The study investigates biomass chemical looping gasification (BCLG) using nickel smelter slag as an oxygen carrier (OC). Key operating parameters, including reactor temperatures (800–900 °C), OC-to-biomass ratio (OCBR, 4:1–15:1), and steam as a gasification medium, were evaluated in a 5kW_th fluidized bed reactor using pine forest residue. Performance metrics including gas composition and process efficiencies were assessed. OCs were characterized using XRD, BET and SEM-EDS analyses. Optimal performance was achieved at 850 °C, an OCBR (10:1) and a steam-to-biomass ratio (1.4). The gas composition was 38.87 vol% H₂, 19.65 vol% CO, 34.48 vol% CO₂, and 6.61 vol% CH₄, with a product gas yield of 1.24Nm³/kg-biomass. Carbon conversion efficiency was 77.85 %, cold gas efficiency 58.70 %, and levelized cost of fuel was 0.15 €/Nm³ for product gas and 4.55 €/kg for H₂.The results suggest that steam addition significantly enhanced char conversion, improving overall BCLG efficiency. Moreover, nickel smelter slag demonstrated stability, consistent reactivity, and limited sintering behavior.