Coupling biomass gasification with in situ CO2 Capture significantly enhances the yield of hydrogen. For this process, CaO is the most likely CO2 sorbent. However, the development of a sorbent that is resistant to physical deterioration and maintains reactivity through multiple cycles is a limiting step in the scale-up and commercial operation of a continuous process. To this end, we describe an experimental protocol for screening CO2 sorbents and then use this to assess the performance of six targeted CaO-based sorbents: CaO derived from commercially available CaCO3 (d(p) = 25.8 mu m), commercially available Ca(OH)(2) (d(p) = 9.2 mu m), precipitated CaCO3 (d(p) = 3.2 mu m), CaCO3 nanoparticles (d(p) = 509.4 nm), and presintered CaO doped with Li2CO3 and with K2CO3. The protocol allows the measurement of reactivity through multiple CO2 capture-and-release cycles; this is a significant step in determining the overall consumption of sorbent and, hence, the cost of one of the key parts of the process.