eFuel Synthesis: FT vs MTG vs Direct CO2 Hydrogenation

The Decision in 60 Seconds

Three commercial-ready pathways convert renewable H₂ and captured CO₂ into liquid e-fuels. Each pathway has different product slates, capital intensity, and TRL.

Fischer-Tropsch (FT) — Highest-carbon-number products (SAF, diesel, waxes). Pick when: target is SAF / heavy distillate, site has space for reverse water-gas shift (RWGS) + FT + upgrading.
Methanol-to-Gasoline / Jet (MTG/MTJ) — Methanol intermediate, then zeolite conversion. Pick when: gasoline is primary product, or phased build (sell MeOH first, add MTG later).
Direct CO₂ hydrogenation to hydrocarbons — Single-reactor systems (CRI MeOH, Sabatier, modified FT). Pick when: TRL risk is acceptable; benefits are simpler layout and fewer unit ops.

Rule of thumb: For >5,000 bbl/d SAF, FT is the default (Infinium, Twelve, HIF, Nordic Electrofuel, Sunfire). Below 1,000 bbl/d of gasoline-only product, MTG becomes cost-competitive. Direct routes are still first-of-a-kind at scale.

Pathway Comparison

Attribute	FT (RWGS + FT + upgrading)	MTG (CO2 + H2 → MeOH → GAS)	Direct CO₂ Hydrogenation
TRL (2024)	8-9 (Infinium commercial 2023; Shell, Sasol FT mature)	8 (ExxonMobil MTG gasoline-only; Topsoe TIGAS)	5-7 (pilot/demo; commercial scale < 2026)
Primary products	SAF (45-60%), diesel (25-35%), naphtha (10-20%)	Gasoline (86%), LPG (10%), fuel gas (4%)	Gasoline or diesel or MeOH (tunable)
Carbon efficiency (CO2 in → HC out, C%)	85-90%	90-95% (via MeOH)	75-90% (varies by catalyst)
Thermal efficiency (HHV basis, renewable electricity → fuel)	50-55%	52-58%	45-55%
Capex (rough, $/bbl/day, incl. electrolyzer & DAC?)	$600k-$1.2M (w/o DAC/elec)	$500k-$900k	$700k-$1.3M (limited scale data)
Process complexity	High (RWGS + FT + hydrocracker + hydroisom)	Medium (MeOH synth + MTG)	Low-medium (single reactor)
Footprint	Large (multiple reactors + upgrading)	Medium	Small (attractive for modular)
Catalyst	Co or Fe (FT); Ni or Fe (RWGS)	Cu/ZnO/Al2O3 (MeOH); ZSM-5 (MTG)	Cu-based, Fe-based, or dual-function
H₂/CO or H₂/CO₂ ratio	H2/CO = 2.0-2.2 (Co); 0.5-2.0 (Fe)	H2/CO2 ≈ 3.0 for MeOH	H2/CO2 = 3-4
Operating pressure	FT: 20-35 bar (LTFT); 30-45 (HTFT); MTG 15-25 bar	MeOH: 50-100 bar; MTG: 15-25 bar	30-80 bar typ.
Operating temperature	FT LTFT 200-240 °C; HTFT 310-340; RWGS 700-900	MeOH 220-300; MTG 360-420	220-350 (typ.)
Key licensors / developers	Infinium, Topsoe, Shell (SGI), Sasol, BP (Velocys)	ExxonMobil, Topsoe TIGAS, Gunvor (LGFuels)	Carbon Engineering (air-to-fuel), Nordic Blue Crude, CRI (MeOH)

Product Slate — What You Actually Get

Fischer-Tropsch (Cobalt LTFT)

FT produces a wide Anderson-Schulz-Flory (ASF) distribution of n-paraffins and olefins. Typical LTFT syncrude:

C1-C4 (fuel gas and LPG): 10-15 wt%
C5-C10 (naphtha): 15-25 wt%
C11-C20 (middle distillate / jet + diesel): 30-45 wt%
C21+ (waxes): 20-35 wt%

Wax is hydrocracked and isomerized to maximize jet (paraffinic SAF) yield. Final jet-to-diesel ratio can be tuned 50:50 to 70:30 via hydrocracker severity.

Methanol-to-Gasoline (ExxonMobil ZSM-5)

Nearly all C5+ product is gasoline-range. Olefin content is low after treating. Near-zero sulfur and nitrogen. Octane is typically 87-92 RON without blending. No jet product unless further isomerization is added (MTJ variant).

Direct Routes

Catalysts today are not as selective as separated syngas pathways; product is typically a mix of light olefins + gasoline + oxygenates requiring downstream separation. Carbon Engineering's "Air-to-Fuels" uses FT at the back end (not truly "direct").

Decision Matrix

Scenario	Recommended Pathway	Why
Commercial SAF, >10,000 bbl/d, regulated market (EU RED III, US 40B/45Z)	FT	SAF-dominant product; mature tech; licensor bankable; paraffinic jet meets ASTM D7566 Annex A1
Small/modular (500-2,000 bbl/d), gasoline market, first-of-a-kind remote site	MTG	Simpler unit ops; MeOH intermediate can be shipped if MTG delayed; ExxonMobil licensor
Sell e-methanol to shipping + optional future MTG for land fuels	MTG (phased)	MeOH directly valuable to shipping (MAERSK, CMA CGM); flexible back-end
Diesel/heating oil market, small capacity	FT (cobalt, mild upgrading)	FT diesel is paraffinic, CN > 70; excellent blendstock or drop-in
Emerging demo/pilot (learn-by-doing)	Direct CO2 hydrogenation	Lower capex; faster build; accept TRL risk for learning
Hydrogen-poor site (e.g., only 10 MW electrolyzer)	MeOH only (skip MTG)	MeOH synthesis is the most energy-efficient intermediate

Key Sizing Heuristics

Hydrogen Demand

FT (Co, via RWGS): ≈ 0.5 kg H₂ / kg fuel (incl. shift losses)
MTG: ≈ 0.48 kg H₂ / kg gasoline
Direct CO₂: ≈ 0.50-0.55 kg H₂ / kg liquid fuel

CO₂ Demand

All pathways: ≈ 3.2 kg CO₂ / kg liquid fuel (stoichiometric, adjusted for efficiency)

Electric Power Demand (Well-to-Tank)

Electrolysis (PEM): 50-55 kWh/kg H₂ → dominates overall demand
DAC (temp-swing): 5-8 GJ/t CO₂ ≈ 1.4-2.2 MWh/t CO₂
Balance of plant: 5-10% of total demand

Rule of thumb: roughly 17-22 MWh of renewable electricity to produce 1 ton of liquid e-fuel, regardless of which synthesis route (FT vs MTG). The electrolyzer dominates; pick route based on product and scale, not power demand.

What to Lock Down Before Choosing

Product slate by offtake: SAF vs gasoline vs diesel vs MeOH has massive downstream implications. Don't let a catalyst vendor drive this backward.
Licensor bankability: FID lenders ask for a licensor with >3 commercial references. That favors FT (Shell, Sasol, Topsoe) and MTG (ExxonMobil, Topsoe) over novel direct routes.
Electrolyzer + DAC integration: The synthesis island is <30% of total capex. Don't optimize it at the expense of power island operability.
Part-load flexibility: FT wants steady syngas composition; MeOH is very tolerant; direct routes vary. Match to power availability profile (wind curtailment scenarios).
Hydrogen storage: All pathways tolerate ±10% H₂ swings with buffer; ±30% typically needs intermediate H₂ or MeOH storage.

Common Pitfalls

Ignoring upgrading capex. FT syncrude is not drop-in — you need hydrocracker, hydrotreater, isomerization, and fractionator. Budget 30-40% of synthesis island capex for upgrading.
Overstating direct-route efficiency. Published efficiencies often exclude purification, recycle compressor duty, or steady operation losses. Use 0.85 factor on vendor-quoted efficiency at FID.
Assuming RWGS is "easy." Endothermic, high temp, Ni/Fe catalyst coking, heat integration complicated. Plan for 10-15% of FT capex on RWGS alone.
Using grid-average CI for hydrogen. RFS2 and EU RED require additionality + temporal correlation. Grid-tied electrolyzer = gray H₂ on paper.

References

NREL TP-5600-81564 — Power-to-Liquid Fuels: Techno-Economic and Environmental Assessment (2021)
IEA (2023) — The Role of E-fuels in Decarbonising Transport
ICCT (2018) — The potential of electrofuels to reduce transportation GHG emissions
ASTM D7566 Annex A1 (FT-SPK) — Paraffinic SAF specification
Dry, M. E. (2002) — The Fischer-Tropsch process: 1950-2000, Catal. Today 71(3-4): 227
Keil, F. J. (1999) — Methanol-to-hydrocarbons, Microporous & Mesoporous Mater. 29: 49
Infinium technical bulletins (2023) — Pacific eFuel project references