Page 83 - 2417

Page 14 of 26 Salmerón et al. Carbon Footprints 2026, 5, 17

to a negative net impact (-0.11 Mt CO -eq·year ). Although managing this extra biomass increases the
-1
2
impacts of biochar production by 33% and transport by 47% compared to S2, these operational costs are
outweighed by -1.10 Mt CO -eq·year and -2.54 Mt CO -eq·year from the soil carbon sequestration and
-1
-1
2
2
electricity benefits, respectively.
Scenarios S4 and S5 with higher AVS deployment lead to greater mitigation. In S4, the extensive PV
infrastructure adds 1.48 Mt CO -eq·year of positive emissions. However, this is overwhelmed by the
-1
2
negative emissions from electricity generation (-5.25 Mt CO -eq·year ), resulting in a total net impact of
-1
2
-0.94 Mt CO -eq·year . Finally, scenario S5 delivers the largest climate benefit, combining high AVS
-1
2
deployment with maximum biochar production to reach -2.08 Mt CO -eq·year . Here, positive emissions are
-1
2
driven by farming operations (63%) and PV manufacturing (35%), while the system's negative emissions are
derived 83% from electricity benefits and 17% from the durable biochar sink.
The application of biochar creates a long-lasting carbon sink at an annual rate of 0.82 Mt CO -eq·year (S1,
-1
2
S2) to 1.1 Mt CO -eq·year (S3, S5). This represents a significant contribution, equivalent to offsetting 13% to
-1
2
17% of Andalusia's 2023 agricultural emissions (6.36 Mt CO -eq·year ) . While diverting biomass from
-1 [79]
2
combustion to soil storage promotes a circular model, it introduces an energy trade-off, as baseline power
plants achieve a lower carbon intensity (32 g CO -eq kWh ) compared to the pyrolysis unit
-1
2
(55 g CO -eq kWh ). Nevertheless, our estimates show that agrivoltaic systems occupying just 0.11% of the
-1
2
total olive grove area can fully offset this deficit, thereby securing the agronomic and sequestration benefits
of biochar without compromising the region's energy capacity.
A sensitivity analysis, using the projected 2030 electricity mix (72% lower carbon intensity than 2024 ) is
[49]
used to estimate the future energy benefits, shows that mitigation benefits are drastically reduced [Figure 5B].
Under these conditions, baseline and scenario S1 remain unchanged, while net impacts shift to 1.98 ± 0.48
(S2), 1.72 ± 0.49 (S3), 2.84 ± 0.56 (S4), and 1.71 ± 0.54 (S5) Mt CO -eq·year . Despite this reduction, most
-1
2
scenarios still deliver average emission reductions compared to the baseline (30% for S2, 39% for S3, and 40%
for S5), but uncertainty ranges are closer. Notably, S4 resulted in a negligible reduction of just 0.08%
compared to the baseline, with uncertainty ranges that overlap significantly. Regardless, the structural decline
in substitution credits underscores the essential role of biochar in providing robust climate change
mitigation, ensuring net-negative emissions even when grid decarbonization diminishes the environmental
value of renewable energy generation.

Although the sensitivity analysis frames the climate benefits from large-scale electricity generation as a
temporary climate offset, this should not mask its profound contribution to national decarbonization goals.
The 26 to 52 TWh of renewable electricity generated annually [Table 2] corresponds to a regional renewable
surplus of 115%-230% identified in Section "Scenarios potentials" [Figure 4B]. This capacity is essential for
the energy transition, enabling the decarbonization of the grid and improvements in energy security. In
addition to promoting more sustainable land uses, the proposed scenarios offer two complementary
pathways for climate change mitigation: a durable carbon sink through biochar-carbon storage in
agricultural soil and a large source of clean energy through AVS that can support a phase out of obsolescence
fossil fuel energy from the grid.

Other environmental impacts
Figure 6 provides the results for other environmental impact categories, normalized to the baseline to allow
for comparative interpretation. Absolute values are provided in Supplementary Tables 17-22.