Commissioning, performance benchmarking, and investigation of alkali emissions in a 10 kWth solid fuel chemical looping combustion pilot

•Carbon capture efficiency is >99% for high-volatiles biomass, >94% for char fuels.•Volatiles distributor helps achieve gas conversion efficiencies of up to 95%.•Ilmenite bed material absorbs >96% of biomass fuel alkali.•AR alkali emissions are constant and independent of the fuel alkali content.•FR alkali emissions exceed AR emissions only for the straw pellet mixture fuel.