Here is a brief introduction to the twelve main methods to produce sustainable fuel from biomass and an analysis.

Esterification of fatty waste

Primarily produces a biodiesel fuel similar to diesel. For 1 tonne of dry matter input, it yields 10.7 MWh of liquid fuel and 0.15 tonnes of glycerin. The accessible resource potential in 2050 is 0.5 MtMS.

Hydrogenation of fatty waste

Produces Hydrotreated Vegetable Oil (HVO), a high-quality diesel and kerosene-like fuel. It yields 11.5 MWh of diesel + kerosene and 0.88 tonnes of product per tonne of dry matter input. The accessible resource potential in 2050 is 0.5 MtMS.

Fast pyrolysis

Produces bio-oil, which can be further refined into diesel and kerosene. It yields 2.5 MWh of diesel + kerosene and 0.2 tonnes of product per tonne of dry matter input. The accessible resource potential in 2050 is 38 MtMS.

Hydrothermal liquefaction

Produces a bio-crude that is then upgraded to diesel and kerosene, along with naphtha. It yields 3 MWh of diesel+kerosene and 0.2 tonnes of product, along with 0.5 MWh and 0.08 tonnes of naphtha per tonne of dry matter input. The accessible resource potential in 2050 is 40 MtMS.

Hydrothermal gasification

Produces a syngas rich in methane (biomethane). It yields 3.3 MWh of methane and 0.3 kg of methane per kg of dry matter input, along with 0.25 kg of CO2. The accessible resource potential in 2050 is 40 MtMS.

Pyrogasification (Fischer-Tropsch)

Produces a syngas that is converted into various hydrocarbons, including diesel, kerosene, and naphtha. It yields 2.6 MWh of diesel+kerosene, 0.2 tonnes of product, 0.4 MWh and 0.03 tonnes of naphtha, and 1.2 tonnes of CO2 per tonne of dry matter input. The accessible resource potential in 2050 is 38 MtMS.

Pyrogasification (methanation)

Produces a syngas that is then converted into biomethane (CH4). It yields 3.3 MWh of methane and 0.2 kg of methane per kg of dry matter input, along with 0.9 kg of CO2. The accessible resource potential in 2050 is 37 MtMS.

Pyrogasification (methanolation)

Produces a syngas that is converted into methanol, which can then be used to produce diesel and kerosene (via Methanol-to-Jet fuel - MTJ). It yields 2.3 MWh of diesel+kerosene and 0.17 tonnes of product, along with 0.24 tonne of CO2 per tonne of dry matter input. The accessible resource potential in 2050 is 38 MtMS.

Fermentation

Produces ethanol from lignocellulosic biomass, which can be further converted into kerosene and synthetic diesel (via Alcohol-to-Jet fuel - ATJ). It yields 1.5 MWh of diesel+kerosene and 0.11 tonnes of product, along with 0.2 tonne of CO2 per tonne of dry matter input. The accessible resource potential in 2050 is 33 MtMS.

Methanisation (methanolation)

Uses biogas (methane and CO2) from anaerobic digestion to produce biomethanol, which can then be converted to diesel and kerosene (via MTJ). It yields 2.3 MWh of diesel + kerozene, 0.18 tonne of product, 0.17 tonne of CO2, and allows for 0.5 tonne of organic matter to return to the soil per tonne of dry matter input. The accessible resource potential in 2050 is 63 MtMS.

Methanisation (purification)

Produces biomethane (CH4) and CO2 through anaerobic digestion and subsequent gas purification. It yields 2.5 MWh of methane, 0.16 tonne of methane, 0.32 tonne of CO2, and allows for 0.5 tonne of organic matter to return to the soil per tonne of dry matter input. The accessible resource potential in 2050 is 63 MtMS.

Combustion

Directly produces heat from dry biomass. It yields 4.9 MWh of heat per tonne of dry matter input. There is no mass yield of a fuel vector in this direct energy conversion process. The accessible resource potential in 2050 is 43 MtMS.

Analysis

Several key trends emerge from the analysis of these biomass valorization pathways. Firstly, there's a clear distinction between more mature technologies like esterification, hydrogenation of fatty wastes, and combustion (TRL 9), and those still in demonstration or early commercial stages, such as various pyrogasification routes and hydrothermal liquefaction (TRL generally below 8). Fermentation, while having mature technologies, faces economic challenges in large-scale deployment.

Secondly, the intended use of the energy vector significantly influences the chosen pathway. Many of the fuel production routes (esterification, hydrogenation, pyrolysis, liquefaction, Fischer-Tropsch, methanolation, ATJ) are primarily targeting the aviation and maritime sectors, characterized by extraterritorial usage. In contrast, biomethane production via hydrothermal gasification or methanisation (followed by purification) serves a more local and territorial market through injection into gas networks and as bioGNV. Combustion also has a strong local dimension for heating purposes.

Thirdly, the accessible resource potential in 2050 varies greatly. Pathways utilizing dedicated energy crops and forestry residues (pyrolysis, hydrothermal liquefaction, gasification routes, fermentation, combustion) have a significantly larger potential (in the range of 33-43 MtMS) compared to those relying on waste streams like fatty waste (0.5 MtMS) or specific industrial byproducts. This suggests that long-term energy transition strategies need to focus on pathways with larger and more sustainable feedstock potential.

Fourthly, the energy return on investment (TRE) and mass yield differ considerably. For instance, hydrogenation of fatty waste shows a high energy return, while pyrolysis has a lower mass yield towards the desired fuel vector. Pathways like methanisation, while having a limited mass yield to methane, offer significant co-production of CO2 and the potential for nutrient and carbon return to the soil via digestate, indicating a more circular approach. The possibility of valorizing CO2 co-products in power-to-X processes is another important trend highlighted across several pyrogasification and methanisation routes.

Finally, the cost of production remains a critical factor. The sources indicate that more mature technologies generally have better-defined costs, while those with lower TRLs have more varied and often higher estimated costs. Achieving economies of scale appears to be crucial for reducing costs, particularly for less mature pathways like Fischer-Tropsch pyrogasification.

Conclusion

The future of biomass valorization for energy transition will likely involve a diversified portfolio of technologies, each playing a role depending on the available feedstock, the desired energy vector, and the specific application. While mature technologies can provide immediate contributions, further research, development, and deployment are needed to scale up promising but less mature pathways that can utilize larger resource potentials and offer better environmental integration through co-product valorization and nutrient recycling. The economic viability of these pathways will be crucial for their widespread adoption.

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