12 figures, 3 tables. Biomass Chemical Looping Gasification (BCLG) is an autothermic gasification process that provides pure syngas for many applications, including liquid biofuels production. Finding low-cost materials that can be used in the process is a key issue, especially when they come from waste. In this sense, LD Slag is a by-product of the steel industry used as an oxygen carrier in Chemical Looping Combustion with good results. This work investigates the use of LD Slag as oxygen carrier in a continuous 1.5 kW BCLG unit. The effect of the main operational variables (temperature, oxygen-to-fuel and steam-to-biomass ratios) and the use of CO instead of steam as gasification agent were analysed. LD slag allowed the process with high biomass conversions, X > 90%, carbon conversion efficiencies, η > 90%, and syngas yields, Y ≈ 0.66 Nm/kg of dry biomass, at conditions corresponding to autothermal operation. A lifetime of 300 h under reducing conditions was inferred and agglomeration problems were never detected. LD slag can be considered a suitable material for BCLG since it is possible to obtain high-quality syngas at autothermal conditions from different types of biomass with low tar generation and CO emissions. This work has been supported by the European Union’s Horizon 2020-Research and Innovation Framework Programme under grant agreement No 817841 (Chemical Looping gAsification foR sustainable production of biofuels - CLARA), and by the AEI/FEDER, UE - ENE2017-89473-R.