A bioreactor designed to produce N2O from organic nitrogen and/or reactive nitrogen in waste is coupled to a hardware reactor device in which the N2O is consumed in a gas phase chemical reaction, e.g., catalytic decomposition to form oxygen and nitrogen gas.Heat from the exothermic reaction may be used to generate power. The N2O may alternatively be used as an oxidant or co-oxidant in a combustion reaction, e.g., in the combustion of methane. The bioreactor may have various designs including a two-stage bioreactor, a hollow-fiber membrane bioreactor, or a sequencing batch reactor. The bioreactor may involve Fe(II)-mediated reduction of nitrite to nitrous oxide.