CDR & carbon management
Removed carbon is carbon that does not come back; each method has its own retention chemistry and its own measurement problem.
The cluster holds on a distinction that is easy to lose: CO₂ utilisation is not removal. Fuel, feed protein or plastic made from captured carbon only delay its return to the atmosphere; removal means the carbon is locked away for centuries and longer. Three questions recur from there.
First, permanence: what exactly holds the carbon — the condensed aromatic clusters of biochar, geological storage, carbonate mineralisation — and how fast the process can take it back. Second, the per-cycle price: nearly every method spends some of the carbon or energy it gathers on its own operation, and honest accounting starts after that toll. Third, measurability: in the open ocean or on a forest hectare the result must be separated from natural variability, and it is usually the measurement, not the chemistry, that turns out to be the hard part.
Start with biochar carbon removal: it shows most clearly how a material’s chemical stability turns into the price of a carbon credit.
Articles 9
| Biochar carbon removal Pyrolysis buys carbon stability with carbon loss: the aromatic char that survives decomposition is paid for in the biomass that does not. |
| Biochar pyrolysis equipment Heating rate, peak temperature and vapour residence time form one set of physical settings, and the optimum for liquid and the optimum for char are different points in that space. |
| BECCS Burning biomass and storing its CO2 underground can subtract carbon from the air — but only because photosynthesis put it there first, and only after the capture plant's own appetite is paid. |
| Biological carbon capture and utilization CO2 is fully oxidised carbon, so every biological conversion must repay the energy — and unless the product is durable, the carbon is delayed, not removed. |
| Enhanced rock weathering The reaction that has regulated Earth's climate for aeons, run deliberately and fast — and the reason nobody can yet say exactly how much it removes. |
| Ocean alkalinity enhancement The ocean is willing to absorb more CO2 than its carbonate buffer allows; adding alkalinity raises the ceiling — but proving the drawdown happened is harder than causing it. |
| Hybrid bio-DAC Biology can lower the temperature at which a sorbent lets go of CO2 — but it cannot repeal the dilution of air, and the biological parts add their own fragility. |
| Bio-cementation and MICP materials Bacteria can grow a cement from calcium carbonate at room temperature — but the carbonate usually arrives as urea, and every mole of binder drags two moles of ammonium behind it. |
| Gas fermentation: microbes as carbon-fixation machinery Three metabolic classes — acetogens, methanotrophs and hydrogenotrophs — turn carbon-bearing gases into ethanol and protein at ambient conditions; the reactor, not the microbe, sets the ceiling. |