Carbon farming in Mediterranean olive groves: potential for carbon credits and policy implications

In the Mediterranean basin, the olive oil sector holds strong potential for carbon credit generation, although it has not yet been assessed following international standards. This study assessed the potential of carbon farming (CF) in 15 farms of Andalusia (Spain) over a five-year crediting period. The CF scenario, involving cover crops, manure, and olive pomace compost, was compared with two baselines: a standardized baseline (StaBL), reflecting typical practices, and an activity-specific baseline (SpeBL), reflecting each farm's current management. Three soil strata were sampled per farm: under canopy, pruning mulch strip, and remaining soil. SOC dynamics were modeled using RothC, whereas emissions from management were estimated with Tier 1 coefficients. Results showed that over the five-year period, soils under both baselines acted as net carbon sources (7.14 Mg CO₂ ha^-1), whereas CF shifted them to a net sink (-9.66 Mg CO₂ ha^-1). Emissions from operations and fertilization were slightly higher under CF, but always below 2.50 Mg CO₂ ha^-1. Carbon credits generated ranged from 13.98 to 19.83 Mg CO₂ ha^-1 when compared to the StaBL and from 5.32 to 31.42 Mg CO₂eq ha^-1 when compared to SpeBL. The choice of a StaBL distribute credits more evenly across the farms than SpeBL. In total, the 15 farms generated 7,181 Mg CO₂eq (StaBL) or 7,255 Mg CO₂eq (SpeBL), corresponding to ∼€47,000 at €6.6 per Mg CO₂eq. Extrapolated to the 50,000 ha of the PDO Estepa, potential revenues could reach €5.3 million. This case study highlights that considerable potential of carbon farming in Mediterranean olive groves to enhance large-scale atmospheric carbon removal and generate revenue for smallholders.