In the context of growing demand for renewable energy sources and greenhouse gas emission reductions, increasing attention is being paid to the use of agricultural waste as bioenergy feedstock. The energy potential of biomass in the form of vine stems and pomace from the Regent variety of grapes, grafted onto their own roots and various types of rootstocks (125AA, SO4, 161-49), was assessed, where the control group consisted of ungrafted shrubs growing on their own roots, cultivated in south-eastern Poland. The analyses included the determination of technical and elementary parameters, pollutant emission indicators, and exhaust gas composition parameters. Compared to stems, pomace had a higher calorific value, higher C and H content, and lower dust emissions, while at the same time emitting more CO2. Stems, on the other hand, showed higher ash content and higher dust emissions, which may limit their energy potential. Among the analysed substrates, pomace from 125AA achieved the highest calorific values at a low moisture content, while biomass from substrate 161-49 was distinguished by the lowest sulphur content and a favourable emission balance. Cluster analysis showed clear grouping of substrates in terms of fuel and emission parameters, indicating the possibility of optimal substrate selection for the production of bioenergy feedstock. The results confirm that the appropriate selection of rootstocks in viticulture can significantly increase the energy value of waste biomass and reduce emissions, supporting the development of local renewable energy systems.