Combining capture and disposal
NANCY W. STAUFFER MAY 15, 2019 MITEI
Some power plants use materials called sorbents to remove carbon dioxide (CO2) from their exhaust so it can be sequestered from the environment. But separating the CO2from the sorbent requires high temperatures and produces CO2 gas that must be put into long-term storage—a prospect that raises safety and security concerns. In a proof-of-concept study, MIT researchers have demonstrated a battery-like system that uses the same CO2-capturing sorbent in a specially designed electrolyte that drives electrochemical reactions with three benefits: They separate the CO2 from the sorbent; they promote the discharge of electricity from the battery; and they incorporate the CO2into a solid that can serve as electrode material or be safely discarded. Their system—made of lithium and carbon electrodes plus the special electrolyte—achieves discharge voltages similar to those of other lithium-gas batteries under development. The researchers are now working to understand and optimize their lithium-based system and to see whether less-expensive, earth-abundant metals might work as well.
Reducing CO2 emissions from power plants is widely considered an essential component of any climate change mitigation plan. Many research efforts focus on developing and deploying carbon capture and sequestration (CCS) systems to keep CO2 emissions from power plants out of the atmosphere. But separating the captured CO2 and converting it back into a gas that can be stored can consume up to 25% of a plant’s power-generating capacity. In addition, the CO2 gas is generally injected into underground geological formations for long-term storage—a disposal method whose safety and reliability remain unproven.