Integrated artificial photosynthesis and microbial bioprocessing systems for solar biofuel and bioproduct production

Abstract Coupling abiotic solar capture with microbial biosynthesis integrated artificial photosynthesis–microbial bioprocessing (IAP-MB) could convert sunlight, water and CO 2 into fuels and polymers at areal efficiencies well above those of crops, which typically remain below 1%. Here we critically review three architectures decoupled photovoltaic–electrolysis/fermentation (A), electrode-attached biofilms (B) and photosensitised cells (C) and combine the literature with transparent screening calculations. A cascade analysis bounds the solar-to-chemical efficiency of Architecture A at 4.0–10.9% (base case 7.2%) and identifies electrolysis and bioconversion as the main leverage points. Substrate-inhibited uptake kinetics (Andrews model) imply an unstable operating branch above the optimum carrier concentration (9.8 mM for the constants used), so unmanaged supply–demand mismatch causes runaway accumulation; in simulation, a PI controller with back-calculation anti-windup reduced the peak formate concentration from 207 to 48 mM relative to an unprotected PI loop. Using the authors’ preliminary plant model (10,000 t PHB yr − 1 ), recomputed levelised costs are US$2.19 kg − 1 (A) and US$3.23 kg − 1 (B), dominated by discount rate and operating cost, and photoelectrode lifetimes near one year add roughly US$0.8 kg − 1 to B. Stoichiometrically consistent life-cycle accounting shows that the climate benefit of PHB routes hinges on the biogenic carbon credit (2.04 kg CO 2 per kg PHB): burdens alone are 1.80 (A) and 3.10 (B) kg CO 2 -eq kg − 1 , versus 1.98 for polypropylene. A research roadmap and reporting recommendations close to the paper.