moisture content, etc.) obtained from wide-area images taken from the sky. This evaluates the amount of carbon stored in the roots out of the carbon taken in by photosynthesis. Furthermore, it grasps the variation in crop growth (crop growth unevenness) across the entire farmland from the non-uniformity of the root growth distribution.

・Constructed an 'organic matter decomposition model' that simulates the process of microorganisms decomposing organic matter and releasing CO2 in conjunction with soil environment data such as weather conditions, soil temperature, and moisture content.

・Highly accurately estimates the net increase/decrease of carbon accumulated in the soil with a 'carbon cycle model' that integrates the models of 'inflow (roots)' and 'outflow (decomposition)'. Furthermore, by correcting the predicted values of wide-area image analysis using the results of ground-based spectral measurement, the entire carbon cycle model is made more accurate, enabling wide-area soil monitoring in a short time and at a low cost.

3. Support for creating various reports and farmland management by providing a reliable MRV process

・In anticipation of the MRV (Monitoring, Reporting, and Verification) required by the GX-ETS scheduled for full operation from FY2026, outputs data that can be used as objective evidence for third-party verification. Supports the creation of various reports, including supply chain emissions.

・Quantifies the impact of farmland management methods such as no-till cultivation and compost application on organic matter decomposition and root formation. This supports the provision of guidelines for effective decarbonized agriculture and accelerates its practice, contributing to productivity improvement.

Future Plans and Prospects

We have been continuing demonstration tests in Toyotomi-cho, Hokkaido since FY2024, and plan to complete the measurement and evaluation by March 2027. Toward the provision of a 'Soil Carbon Monitoring Service' based on this technology, we will proceed with the development of higher-precision measurement technology, and in the future, we will work to maximize the value of natural capital by adapting this model to diverse soils and vegetation both in Japan and overseas. We also aim to contribute to the realization of a carbon-neutral society through the provision of reliable carbon data.

About the Mitsubishi Electric Group

The Mitsubishi Electric Group, under 'Our Philosophy,' places sustainability at the core of its management and engages with stakeholders including society, customers, shareholders, and employees.