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Due to the observed impacts of climate change on the natural environment, the demand for energy from renewable sources is growing, especially in the last decades. One of the possibilities in this respect is the use of forest biomass, especially that one which comes from logging residues. This type of wood raw material is obtained primarily in mature forests and during late thinnings. Estimation of the expected volume of logging residues from a particular cutting site is currently carried out in the State Forests, National Forest Holding with an accuracy oscillating at an acceptable level of ±40%. The purpose of this study was to estimate the share of logging residues in the total volume of the harvested biomass and to determine the difference and error between the estimated volume to be sold and actually harvested. The research was carried out at the 164 logging sites located in 10 forest districts of north−eastern part of Poland. The average volume of logging residues was 37.7 ±14.4 m³/ha, and the average error of their estimation was –6.1%.
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Sektor biomasy drzewnej w kreowaniu miejsc pracy

84%
The objective of the study was to estimate the number of jobs created by sector of wood biomass used for the energy production. The study presents direct employment (the persons who are employed in the production of wood biomass, its harvesting, industry processing, transport or combustion), indirect employment (the employment in the related sections according to Polish Classification of Activites) and induced employment (the jobs created as a result of purchases of the persons directly employed in the biomass sector). The data used in the analyses were obtained from various official sources and statistics as well as previously published studies. The calculation included the whole area of Poland and focused on the data from the year 2012. The results lead to the conclusion that the direct employment in biomass sector in Poland in the year 2012 amounted 15.6 thousand jobs, of which 5.3 thousand in fuelwood harvesting and using. The indirect employment varied between 19 (by forestry sector) to 25 people (by public utilities sector) per 10 million PLN purchases by biomass sector. In turn, the induced employment amounted to 1.8 thousand employees, of which the largest share was observed for the education services section (29%), the manufactured products (19%), and human health services (17%).
The paper describes the accuracy of estimation of silver fir stem fresh mass on the basis of volume to weight conversion factor, derived from samples, collected from few different places along the stem. The research material contained 13 sample trees selected from homogenous 70−years old stand, situated in mountainous area of the Beskid Sądecki in Polish part of the Carpathians (S Poland). Volume over the bark of sample trees was calculated with section−wise method and the whole stem fresh biomass was directly weighted. For each sample tree three stem discs were collected at ⅙, ½ and ⅚ of tree height, their weight and volume were precisely determined and the biomass conversion factors (equivalent of stem density) were calculated. The assessment of the accuracy of whole fresh stem biomass was conducted according to five variants: for the biomass conversion factors derived from each individual stem disc (lower, middle or upper), from weighted mean density and on the basis of the constructed mixed model, where relative height and diameter were treated as fixed effects and influence of individual trees was included as a random term. The volume of sample fir stems ranged from 0.15 to 2.22 m³, while their fresh biomass varied between 138.1 and 1896.7 kg. Obtained results show that variation of the density was higher within stems than between them (coefficient of variation amounted to 8.4% i 3.3% respectively). The average density increased along stem, from 835.6 kg/m³ for lower part (⅙H) to 986.8 kg/m³ for the upper part (⅚H). Estimating the biomass on the basis of just lower stem disc resulted in the average relative error equal to –5.8%, while for middle stem disc the error was +1.2%, and for upper disc +11.3%. The use of conversion factors derived from weighted average density of all three stem discs resulted in average bias equal to –1,7% with standard error 1,0%. Despite the presence of mean bias of –2.3%, the constructed density model gave the most precise estimation of the stem biomass (standard error 0.7%), which indicates the reasons for its further improvements and usage.
W pracy przedstawiono metodykę szacunku efektów ekologicznych rozumianych jako zmniejszenie zanieczyszczenia powietrza atmosferycznego wynikających z zastosowania wierzby energetycznej jako paliwa alternatywnego dla węgla kamiennego w gminie Skała w województwie małopolskim. Bazę badawczą stanowiła szczegółowa inwentaryzacja terenowa odłogów występujących na badanym obszarze. W konkluzji Autorzy wykazali efekty ekologiczne wyrażone niewyemitowaniem do powietrza takich zanieczyszczeń jak dwutlenek węgla i dwutlenek siarki oraz istotnym zmniejszeniem emisji tlenków azotu. Uzyskane efekty ekologiczne są szczególnie istotne dla analizowanej gminy ze względu na to, że bezpośrednio sąsiaduje z Ojcowskim Parkiem Narodowym.
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