In this study, the design, construction and operation of an Internally Circulating Fluidized-bed Gasifier (ICFG) are introduced in detail. ICFG design provides a multi-stage gasification process, with bed material acting as the medium for char combustion and heat exchange by its internal circulation. And it is used for the steam gasification of animal waste at low temperature in view of producing fuel gas. The effects of pressure balance, pyrolysis temperature, catalytic temperature and steam/feedstock ratio on the gasifier performance (e.g. product gas yield, gas composition, tar content) are also discussed. Hydrogen-rich and low-tar product gas can be produced from the low-calorific feedstock, in the properly designed process together with high-performance catalyst. (C) 2009 Elsevier B.V. All rights reserved.