Strategies for sustainable aviation fuel production

Dr Kok Siew Ng (Oxford), Danial Farooq (UCL) and Prof Aidong Yang (Oxford) have written a review article on "Global biorenewable development strategies for sustainable aviation fuel production", published in Renewable and Sustainable Energy Reviews. 

Summary

Over the coming years, the world is projected to witness an upsurge in “drop-in” aviation biofuel production as part of the renewable energy and bioeconomy developments. This paper presents a comprehensive review of the current status of biojet fuel development and uptake in global commercial aviation industry, including state-of-the-art certified technologies (i.e. Fischer-Tropsch (FT); hydroprocessed esters and fatty acids (HEFA); alcohol-to-jet (ATJ); and hydroprocessing of fermented sugars (HFS)); potential feedstock that can be deployed; a comparison of techno-economic and environmental performances of biojet fuel production routes; airlines’ commitment in promoting higher biofuel uptake; and global initiatives and policies. This review shows that the HEFA route using oil-based crops is best performing in terms of lowest production cost and greenhouse gas emissions, however it is in competition with the existing road transport biofuel market. Lignocellulosic biomass and waste feedstock should be promoted in view of replacing food/feed crops which have high indirect land use change emissions. Therefore, further improvement should be focused on FT, ATJ and HFS routes to enhance the cost effectiveness of biojet fuel production and promote commercialisation of these technologies. The selection of feedstock and technologies for SAF production should be justified based on production cost and environmental footprint, while avoiding competition with the existing road transport biofuel market. The shortcomings in the SAF policies such as blending mandate and multiplier in RED II should be addressed to reduce the negative impacts of feedstock competition between the road and aviation biofuel sectors and to meet the decarbonisation targets.

Recommendations

A few recommendations on promoting the development and uptake of SAF are made:

• The utilisation of lignocellulosic biomass and waste feedstock should be promoted in lieu of food/feed crops unless the choice of feedstock can be justified through a lower cost and higher GHG savings. A preferred SAF feedstock should be the one which avoids competition with existing road biofuel market and land use for food production.
• Future research and development should be focused on non-HEFA routes, such as FT, ATJ and HFS–SIP routes to further improve the cost effectiveness through optimising, integrating and scaling up the technologies.
• Imposing a blending mandate is more effective than a voluntary approach. However, sustainability criteria of feedstock should be considered and food/feed crops should be avoided. An alternative policy instrument using a GHG intensity reduction target could be more effective than a blending mandate.
• Enhancing multi-stakeholder collaboration (airports, biofuel producers, aircraft manufacturers, airlines and government) is the key to accelerating the uptake of SAF.
• Introducing incentives for SAF adoption as well as penalties for GHG emissions through carbon tax schemes are needed to promote higher uptake of SAF. This should be further studied by taking into account the competition and impact between aviation and road transport sectors.

The SYNERGORS Project

The SYNERGORS project (“A systems approach to synergistic utilisation of secondary organic streams”), funded by the Natural Environment Research Council (NERC), is led by Dr Kok Siew Ng from the Department of Engineering Science, University of Oxford. This project aims to develop new systems approaches and decision-making tools for promoting resource recovery from secondary organic waste streams including fossil- (e.g. used plastics) and biomass-derived waste (e.g. food waste, residual biomass).

SYNERGORS will provide significant insights into various options for organic waste reduction and utilisation, and propose viable business models to attract stakeholders in the commercial sectors to invest in these areas. Furthermore, the research will address various socio-environmental challenges faced by human and living communities, the rising global demands in energy and commodities, and lessening burdens on the landfill, water and atmosphere.

It is envisaged that the outcomes from this project (e.g. decision-making tool and roadmap) can be adopted in the UK and other developing countries in improving the policies and practices in relation to organic waste management. The objectives of the project are well aligned with the UK Industrial Strategy in enhancing resource efficiency while achieving a sustainable industrial growth and a more resilient economy. The project has received support from a number of UK and international organisations (academia, industry and government), providing multidisciplinary expertise to address the global challenges in waste management.

Acknowledgement

This work was supported by the Natural Environment Research Council (NE/R012938/1) through the UKRI/NERC Industrial Innovation Fellowship Programme.

Further information

Please contact Dr Kok Siew Ng (kok.ng@eng.ox.ac.uk) if you are interested in learning more about the project.