Page 71 - 2417

Page 2 of 26 Salmerón et al. Carbon Footprints 2026, 5, 17

decrease irrigation demand and provide up to 53 TWh of renewable energy. Trade-offs occur with terrestrial
ecotoxicity and freshwater eutrophication, but using more advanced and efficient panels can mitigate these burdens.
Overall, the combined implementation of biochar and agrivoltaics can co-deliver across multiple environmental
challenges, from local valorization of residue streams to enhanced agroecosystem resilience, climate change
mitigation, adaptation, and renewable energy generation.

INTRODUCTION
The Mediterranean agricultural sector faces increasing vulnerabilities due to climate-driven threats and
farming intensification, exacerbating primarily water scarcity and soil erosion, threatening regional food
security and international economies [1-4] . Water availability is usually a main constraint for agricultural
output, a challenge intensified by severe soil degradation processes . Conventional efforts to maximize crop
[5]
yields through intensive irrigation and fertilization have created negative feedbacks, paradoxically
accelerating soil degradation and deepening the water crisis [1,6,7] . Breaking this cycle and sustaining long-term
agricultural productivity requires innovative solutions that deliver multiple co-benefits. Among these,
negative emission technologies (NETs) like biochar from agro-industrial waste and the deployment of
agrivoltaic systems (AVS) are promising strategies that can simultaneously counteract land degradation
processes, contribute to climate change mitigation and adaptation, improve soil water and nutrient retention,
reduce crop water stress, and generate renewable energy [1,8-11] .

Spain, a leading European agricultural producer , is experiencing severe soil degradation in a relatively
[12]
large share of its agricultural area . The problem is particularly acute in the Andalusia region, where over
[13]
20% of agricultural land suffers from soil erosion rates exceeding 11 t ha year , a threshold defined by the
-1
-1
European Union as “severe” [5,14] . Andalusia dominates global olive oil production, accounting for
approximately 37% of the world's supply, and in turn it is the largest producer of residues from olive process
industries . To meet rising global demand, the Andalusian olive industry has been shifting from traditional
[15]
to intensive cultivation, characterized by high-density planting and mechanization . This intensification
[16]
increases the dependency on irrigation, adding a critical vulnerability in a water-scarce region, and
accelerates soil erosion trends . Projections of climate change impacts further increase risks of water
[6,7]
scarcity and soil degradation processes, creating an urgent need for sustainable management solutions in
olive grove systems [17,18] .

As the olive oil industry expands and intensifies, it creates new opportunities for higher-value utilization of
the organic residues generated at both the agricultural and industrial stages. The Andalusian olive industry
generates over 7 million tonnes (Mt) of residual biomass annually, derived from both olive oil processing
plants and field pruning . About 80% of olive pruning biomass (OP) is crushed and chipped into the soil
[19]
allowing for nutrient recycling, although the benefits for soil organic carbon are minimal as residues quickly
oxidize and their biogenic carbon content is returned to the atmosphere within a couple of years [15,19] .
Another primary residue stream is wet pomace (WP), a residue from the olive oil extraction process
consisting of a mix of pulp, stone, and water. WP has a high organic load and requires further treatment,
often in pomace oil mills where a second oil extraction is carried out, yielding exhausted olive pomace (EOP)
as a by-product. The most common management practice of EOP is combustion for electricity production in
biomass power plants .
[19]

Given the existing local challenges that olive farms are facing and the need to deploy more sustainable
farming practices, these residues represent an opportunity to contrast land degradation and increase climate
resilience. A key strategy for valorizing these residues is the production of biochar, one of the most
promising NETs [20,21] . Biochar is produced from biomass via pyrolysis, a process of thermal decomposition in