Plant residues are a promising source of carbon-neutral biomass that can be used to produce pyrogenic organic matter (PyOM) with small-scale pyrolysis systems. These residues cab be considerably rich in nitrogen (N) and their thermal transformation through pyrolysis can serve as a mechanisms of N retention in terrestrial ecosystems. This study focused on three main areas of the process transformation and stabilization of plant residue organic N; (1) the availability of plant residues for the production of PyOM; (2) the operating conditions of pyrolysis cookstoves which affect the production of C and N pollutants and heat transfer for cooking and (3) the thermal and biological transformation of organic N from plant residues. In a plant residue resource availability analysis, a segmentation protocol was developed to evaluate the multiresolution segmentation (MRS) quality of an agricultural high resolution image. High quality image segmentation is essential for subsequent classification and quantification of plant residue availability. The main segmentation error occurred when an image object was missing in the segmentation layer. Missing objects can result in considerable over or underestimation of plant residues availability, depending on the final land cover classification. The subsequent thermal conversion of plant residues was performed in an indirect pyrolysis cookstove. The rate of pyrolysis fuel consumption was the main driver of carbon monoxide (CO) and nitric oxide (NO) emissions and heat output of the stove accounting for up to 70% of the variation in multivariate linear regression analysis. Meaning that the speed of cooking and the choice of fuel used, significantly affected the production of gaseous pollution while the amount of fuel used controlled the amount of heat produced for cooking. Finally, the thermal transformation of organic matter nitrogen (OM-N) into PyOM-N was characterized using N near edge X-ray absorption fine structure. Our study revealed that the formation of aromatic N heterocycles was significantly correlated (R2=0.44; p<0.0001) with the initial N content in uncharred OM. In an incubation study, PyOM-C mineralization was inhibited by aromatic N heterocycles found in extracted PyOM, while aromatic N heterocycles in oxygenated rings found in the PyOM extract promoted PyOM-C mineralization. These findings support that PyOM-C mineralization is affected by the molecular structure of N rather than N content or C:N ratio.