This study presents a novel bottom-up approach to co-design inclusive biohubs based on field residues, namely olive tree pruning, coffee pulp, and acacia bush in Spain, Colombia, and Namibia, respectively, to produce “drop-in” marine biofuels (MBF) via hydrothermal liquefaction (HTL). The economic feasibility and environmental footprint of the designed biohubs are investigated through a detailed techno-economic and attributional-environmental life cycle assessment. This study introduces an early-stage, context-specific, capability-sensitive, and stakeholder-inclusive approach to conceptual design by integrating process simulations, process economics, and life-cycle environmental assessment. The outcomes indicate that an MBF yield of 5–10 wt% is achievable at a production cost of 1.2–3.9 EUR/kgbiocrude. The upgrading costs were estimated between 0.12 and 0.90 EUR/kgbio-oil, resulting in a minimum fuel selling price (MFSP) of 0.94–4.45 EUR/kgMBF, after fractionation, which is 1.05 to 5.50 times (without carbon credits) that of the current fossil marine fuel (0.8–0.9 EUR/kgMGO). After mass allocation, the greenhouse gas (GHG) emissions of the derived MBF were estimated in the range of −43.4 to 10.9 g-CO2 eq./MJmarine biofuel, thereby indicating an immense potential to reduce global warming impacts. A sensitivity analysis showed that i) At smaller scales, the MFSP is found to be more sensitive to the HTL equipment costs than to feedstock prices; ii) The process economics could be improved through technological advancement and scale-up, and iii) Contextual factors plays crucial role in process design and sustainability of the biofuels. This study concludes that the proposed approach will aid in improving acceptability and in achieving global commercial-scale deployment of the bioeconomy.

Biobased value chains (BBVCs) are increasingly seen as a promising pathway for fossil-free transition. For hard-to-abate sectors, such as maritime industry, drop-in biofuels are considered as short- to mid- term solution for achieving the climate targets by 2030 and 2050. However, after decades of research and development, biobased value chains still faces numerous challenges for real-world implementation. These challenges are diverse and complex in nature such as technical, economic, environmental, and social. These barriers are to be addressed, to enable large-scale commercial deployment of bio-based value chains which is needed for bulk sectors such as maritime biofuels. This dissertation approaches the problem in a holistic manner and aims to develop context-specific, inclusive, and sustainable design of bio-based value chains for marine biofuels through hydrothermal liquefaction (HTL) technology. A transdisciplinary approach (including process simulation, participatory methods for stakeholder engagements, and integral sustainability analysis) is implemented to integrate the technical and non-technical aspects of the value chain in the early stages of conceptual design. The investigation focuses on the underutilized or mismanaged lignocellulosic residues from the olive sector in Spain, Coffee sector in Colombia, and the encroacher bush sector in Namibia with a special consideration on local socio-economic development at or near the region of biomass production. As a result, various biohub models were co-designed using multi-actor approach tailored to local context of BBVC implementation. The techno-economic assessments indicated that the economic performance of the HTL biofuels are expensive than their fossil counter parts, however with a potential to compete when existing infrastructures are utilized. In terms of environmental performance, the HTL biofuels were able to reduce emissions, specifically carbon-di-oxide, by at least 89% adhering to the policy regulations. This dissertation concludes that early stage integration of (technical and non-technical) contextual knowledge in the conceptual design has the ability to identify, address, and overcome the existing challenges for implementing bio-based value chains in more responsible manner thereby leading to a global, sustainable, and inclusive fossil-free future.

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.

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.

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.