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The delayed harvest system for grass crops in which the harvest of the previous year's crop is undertaken after it has over-wintered in the field significantly improves the fuel quality for both combustion and gasification. The critical elements that cause fouling and corrosion problems in boilers are alkali and chlorine which are released during combustion. The concentrations of these are reduced by a factor of 2 to 6 by using the delayed harvest system rather than harvesting in the end of the growing season. The loss of some leaf material and leaching of alkali also contributes to an increase in the ash fusion temperature from 1070°C to 1400°C. This work is part of a project in progress involving 14 different field trials distributed all over Sweden. Results are presented demonstrating that ash content is influenced by the type of soil. The most extreme variations are between reed canary grass grown on high clay content soils and those produced on very humic soils, with ash contents of 10.1% and 2.2%, respectively.

Abstract In this research, we evaluated the intent of engaged private forest landowners to supply woody biomass for bioenergy production. The study was conducted in a U.S. state (Kentucky) where private individuals own a majority (78%) of the state's forest resources. Intent of family forest owners was measured using a mail-based survey. We used the Theory of Planned Behavior to model factors that affect landowner intention, and we tested the effect of educational materials on participates' reported intent. Two-thirds of respondents indicated that they intend to include energy wood in future harvests, but the educational material treatment did not affect intentions. Respondents' attitudes, perceived subjective norms, and perceived control each had a significant effect on intent to harvest. No demographic or land ownership characteristics had an effect on behavioral intent. The only prior harvest activity that significantly increased intent was whether the subject had harvested pulpwood from their forest in the past. Respondents identified barriers that may prevent them from harvesting energy wood, providing forestry professionals with a list of challenges to overcome if supply is to be maximized. Lack of bioenergy markets and woodland access issues were the most frequently reported barriers.

Abstract Eucalyptus plantations in the Southern United States offer a viable feedstock for renewable bioenergy. Delivered cost of eucalypt biomass to a bioenergy facility was simulated in order to understand how key variables affect biomass delivered cost. Three production rates (16.8, 22.4 and 28.0 Mg ha −1 y −1 , dry weight basis) in two investment scenarios were compared in terms of financial analysis, to evaluate the effect of productivity and land investment on the financial indicators of the project. Delivered cost of biomass was simulated to range from $55.1 to $66.1 per delivered Mg (with freight distance of 48.3 km from plantation to biorefinery) depending on site productivity (without considering land investment) at 6% IRR. When land investment was included in the analysis, delivered biomass cost increased to range from $65.0 to $79.4 per delivered Mg depending on site productivity at 6% IRR. Conversion into cellulosic ethanol might be promising with biomass delivered cost lower than $66 Mg −1 . These delivered costs and investment analysis show that Eucalyptus plantations are a potential biomass source for bioenergy production for Southern U.S.

Abstract Morphological characteristics of poplar and willow clones were determined in order to identify main characteristics leading to superior growth under increased plant competition with low or high nitrogen (N) availability. Seven hybrid poplar ( Populus spp. including one hybrid aspen) and five willow ( Salix spp.) clones were grown under greenhouse conditions for 13 weeks at three spacings (20 × 20, 35 × 35, and 60 × 60 cm) and two N levels (20 and 200 mg kg −1 ). The decrease in spacing from 60 to 20 cm reduced leaf area by 50% but clones had similar aboveground biomass per tree under all spacings, with increasing their height per unit leaf area. More productive clones had greater leaf area (+102%), leaf area per unit plant biomass (+12%) and lower root-to-shoot ratios (−27%) compared to less productive clones. There were positive relationships between leaf area and above-ground biomass per tree for both more and less productive clones. Compared to low N level and 60 cm spacing, trees growing in high N level and 20 cm spacing reached similar root collar diameter, crown width, and leaf area values and even greater height, suggesting that an addition of N could help mitigate negative effects of tree competition.

The current and future costs of willow short rotation coppice production in Sweden are analysed, considering all relevant cost factors explicitly. The future production costs are estimated considering effects of coppice area expansion and learning. The current and future costs of land and of risk premiums are subsequently estimated. Subsidies for farmers are not considered. If the area of willow cultivation were to expand enough to generate economies of scale, the production cost could be cut by about 10% compared to the current level. When learning effects are also considered, the total cost reduction potential is about 35%. Two major cost components (fertilization and road transport) are roughly stable while two other major cost components (establishment and harvest) have larger prospects for cost reduction, primarily due to potential for learning. Land costs and risk premiums vary and are uncertain, but both are estimated to be potentially significant compared to other cost components. Requirements of risk premiums may become lower as a consequence of area expansion and learning. Land costs are subject to many factors that are inherently uncertain, not the least future food prices. Efficient policies promoting an expansion of willow cultivation are discussed.

In this study we estimate the effects of climate change on forest production in north-central Sweden, as well as the potential climate change mitigation feedback effects of the resulting increased carbon stock and forest product use. Our results show that an average regional temperature rise of 4 degrees C over the next 100 years may increase annual forest production by 33% and potential annual harvest by 32%, compared to a reference case without climate change. This increased biomass production, if used to substitute fossil fuels and energy-intensive materials, can result in a significant net carbon emission reduction. We find that carbon stock in forest biomass, forest soils, and wood products also increase, but this effect is less significant than biomass substitution. A total net reduction in carbon emissions of up to 104 Tg of carbon can occur over 100 years, depending on harvest level and reference fossil fuel. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract Past research on identifying potentially negative impacts of forest management activities has primarily focused on traditional forest operations. The increased use of forest biomass for energy in recent years, spurred predominantly by policy incentives for the reduction of fossil fuel use and greenhouse gas emissions, and by efforts from the forestry sector to diversify products and increase value from the forests, has again brought much attention to this issue. The implications of such practices continue to be controversially debated; predominantly the adverse impacts on soil productivity and biodiversity, and the climate change mitigation potential of forest bioenergy. Current decision making processes require comprehensive, differentiated assessments of the known and unknown factors and risk levels of potentially adverse environmental effects. This paper provides such an analysis and differentiates between the feedstock of harvesting residues, roundwood, and salvage wood. It concludes that the risks related to biomass for energy outtake are feedstock specific and vary in terms of scientific certainty. Short-term soil productivity risks are higher for residue removal. There is however little field evidence of negative long-term impacts of biomass removal on productivity in the scale predicted by modeling. Risks regarding an alteration of biodiversity are relatively equally distributed across the feedstocks. The risk of limited or absent short-term carbon benefits is highest for roundwood, but negligible for residues and salvage wood. Salvage operation impacts on soil productivity and biodiversity are a key knowledge gap. Future research should also focus on deriving regionally specific, quantitative thresholds for sustainable biomass removal.

Abstract Shortage of oil, large variations in exports from Russia of wood to Europe, plenty of abandoned agriculture land, new ideas about a more intensive silviculture; these circumstances are driving forces in Sweden for planting fast-growing poplar and hybrid aspen clones on suitable land. The advantage of such trees is that the wood can be used for both energy (heat, biofuels, electricity), paper and for construction. Poplar clones bred in the USA and Belgium, and older hybrid aspen clones from Sweden, together with new poplar clones collected and selected for Swedish conditions from British Columbia, Canada, were planted during the 1990s in south and central Sweden. The stem diameters and heights of the trees have been measured during the last 10 years and the woody biomass production above ground has been calculated. MAI for all the plantations is 10–31 m3 or 3–10 ton DM per hectare with the highest annual woody production of 45 m3 or 15 ton DM per hectare in some years in a very dense plantation in the most southern part of Sweden. All the plantations have been fenced for at least the first ten years. The damage has been caused by stem canker, insects, leaf rust and by moose after removal of the fences. The possibilities for the use of poplar plantations as energy forest and vegetation filters are discussed.