May-2024

SAF production via co-processing in the kerosene hydrotreater

Guide to co-processing for SAF production, covering relevant regulations, why kerosene hydrotreaters are preferred, and addressing challenges with solutions.

Maria J L Perez, Gitte Thomsen Nygaard and Sylvain Verdier
Topsoe

Article Summary

Sustainable aviation fuels (SAF) have been at the forefront of the fuel industry’s agenda for several years, with increasing attention driven largely by regulatory pressures. Across the globe, from the European Union and the UK to Japan, Brazil, India, and Singapore, SAF mandates are being implemented, sometimes accompanied by significant penalties for non-compliance, as exemplified by the ReFuelEU aviation initiatives. These mandates are set to significantly accelerate the deployment of SAF production, and projections indicate that bolstered by such measures, SAF production could reach approximately 13 million tons by 2030 and potentially soar to around 120 million tons by 2050.¹

Simultaneously, regulators are incentivising SAF supply through attractive credit schemes. In the US, SAF suppliers can benefit from Renewable Identification Number (RIN)credits, Low Carbon Fuel Standard (LCFS) credits, Inflation Reduction Act (IRA) production tax credits, and state-based credits from states like Washington, Minnesota, and Illinois.

However, there are significant challenges to overcome to increase the supply of SAF. Production of SAF in standalone plants is capital intensive, and the process of revamping an existing unit or constructing a new one can span several years. This is where co-processing in a kerosene hydrotreater presents a compelling alternative. Not only is it a low-capital expenditure (Capex) approach, but it also allows for the rapid deployment of SAF production within a few months (given the right conditions).

With more than 50 cycles of units co-processing renewable feedstocks in various hydroprocessing units worldwide and with a wide range of renewable feedstocks, Topsoe has accumulated extensive experience in this field. This article is intended to offer a starting guide to anyone considering going down the co-processing path by comprehensively covering the regulations to be aware of, why co-processing in the kerosene hydrotreater is the preferred choice for SAF production, and the challenges and solutions.

What is co-processing?
In co-processing, even small amounts of fossil feedstock, such as crude oil, can be replaced with renewable feedstock, such as vegetable oil, animal fat, and used cooking oil (UCO). These are processed together in the hydrotreater or hydrocracker (for example) to produce renewable fuel. Co-processing of renewable feedstocks, such as virgin oils or waste oils and fats, in hydroprocessing units has been common practice for over a decade, primarily to produce renewable diesel.

The amount of renewable feedstock added is typically at relatively low levels of less than 5%. Such a low ratio generally only necessitates a catalyst change, which makes the process relatively straightforward and makes co-processing a simpler alternative to major revamps.

In cases where the co-processing ratio is increased to 10% or higher, revamps are typically required to address common challenges, such as managing high exotherms or mitigating corrosion issues.²

As written in the first quarter of 2024, most refineries in the EU have become familiar with co-processing, and few consider it a significant obstacle. Coupled with the numerous benefits of co-processing for both producers and off-takers, this is becoming an increasingly attractive option for renewable fuel production.

Regulations on co-processing
As mentioned in the introduction, regulatory initiatives supporting the supply or demand of SAF are being implemented globally. This section outlines the key regulatory initiatives introduced across various regions, as well as the regulatory fuel compliance standards for co-processing.

In the EU, the ReFuelEU initiative targets a 70% SAF share by 2050, split evenly between biogenic jet fuel and eSAF. Non-compliance penalties enforce this obligation on fuel suppliers. The UK is developing a similar SAF regulatory framework, potentially including a revenue certainty scheme.

In the US, the SAF Grand Challenge promotes SAF production, bolstered by incentives like RIN credits from the Renewable Fuel Standard (RFS), LCFS credits from California, Federal production tax credits (IRA), and additional credits from specific states. British Columbia, Canada, has also issued SAF mandates, targeting 1% SAF by 2028 and 3% by 2030.

Other countries are also embarking on the SAF journey. Japan aims for 10% SAF by 2030, India targets 1% SAF by 2027 initially for international flights, Brazil seeks a 1% reduction in GHG emissions by 2026, potentially rising to 10% by 2037, and Singapore announced that it is aiming for a 1% SAF target from 2026 with plans to raise it to 3-5% by 2030.

Furthermore, discussions on mandates and incentives are underway in numerous countries, including the United Arab Emirates (UAE), Turkey, New Zealand, South Korea, Australia, China, Chile, Colombia, Thailand, Malaysia, Indonesia, and more.

From a fuel compliance perspective, the production of SAF is guided by two key ASTM standards: ASTM D7566, which currently outlines eight SAF pathways for standalone plants, and ASTM D1655, which details the three current co-processing pathways. The co-processing pathway discussed in this article involves the co-processing of mono-, di-, and triglycerides, free fatty acids (FFAs), and fatty acid esters (FAEs), allowing co-processing up to 5 vol% with fossil feedstocks (further details can be found in Annex A1.2.2.1 of ASTM D1655).

Regulatory considerations extend beyond fuel compliance to also include questions about permissible feedstocks, minimum greenhouse gas (GHG) savings, and GHG calculation methodologies. These complex issues are addressed in various forums, but in this article, we will focus on regulations related to co-processing. In the EU-27, the Delegated Act on co-processing, issued on June 5, 2023, clarified the methodologies for calculating the share of renewable fuels via co-processing.³

This regulation supersedes the methodologies previously established by specific member states like Spain and the Netherlands, which were developed in the absence of a common EU approach. The Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) scheme developed by the International Civil Aviation Organization (ICAO) also covers SAF by co-processing, with the co-processing methodology described in the methodology of a life-cycle assessment (LCA) and default LCA values.⁴

What types of feedstocks?
The feedstocks eligible for SAF production via co-processing vary by jurisdiction. In the EU, three types of biogenic feedstocks are permitted (according to ReFuelEU Aviation):
• Waste listed in Annex IX part A
• Waste listed in Annex IX part B
• Other biogenic feedstocks not listed in Annex IX, provided they are not food and feed crops, intermediate crops, palm fatty acid distillate, palm and soy-derived materials, or soap stock and its derivatives. To comply, these feedstocks must achieve a minimum of 65% GHG emission savings.