The paper presents the results of research on the physicochemical properties of plant biomass consisting of four mint species, these being Mentha × piperita L. var. citrata Ehrh.-'Bergamot', Mentha × rotundifolia L., Mentha spicata L., and Mentha crispa L. The research conducted consisted of the technical analysis of biofuels-determining the heat of combustion and the calorific value of the material under study, and the content of ash, volatile compounds, and humidity. In addition, elemental analysis was carried out for the biomass under study by determining the content of carbon, hydrogen, nitrogen, and sulfur. The research demonstrated that Mentha × piperita L. var. citrata Ehrh.-'Bergamot' had the highest energy potential with a gross calorific value of 16.96 MJ·kg −1 , and a net calorific value of 15.60 MJ·kg −1 . Among the tested materials, Mentha × rotundifolia L. had the lowest content of ash at 7.23%, nitrogen at 0.23%, and sulfur at 0.03%, and at the same time had the highest content of volatile fraction at 70.36%. When compared to hard coal, the estimated emission factors indicated a CO reduction of 29-32%, CO 2 reduction of 28-31%, NO x reduction of 40-80%, SO 2 reduction of 92-98%, and dust reduction of 45-61%, depending on the type of biomass used.Energies 2020, 13, 55 2 of 13 of harmful gas and dust emissions (CO 2 , NO, SO 2 ) [10], and reduction of mineral extraction and thus curbing environmental degradation caused by uncontrolled decomposition of unused biomass [11,12].One of the basic goals of a low-emissions economy is to reduce the flow of biodegradable waste mass within certain time limits. Reaching this objective will not be possible without the implementation and development of installations for the thermal conversion of residues from agricultural and agriculture-related production, especially in systems for managing residues in the herbal product industry [13]. Installations for the conversion of residues from the sector of agricultural, horticultural, and herbal production should ensure the possibility of fulfilling the adopted obligations to reduce biodegradable waste, and secondly, they should provide significant amounts of electricity and heat, mainly treated as energy from renewable sources [14,15]. In addition, it is still important to search for new, alternative energy sources characterized by low emission levels, including, apart from greenhouse gases, low dust emission [16,17]. Due to the growth of the herbal production sector, one can observe high potential for energy generation in the residues from herb production and, more importantly, in residues that cannot be offered on the consumer market.Poland is considered as a country with great capabilities in both the production of high-quality herbal raw materials and herbal processing. This is due to the fact that over the last decade the number of farms growing herbs in Poland has increased from 18,000 to 30,000, and plantations of herbs now cover an area of over 30,000 ha, whereas in the countries of the entire European Union, th...