The olive oil market, valued at almost €14 billion in 2023 has tripled its produc-tion over the last 60 years, reaching 3.27 109 kg in 2020. Spain leads the production, accounting for 70% in the European Union and 45% worldwide. This land-intensive in-dustry has significant social, environmental, economic, and territorial impacts, with de-centralized waste generation being a major concern. Sustainable waste management is a fundamental objective. One potential solution is using this waste for low-carbon hydro-gen production through thermochemical processes (e.g. gasification or pyrolysis). This is particularly relevant when hydrogen-consuming industries are nearby. Given this con-text, this work proposes a methodology for assessing the potential of olive grove residues from a sustainability perspective. Our approach uses high-level data from public sources to estimate transport costs and greenhouse gas emissions associated with biomass collec-tion. We identify and quantify suitable waste sources, their locations, and associated hy-drogen production potential. The application of the method is validated through a case study in southern Spain, a major olive oil producer with significant industrial hydrogen consumers nearby. Results indicate that using only available olive grove residues is not currently sustainable for meeting the region’s hydrogen demand, covering merely 0.6% of requirements. This result is the consequence of the current use of olive grove biomass, suggesting the need for revised waste management strategies or alternative resources to increase sustainable hydrogen production. The application of the proposed methodology to other regions can help identify the sustainable potential of using this and similar wastes to produce low-carbon hydrogen.

Electrochemical ammonia synthesis via the nitrogen reduction reaction (NRR) has been poised as one of the promising technologies for the sustainable production of green ammonia. In this work, we developed extensive process models of fully integrated electrochemical NH ₃ production plants at small scale (91 tonnes per day), including their techno-economic assessments, for (Li-)mediated, direct and indirect NRR pathways at ambient and elevated temperatures, which were compared with electrified and steam-methane reforming (SMR) Haber-Bosch processes. The levelized cost of ammonia (LCOA) of aqueous NRR at ambient conditions only becomes comparable with SMR Haber-Bosch at very optimistic electrolyzer performance parameters (FE > 80% at j ≥ 0.3 A cm ⁻²) and electricity prices (<$0.024 per kW h). Both high temperature NRR and Li-mediated NRR are not economically comparable within the tested variable ranges. High temperature NRR is very capital intensive due the requirement of a heat exchanger network, more auxiliary equipment and an additional water electrolyzer (considering the indirect route). For Li-mediated NRR, the high lithium plating potentials, ohmic losses and the requirement for H ₂, limits its commercial competitiveness with SMR Haber-Bosch. This incentivises the search for materials beyond lithium.

Hydrogen is believed to be an important energy vector in the transition to a more sustainable future. However, there is a scarcity of relevant studies analysing the realistic potential for hydrogen production in specific European regions. In this study, the potential for biomass-derived hydrogen is comprehensively analysed considering a realistic use of current biogenic residues in relevant sectors. However, not all residues can be used for the production of hydrogen and an analysis has to be made to find how much biomass is suited for hydrogen production, what amounts of hydrogen can be produced from biomass and how these amounts compare to the specific needs for renewable hydrogen in this region. This study focused on hydrogen production from agricultural residues to provide hydrogen for oil upgrading processes in petroleum refineries. The results indicate that around 92% of all agricultural residues in west-Andalusia can be used for hydrogen generation. Gasification and pyrolysis have been identified as the best candidates for the processing of the selected residues. An annual amount of 33,029 tons of biomass-based hydrogen can be used to provide 14% of the hydrogen demand for petroleum upgrading processes, thereby reducing the need natural gas in this industry.