Overcoming the Soil Carbon MRV Bottleneck: A Large-Scale LIBS Implementation in Brazil

The implementation of robust Monitoring, Reporting and Verification (MRV) protocols remains a major bottleneck for the international soil carbon credit market due to high costs, operational complexity, and limited scalability of conventional laboratory methods for soil organic carbon (SOC) and bulk density (BD) determination.

This work presents a Brazilian success case in which laser-induced breakdown spectroscopy (LIBS) has been validated and implemented as a high-throughput MRV tool for soil carbon stock assessment. LIBS methodologies for SOC quantification have been developed and validated over the last 10 years through research in long-term experimental areas of Embrapa and private-sector initiatives, covering diverse Brazilian soil types and management systems.

More recently, machine learning-based LIBS models trained on thousands of soil samples achieved limits of detection of 0.3% SOC, enabling sensitive and robust carbon measurements. In parallel, Embrapa Instrumentation reported the use of LIBS to estimate soil bulk density and soil carbon stocks in disturbed samples, achieving an R² of 0.78 and an RMSE of 4.1 Mg C ha⁻¹ in a peer-reviewed publication.

The technology was transferred to the startup Agrorobótica, resulting in an automated LIBS platform capable of analyzing more than 1,000 soil samples within 8 hours, currently deployed across 18 Brazilian states. Beyond scalability and cost reduction, LIBS provides co-benefits by simultaneously determining soil carbon and key fertility parameters using a single analytical platform. The approach has been accepted by the Verra certification framework, demonstrating readiness for compliance-oriented MRV and potential to overcome a critical bottleneck in global soil carbon markets.