Methodology for estimating the impact of no tillage on the 4perMille initiative: The case of annual crops in Spain

•New methodology for regional objectives of 4perMille Initiative through No Tillage.•Based on modelling in Carbon Benefits Project online tool for 15 Spanish regions.•Carbon sequestration modelled was compared to organic carbon contained in the soil.•New geographical data useful for policy makers involved in climate change mitigation.•This methodology can be easily replicated in regions and countries around the world.