What is syngas fermentation and how does it produce biofuels?

Syngas fermentation uses acetogenic bacteria to convert synthesis gas (CO, CO2, H2) into ethanol, butanol, or other chemicals. Process: Biomass is gasified at high temperature (>700C) to produce syngas mixture. Syngas is cleaned to remove tars, sulfur, and particulates that inhibit fermentation. Acetogenic bacteria (Clostridium ljungdahlii, C. autoethanogenum, C. carboxidivorans) use Wood-Ljungdahl pathway to convert syngas to acetyl-CoA, then to products. Fermentation occurs in specialized bioreactors with efficient gas-liquid mass transfer. Advantages: can use any carbon feedstock (including waste), avoids pretreatment/enzyme costs for lignocellulosics, tolerant to feedstock variability. Challenges: low gas-liquid mass transfer rates, product inhibition, low product titers requiring energy-intensive separation. Commercial development by companies including LanzaTech producing ethanol from industrial waste gases. Genetic engineering improving yields and product range.