Decarbonisation Technology August 2022 issue

Hazardous Materials and Waste Management Hierarchy, 2022). Recycled carbon feedstocks serve important societal purposes: to increase recycled content in the plastics value chain and reduce plastic waste, while at the same time reducing the amount of fossil fuels required. However, they do not carry the same decarbonisation benefit that bio- based feedstocks carry in the fuels value chain. Instead, these feedstocks act more like fossil resources with respect to their contribution to global emission inventories. So, while processing recycled materials is an important future role for refining, it is important to differentiate recycled carbon feedstocks from bio-based feedstocks with respect to the impact on global emissions inventories. What is necessary to co-process bio-based feedstocks? Generally, bio-based feedstocks introduce new challenges in the refining system. There are several possible unit operations in a refinery where bio-based feedstocks can be introduced, but the FCC unit has received significant attention. Table 2 presents representative properties of a selection of renewable feedstock types that Grace has received from refiners, along with a comparison to typical FCC feedstock. The primary difference to note between the renewable feedstocks and traditional FCC feedstock is the high level of oxygen content found in many of the renewable feeds. However, beyond the challenges that come with high oxygen content, many of the renewable feedstocks contain elevated and highly variable levels of metals. Both the overall contaminant

Materials used to prepare bio-based refinery feedstocks

Seed oils (rapeseed, sunflower, palm, soybean, etc.)


Animal fats

Algal oils

Waste cooking oils


Oils extracted from biomass Bio-based pyrolysis oils (Hydrotreated, demetallated,

Corn stover

Organic fraction of municipal solid


waste (MSW) Crude glycerin

Cellulose-based oils


Nut shells



Table 1

Directive [EU RED-II], US Renewable Fuel Standard [US RFS], or California’s Low Carbon Fuel Standard [CA LCFS]), driven by corporate strategic directives, or the result of stakeholder engagement initiatives with refiners. Some of these frameworks can provide a financial return (often in the form of credits, which are used to demonstrate compliance and can be traded to other market participants). Recently, there has been an increase in the use of recycled carbon fuels. The best example of these types of feedstocks is oil derived from hard-to-recycle plastics or other hydrocarbon- based materials that cannot be recycled. The US EPA’s Waste Hierarchy dictates that avoidance of waste, by first reuse/recycling and then energy recovery, is preferred to disposal, and care must be taken to ensure recycled carbon feedstocks for refinery use are sourced from materials that cannot be easily recycled via other means (Sustainable Materials Management: Non-

Selected renewable feedstock (and traditional FCC feedstock) compositions

Soybean Rapeseed


Tallow 2 Pine-based


Median value

Typical ranges

oil 1, 5

oil 1

oil (refined) 1

pyrolysis oil 3 tall oil 4 FCC feedstock 5 FCC feedstock 5

Oxygen, wt% Na, mg/kg Mg, mg/kg

10.5 0-2 1-40 0-88 3-60 6-150





9.9 Alkali & alkaline earth metals reported as 56 mg/kg


0-0.5 0-10


0 0 0 0 0



0.3 0.1 0.0 0.4 0.0



130 160 400

0-5 0-5

K, mg/kg Ca, mg/kg P, mg/kg


no data


40 60



no data



References: 1 Watkins et al, 2008. 2 Riley & Willets, 2011, 3. Pinho et al ., 2017, 4. Anthonkutty et al ., 2015, 5. Grace internal data.

Table 2


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