Flue gases contain SO2 and NOx that can be treated together for elemental sulfur recovery in bioscrubbers, a technology that couples physical-chemical and biological processes for gaseous emissions treatment in a more economic manner than classical absorption. Sequential wet-absorption of SO2 and NOx from flue gas is thoroughly studied in this work in a two-stage bioscrubber towards elemental sulphur valorisation pursuing reuse of biological process effluents as absorbents. The optimal operating conditions required for SO2 and NOx absorption in two consecutive spray-absorbers were defined using NaOH-based absorbents. Overall, removal efficiencies of 98.9 and 55.9% for SO2 and NOx abatement were obtained in two in-series scrubbers operated under a gas contact time of 1 and 100 s, and a liquid-to-gas ratio of 7.5 and 15 L•m -3 , respectively. Higher NOx removal efficiency to clean gas emission was obtained by oxidants dosing in the absorber for NOx absorption. High NaHCO3 concentration in two-stage bioscrubber effluent was exploited as alkaline absorbent for flue gas treatment. The performance of scrubbers using an absorbent mimicking a reused effluent exhibited same removal efficiencies than those observed using NaOH solutions. In addition, the reuse of bioprocess effluent reduced reagents consumption by a 63.7%. Thus, the two-stage bioscrubber proposed herein offers an environmentally friendly and economic alternative for flue gas treatment.