Biofilm permeability regimes split hydrogen transport outcomes in fracture simulations

Researchers at the lead author's institution ran pore-scale simulations coupling fluid flow, biofilm growth, and microbial hydrogen consumption inside a rough-walled fracture with reactive surfaces. They systematically varied Darcy-scale flow rates and intrinsic biofilm permeability, tracking biomass accumulation, effective fracture permeability, and time-evolving outlet hydrogen concentration. Two regimes emerged, separated by a Reynolds number threshold based on initial permeability.

Type I biofilms permitted internal advection so that roughness-induced vortices initially limited transport before growth suppressed them, yielding non-monotonic outlet concentrations. Type II biofilms created transport barriers plus consumption losses, producing steady monotonic declines. Temporal concentration signatures could therefore fingerprint in-situ biofilm properties.

The work directly informs stimulated geologic hydrogen recovery, where biofilm clogging may cut yields but diagnostic signals could guide flow management. No experimental validation or field data yet exist; the purely computational design leaves open whether real microbial mechanics match the modeled permeability thresholds.

Next steps include laboratory fracture experiments that measure both permeability evolution and hydrogen breakthrough curves under controlled biofilm conditions to test the predicted regime boundary.