Modified Water Treatment Sludge as High Performing and High Stability Oxygen Carriers for Efficient Chemical Looping Combustion and Subsequent Carbon Capture
1 October 2026
Affiliation
NTU
Focus topic
CO2 Capture
Water treatment sludge as chemical looping oxygen carrier
Summary
Rather than making capture equipment cheaper, this removes the need for a separate capture plant altogether. Ferric sludge from a Singapore water treatment plant, a landfill waste, is blended with 10% copper oxide and 30% calcium aluminate cement, cured, calcined at 950oC and sieved to 0.25-0.5 mm to make an oxygen carrier for chemical looping combustion. The carrier feeds oxygen to the fuel in place of air, so the exhaust is an almost pure, sequestration-ready CO₂ stream with no nitrogen oxides and no separation step.
Achievements: The best carrier, at roughly 37% iron, 13% copper, 23% calcium, 13% aluminium and 9% silicon, held CO combustion efficiency between 93.3% and 97.0% across 50 cycles at 850oC; extended runs reached 1,000 cycles at above 89%, stable for the first 300. Unmodified sludge could not complete 50 cycles at all because of severe agglomeration, whereas the modified carrier agglomerated only 3.19% and lost 3.44% to attrition.
What makes this novel compared to best-in-class technology?
Most capture technologies add a separate plant to separate CO₂ out of the exhaust. This approach removes the need for one entirely, by supplying oxygen to the furnace so the exhaust emerges almost pure. The oxygen carrier is made from waste sludge rather than manufactured.
TRL Level
1-3
Relevant for
Waste-to-energy and biomass combustion plants, water utilities with sludge to dispose of, industrial boilers
About
Inventors: Koh Yang Chat How Joewin, Liu Guicai, Chan Wei Ping, Grzegorz Lisak
Affiliation: Nanyang Technological University, Singapore (NTU), School of Civil & Environmental Engineering (CEE); Residues & Resource Reclamation Centre (R3C); Nanyang Environment & Water Research Institute (NEWRI)
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