Calcium Looping with Biomass Co-Firing for Carbon-Negative Cement Production: Pilot Plant Demonstration

Abstract

Cement manufacturing accounts for 8% of global CO₂ emissions, with roughly 60% arising from limestone calcination (process emissions) that cannot be eliminated by fuel switching alone. We demonstrate a 1 MWth calcium looping (CaL) pilot plant integrated with a cement precalciner that captures 93% of flue gas CO₂ while co-firing 30% torrefied biomass, achieving net carbon-negative operation (-0.12 t CO₂/t clinker vs. +0.83 t CO₂/t clinker for conventional cement). The spent CaO sorbent is directly recycled as cement raw meal, eliminating sorbent disposal costs. Over 500 hours of continuous operation demonstrate stable capture efficiency with CaO conversion declining from 42% to 28% over 50 carbonation-calcination cycles, manageable through fresh limestone makeup at 2.5% per cycle.