The impact of nitrogen contained in biofuels and biomass on combustor/boiler performance (throughput and power) is assessed. It is shown that, at 40% excess air, throughput may decrease by more than 6% and power may decrease by similar to 5%. Higher feed rates of nitrogen-rich constituents (paper, wood, textiles, tires, leather, biosludge, biomass, animal byproducts) imply higher throughput and power losses. Losses increase with rising conversion factors of fuel-nitrogen to NOx and with excess air (EA). Flue gas NOx flow rates increase almost proportionally to the conversion factor. However, offgas NOx emission rates may increase faster, because of lower residence times and removal efficiencies in the air pollution control system resulting from higher offgas flow rates. Compensation mechanisms are quantified, including manipulation of EA, flue gas recirculation (FGR), and flue gas heat recovery (FHR), independently from FGR and oxygen enrichment,(OXE). Offgas NOx emission rates still increase faster than flue gas rates when the combustor is controlled by stand-alone lower EA or higher OXE. In contrast, combining higher FGR with higher OXE or lower EA results in a milder increase of offgas NOx emission rates. Introduced for thermal NOx control, FGR is emerging as a key parameter for efficient fuel-NOx abatement. The results may be useful toward improved design for enhanced resource/energy recovery.