Nitrogen oxides are an unavoidable part of emissions in the off-gas of thermal plants in the industry, such as power plants, waste incineration plants and metallurgical furnaces. As they are harmful to the environment and humans, high demands are layed out on off-gas purification to minimise NOx emissions within the focus on environmental protection. The NOx issue is an increasing problem in thermal processes in which raw materials are processed with bound nitrogen. For example, electronic scrap has an increased content of nitrogen in the plastics of printed circuit boards. This thesis has a focus on the basics of nitrogen oxide formation in general, as well as measures to reduce nitrogen oxides and measurement principles. Another part is dedicated to the legal aspects regarding the emission limits. Furthermore it also concerns the recycling of e-waste and the consideration of printed circuit boards as a potential source of nitrogen oxide emissions. The experimental section sets its aim on the specially designed experimental setup, where the melting of various plastic mixtures takes place in an oven filled with a certain amount of copper. The goal comprises the establishment of a correlation between the bound nitrogen contained in the mixtures and the measured nitrogen oxide emissions. In order to reduce these emissions, an post-combustion burner is installed, which allows various sub-stoichiometric operation modes. It could be determined, that there exists a clear correlation between the addition of nitrogen-containing material and measured emissions. The effectiveness of the simple post combustion by means of sub-stoichiometric operation can be recognised.