The purpose of this study was to evaluate the suitability of leaves of four hazel (Corylus avellana L.) cultivars – ‘Kataloński’, ‘Olbrzymi z Halle’, ‘Olga’ and ‘Webba Cenny’ - as waste biomass for energy purposes. A comprehensive morphometric and biometric analysis of the leaves was carried out, as well as physicochemical tests including calorific value, elemental composition, ash and moisture content. In addition, emission factors for gaseous pollutants (CO, NOₓ, CO₂, SO₂) and dust, as well as flue gas composition parameters, were determined to determine the effect of variety on energy and environmental efficiency of biomass. The results showed significant differences between varieties - especially in terms of calorific value and pollutant emissions. The ‘Kataloński’ variety had the highest calorific value (17.63 MJ·kg⁻1), carbon content (43.46%) and lowest moisture content (6.24%), making it the most energy-efficient feedstock, but with the highest flue gas emissions. In contrast, ‘Olga’ showed the lowest emissions, with a slightly lower calorific value and higher moisture content. Dendrogram analysis confirmed the energy differentiation of varieties, indicating a significant influence of varietal characteristics on the energy potential of leaves. The results confirm the possibility of using hazel leaf biomass as a renewable resource, in accordance with the principles of a circular economy.