Analysis of Selected Physical Properties of Conifer Cones with Relevance to Energy Production Efficiency

The paper presents gross and net calorific values, ash content, conversion factors, and bulk density for different-sized spent cones of Scots pine Pinus sylvestris L., Norway spruce Picea abies L., European larch Larix decidua Mill., and Silver fir Abies alba Mill. harvested from various sites. Gross and net calorific value and bulk density were measured in accordance with the relevant EN and ISO standards. The density conversion factors were determined based on free space measurement by means of water immersion. Gross calorific value for Scots pine, Norway spruce, European larch, and Silver fir was 19.04 +/- 0.70 MJkg(-1), 20.08 +/- 0.87 MJkg(-1), 20.37 +/- 0.48 MJkg(-1), and 20.79 +/- 0.61 MJkg(-1), respectively. The bulk density of larch cones was the highest at 223 kgm(-3), which corresponds to 9%-18% of their specific density. The ANOVA test showed that the bulk density depends on the origin of the cones and is different for individual species. The conversion factors for the cones of Scots pine, Norway spruce, and Silver fir were similar and ranged from 0.18 to 0.26, while those for the European larch were much greater with a maximum of 0.55. All of the studied cones have shown a good potential as energy source, based on their physical characteristic and can be considered as a supplementary fuel. In the future, the study of chemical properties, such as the elemental composition and the ash melting temperature, will allow for a comprehensive characterization of the energy potential of the tested raw material.