Chemical looping combustion of wood pellets (WP), char (WC), and straw (SP) was conducted in a 60 kW CLC pilot with ilmenite braunite oxygen carriers (OCs). Alkali emissions were investigated impactor-based surface ionization detector (SID) measurements. Particle size distributions for WP WC fuels dominated by coarse particles formed refractory species. For SP fuel, the distribution bimodal dis...