Technology readiness level of some biojet fuel technologies
Biojet technology
Company
Feedstocks
Capacity L/year
Status
HEFA/HRJ
Neste (Espoo, Finland)
Veg. oil, UCO, animal fat
2 B
Operational Operational Operational
ENI (Rome, Italy)
Veg. oil
155 M 2.13 B
Valero Energy Corp. and Darling Ingredients Inc. (Norco, CA, USA) World Energy (Boston, MA, USA), AltAir Fuels
Veg. oil, UCO, animal fat
Non-edible oil,
150 B
Operational
(Paramount, CA, USA) Total (Courbevoie, France) UPM (Helsinki, Finland)
waste oil
UCO, Veg oil. Crude tall oil
453 M 120 M
Operational Operational
Renewable Energy Group (Ames, IA, USA)
High and low free fatty acid feedstocks
284 M
Operational
FT
Fulcrum Bioenergy (Pleasanton, CA, USA) Red Rock Biofuels (Fort Collins, CO, USA) Swedish Biofuel Technology (Stockholm, Sweden)
MSW Wood
1.8 B
Planned Planned
909.2 M
ATJ
Ethanol
10 M
Operational Operational Operational
Biochemtex (Ortona, Italy) LanzaJet (Skokie, IL, USA)
Lignocellulosic biomass
<10 M 180 B
Ethanol
Table 1
incentives, and subsidies for RD, contrasted with the more global, fungible nature of jet fuel, offer the potential to drive SAF production. Nonetheless, near-term projections still put RD demand a factor of four or five above that for SAF, highlighting certain alternatives that could offer fuels pro- viders some risk mitigation. One set of alternatives, considering the vast hydropro- cessing infrastructure in place for the production of fossil fuels, is hydroprocessing paths. These are often denoted as HEFA-SPK (hydrotreated esters and fatty acids to synthetic paraffinic kerosene) or HRJ (hydroprocessed renewable jet). Hydrotreated vegetable oil (HVO) is another generic term used to describe diesel and jet range products despite the implication that animal fats are excluded. Technically, HVO is a HEFA; hence, the latter term is more inclusive. Co-processing routes to SAF, as well as revamped hydrotreaters and hydrocrackers for full renewables pro- duction, allow not only selectivity adjustment to yields for SAF and RD but can also enable a total pivot between fossil fuel production and renewable fuel production as market climate and regulatory pace dictate. High SAF yield technologies, approaching 100% or more liquid yield from renewable feedstocks, merit consideration such as ethanol-to-jet (ATJ-SPK) and gas-to-liquids (GTL- SPK) production of SAF. Significant projects are underway for the latter two paths. Table 1 (adapted from reference 6) provides some perspective on players and technologies. It should be noted that some of the companies listed are no longer financially stable. Fundamental chemistry of HEFA processes The first step in SAF production is the complete hydro - genation and deoxygenation of the lipid triglycerides found in the renewable feeds that have been pretreated to make them suitable for hydroprocessing. The triglycerides are comprised of three linear fatty acid chains bound by a glyc- erol backbone. Figure 4 7 illustrates the potential reaction pathways for a representative triglyceride molecule found in rapeseed oil. The hydrodeoxygenation path (HDO) is
favoured because it conserves renewable carbon atoms in the fuel being produced rather than in CO and CO₂ as byproducts. Specific heterogeneous catalyst systems allow selectivity to the favoured reaction sequence, as will be noted later. Several points are key from Figure 4, including consid- erably more hydrogen is consumed for the HDO path- way than in fossil fuel hydrotreating operations (four to five times greater), more even in the range beyond most hydrocracking operations (up to twice as much). The pro - duction of water by deoxygenating fatty acid chains and the saturation of olefin bonds are highly exothermic. This predicates a hydrogen supply not only for chemical con- sumption but also for quench gas, the latter depending on how much liquid recycle is employed to control tempera- ture rise. High amounts of propane, water, carbon monoxide, carbon dioxide, and methane off-gases are generated compared to fossil fuel hydroprocessing. The various lipid sources for HEFA contain a myriad of variable contami- nants that must be removed to tenable levels for hydropro- cessing. Table 2 lists typical contaminants and levels and the range of levels specified by technology providers for their hydroprocessing systems.8 Contaminant metals include alkali and alkali earth metals (Na, K, Ca, Mg) that are often part of acid salts, as well as Fe, B, Si, Zn, and Al. The presence of phospholipids, com- pounds similar to triglycerides except one fatty acid chain has been replaced by a phosphate group chain, in renew- able feeds can be an issue in deactivation by phosphorus, even at parts per million levels. Operators of HEFA units must either install pretreatment units (PTUs) or purchase pretreated renewable feedstocks. When considering the fatty acid chain composition range of a number of representative renewable feedstocks, it is easily noted that the resultant paraffin products from HEFA processes will produce a significant amount of C18 + (and C 17 paraffins if appreciable decarboxylation occurs), which exceeds the desirable C 8-C16 range for jet fuel. This dictates
68
PTQ Q1 2025
www.digitalrefining.com
Powered by FlippingBook