This article examines both oxygen looping cycles (otherwise known as chemical looping combustion), and lime-based CO2 looping cycles, where calcined limestone is used for in Situ CO2 capture. There has been a rapid rise in the amount of research carried out recently, and both technologies are likely to see practical application in the near future. However, these technologies urgently require demonstration at the large pilot-plant level - in the case of chemical looping cycles for use with high-pressure syngas of the type likely to be produced by current coal gasification technologies and in the case Of CO2 looping cycles both for combustion and gasification applications with coal. Both approaches have potential for application in schemes for H, production, but these have not been considered here, although such applications will also inevitably follow in the medium to long term.