Biological carbon capture & utilization (bio-CCU: gas fermentation, CO2-to-protein, e-fuels)

Biological carbon capture and utilization (bio-CCU) converts captured carbon dioxide — from industrial point sources, biogenic emissions or the atmosphere — into fuels, chemicals, proteins and materials using microbial gas fermentation, engineered microbes or microalgae. It reframes a waste gas as a feedstock, displacing fossil carbon while generating revenue that can help finance abatement. LanzaTech’s gas-fermentation platform alone reported 55.8 million dollars of revenue in 2025, Newlight’s AirCarbon polyhydroxyalkanoate is certified carbon-negative, and Deep Branch’s Proton single-cell protein reaches about 70% protein content at roughly 90% lower carbon footprint than alternative proteins. On the catalytic-utilization flank, Carbon Recycling International’s Vulcanol renewable methanol embeds about 1.4 tonnes of CO2 per tonne of methanol, and its planned Iceland e-fuel plant targets up to 70,000 tonnes per year of sustainable aviation fuel. Policy now pulls demand: the US 45Q tax credit pays up to 85 dollars per tonne for captured and utilized CO2, the EU’s Carbon Removals Certification Framework is in force, and China’s green finance catalogue lists CCUS as item 1.5.1.

The key directions of biological carbon capture & utilization are:

1. Gas fermentation to fuels and chemicals (LanzaTech): autotrophic microbes ferment CO/CO2-rich syngas into ethanol and onward into SAF and marine fuel; LanzaTech’s municipal-solid-waste-to-ethanol pilot in Kuji City, Japan runs at about 400 t/yr at one-tenth commercial scale with guaranteed performance.
2. Microbial CO2-to-biopolymers (Newlight AirCarbon): an ocean-microbe-inspired process fixes CO2 and methane into polyhydroxyalkanoate — a carbon-negative, ocean-biodegradable polymer already in straws, utensils and eyewear.
3. CO2-to-protein and nutrition (Deep Branch, Cemvita): gas fermentation converts CO2 and hydrogen into single-cell protein (Proton, about 70% protein) and renewable oils (Cemvita FermOil, demonstrated at 75,000 litres).
4. CO2-utilization to e-fuels and methanol (CRI, Cemvita e-kerosene): catalytic and bio-catalytic hydrogenation of CO2 with green hydrogen yields renewable methanol (Vulcanol) and onward e-SAF, with CRI studying a 70,000 t/yr facility with Honeywell UOP.

Sectoral value chain#

[CO2 source: industrial / biogenic / atmospheric] ──> [Capture & conditioning] ──> [Bio-conversion: fermentation / engineered microbes / microalgae]
                                                                                          │
                                                                              (product recovery and purification)
                                                                                          │
                                                                                          ▼
[End-use: fuels · feed protein · polymers · methanol] <─── [Circular carbon products]

Value chain levels#

Cross-cutting technologies of the sector:

• Green hydrogen integration: CO2-plus-hydrogen routes (Deep Branch protein, CRI methanol) tie bio-CCU economics to the cost of renewable hydrogen and electrolyser scale-up.
• Synthetic biology and strain engineering: Cemvita and Newlight re-engineer microbial carbon flux to channel CO2 toward target products (oils, PHA, kerosene precursors) at higher titres.
• Carbon accounting and certification: ISCC PLUS, the EU CRCF and the US 45Q credit convert tonnes of utilized CO2 into bankable value, the linchpin of project finance.

The bio-CCU technology stack rests on four pillars: gas-fermentation biology, microbial polymer synthesis, single-cell protein production, and CO2 hydrogenation to methanol and e-fuels — together turning point-source carbon into merchant products.

1. Gas-fermentation biology:
   • Autotrophic acetogens (LanzaTech) and hydrogen-oxidizing microbes (Deep Branch) fix CO/CO2 into ethanol and protein; LanzaTech’s 55.8 million dollar 2025 revenue shows the route reaching commercial tonnage from waste gases.
   • Strain tolerance to syngas impurities (tar, sulfur) and gas-liquid mass transfer set the ceiling on reactor productivity and feedstock flexibility.
2. Microbial polymer synthesis:
   • Newlight’s AirCarbon uses methane-oxidizing ocean microbes to channel CO2 and methane into polyhydroxyalkanoate granules, yielding a polymer that is carbon-negative and ocean biodegradable.
   • Patented engineered strains tune carbon flux toward PHA, raising titre and lowering the energy cost of cell harvest and polymer extraction.
3. Single-cell protein production:
   • Deep Branch’s Proton ferments CO2 with hydrogen and oxygen into a single-cell protein of about 70% content, replacing soy and fishmeal in aquafeed at roughly 90% lower carbon footprint.
   • The bottleneck is gas-fermentation scale-up and feed-grade safety clearance rather than biology, making partners and offtake decisive.
4. CO2 hydrogenation to methanol and e-fuels:
   • CRI’s Emissions-to-Liquids process catalytically hydrogenates CO2 into Vulcanol methanol (about 1.4 t CO2 per tonne), which Honeywell UOP’s eFining can upgrade into e-SAF.
   • Economics hinge on cheap green hydrogen and electrolyser capacity, tying bio-CCU to the broader power-to-liquids build-out.