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Page 8 of 26 Salmerón et al. Carbon Footprints 2026, 5, 17

Soil benefits
This study considers a biochar application rate of 5 t·ha in all scenarios, a dosage that ensures agronomic
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benefits while remaining economically and logistically feasible by contributing to yield enhancement, soil
fertility, and carbon sequestration [11,23,25,62] . Biochar application is prioritized to deliver soil restoration benefits
to those soils affected by a high erosion rate, considered as the key indicator of degradation of olive groves.
Soil erosion is a primary driver of land degradation, leading to losses in soil structure, organic carbon, and
water retention capacity [5,13,63] . Biochar application directly counteracts these degradation processes by
enhancing soil carbon storage, improving soil structure [11,17,23] , and reducing soil loss and nutrient runoff [62,64] ,
thus alleviating common deficiencies in eroded soils .
[65]
Based on a global meta-analysis and the local climatic conditions, we adopt an average reduction of 9% in
soil erosion when biochar is applied . Given the biochar's established effect on increasing soil water holding
[66]
capacity (with values reported in the 10%-30% range), we considered an estimate of 10% reduction in
irrigation requirements [17,25,62,67] . Yield improvements of about 15% have been reported after biochar
application to olive groves with field trials in Andalusia [17,68] , which is the value used in this study. A 15%
reduction in nitrogen fertilizer, and 7% reduction in phosphorus and potassium fertilizers, is considered
according to the reported increases in nutrient use efficiency driven by biochar [23,26,45,67,69] . Direct soil N O
2
emissions for the baseline scenario were quantified using the IPCC default emission factor of 1% of N
applied [70] . Indirect emissions were derived from estimated N losses, including 5% for ammonia
volatilization and 71% for nitrate leaching in the irrigated intensive system , with subsequent conversion
[71]
[72]
to N O using factors of 1% and 0.75% , respectively. Biochar's influence was quantified based on a
[11]
2
European-scale analysis , with direct N O emissions reduced by 13.7% and nitrate leaching losses reduced
[11]
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by 17.5%.
Finally, net carbon removal was calculated using the Verified Carbon Standard (VCS) methodology. Our
olive pomace-based biochar had an average carbon content of 66.22% [Supplementary Table 10]. According
to VCS guidelines, biochar produced between 450-600 °C has a permanence factor of 80% [73,74] . This yields a
net carbon sequestration of 1.94 t CO eq per tonne of biochar applied to the soil, resulting in a carbon sink
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of 9.71 t CO -eq ha for the 5 t ha application rate, a value consistent with previous findings [11] .
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2
Supplementary Table 11 summarizes biochar benefits stated in this section and Supplementary Text 3
provides a complete description of the biochar application method, where olive cultivation hectares within
the different erosion thresholds are quantified and located [Supplementary Table 12 and
Supplementary Figure 6]. There are about 55% of olive groves affected by soil erosion rates above
25 t ha yr , with most of them located in the provinces of Jaén and Córdoba, with 382,700 and 210,500
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hectares affected respectively [Supplementary Table 13 and Supplementary Figure 7].
In addition to renewable energy, AVS provides co-benefits by creating a more favorable microclimate. The
partial shade from solar panels reduces soil temperature and evaporation, which lowers crop
evapotranspiration and improves water use efficiency, with literature reporting water savings ranging from
10%-30% [9,34-36] . Based on these findings and to account for regional variability, a 20% reduction in irrigation
water requirements for all land where AVS is deployed is considered. We also assume no yield penalty for
the olive groves, as the AVS is configured with a 2-axis tracking system to optimize light distribution,
consistent with best-practice designs [30,32,59] .

Uncertainty analysis
To test the robustness of the LCA results, a Monte Carlo simulation with 10,000 runs was performed. For
each run, the simulation randomly selected a value from the defined uncertainty range for each key
parameter. We used a triangular distribution, following the approach of other studies in similar cases, where