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The aim of the research was to determine the production viability and mechanical durability of briquettes made of shredded cones of three species: Scots pine, Norway spruce and European larch The agglomeration was carried out under constant operating conditions (at 20% of material moisture content, briquette diameter of 50 mm, at throughput of 50 kg h −1 ) in an industrial briquetting press. The particle size distribution of the shredded material was determined. The produced briquettes were evaluated for their density, mechanical durability and compressive strength. At moisture content of approximately 20%, the highest briquette density (1078 kg m −3 ), durability (97.87%) and compressive strength (9.69 MPa) were obtained for spruce briquettes. Pine cone briquettes showed the lowest density (938 kg m −3 ) and compressive strength (2.81 MPa), while larch cone briquettes had the lowest durability (87.58%). The produced briquettes were of high quality in terms of physical and mechanical characteristics. The novelty of research was the use of crushed cones of coniferous species, which are waste in seed extraction facilities, and due to the low bulk density, they are difficult to store and transport over long distances. After agglomeration, they form briquettes with good physical and mechanical parameters that can be used in local heating plants and stoves. [ABSTRACT FROM AUTHOR]

• Spruce, pine and larch cones were compared to spruce wood. • The cones had comparable energy content to spruce wood. • Pine cones showed the lowest emission levels, while larch cones had the highest. The aim of the research was to determine selected fuel properties and basic emission characteristics of briquettes made from cones of three tree species: Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies H. Karst.) and European larch (Larix decidua Mill.). Combustion tests were carried out under stabilized operating conditions (heat output, excess air coefficient) on a grate-fired combustion device. The elemental composition of the cone samples and the heating values were determined. The briquettes were evaluated in terms of carbon monoxide and nitrogen oxide emission concentrations depending on the excess air factor and the flue gas temperature. The composition and energy content of the cone materials were comparable to wood. In the dry state, the ash content was between 0.69 and 1.29% wt. and the lower heating values between 18.77 and 19.58 MJ·kg−1. This suggests favourable properties for use as a solid biofuel. However, during combustion all cone briquettes achieved higher emission levels of nitrogen oxides as well as carbon monoxide compared to spruce wood briquettes. Larch cone briquettes were consistently the highest in emissions which reached concentrations of carbon monoxide in flue gas up to 3500 mg·m−3. On the other hand, spruce and pine cone briquettes kept concentrations of carbon monoxide below 2000 mg·m−3 at excess air coefficients under 2.4. The amount of excess air significantly influenced the temperature of the exhaust gas, which was maintained above 300 °C during the tests. In the tested areas and the excess air coefficients the concentrations of nitrogen oxides did not exceed 200 mg·m−3 and were low for all samples. [ABSTRACT FROM AUTHOR]