Our goal is to mitigate climate change by producing clean energy from biomass without of harmful air pollutants such as NOx. One of the main sources of harmful air pollutants such as NOx is biomass boilers of thermal power generation stations. They cannot burn fuel in the boilers without excess of outdoor air but excess of oxygen in zone of fuel combustion create harmful air pollutants such as NOx. We propose them to use our a low cost devices under tread mark REAEGR that allows keeping sustainable regime of clean combustion of fuel close with the stoichiometric. It means significant reduction of NOx formation and savings of energy, lower CO2 emissions and lower operation and maintenance costs of the boilers.