Soil organic carbon quantification for carbon credit generation under the Verified Carbon Standard

Verra, a nonprofit organization, manages the world's leading voluntary carbon markets program, the Verified Carbon Standard (VCS) Program. The VCS Program is the world's most widely used greenhouse gas (GHG) crediting program. The VCS Standard lays out the rules and requirements that projects must follow in order to be certified. In addition, the VCS Program includes three other essential components: independent auditing, accounting methodologies and the publicly accessible registry system. The Methodology for Improved Agricultural Land Management VM0042 is the most widely used methodology in the agriculture sector within the VCS Program. The VCS registry lists 113 projects in 26 countries being under development, under validation or with registration requested (status 8 Jan 2024). One project has been successfully registered. The major carbon pool affected by the implemented project activities that is expected to increase in the project scenario is the soil organic carbon (SOC) pool. Further CO2, CH4 and N2O sources must be monitored if they are impacted by the implemented land management activities. SOC is allowed to be quantified via two approaches: 1. Measure and Model, and 2. Measure and Re-Measure. Direct measurements of SOC stocks are required under Quantification Approach 1 as model inputs for baseline setting and at minimum every five years after for model true-up. Direct measurements of SOC stocks are also required under Quantification Approach 2 to determine the baseline (in baseline control sites) and project SOC stocks at the project start date and at each verification event. Soil sampling must be conducted following the stratified random sampling strategy. This contribution aims to present Verra's latest requirements for soil sampling with specific consideration of: capturing variability across large project areas of several thousands of hectares estimating SOC stock increases over short periods of time to enable robust carbon crediting providing flexibility in the measurement protocols to allow inclusiveness across different geographies