Abstract
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 MJ·kg−1, 20.08 ± 0.87 MJ·kg−1, 20.37 ± 0.48 MJ·kg−1, and 20.79 ± 0.61 MJ·kg−1, respectively. The bulk density of larch cones was the highest at 223 kg·m−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.
Highlights
In face of the gradual depletion of fossil fuels, new renewable energy sources are sought, including medium- and small-diameter trees or branches and tops, which is mostly processed into pellets and chips to be burned in boiler stations or cogeneration plants [1,2,3]
An additional factor favoring various types of forest residue biomass for heat and electricity production is the opportunity to offset greenhouse gas emissions, which could make biomass use more economically viable [10]. Another interesting forest biomass alternative for both small- and large-scale consumers is offered by spent cones which are waste products of seed extraction facilities
The study material consisted of spent cones of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.), and European larch (Larix decidua Mill.), as well as Silver fir scales and rachises (Abies alba Mill.)
Summary
In face of the gradual depletion of fossil fuels, new renewable energy sources are sought, including medium- and small-diameter trees or branches and tops, which is mostly processed into pellets and chips to be burned in boiler stations or cogeneration plants [1,2,3]. An additional factor favoring various types of forest residue biomass for heat and electricity production is the opportunity to offset greenhouse gas emissions, which could make biomass use more economically viable [10]. Another interesting forest biomass alternative for both small- and large-scale consumers is offered by spent cones which are waste products of seed extraction facilities. There are 16 such facilities in Poland, including some dating to before the Second World War, some modernized ones, and some employing state-of-the art Swedish technologies [11,12]
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