The use of agro-food waste in the co-fermentation process is associated with the possibility of the formation of potentially odorous substances in anaerobic conditions. Their presence in the resulting biogas is undesirable mainly due to the potential corrosive processes that may occur in further elements of the installation, especially in the case of contact with water vapor. Some of these compounds may also have a negative impact on human health. This refers to both the phenomenon of odor nuisance, i.e. psychological discomfort associated with contact with odorous compounds, and the impact on general well-being and health (some odorous compounds have cancerous properties). Unfortunately, there are no reports in the scientific literature on the possibility of determining this group of compounds in substrates used in the methane co-fermentation process. The planned research task involves the development and validation of a method for the qualitative and quantitative determination of potentially odorous compounds based on the headspace analysis technique combined with gas chromatography coupled with mass spectrometry (HS-GC/MS). The research material will be substrates of agricultural and food origin, such as: cattle and pig slurry, fish slurry, distillery slurry added to excess sludge in the methane co-fermentation process. Samples of the tested substrates will be analyzed both before the fermentation process and during the process conducted in laboratory conditions using a dedicated system, the Automatic Methane Potential Test System (AMPTS, Bioprocess Control, Sweden). Optimization of the proposed procedure will include: selection of extraction conditions of the compounds to be determined to the headspace phase (incubation temperature, incubation time, volume of gas phase dosing to the GC system), selection of chromatographic analysis conditions (temperature program, type of chromatographic column used, duration of a single analysis) and mass spectrometer detection system (selection of mass spectrometer operating parameters). Validation of the proposed analytical procedure will include determination of such parameters as: repeatability, reproducibility, linearity of the developed method.