Reference

Biofuels & bioenergy

The routes from biomass to energy carriers — biochemical and thermochemical — their physical limits and what makes each of them expensive.

Biomass stores recent carbon in tough polymers, and the whole cluster rests on one fact: before any fuel molecule exists, a toll is paid to take that structure apart. The cluster’s key quantity is lignocellulose recalcitrance — the cost of opening the polymer matrix. It splits every route into two families: biochemical (microbes build molecules selectively, but demand an accessible substrate) and thermochemical (will accept almost any feedstock, but destroys the molecule wholesale).

Three ideas recur from page to page. First, the trade between selectivity and throughput: the more precise the path to a target molecule, the fussier the feedstock. Second, water as the boundary between the families: wet biomass naturally goes to anaerobic digestion, dry biomass to gasification. Third, compatibility with infrastructure: a fuel is valuable not in itself but as a molecule that existing engines, pipelines and standards will accept.

Start with biomass for energy: it sets the route vocabulary and explains why the recalcitrance toll governs the economics of everything after it.

  • Biomass for energy The framework for the cluster: what biomass is chemically, the thermochemical and biochemical route families, and why lignocellulose recalcitrance sets the economics of all of them.
  • Biogas and anaerobic fermentation The four stages of the anaerobic consortium, the syntrophic coupling that holds it together, and why the thermodynamics of the two methanogenesis paths cap both rate and yield.
  • Advanced biofuels: why drop-in compatibility rules the chemistry How HEFA hydrotreating, alcohol-to-jet catalysis and biomethane produce spec-compatible hydrocarbons, what the compatibility requirements physically demand, and where each route hits its limit.
  • Anaerobic digestion of municipal waste Why the same microbial chain that digests clean farm feedstock struggles on municipal organics — rate mismatch and souring, ammonia chemistry, and heterogeneity as the operating tax.
  • Gasification and Fischer-Tropsch SAF Gasification chemistry, why tar and sulfur removal is the true hard part, and how the Anderson-Schulz-Flory distribution caps the jet fraction Fischer-Tropsch synthesis can deliver.
  • Marine biofuels: biomethanol and bio-LNG Why ocean shipping converged on methanol and liquefied biomethane, the synthesis routes from syngas and biogas that produce them, and the volumetric, cryogenic and slip limits each carries.
  • Hydrogen fuel from biomass The gasification, shift and purification chain that turns biomass carbon into a hydrogen carrier, the thermodynamic ceiling on yield, and the narrow conditions under which it beats water electrolysis.
  • Gas fermentation to chemicals The Wood-Ljungdahl pathway as the metabolic core of steel-off-gas fermentation, why acetogens beat Fischer-Tropsch on selectivity and lose on speed, and why gas-liquid transfer sets the reactor design.
  • Microbial electrosynthesis How cathode electrons reach acetogens directly or via hydrogen and formate, why the Wood–Ljungdahl pathway makes carbon fixation cheap, and where coulombic efficiency and titres set the limits.
  • Engineered photosynthesis and artificial chloroplasts Why RuBisCO's slow, promiscuous chemistry and photorespiration limit biomass yield, what C4 engineering changes, and how the synthetic CETCH cycle in a cell-free chloroplast tests the ceiling.
  • Microbial fuel cells How exoelectrogens perform extracellular electron transfer, what thermodynamics sets as the ceiling on cell voltage, and why internal resistance collapses power density.
  • Bio-powered IoT charging Where the microwatts come from in soil, plant and enzymatic cells, what duty cycling can and cannot buy, and why average power is the binding limit.
  • Bio-based phase-change materials The physics of latent-heat storage, how fatty-acid blends and eutectics tune the transition temperature, and why encapsulation is the enabling discipline.
  • Bio-degradation of engine carbon deposits What engine lacquers are made of chemically, what an enzyme in fuel can and cannot do, and where the mechanism tops out.
  • Microbial enhanced oil recovery The capillary-number physics of trapped oil, the in-situ MEOR mechanisms from biosurfactants to selective plugging, and why controllability rather than biology sets the limit.