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Page 6 of 26 Salmerón et al. Carbon Footprints 2026, 5, 17

The pyrolysis process is modeled using primary data from a local biochar producer . The system is
[47]
energetically self-sufficient by combusting the pyrolysis co-products in an on-site Combined Heat and Power
(CHP) unit; the generated energy covers plant operations, and the excess power is exported to the market.
To ensure a fair comparison with the baseline scenario (where biomass is combusted for energy),
environmental credits are only claimed for the net surplus electricity generated beyond the baseline output,
where power plants are reported to produce 0.77 kWh per kg of EOP processed . This surplus electricity is
[45]
credited by displacing the 2024 Spanish grid mix [Supplementary Figure 2], which had a 56% renewable
share and an average emission factor of 0.10 kg CO2-eq kWh -1[48,49] . To reflect the future decarbonization of
the grid, we performed a sensitivity analysis on the substitution credit for surplus electricity. The impact of
using the energy mix forecast for Spain in 2030 (81% renewable energy; 0.029 kg CO2-eq kWh -1[49] ) was
compared with the results based on the Spanish grid in 2024.

For the AVS technology, LCI data includes all material inputs and the water requirements for panel
cleaning . The irrigation activity from the agricultural stage is modified in AVS-equipped scenarios to
[33]
reflect associated water savings. As with the CHP, electricity produced from AVS is credited as a replacement
for the Spanish electricity mix.

Because the credit for displaced electricity is a methodological assumption that does not account for
potential changes in electricity demand, market dynamics, or national policies (such as increased export
targets), these credits are reported separately in the results. This allows the findings to be interpreted either
with or without their contribution.

Biochar production
The pyrolysis system is modeled based on the region feedstock availability [Supplementary Table 7]. We
model a biomass throughput of 80 t hr and 7,000 operating hours per year [11,50] , which corresponds to 4
-1
plants with a capacity of 510 kt year of dry biomass.
-1

The pyrolysis process requires a biomass moisture content lower than 10% . While EOP already meets this
[51]
moisture requirement , the OP has a higher water content, meaning that the EOP-OP feedstock mix needs
[19]
to be pre-dried from 26% to 10% . Then, the biomass undergoes slow pyrolysis at 500 °C, modelled using
[39]
primary data from a local biochar production facility, with a biochar yield of 28% . The remaining
[47]
co-products, bio-oil and pyrolytic gases, are combusted in an on-site CHP unit to produce electricity and
heat at 28.5% and 65% efficiencies, respectively . The heat is used to satisfy the energy demands of the
[52]
drying process and the pyrolysis unit , while the surplus electricity is exported to the Spanish national grid,
[47]
with displacement credits applied solely to the net generation exceeding the baseline. Emissions to air from
the CHP combustion are from operational data, validated with literature [47,52,53] . The resulting flue gas is
considered to go through a scrubber with efficiency 90% in order to remove SO and NO , pollutants that
X
2
surpass the limit set for the national regulation . The complete life cycle inventory of the pyrolysis system is
[54]
presented in Supplementary Table 2.
The plant locations were modeled to minimize transport distances from feedstock collection points to the
pyrolysis unit, and from the unit to the biochar application fields. The methodology for estimating these
distances is provided in Supplementary Text 1, with its visualization in Supplementary Figure 1 and the
specific distances shown in Supplementary Table 6.

Agrivoltaic systems deployment
The agrivoltaic system is designed for integration into existing olive groves in Andalusia. The feasibility and
performance of such a system are highly dependent on its design, with key parameters like panel height, row