This study aims to design and evaluate the techno-economic feasibility of socially just and context-specific biohubs for producing marine biofuels based on olive residues with hydrothermal liquefaction (HTL) in Spain, using existing infrastructures. The conceptual process and biohubs design are co-designed using a multi-actor approach, involving local stakeholders through participatory methods, with the help of a Capability-sensitive design. The material and energy balances (from Aspen Plus simulations) are used to evaluate the technical and economic performance (such as capital expenses, operational costs, and minimum fuel selling price) of biohub. 21 possible scenarios are investigated to understand the impact of design aspects (such as scale, distributed configuration, and co-processing) on the minimum fuel selling price (MFSP). The MFSP of the HTL biofuels varied by a factor of 0.6–3.1 compared to the conventional fossil-based fuels. Additionally, co-processing of HTL bio-crude at existing petroleum refineries reduces equipment costs by 16%. The study also recommends that the minimum scale of the HTL facilities should be between 588–882 dry tons per day (DTPD) of crude olive pomace processing capacity, to benefit from economies of scale. Overall, the investigation shows an economically feasible way to develop context-relevant olive residue-based biohubs for marine biofuel production with existing infrastructures in Spain, while ensuring social justice near biomass production sites. We argue this approach can be replicated in the other olive-producing regions in the Mediterranean and conclude that olive residues from the Mediterranean region have a huge potential to provide alternative advanced “drop-in” biofuels for the shipping sector.

The bioeconomy has the potential to contribute significantly to sustainable development and a just transition. To ensure the sustainable production of bio-based products, it is essential to understand their potential environmental, economic, and social impact. However, the social dimension receives far less attention in sustainability literature and assessments than the environmental and economic dimensions. Especially in the Global South, where a large part of the world's biomass is produced, vulnerable communities are at higher risk of being negatively affected by the bioeconomy. These risks include food insecurity, monoculture expansion, and unequal wealth distribution. Therefore, it is crucial to understand new bio-based value chains' (potential) social impacts better. This paper contributes to this debate by developing a prospective Social Life Cycle Assessment (SLCA) for a bush-based value chain in Namibia. We assessed the existing charcoal value chain and identified potential social risks, impacts, and opportunities of a prospective value chain to produce marine biofuels from encroacher bush. We use this case study to reflect on the SLCA methodology and compare the SLCA results with our qualitative fieldwork based on interviews and a multi-stakeholder workshop. We found that the current methods for SLCA do not adequately capture salient aspects of the local context. SLCA is a good method to quantify some social impacts and to identify social risks in the value chain, such as labor conditions and existing policies. However, the methodology of SLCA currently misses a more nuanced understanding of the context and potential social issues, like issues related to gender and ethnicity, and the adherence to existing policies. We propose adding more context-specific indicators to the risk assessment. In addition, stakeholder engagement is crucial for identifying and assessing relevant social impact categories, and we advocate for incorporating local stakeholders' subjective assessments. This approach allows for the inclusion of softer social impact categories, such as gender and ethnicity-related social norms, which are not easily captured by general indicators.

To be the first carbon-neutral continent by 2050, the European Union (EU) should decarbonize the aviation sector. According to the ReFuel initiative, sustainable aviation fuels (SAFs) are crucial in reducing carbon emissions from the sector. The Clean Sky 2 program by the EU commission, shortlisted four promising technologies - hydro-processed esters and fatty acids (HEFA), Fischer–Tropsch (FT), fast pyrolysis (FP), and alcohol-to-jet (ATJ) for the production of SAFs from bio-based sources. This study addresses the potential of these four technologies to reduce net and total greenhouse gas (GHG) emissions in the aviation sector. With a focus on mapping feedstock availability in 33 European countries for meeting the national demand in 2030. The investigation identified the best pathway combinations for each country, having the highest GHG emissions reduction while satisfying fuel demand when considering different degrees of biomass competition. Without any political and economic barriers to SAF production and biomass competition, we estimated a sufficient biomass supply exists to support the European SAF demand across all forecasted scenarios in 2030.

Advanced biofuels from thermochemical liquefaction, such as pyrolysis (PY) and Hydrothermal liquefaction (HTL), of olive residues in the Andalusian region of Spain (specifically in the province of Jaen) can potentially play a crucial role in the reduction of greenhouse gas (GHG) emissions in the maritime sector. In this study, an attributional life-cycle assessment (ALCA) was performed to estimate and compare the GHG emissions for producing marine biofuels via pyrolysis and HTL from olive pomace (COP) and pruning biomass (OTPB), to provide 1 megajoule (MJ) of marine biofuel, as a functional unit. For convenience, the different technology-feedstock combination scenarios are represented as scenario 1 (PY_COP), scenario 2 (PY_OTPB), scenario 3 (HTL_COP), and scenario 4 (HTL_OTPB). The life-cycle GHG emissions of the biofuels were 42.0, 44.1, 22.1, and 32.1 g CO₂-eq/MJ for PY_COP, PY_OTPB, HTL_COP and HTL_OTPB scenarios, respectively, corresponding to 47–73% GHG emissions reduction compared with petroleum fuels. The scenarios were also evaluated based on other impact categories such as Sulphur dioxide in the air, Nitrogen oxides in the air, Particulates in the air, and Non-methane volatile organic compounds (NMVOCs) in the air. The scenarios reduced the SO₂ emissions, Nitrogen emissions, NVMOCs, and particulates in the air by at least 50%, 90%, 20%, and 25% respectively in comparison to fossil fuels. A contribution analysis revealed that olive cultivation and upgrading as hot spots for emission in pyrolysis-based systems. Likewise, HTL conversion and upgrading steps were emitting more emissions for an HTL-based system. Therefore, marine biofuel obtained through the thermochemical conversion of olive residues has better environmental performance on a life cycle basis, with a preference for HTL based system over pyrolysis.