Engineered microbial carbon capture

01Overview and value chain#

Markers EC: US 45Q sequestration credit + EU Innovation Fund CCU demonstrations | OECD: Carbon management | Regulator: EPA (USA), EFSA (EU), MOA (China)

Engineered microbial carbon capture fixes carbon-bearing gases into product molecules with cultivated microorganisms instead of solvents or sorbents. Three metabolic classes do the work: acetogenic bacteria read carbon monoxide and carbon dioxide through the Wood–Ljungdahl pathway and excrete ethanol; methanotrophs such as Methylococcus capsulatus oxidize methane-derived gas into single-cell protein; hydrogenotrophs combine CO₂ with electrolytic hydrogen to build biomass. The biology sets the economics — microbes operate at ambient temperature and pressure where a chemical catalyst needs steel and heat, but gas-to-mass transfer at industrial scale remains the binding constraint, which is why the sector’s reactors, not its strains, carry most of the capital cost. Deployed capacity is still pilot-to-demonstration: the largest single train in the corpus, the Calysseo joint-venture plant in Chongqing, is designed for 20,000 tonnes of protein per year, while LanzaTech’s Kuji City pilot produces on the order of 400 tons of ethanol per year at roughly one-tenth commercial scale. Certification is the second frontier — the first ISCC EU pathway for recycled-carbon fuels, applied to Chinese gas-fermentation output, is being undergone right now, and every tonne of microbial product has to prove both its carbon accounting and its feed-safety status before it sells.

Key directions of engineered microbial carbon capture:

1. Steel-mill gas to ethanol (CO Fermentation): acetogenic Clostridia fermentation of blast-furnace and steelwork off-gases; LanzaTech’s platform converts industrial emissions and gasified waste into recycled-carbon ethanol with around 26 regulatory approvals for biocatalyst products across the USA, China, India, Austria, Belgium and Japan.
2. Methane to protein (Methanotroph Protein): methanotroph biomass from natural gas and biogas streams — Calysta’s FeedKind is approved for aquaculture feeds in China, the EU, Japan and Thailand, with a 20,000 t/yr Chongqing facility operated by the Calysseo joint venture.
3. Power-to-protein (Hydrogenotroph SCP): CO₂ plus renewable-electricity hydrogen fed to hydrogenotrophic microbes; NovoNutrients runs this route at pilot scale in the San Francisco Bay Area targeting aquafeed and food ingredients.
4. Methane to value in India (Tropical Gas Fermentation): String Bio ferments methane into PRO-DG microbial protein with US FDA GRAS status and an initial 30,000 kg annual capacity in Bengaluru.

Sectoral value chain#

[industrial off-gas] ──> [gas conditioning] ──> [bioreactor fermentation]
                                                        │
                                              (C fixation to biomass)
                                                        │
                                                        ▼
[certified product] <── [downstream separation] <── [microbial conversion]

Value chain levels#

Cross-cutting technologies of the sector:

• Gas-fermentation reactors (Mass-Transfer Bioreactors): reactor designs whose capital cost is dominated by getting gas into liquid at industrial rate.
• Strain engineering (Synthetic Metabolism): tuned Wood–Ljungdahl and methane-oxidation pathways for yield and titers.
• Recycled-carbon certification (ISCC PLUS Chains): mass-balance chains that let fossil-comparable fuels and chemicals carry a recycled-carbon claim.

02US#

The US hosts the sector’s corporate centers and its strongest carbon-accounting incentive: the 45Q credit pays per tonne of securely stored or utilized CO₂, which is the commercial floor under gas-fermentation projects.

LanzaTech headquarters, 45Q utilization credit, Bay-Area power-to-protein#

• LanzaTech (Skokie, Illinois): the corpus’s flagship gas-fermentation company — 2025 revenue of $55.8 million, 192 employees, and a Kuji City (Japan) municipal-solid-waste pilot producing about 400 t/yr of ethanol at one-tenth commercial scale.
• Calysta (Mountain View, California): $177.6–228 million raised across rounds for FeedKind methanotroph protein, commercialized through the Calysseo joint venture in China.
• NovoNutrients (Sunnyvale/Emeryville, California): over $22 million raised including an $18 million Series A to build CO₂-plus-hydrogen single-cell protein for aquafeed; pilot-scale capacity only, with Bay-Area assets recently acquired by Biosphere.

03CN#

China is where gas fermentation has reached industrial scale first, because feed demand and steel-plant emissions sit in the same provinces.

Chongqing protein plant, Chinese aquaculture approvals, first ISCC recycled-carbon pathway#

• Calysseo Chongqing facility: Calysta’s joint-venture plant operated with a Chinese partner — 20,000 t/yr FeedKind capacity, with the JV booking $710k of unaudited 2025 revenue as it ramps.
• FeedKind approvals in China: the product is approved for aquaculture feeds in China alongside the EU, Japan and Thailand — the broadest feed-approval footprint in the sector.
• LanzaTech biocatalyst approvals in China: a share of LanzaTech’s roughly 26 regulatory approvals for biocatalysts covers Chinese deployments, and the world’s first ISCC EU certification pathway for recycled-carbon fuels is being undergone on Chinese gas-fermentation output.

04EU#

The EU’s role is regulatory and offtake-side: its feed approvals and its certification machinery define what microbial products must prove to enter the single market.

FeedKind EU feed approval, ISCC recycled-carbon chains, Innovation Fund demonstrations#

• EU aquaculture feed approval for FeedKind: one of the four jurisdictions that have cleared Calysta’s methanotroph protein for aquafeed use.
• ISCC EU certification pathway: the first recycled-carbon-fuel pathway under ISCC EU is being undergone by Chinese gas-fermentation production — the chain-of-custody template future EU plants will inherit.
• Japanese demonstration with Japanese Ministry of the Environment backing: LanzaTech’s Kuji City pilot is carried by an SBR joint-venture investment that includes Japan’s environment ministry — the demonstration template EU ports and steelworks are watching before committing capital.

05Leading companies and research institutes#

06Tech stack and innovations#

The stack is a metabolic toolkit — one pathway family per feedstock gas — wrapped in reactor and certification engineering.

1. Acetogenic gas fermentation (Wood–Ljungdahl Platform):
   • Clostridial metabolism fixes CO and CO₂ into acetyl-CoA and exports ethanol, working at ambient temperature where thermochemical routes need reformers.
   • case: LanzaTech’s Kuji City plant converts municipal-solid-waste gasifier output to about 400 t/yr of ethanol.
2. Methanotroph biomass (Methane-to-Protein Platform):
   • Methylococcus capsulatus grows directly on methane, turning a fuel molecule into a complete protein with a fermentation footprint far below soymeak agriculture.
   • case: Calysseo’s Chongqing joint-venture plant, 20,000 t/yr of FeedKind capacity in China.
3. Hydrogenotroph power-to-protein (CO₂ + H₂ Platform):
   • hydrogenotrophs combine electrolytic hydrogen with CO₂ to build biomass without any carbon-rich feedstock at all.
   • case: NovoNutrients’ Bay-Area pilot targeting aquafeed-grade single-cell protein, funded by over $22 million including an $18 million Series A.

07Value chains and production pipelines#

Industrial pipeline of a gas-fermentation plant (ISCC recycled-carbon chain)#

┌───────────────────────────┐      ┌───────────────────────────┐
│ 1. Source-gas assessment  │ ───> │ 2. Gas conditioning       │
└───────────────────────────┘      └───────────────────────────┘
                                                 │
                                                 ▼
┌───────────────────────────┐      ┌───────────────────────────┐
│ 4. Downstream separation  │ <─── │ 3. Bioreactor fermentation│
└───────────────────────────┘      └───────────────────────────┘
              │
              ▼
┌───────────────────────────┐      ┌───────────────────────────┐
│ 5. Upgrading/formulation  │ ───> │ 6. Certification, monitoring│
└───────────────────────────┘      └───────────────────────────┘

Stage 1: Source-gas assessment

Steel, refinery, biogas or gasified-waste streams are screened for CO, CO₂, H₂ and hydrogen-sulfide content, because contaminant tolerance decides the microbial choice before anything else.

Stage 2: Gas conditioning

Particulates, sulfur species and moisture are stripped and pressure is controlled, delivering a reactor-inlet gas the culture can metabolize without inhibition.

Stage 3: Bioreactor fermentation

Conditioned gas is sparged through the acetogen, methanotroph or hydrogenotroph culture; gas-to-liquid transfer sets the productivity ceiling, and the broth holds either ethanol or microbial biomass.

Stage 4: Downstream separation

Distillation recovers fuel-grade ethanol from broth; centrifugation and drying harvest bacterial biomass, with separation — not fermentation — often the larger share of plant capital.

Stage 5: Upgrading and formulation

Protein is concentrated and formulated for aquafeed and food specifications; ethanol is refined to fuel or chemical grade for offtake.

Stage 6: Certification and monitoring

Carbon accounting under ISCC, feed-safety approvals (GRAS, EU and Chinese feed registries) and continuous process monitoring decide whether the output sells as recycled-carbon product at all.