Nov-2023

Decarbonisation of transport fuels to reduce emissions

With transportation responsible for almost one-third of global CO2 emissions, the priority is to be able to meet future demands while moving towards net zero.

Yvon Bernard
Axens

Article Summary

Transport emits nearly 8 Gt of carbon dioxide (CO₂) each year, or 30% of global CO₂ emissions (IEA, 2023). Urgent actions are required to meet future demand while lowering the carbon intensity of transport fuels and chemicals. The use of renewable and alternative feedstocks (such as municipal waste, second-generation vegetable oil, and forestry residues) will play an increasing role in this transition. Axens is actively contributing to the energy transition in the industry and society by providing technologies for the production of gasoline and middle distillates (jet fuel and diesel) that meet the most stringent standards.

The decarbonisation of transport fuels and the reduction of greenhouse gas (GHG) emissions, with the relevant Axens technologies, will be discussed in this article. Together, these form part of the solution along with a range of complementary measures (not all of which need technological solutions) for reducing emissions across different transport modes:
• Avoid unnecessary journeys for the movement of people or goods.
• Incorporate energy efficiency across the transport system value chain. Obvious examples are refinery processing efficiency, including carbon capture, and using energy efficiency indices for new ship design (maritime) and retrofitting existing ships.
• Encourage more sustainable use of transport. In cities, this includes behavioural measures such as switching from cars to forms of transport with lower emissions, including electrified public transport and cycling (one of the most economical ways of commuting).
• Government policies that drive and support the transition, include mandates such as ReFuelEU, tax incentives such as the US IRA, project funding from research through to first projects, with the Horizon Europe funding a good example, and finally the permitting process to build out renewable capacity and sites for long-term carbon storage.

In the following sections, various technologies will be presented using different inputs and producing different products, addressing the fuel market and other industries that also need to reduce their carbon footprint.

Potential to reduce the carbon intensity of the transportation sector with biofuels
ΠSustainable/low-carbon road fuels
Emissions from road transport were 5.87 Gt CO₂ in 2022 (IEA, 2023). Major economies, including Australia, China, the EU, India, the UK, and the US, have adopted policies that support the uptake of battery electric vehicles (BEVs) and the decarbonisation of transport. In Europe (EU and UK), mandates banning the sales of internal combustion engines (ICE) in passenger vehicles and vans will become effective from 2035. Even then, it will take another decade or more for the turnover of the light-duty fleet to BEVs. Progress in rural communities is likely to lag that in the bigger cities, where BEVs are also seen as part of the solution for air pollution. Given that in 2023, more than 80% of the existing fleet of cars and vans on the road are powered by internal combustion engines, substituting fossil fuels with renewable/low-carbon fuels is vital for rapid action to reduce emissions from road transport.

Sustainable aviation fuels
Aviation transport emissions totalled 0.89 Gt eqCO₂ per year in 2022 (IEA, 2023). The International Civil Aviation Organisation (ICAO) adopted a long-term aspirational goal of net-zero carbon emissions by 2050. The Air Transport Action Group (ATAG), an industry body, proposed a range of technical, operational, and behavioural solutions to reach the goal of net zero by 2050. The deployment of sustainable aviation fuels (SAFs) is expected to contribute a minimum of 53% towards this goal (ATAG, 2021).

Seven fuels are qualified under ASTM-D7566 for the production of SAF (CAAFI, 2023). Axens provides mature technologies for the three main pathways:
• The HEFA pathway with the Vegan process for hydrotreatment of lipids to produce hydroprocessed esters and fatty acids (HEFA)
• The Fisher-Tropsch (FT) pathway with the BioTfueL process (gasification and FT) to produce SAF from lignocellulosic biomass (Annex 1)
• The Alcohol-to-jet (ATJ) pathway with the Jetanol process to produce SAF from low-carbon/renewable ethanol.

SAFs are drop-in fuels, fully fungible with conventional aviation jet fuels, that do not require equipment change, special infrastructure or modification of the supply chain. However, SAFs are currently a few factors more expensive than conventional aviation kerosene.

ω Sustainable marine fuels
Marine transport accounted for 0.78 Gt eqCO2 per year in 2022 (IEA, 2023). In its initial strategy, the International Maritime Organization (IMO) had already adopted the use of energy efficiency and carbon intensity indices for new ship designs and retrofitting existing ships. In July 2023, the IMO adopted a revised strategy with the goal of reaching net zero emissions by 2050, which will require the uptake of alternative zero and net-zero GHG emission fuels (covered in more detail elsewhere in this issue).

Marine transport accounted for 0.78 Gt eqCO2 per year in 2022 (IEA, 2023). In its initial strategy, the International Maritime Organization (IMO) had already adopted the use of energy efficiency and carbon intensity indices for new ship designs and retrofitting existing ships. In July 2023, the IMO adopted a revised strategy with the goal of reaching net zero emissions by 2050, which will require the uptake of alternative zero and net-zero GHG emission fuels (covered in more detail elsewhere in this issue).

In contrast to SAF, a wider range of fuel types are under consideration for the decarbonisation of marine fuels, from gases such as hydrogen, ammonia, and bio-methane to lighter liquids, such as methanol and heavier bio-diesels. In common with SAF, these lower-carbon intensity alternative marine fuels are more expensive than conventional marine diesel.

Reducing the carbon intensity of fuels is possible, and some plants are already producing biodiesel, SAF, and bioethanol. The following section will discuss available technologies from Axens to support the effort of GHG emission reduction.