Abstract: A system for generating NOx gases for growth of algae comprises: (a) a closed system combustion stage to combust carbonaceous material at a flame temperature and pressure promoting generation of an exhaust gas comprising controlled proportions of carbon dioxide and a determined quantity of NOX gases; (b) a closed system algae growth and oxygen generation stage for receiving the exhaust gas from the closed system combustion stage and delivering said exhaust gas as at least a portion of a feedstock gas for growing algae in an algae growth medium in which solubilised species of nitrogen including at least acid forming NOx and its reaction products with algae growth medium are metabolised by growing algae and directing an exit gas comprising carbon dioxide and non-solubilised NOx in controlled proportions to the closed system combustion stage; (c) dissociating insoluble NOX received from the closed system algae growth and oxygen generation stage in the closed system combustion stage and reforming said NOx into th