Carbon Carriers Driving the Net-Zero Future: The Role of Torrefied Biomass Pellets in Power-To-X

Abstract

The latest Intergovernmental Panel on Climate Change Sixth Assessment Report urgently calls for sweeping action to mitigate the unprecedented impacts of climate change. The path to a carbon-neutral future is intricate, necessitating a multi-faceted approach that integrates decarbonization, defossilization, and energy/resource efficiency. Power-to-X (PtX) stands as a technological linchpin, converting renewable electricity into a range of sustainable products, from fuels to chemicals. However, its full potential is intrinsically tied to the availability of sustainable carbon sources. This paper evaluates the various avenues for carbon sourcing for PtX: direct air capture (DAC), biogenic carbon, and Long-cycle Industrial Carbon. DAC, although promising for the long term, has limitations in scalability and land requirements. Industrial long-cycle carbon capture technology is improving but requires a thorough Life Cycle Assessment for evaluating its sustainability. This study examines the environmental impacts, scalability, and logistical considerations of each carbon source. Biogenic carbon offers a near-term solution, and its various forms could simplify transportation logistics. An analysis of gasification processes, syngas cleaning, and hydrogen integration was conducted to assess the technical viability of these carbon sources in PtX applications. The results show that torrefied biomass pellets, after a thorough technical assessment, present a globally feasible and sustainable carbon carrier, setting the stage for industry standardization and easier global transportation. Syngas produced through the gasification of the pellets complemented by green hydrogen can be utilized in Fischer–Tropsch, methanol synthesis, and methanation, allowing PtX to synthesize practically any type of organic compounds in a hybrid Biomass–PtX (HBPtX) process. This study provides key insights for industries and policymakers by demonstrating the technical feasibility and sustainability of torrefied biomass as a carbon carrier, thereby supporting the development of comprehensive climate mitigation strategies.

1. Introduction

The latest Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report confirms the severe and wide-ranging impact of human activity on the planet, from altering the atmosphere to amplifying extreme weather events [1]. Climate change is no longer speculative; it is our current reality with consequences that are historically unprecedented. The report makes clear that without immediate, decisive action, thresholds like 1.5 °C or 2 °C global temperature rises are not just risks but certainties this century. The IPCC’s findings highlight the urgent need for comprehensive measures to mitigate future devastation and steer toward sustainability.

The journey towards a carbon-neutral or net-zero future is multi-dimensional, requiring both immediate and long-term transformative strategies mainly based on decarbonization and defossilization. The foremost priority is to decarbonize the global economies extensively. Central to this endeavor is electrification, replacing traditional energy processes with systems powered by renewable electricity. For those processes and applications where direct electrification is not feasible, renewable hydrogen emerges as a promising alternative. Its versatile nature allows it to be a clean energy vector in sectors such as heavy industry and transport, enabling a broader scope for decarbonization. Some industrial processes resist full decarbonization due to their inherent complexities. For these, the strategy shifts to defossilization—ceasing the use of fossil-based carbon. Herein lies the relevance of sustainable carbon. In some instances, products, processes and applications can be based on sustainable carbon serving as an intermediate solution, bridging the gap between the current reliance on fossil fuels and a fully decarbonized future.

In aviation, carbon-based fuels remain crucial due to the sector’s reliance on high energy density fuels [2]. While fossil-based jet fuels are the norm, there is growing momentum towards adopting sustainable aviation fuels (SAFs) as an interim solution [3]. SAFs, currently mostly derived from biogenic sources, offer a “drop-in” alternative that can be used in existing airplanes without the need for significant modifications to infrastructure or engines [4]. These sustainable fuels are seen as a bridge to future zero-carbon aviation technologies, such as hydrogen-powered or electric aircraft. However, these emerging technologies face significant technical and economic challenges and are expected to be used in the long term. Therefore, the aviation sector must continue to scale up production, ensure sustainability, and innovate within the realm of SAFs, increasing the use of biofuels and adopting synthetic renewable fuels while, at the same time, decreasing their cost.

The shipping industry, like aviation, is also highly dependent on heavy fossil oil fuels [5]. Most vessels currently in operation have been designed for long lifespans, with many having operational lives of many decades [6]. Retrofitting or replacing these fleets with decarbonized/defossilized alternatives presents significant logistical and financial challenges [7]. As a result, and in line with the 2023 IMO GHG Strategy [8], the sector is turning to drop-in fuels, like renewable methanol and ammonia, for the short to medium-term decarbonization.

Agriculture is another sector facing comparable challenges. Traditional farming practices contribute large amounts of greenhouse gases through the use of fossil-based fuels (mainly diesel) in farm equipment and the application of synthetic fertilizers and pesticides, with their majority derived from fossil carbon [9,10,11]. Improving energy efficiency and adopting renewable energy and biofuels for farming activities is gaining momentum. Additionally, there is a push towards organic [12], conservation [13], and regenerative agriculture [14] farming practices that reduce the reliance on fossil-based chemical inputs. A major innovation in this regard is the development of bio-based fertilizers and pesticides, and the future PtX-derived fertilizers and pesticides. The sector also sees the potential soil carbon sequestration, which can store atmospheric CO₂ into agricultural lands, further supporting the achievement of sustainability goals [15].

The mining sector, with its energy-intensive operations, has historically been a large consumer of fuels like diesel for machinery and transportation [16]. Mining is a key industry supporting global supply chains, but its carbon emissions, both from energy use and process-related emissions, are substantial. Efforts to decarbonize mining are focused on transitioning towards electrification and green hydrogen use [17]. While full decarbonization through electrification is possible in the long term, the sector faces near-term challenges that require drop-in renewable fuels in existing infrastructure.

In the pharmaceutical industry, organic compounds are essential. The most common carbon building blocks used in this sector are derived using fossil fuels and crude oil. However, the sector now faces pressure to transition towards sustainable carbon sources [18].

Currently, plastics are used extensively, with the vast majority produced from fossil carbon in the form of petrochemical feedstocks like ethylene and propylene [19]. The industry is exploring bio-based plastics derived from biomass or algae in a path towards defossilization. Research is ongoing in synthetic plastics utilizing sustainable carbon and renewable energy for their production [20].

The textile industry is another major consumer of carbon for the production of fibers, dyes, and treatments. In the past decades, textiles relied heavily on synthetic materials like polyester, which are synthesized from petrochemicals. In recent years, there has been a growing movement towards sustainable textiles, with efforts on using, again at a higher degree, traditional bio-based fibers such as cotton, hemp, and bamboo [21].

Finally, the chemical industry utilizes carbon feedstock to produce an array of products that are in essence organic compounds. The industry has been heavily dependent on fossil carbon both as a feedstock and an energy source. To achieve decarbonization, the chemical sector must innovate across multiple areas, from the development of green catalysts to the use of sustainable carbon [22]. One promising approach is the use of sustainable carbon in Power-to-X processes to synthesize chemicals traditionally made from fossil feedstocks.

These sectors underline the complexity of the decarbonization challenge and also why defossilization is the only approach in specific sectors. Each sector demands a tailored approach, balancing innovation with sustainability, to pave the way to a carbon-neutral future. Parallel to these strategies is the ongoing imperative of enhancing energy efficiency, which further extends to resource efficiency. As the earth transitions through the various phases of energy transformation, this aspect remains consistently relevant. An intrinsic link binds energy efficiency and the principles of the circular economy. By championing a system where resources are reused, recycled, and regenerated, we not only optimize energy usage but also ensure sustainable consumption, creating a cycle of efficiency and sustainability. In sum, the forward trajectory must be systematic, integrating extensive decarbonization, targeted defossilization, and overarching energy/resource efficiency while efforts to sequester and store already emitted CO₂ from the atmosphere open the possibilities of a carbon-negative future.

In the pursuit of this future, there is a realization that, while the journey is multifaceted, one remarkable approach stands out with the potential to address many of the challenges: Power to X (PtX) [23]. PtX embodies the nexus of cutting-edge technology and sustainability, converting surplus renewable electricity into multiple applications. This process can produce gaseous and liquid fuels and chemicals—the ‘X’ in PtX. Sustainable chemicals, a cornerstone for industries ranging from pharmaceuticals to textiles, emphasize the expansive reach of PtX technologies beyond the energy sector. But for PtX to truly revolutionize and defossilize our world, it requires a sustainable carbon source. This connection underscores the symbiotic relationship between PtX and a sustainable, carbon-neutral ecosystem. With PtX, the potential rises not only to innovate but to rejuvenate industries, anchoring them in sustainability and propelling the world closer to the vision of a carbon neutral future.

The primary objective of this study is to evaluate torrefied biomass pellets as a viable, sustainable carbon carrier for use in Hybrid Biomass Power-to-X (HBPtX) processes. Specifically, this study aims to explore the potential of these pellets to maximize carbon efficiency in renewable fuel production, by integrating biomass gasification with green hydrogen supplementation for optimal syngas generation. This study’s approach includes the following: (i) a comprehensive review of different carbon sourcing methods (direct air capture, biogenic carbon, and industrial long-cycle carbon) in the context of PtX technologies; (ii) a comparative analysis of various biomass-derived carbon carriers, focusing on their technical feasibility, scalability, and transportability; and (iii) the proposal of a novel HBPtX pathway that optimizes the H₂-ratio for a Fischer–Tropsch synthesis and other chemical processes and also opens up the possibilities for the combined simultaneous use of bio-hydrogen and green hydrogen in PtX. This work offers an original contribution by presenting torrefied biomass pellets as a globally scalable and standardized carbon solution for decarbonizing hard-to-electrify sectors like aviation and heavy industry.

2. Sustainable Carbon

Carbon’s role in our planetary climate is fundamentally determined by its cycling duration within our atmosphere. The IPCC differentiates between short and long-cycle carbon. Short-cycle carbon is released and absorbed within relatively brief timeframes, typically through processes involving living organisms, while long-cycle carbon remains in the atmosphere for extended periods, often due to human-induced activities like the burning of fossil fuels. As we strategize towards a sustainable future, especially through the lens of PtX applications, understanding the sources of carbon becomes paramount. There are primarily three approaches to obtaining carbon other than using fossil fuels, each with its nuances rooted in the context of these carbon cycles.

Direct Air Capture (DAC) is the first method. It uses chemical processes to extract CO₂ from the atmosphere, turning it from a greenhouse gas into a usable resource. Unlike other methods, DAC does not rely on industrial waste or biological cycles and can be installed almost anywhere. However, the technology faces hurdles in scalability, energy demands, and economic viability. Current systems require substantial energy, which needs to be sourced from renewable sources to operate carbon neutrally. Initial studies over a decade ago projected costs of ~USD 600/t [24]. Companies developing DAC technologies were optimistic in 2018, citing costs of ~USD 100/t. In [25], the cost was projected between USD 94 and 232/t depending on assumptions. Pioneering companies like Climeworks (Zürich, Switzerland) stated in 2024 a projected cost between USD 250/t to USD 350/t by 2030, while acknowledging that the current cost is around USD 1000/t [26]. A recent scientific study estimates the cost between USD 230/t and USD 540/t [27]. Finally, one aspect that is usually ignored is the land required for PV/Wind parks to generate the power for such a facility. A major land requirement between 30–60 km²/MtCO₂ to deploy PVs or wind turbines would be needed [28]. While promising, DAC’s mainstream adoption is likely a medium to long-term prospect, pending further research into its lifecycle and infrastructural requirements, as well as overall cost decreases [29].

Biogenic carbon, a form of short-cycle carbon, comes from biological sources like plants and waste products. Its renewable nature makes it an attractive option for industries looking to reduce fossil carbon use. Particularly, point-source emissions from industrial sites using biomass as primary fuel represent the “lowest hanging fruit” for biogenic carbon capture but with the caveat that the use of CO₂ takes place in the vicinity or otherwise expensive and challenging pipelines would need to be deployed [30]. Other forms of biomass (e.g., solid or liquid) can be transported with more ease. Advancements in technology have also expanded biogenic carbon applications to include biofuels, biochemicals, and bioplastics [31]. However, it is essential to recognize that, while biogenic carbon is part of a natural cycle, the scale and manner in which it is harvested and utilized can influence its sustainability attributes.

The final category, Long-cycle Carbon Captured from Industrial Sites, mainly involves capturing carbon from fossil fuel-based processes, as well as “unavoidable carbon” from materials like lime in cement production. Although capturing this CO₂ can offer immediate benefits, it is not inherently sustainable given it is long cycle. It would be optimal for this captured carbon to be stored rather than utilized, to prevent its eventual release into the atmosphere. While CO₂ capture technology has advanced significantly with improved efficiency and lower costs, its integration into industrial operations remains a complex issue [32], considering also the challenges in transporting CO₂ if collocation is not possible. A detailed Life Cycle Assessment is crucial to determine the environmental impact of using captured carbon, especially as industries aim to lower their carbon footprints and mitigate climate change effects [33].

Navigating the transition to a carbon-neutral future necessitates scrutinizing available carbon sources. DAC stands out for its ability to directly remove atmospheric CO₂, but current limitations in technology, energy, and costs impede its immediate deployment. The projected DAC costs for 2030 are considered high [26]. Industrial carbon capture offers a practical way to repurpose existing emissions, although it poses sustainability issues when sourced from fossil fuels. Fuels derived from long-cycle carbon (incl. unavoidable carbon) often fail to meet the stringent LCA limits set in legislations around the world (e.g., the EU’s Delegated Acts on Renewable Fuels of Non-biological Origin) to be classified as renewable. As an example, according to IRENA [34], renewable methanol produced by renewable electricity and CO₂ captured from a coal plant has raw material to final use GHG emissions of 33.1 g CO_2eq/MJ in comparison to just 0.5 g CO_2eq/MJ of renewable methanol produced by renewable electricity and CO₂ from a biogas process. Biogenic carbon, on the other hand, presents a short-term solution that leverages nature’s carbon cycle, and different forms are available in solid, liquid, or gaseous states. While DAC technologies continue to evolve, biogenic carbon serves as an essential bridge strategy, relevant both now and in the long term when other methods attain commercial viability, especially given the fact that it can be made available in a form other than a gas facilitating transportation logistics.

3. Investigation of a Sustainable Carbon Carrier

Biomass, derived mainly from plants, is not just a renewable energy source but also a carbon reservoir. Carbon extraction from biomass employs methods like gasification, converting organic matter such as agricultural residues into usable carbon forms. However, the label ‘sustainable biomass’ entails meeting environmental, social, and economic standards [35]. Environmentally, it should not cause deforestation, change land use, or cause biodiversity loss and should ideally sequester more carbon than it emits. Socially, it must respect land rights and ideally benefit communities. Economically, its long-term viability should not disrupt markets or food security. As a potential carbon source for a greener future, the responsibility is on both industries and policymakers to ensure that biomass is sustainably managed.

Research into biomass, particularly forestry and agricultural residues, reveals substantial global potential for sustainable carbon. An estimated 4.6 Gt of wood biomass waste is generated annually, with about 20% considered production losses [36]. Estimates for crop residues vary, but they generally range between 3700 and 5409 million tonnes of dry matter [37]. Technical recovery varies by factors like crop type and geography. Some studies assess the global technical energy potential from crop residues to be between 39 and 42 EJ currently, and 38–41 EJ by 2050, factoring in that 70% is harvestable [38]. Other studies estimate for a 2050 range from 10 to 32 EJ, highlighting variability and challenges in calculating sustainable use [39].

For the quest of a sustainable carbon carrier to be truly global and impactful, it must embody a set of characteristics that addresses both functional needs and environmental concerns. To effectively identify the most suitable biogenic carbon carrier for integration into PtX processes, a robust framework of characteristics is essential. The chosen criteria—global scalability, standardized production, universal applicability, transportability, simplicity, flexibility in end use, and immediate technological feasibility—were selected to ensure that the carbon carrier can be seamlessly integrated into existing energy and industrial systems worldwide. These characteristics address key logistical, technical, and economic challenges associated with implementing biogenic carbon at scale, while prioritizing sustainability. Together, they provide a comprehensive framework to evaluate the viability of carbon carriers across diverse geographic, technological, and market contexts [40]:

• Global Scalability: The carbon carrier process should be universally viable, cost-effective, and adaptable to various biomass types and climates. Its scalability must meet global sustainability demands.
• Standardized Production: Standardized carbon carriers are crucial for consistent quality, performance assessment, and regulatory compliance, regardless of geographic origin.
• Universal Applicability: The process should enable global inclusivity, letting countries use local biomass to create a standardized carbon carrier, provided they meet sustainability criteria.
• Transportability: The carbon carrier’s design should facilitate global shipping and integrate easily with existing logistic infrastructure, avoiding the need for major changes. Transport costs vary; they are location-dependent and also depend on the carrier physical state—solid (e.g., wood logs, pellets, or torrefied biomass pellets), liquid (e.g., biocrude), or gaseous (e.g., CO₂ or CO). Solid carriers like pellets offer higher volumetric density and are generally easier and cheaper to transport using conventional logistics infrastructure. Liquid and gaseous forms require more specialized handling, with liquids like biocrude offering medium transport costs and gases like CO₂ or CO demanding high costs due to pressurization or refrigeration needs.
• Simplicity and Accessibility: The beauty of the ideal carbon carrier lies in its simplicity. Especially for upstream processes typically situated in remote areas often in the developing world, the technology should be straightforward, durable, and not reliant on high-tech apparatus or specialized expertise.
• Flexibility in End Use: The initial production should not be tethered to a specific end fuel or chemical. Given that the Fischer–Tropsch synthesis, methanol synthesis, and methanation are based on CO_x and hydrogen, the carbon carrier should be versatile enough to serve all the above process.
• Immediate Technological Feasibility: Only technologies that are commercially available and ready to be deployed should be integrated into its production process.

The investigation towards finding an ideal carbon carrier began with an exploration of various carbon allotropes (e.g., graphite, carbon black, graphene, etc.), all of which posed at least one attribute, making it very challenging to be used as a carbon carrier [40]. Traditional biomass forms mostly used as energy carriers were investigated afterwards [40]:

• Wood Chips: These have low carbon content and bulk density. Their quality can be impacted by many factors like humidity, storage conditions, and more. Transporting wood chips over long distances would be inefficient due to these factors.
• Wood Pellets: More standardized than wood chips, wood pellets are easier to transport and handle. However, they still have issues, such as sensitivity to moisture and high volatile matter content, which can cause challenges in fuel synthesis.
• Charcoal: It has a higher carbon content, and it is already produced at significant scales in numerous countries around the world. However, the pyrolysis process used to produce charcoal is carbon inefficient, and the charcoal’s low bulk density makes it costly to transport.
• Activated Carbon: This form of charcoal has undergone treatments to increase its surface area, making it highly absorbent. This very feature could be problematic if the activated carbon were to absorb other materials during transport.
• Charcoal Briquettes: By adding a binding agent, charcoal can be formed into briquettes. These have increased bulk density although still requiring large volumes due to large porosity, reducing some of charcoal’s transport challenges. However, the need for binding agents could introduce new issues.
• Torrefied Biomass: It serves as a promising carbon carrier due to its high carbon content, energy density, and renewability. While torrefaction improves many characteristics, the lack of uniform shape or size complicates handling and transport.
• Torrefied Biomass Pellets: An approach bridging the benefits and drawbacks of “white” wood pellets and torrefied biomass, which also benefit from the fact that they do not require binding agents for pelletizing [41].

After evaluating the various options, torrefied biomass pellets stand out as the most attractive choice. Torrefaction, a thermochemical process, enhances the carbon content of the biomass while preserving the majority of the original feedstock’s carbon, also allowing for a uniform product regardless of the feedstock’s origin [42]. The potential to use a diverse range of initial biomass feedstock but arrive at a uniform torrefied biomass pellet can be revolutionary. The pelletized form enhances its utility and sets the stage for industry-wide standardization as well as facilitating transportation. This characteristic makes a global market for torrefied biomass pellets increasingly likely, bolstered by existing sustainability standards like SBP and SURE [40], as well as ISO 17225-8:2023 [43], concerning the actual pellet. However, some challenges remain, such as the multi-step production process and its dual role as a carbon and energy carrier, which can affect its market dynamics, but those can be surpassed [40]. Overall, torrefied pellets emerge as a compelling solution, harmoniously combining sustainability with practicability.

4. Incorporating Biomass in PtX

The transition from a fossil fuel economy to a net-zero future is driven by the need for sustainable energy solutions. Central to this narrative is the integration of biomass in PtX processes. This study introduces a novel process combining bio-hydrogen and green hydrogen for the production of synthetic fuels within the Hybrid Biomass Power-to-X (HBPtX) framework. While technically feasible, this hybrid approach has not been previously proposed due to the historical focus on biomass energy content rather than its carbon potential. In earlier biomass-to-X processes, biogenic CO₂ was released into the atmosphere without concern, or, in recent times, after the introduction of monetary incentives, captured for storage. However, with the evolving focus on decarbonization, the use of biogenic carbon in tandem with green hydrogen presents a new pathway to sustainably transport carbon to where it is needed for synthetic fuel production. This approach aligns with emerging global green hydrogen projects and addresses the limitations of point-source carbon capture, which, while it is indeed the lowest hanging fruit, is insufficient to meet broader climate targets like those outlined in the Paris Agreement and EU Green Deal just because of the carbon quantities that are going to be needed for the global energy transition. The declining cost of green hydrogen further supports the economic feasibility of this new process, offering a promising alternative to traditional biomass-to-X methods.

The intricacies of this integration can be best understood by dissecting the value chain, understanding each step and its significance.

• Harvesting and Preparation:
  • This phase serves as the foundation of the entire chain. Biomass is harvested in line with sustainability requirements that are met following a standard.
  • To ensure efficiency and control costs, research studies recommend a 100 km harvesting radius, serving dual purposes of sustainability and economic feasibility [40].
  • The biomass is subsequently chipped.
• Torrefaction and Pelletization:
  • Biomass undergoes torrefaction.
  • Pelletization follows, transforming the torrefied biomass into uniformly shaped entities.
• Transportation:
  • The torrefied pellets redefine transportation efficiency. Their physical and chemical properties allow integration with existing global logistic infrastructures, negating the need for specific, customized transportation systems. The ability to use standard grain handling equipment is an added bonus.
• Gasification:
  • The torrefied pellets are converted into syngas and any CO₂ byproduct is also captured for use.
• Synthesis of Renewable Fuels:
  • Using processes like Fischer–Tropsch, methanol synthesis, or methanation, the syngas is transformed into renewable fuels and chemicals.

The spatial distribution of this value chain is straightforward. The initial stages focus on biomass sourcing and preparation, while the culmination is centered around the production of green, renewable drop-in synthetic fuels and chemicals. A traditional biomass-to-X (BtX) process has its strengths but also possesses inherent inefficiencies, primarily the mismatch in the H₂:CO ratio when moving from gasification to Fischer–Tropsch synthesis. In detail, the torrefied biomass pellets, already energy-dense due to torrefaction, are gasified. The result is a syngas with a H₂:CO ratio close to 1:1. However, processes like the Fischer–Tropsch synthesis demand a higher H₂:CO ratio, usually around 2:1. The proposed Hybrid Biomass Power-to-X (HBPtX) process addresses this demand by introducing supplementary green hydrogen, adjusting the ratio for optimal synthesis, and further engaging in the conversion of captured CO₂ during the gasification to CO utilizing the inverse water gas shift reaction, maximizing carbon use and minimizing vented carbon in the atmosphere (see also Figure 1). Taking into consideration the expected decreased cost of green hydrogen [44], this approach maximizes short-cycle carbon use while minimizing the overall cost of the end fuel or chemical. The conventional BtX approach, while economically optimized, often neglects carbon efficiency [45]. However, with the growing global emphasis on sustainability, carbon neutrality, and the possibility of a cost increase in sustainable carbon, the focus is shifting. The HBPtX represents a paradigm shift from the conventional BtX by incorporating green hydrogen, which is instrumental in optimizing the syngas ratio for the Fischer–Tropsch synthesis and offering cost optimization as the cost of green hydrogen decreases.

5. Discussion and Conclusions

The integration of biomass in PtX processes, while brimming with promise, is laden with challenges. At the forefront lies the issue of technological maturity. The infusion of biomass in PtX, although making significant strides, is still perceived as a nascent approach. Doubts about its scalability and commercial viability in fluctuating economic terrains are yet to be fully alleviated. Complementing the technological challenges is the complex matrix of supply chain integration. The journey of biomass, from its source to its eventual utility, demands a seamless interlinking of disparate processes. Especially in regions where infrastructure might be needed, ensuring a streamlined flow becomes logistically challenging. Furthermore, sustainability in harvesting becomes pivotal. Yet, despite these roadblocks, the prospects remain tantalizing. It is envisioned that not only can the HBPtX process offset carbon footprints but also potentially tread into the realm of being carbon-negative when soil carbon sequestration strategies are also implemented, while growing and managing the source biomass [46]. Such a feat would be momentous in the current climatic scenario, offering a tangible blueprint to meet, if not surpass, global sustainability benchmarks.

Another aspect that must be highlighted is that defossilization is not only concerned with the energy sector in general and fuels in particular. As presented in the Introduction, there are several sectors that utilize organic compounds currently synthesized using fossil carbon. For these applications, defossilization is the only realistic approach to a net-zero future. PtX has the potential to synthesize the organic compounds required using short-cycle carbon. This is of immense value to industries like pharmaceuticals, textiles, and plastics.

Moreover, the socioeconomic outlook stands to be transformed. As biomass collection, processing, and conversion facilities become integral to this energy landscape, they can potentially invigorate local economies, especially in developing world countries. Employment vistas would broaden, and a renewed vigor might be infused into industries tethered to this energy pivot. If the vision of transforming torrefied biomass pellets into a standardized global commodity materializes, it might recalibrate global trade dynamics, positioning sustainable biomass-abundant nations as energy linchpins.

The geopolitical sphere might also witness novel alignments. Energy accords, reminiscent of oil treaties of the old days, could be sculpted, facilitating biomass trade and technology synergies. It is imagined that nations rich in biomass reserves offering a sustainable short-cycle carbon source might forge pacts with counterparts that boast technological expertise. Such symbiotic alliances could expedite the global embrace of HBPtX. Community dynamics are also poised for a shift. For the HBPtX vision to truly manifest, communities, especially those ensconced in biomass-rich locales, need to be active stakeholders. Their socioeconomic aspirations need to align with overarching sustainability targets.

In summary, this integrated HBPtX approach functions as a crucial interim solution on a global scale as the commercial readiness of DAC technologies continues to evolve. Its significance is not merely short-lived; it is also a long-term consideration. The land/space demands of DAC systems could be impractical in specific settings. In contrast, the biomass pathway offers a viable supplement, particularly in locations where DAC deployment might be unfeasible and where gas transport would incur logistical and financial obstacles.

The primary aim of this research was to identify a scalable, sustainable carbon carrier for Hybrid Biomass Power-to-X (HBPtX) processes that maximizes carbon efficiency and supports global decarbonization efforts. Our findings indicate that torrefied biomass pellets, when combined with green hydrogen, provide a technically feasible and economically promising solution. The original contribution of this study lies in the proposal of a hybrid approach that integrates biogenic carbon and green hydrogen, addressing both carbon efficiency and cost reductions in synthetic fuel production. This hybrid process, while previously unconsidered, emerges as an essential step toward meeting climate targets such as the Paris Agreement and the EU Green Deal. Policymakers should consider incentivizing the development of biomass-based carbon carriers, support the infrastructure for green hydrogen integration, and create market mechanisms that favor carbon efficiency over energy content in biomass-to-X processes.

In conclusion, the foray into HBPtX symbolizes more than an energy transition; it encapsulates a paradigmatic shift spanning economic, social, and environmental dimensions. The challenges, albeit significant, are not insurmountable. With a harmonized global approach, judicious investments, and unwavering sustainability ethos, the promise of HBPtX could well be realized.