Coprocessing and refinery integration present a rapid and lower cost opportunity for SAF production
Susan van Dyk, PhD
Independent Researcher and Biofuel Consultant
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SVD Consulting
SAF production is not taking place at a fast enough pace to meet climate commitments. While hundreds of announcements for new facilities have been made, only about only 31% of announced SAF production capacity out to 2030 has reached at least a final investment decision[1]. A co-processing strategy to make SAF in existing petroleum refineries can offer a near-term solution, as it can be rapidly implemented at a lower CAPEX compared to construction of standalone SAF facilities. Co-processing has been used for more than a decade in multiple facilities to produce renewable diesel (HVO) and naphtha, but has more recently become a common process for SAF production. Learn more about coprocessing and SAF production in the new Sustainable Aviation Futures course in May.
What is coprocessing?
Coprocessing in existing petroleum refineries is the simultaneous processing of renewable or bio-based feedstocks (such as vegetable oils, animal fats, or biocrudes) alongside fossil feedstocks (like crude oil or intermediate distillates) within conventional refinery units.
Why use co-processing?
Co-processing has been used for more than a decade by companies such as Preem (now VAROPreem), Eni, BP, Petrobras, and Chevron to produce renewable diesel (HVO). The introduction of the ReFuelEU Aviation mandate placed pressure on existing fuel suppliers to deliver mandated SAF volumes, resulting in multiple European refineries switching to co-processing[2]. As it does not require construction of new facilities, coprocessing was able to be rapidly implemented with deployment in months, rather than years. Coprocessing also comes at significantly lower CAPEX than investment into standalone facilities.
Feedstocks that can be used for coprocessing
Currently, most co-processing activities use the same oils and fats feedstocks as standalone production facilities. Thus, co-processing for SAF faces the same challenges, namely feedstock availability, sustainability and cost. Waste-based oils and fats are available in limited volumes on a global scale and competition has been driving up the price of these feedstocks. As such, co-processing of waste-based feedstocks presents a relatively short-term solution for the expansion of SAF and other types of drop-in fuels[3].
ASTM D1655 has approved three pathways for co-processing: (1) oils and fats, (2) Fischer-Tropsch liquids, and (3) previously hydrotreated oils and fats. Other applications for ASTM approval are in the pipeline.
There is extensive interest and research into the coprocessing of bio-oils or biocrudes from direct thermochemical liquefaction (fast pyrolysis, catalytic pyrolysis, and hydrothermal liquefaction). VAROPreem (formerly Preem) has been a pioneer in this area and has been co-processing fast pyrolysis bio-oil made from sawdust produced at the Pyrocell[4] facility in Gävle, co-processing it at the Lysekil
refinery. While this process is not ASTM-approved for SAF production, it represents a promising route for the future. Pyrolysis oils and biocrudes can potentially mobilise low-density feedstocks, such as forest residues, by producing a liquid intermediate that can be transported over greater distances for upgrading at a larger scale. These feedstocks are more abundant than oils and fats and availability will not be an obstacle.
Other bio-oil feedstocks that are very promising and currently undergoing ASTM evaluation are waste tyre pyrolysis oil (TPO) and plastic pyrolysis oil. TPO can potentially be a suitable feedstock for SAF production through upgrading the TPO or through gasification of the TPO and Fischer-Tropsch synthesis. TPO can potentially also be used as a coprocessing feedstock, for example, through insertion in the fluid catalytic cracker or hydrocracker for the production of liquid hydrocarbon fuels.
Does coprocessing present a risk for a refinery?
Co-processing biobased feedstocks in a refinery could pose some risks for the refiner in terms of operational challenges, fuel quality issues, corrosion of metallurgy, inactivation of catalysts, increased hydrogen demand, etc. Risk mitigation requires an understanding of the potential impacts of biogenic feeds and the steps that need to be taken to reduce and overcome risks. Several companies are developing technologies and specialised catalysts to facilitate co-processing while mitigating associated risks[5].
Commercial experience has indicated that co-processing lipids at low ratios (e.g. 5%) has a relatively minor impact on refinery operations and the associated risks can be managed with limited investment in new and modified infrastructure. However, as co-processing ratios increase, it is likely that much greater investment will be required and more extensive refinery modifications will be needed.
Current ASTM D1655 approved coprocessing pathways
At this stage, ASTM D1655 only permits low levels of biobased intermediates to be co-processed. Co-hydroprocessing of oils and fats, and Fischer-Tropsch liquids are allowed at a maximum of 5%, while previously hydrotreated fats and oils can be inserted at 24%, although the final biogenic fraction in the jet fuel may not be more than 10%.
ASTM is currently evaluating increasing the 5% limit to 30% to allow higher volumes of SAF to be produced through co-processing (although it has been approved under Def Stan 91-091)[6]. The co-processing of TPO is under active evaluation for coprocessing as well, which could expand the types of feedstocks that can be used.
Measuring the carbon intensity of coprocessed fuels
As the biobased feedstocks are simultaneously co-processed with fossil feeds, the sustainability of the fuel will rely on an accurate assessment of the renewable content to calculate the carbon intensity of the fuel. This will ensure the integrity of the co-processing and accurate application of policies.
Although Carbon 14 measurements are considered to be the “gold standard” way of determining renewable carbon content, this assessment requires expensive equipment, skilled technicians, etc., and is usually done offsite. Therefore, other indirect measurements, such as a mass balance method, can be used, backed up by periodic C14 testing. Various jurisdictions have developed policies for the required procedures around co-processing, including the California Low Carbon Fuel Standard, the Canadian Clean Fuel Regulations, the British Columbia Low Carbon Fuel Standard, the European Union[7], and organisations such as ISCC and RSB.
The upcoming Sustainable Aviation Futures course in May will go into extensive detail on all these topics to provide insight into co-processing and its potential for SAF production.
1 https://documentserver.uhasselt.be/bitstream/1942/48609/1/GlobalSAFcapacity_Feb2026update.pdf
2 European Commission, Regulation (EU) 2023/2405 (ReFuelEU Aviation); SkyNRG SAF Market Outlook 2024
3 https://www.greenairnews.com/?p=2815
4 btg-bioliquids.com/plant/pyrocell-gavle-sweden/)
5 Topsoe, “HydroFlex™ technology for co-processing” (topsoe.com); van Dyk, S. et al. (2019), IEA Bioenergy Task 39 report, “Assessment of likely technology maturation pathways for biojet production”; Pinho, A.R. et al. (2017), “Co-processing raw bio-oil and gasoil in an FCC Unit,” Fuel Processing Technology, 159, 185–197.
6 https://www.greenairnews.com/?p=7289
7 EU Delegated Regulation 2023/1640, Article 4(5) and Annex V