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What are some of the optimal strategies for processing (or co-processing) second- and third-generation renewable feedstocks?

Mar-2023

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Peter Andreas Nymann, Topsoe, PAN@topsoe.com

Like first-generation renewable feedstocks, second- and third-generation feedstocks also contain oxygen, leading to high H2 consumption and temperature rises. Many of the same strategies therefore apply to these as well. Second and third may have different contaminant profiles that need to be dealt with by specialised grading material. Content of particulates from upstream processing and high acidity (like for the first generation) also needs to be managed in storage and equipment. Second- and third-generation renewable feedstocks that are triglyceride based may be treated in HydroFlex units by applying the same strategies as for first-generation feedstocks.

However, in contrast to the first-generation renewable feedstocks, the second- and third-generation often come from solid-to-liquid conversion processes and, therefore, contain different hydrocarbons, not mainly triglycerides. These molecules include ring structures that need saturation and often ring opening. The requirement for hydrocracking catalysts will, therefore, be more pronounced when processing second- and third-generation feedstocks, and co-processing in hydrocrackers of these feeds will be more feasible than processing in medium-pressure hydrotreaters. Several projects and plants processing crude tall oil, pyrolysis oils from plastics or tyres or other second- and third-generation renewables are currently in operation or the late stages of implementation using Topsoe technologies.

Mar-2023
Stefan Brandt, W.R. Grace & Co, stefan.brandt@grace.com

The terms second- and third-generation renewable feedstocks are not defined globally. In a briefing of the European Parliament in 2017, second-generation biofuels were “derived from waste and agricultural residues (such as wheat straw and municipal waste) or non-food crops (such as miscanthus and short-rotation coppice).”1 Third-generation renewable feedstocks are often referred to as being related to algal biomass, for example.

While there are several process units capable of processing second- and third-generation feedstocks, the flexibility of the FCC unit is well suited for the co-processing of unconventional feedstocks. However, challenges exist in the industry to establish a continuous supply of renewable feedstock components, especially for second- and third-generation renewable components. Availability of some of these is expected to grow over the coming years. Therefore, any strategy for co-processing these feedstocks needs to start with a reliable sourcing plan.

The optimal strategy for co-processing renewable feedstocks in an FCC unit is always related to a deep understanding of the properties of the feedstock component in terms of storage, miscibility, physical and chemical properties and its impact on the operation and yield structure of the FCC unit. Thorough characterisation and catalytic pilot plant testing are recommended to identify the opportunities and challenges.

Second-generation renewable feedstocks typically exhibit higher variation in quality compared to first-generation renewable feedstocks derived from edible oil sources. Additionally, miscibility with conventional feedstock can be challenging (see Figure 1). The FCC unit can cope with feedstock quality variation because of its flexibility in operation and catalyst design adaptability. Nevertheless, the variability of the renewable feedstock component might put additional emphasis on the regular FCC unit monitoring.

Depending on the nature of the renewable feedstock, hardware modifications might be required to prevent reliability risks from co-processing. Technology licensors have developed hardware solutions to minimise these risks and optimise the catalytic conversion of the combined feed.

The FCC unit, with its flexibility in catalyst formulation and replacement, is able to adjust to challenges coming in with various feedstock contaminants. Renewable feedstocks bring other contaminants to the FCC unit than crude-derived feedstocks. At low co-processing percentages, depending on the operation, the effect on catalyst deactivation is often unnoticed. However, increased co-processing rates will ultimately put more emphasis on the risks associated with new contaminants in the FCC unit. FCC catalyst suppliers can provide solutions and recommendations based on the individual refinery strategy, operation, and objective.

Second-generation renewable feedstocks derived from lignocellulosic biomass are often high in oxygen and water content. With high oxygen and water content, these feedstocks by their nature will reduce the yields of saleable FCC products from the FCC. Additionally, water and oxygen can impact product quality and downstream processing, and these impacts have to be carefully considered when researching co-processing opportunities. Pilot plant testing with oxygen speciation analysis capabilities is a useful tool to predict the effects of both factors on yield structure, product quality, and ex Rx product processing.
In summary, catalyst and technology providers should be consulted to evaluate the optimal strategy for co-processing second- and third-generation renewable feedstock components in the individual FCC unit. Once established in the plant, increasing the amount of renewable feedstock content should be reviewed by the respective partners as a higher proportion can create new challenges to catalyst, product quality, and operation.

1 European Parliament, EPRS, Advanced biofuels: Technologies and EU policy, Briefing, 8 June 2017.

Mar-2023
Joris Mertens, KBC (A Yokogawa Company), joris.mertens@kbc.global

Renewable feeds are either lipids (vegetable oils and animal fats) or lignocellulosic material. The main strategic challenge around processing these renewable feeds is feed procurement.

The first HVO/HEFA plants were mainly processing palm oil. However, the EU and, to a lesser extent, the US are narrowing the possibility to process such controversial feeds that pose substantial land-change issues. At the same time, REDIII, ReFuelEU legislation in Europe, and similar initiatives in the US and elsewhere have further incentivised the demand for lipid-based mid-distillate production from HEFA technology, and specifically SAF. In about five years, only a limited amount of waste oils and fats is expected to be available for new projects.

Despite its attractive lower cost and fewer feed supply challenges, co-processing in existing units does not address the long-term (post-2030) decarbonisation challenge, which will require a deeper cut in the carbon intensity of fuel than co-processing can deliver.

Theoretically, technologies using lignocellulosic wastes should pose less of a concern with feed availability. However, raw lignocellulosic stock is much less energy dense. Therefore, they must be sourced from shorter distances, typically less than 200km, which brings feed supply assurance to the forefront of strategic considerations. Pre-processing lignocellulosic material, for example pelletising or pyrolysis, can largely address the energy density issues but may add complexity to the feed supply chain. In addition, technological maturity and required capital cost are more challenging for processes using lignocellulosic feeds.

In addition to feed and technology readiness and cost, an optimised strategy needs to consider the product yield structure, which varies widely depending on feed type and technology, including catalyst technology. While the catalyst type impacts HVO yields significantly, with potential differences up to 5%, unit configuration and catalyst type will dramatically affect the SAF yield of Fischer-Tropsch complexes.

Mar-2023
Steve DeLude, Becht, sdelude@becht.com

The optimal strategy is dependent on each site’s specific configuration, level of exposure to GHG emission-related costs (penalties) and/or biofuel production incentives, the logistical considerations related to the available biomass feedstocks, the cost of the feedstock, and corporate capital availability/investment hurdle rates.

The mandates of the Paris accord established requirements for carbon intensity and GHG emission reductions that impact energy firms, regional/national governments, and investors. As part of the transition to lower emissions, traditional fossil fuel-based transportation fuels will be substituted by a combination of electric vehicles and bio-derived and renewable fuel sources. Existing refining and petrochemical assets are seen as key infrastructure in the energy transition equation, as much of the existing processing and distribution infrastructure can be repurposed for this new reality.

This change in the marketplace will drive traditional refiners to examine processing and configuration options to align with the new feedstock and product profile, as well as energy input options. Those entities that are able to meet the changes in this dynamic market while remaining profitable will continue as long-term viable enterprises. Biofuel- related strategies seen in the industry range from:
•   Full biofuel integration with dedicated biofuel units providing fully fungible final product blend components
•   Partial integration and co-processing approach with biofeeds brought on-site and pretreated adequately to match with the site’s existing units.
•   Third-party pretreatment arrangement or an owned, dedicated facility with feed specifications strictly monitored to ensure meeting co-processing/blending requirements
•   Purchase of biofuel blend components via open market
•   Purchase of GHG offsets from other entities.

Finding an optimal strategy requires fully analysing each specific situation and identifying the range of options that could achieve the desired business goals.
The progression of biofuel processing technologies from the current level to those in development is more catalyst-related than process-related. The steady progression of catalyst advancements has improved hydrogen selectivity and isomerisation to final products. As catalyst technologies further improve, opportunities exist for processing more challenging feedstocks and moving from biofeeds in competition with food sources to those which are non-edible.
Europe’s Annex IX describes some of these bespoke biofeeds, with consideration given to the use of non-edible cover crops using non-food-producing lands. The changing feedstock quality imposes increasing levels of contaminants and lower carbon contents. Processing these feeds requires consideration of how to remove the contaminants (including water) and capture the maximum amount of hydrocarbon products.

The future transition to these new feeds requires consideration of thermal pretreatment processes linked with refinery post-treatment to make fungible fuels. (For additional details, see Sayles and Ohmes, Conversion to a green refinery, Decarbonisation Technology, Nov 2022). Refinery configuration and biofeed considerations determine the ease of integration. In general, more complex refineries offer greater opportunities for biofeed integration.

In conclusion, the consideration of co-processing is dependent on the refinery configuration, feedstock selection, catalyst application, and location.

Optimised process designs are just one aspect of the overall solution, with biofeed supply logistics very often being the overall controlling factor determining the most attractive co-processing opportunity.

Mar-2023
Sophie Babusiaux, Axens, sophie.babusiaux@axens.net

Processing and co-processing renewable feedstocks is part of today’s main refineries’ strategies to reduce the carbon footprint of their activities. As defined by the European Union, second- and third-generation biofuels are produced from feedstock that does not compete directly with food and feed crops, such as wastes and agricultural residues (wheat straw, municipal waste), non-food crops (miscanthus and short rotation coppice), and algae.

The starting point strategy to integrate these feeds into a refinery is first to identify the local availability and individual feed challenges. Then, depending on the conversion/hydroprocessing platforms available at site, look for the most suitable unit to cope with these in terms of existing hardware and impact on products. To be sure, more than 50 years of providing solutions in optimising refinery refining schemes throughout the world delivers the repository of experience, know-how, and methodology to conduct detailed dedicated studies in a constantly evolving legislation framework.

Processing second- and third-generation biofeeds represents specific challenges to the operation, for both new units and retrofits, either in co-processing or stand-alone mode. The design shall consider robust and proven solutions. We have developed solutions over the past 30 years to prevent pressure drop, loss of activity, corrosion, and other nuances that have emerged in the processing of renewable feedstocks.

Mar-2023