Effects of wood ash and nitrogen fertilization on Scots pine crown biomass

The crown biomass, being one of the most susceptible components of the above-ground tree biomass, could respond positively to environmental changes and temporary increase in nutrient availability. The influence of wood ash and nitrogen fertilization on crown biomass was studied in a 40-year-old Scots pine (Pinus sylvestris L.) stand growing on a Haplic Arenosol. The 36-model trees for the crown biomass measurements were sampled for 3 growing seasons after the application of 5.0 t wood ash ha⁻¹, 180 kg N ha⁻¹, 2.5 t wood ash ha⁻¹ plus 180 kg N ha⁻¹, and control (untreated plots). The masses of the current, 1-year-old and older needles and shoots, and branches were measured. A significant influence on the current year needles and shoots was found after the application of 180 kg N ha⁻¹ or 2.5 t wood ash ha⁻¹ plus 180 kg N ha⁻¹. When wood ash was applied in combination with nitrogen, an extra response tendency of the crown growth, especially of the top and the middle sections of the crown, was determined. However, there was no short-term influence of wood ash on crown biomass growth.     

Wood ash and nitrogen influence on ground vegetation cover and chemical composition

An experiment was set up in a 38-year-old Scots pine stand (forest type Pinetum vacciniosum) on a sandy soil (Haplic Arenosol). Raw wood ash (WA) and nitrogen (N) fertilizers were applied. There were 6 treatments: (1) 1.25 t WA ha⁻¹; (2) 2.5 t WA ha⁻¹; (3) 5.0 t WA ha⁻¹; (4) 180 kg N ha⁻¹; (5) 2.5 WA t ha⁻¹ together with 180 kg N ha⁻¹; and (6) control (without ash or N). The effects on ground vegetation cover, biomass and chemistry of Pleurozium schreberi (Brid.) Mitt. were studied.The ground vegetation cover measurements were performed from the initial phase of the experiment and continued annually in all treatments. The ground vegetation biomass and the concentrations of the main plant nutrients (N, P, K, Ca and Mg) and some heavy metals (Cr, Cd, Pb, Ni, Cu and Zn) were determined in the 5.0 t WA ha⁻¹ and 180 kg N ha⁻¹ plots 2 years after the application.The study results showed a significant reduction of the moss cover after the application of wood ash, and the higher ash dose gave a higher decrease. N and wood ash applied together with N also decreased the cover of the moss. Small changes in the mean cover of the vascular plants occurred after the N application. The biomass of the moss remained unaffected. Significant increases of the P, Ca and Mg concentrations in P. schreberi were found after the application of 5.0 t WA ha⁻¹, and also higher N concentrations were obtained after N application. No wood ash influence on the heavy metal (Cd, Pb, Cr, Ni, Cu and Zn) concentrations in P. schreberi was found.     

Management alternatives of energy wood thinning stands

Energy wood thinning has become a feasible treatment alternative of young stands in Finland. Energy wood thinnings have been carried out mainly in stands where precommercial thinning has been neglected and the harvesting conditions for industrial wood thinning are difficult. Despite of its positive effects on harvesting costs and on renewable energy potential, whole-tree harvesting has been constantly criticized for causing growth loss. In this paper, the profitability of energy wood thinning was studied in 20 Scots pine-dominated stands where energy wood thinning was carried out. The growth of the stands after thinning was predicted with the help of Motti-stand simulator. Entire rotation time of the stands was simulated with different management alternatives. The intensity of first thinning and recovery level of logging residues varied between alternatives. In order to attain acceptable harvesting conditions, industrial wood thinning had to be delayed. The effect of energy wood thinning on subsequent stem wood growth was almost the same as in conventional thinning. Whole-tree harvesting for energy proved to be profitable alternative if the stumpage price is around 3€ m⁻³, the interest rate is 3% or 5% and the removal of pulpwood is less than 20 m³ ha⁻¹. If the harvestable pulpwood yield is over 20 m³ ha⁻¹, integrated harvesting of industrial and energy wood or delayed industrial wood harvesting becomes more profitable.     

Engineering,nutrient removal,and feedstock conversion evaluations of four corn stover harvest scenarios

Crop residue has been identified as a near-term source of biomass for renewable fuel, heat, power, chemicals and other bio-materials. A prototype one-pass harvest system was used to collect residue samples from a corn (Zea mays L.) field near Ames, IA. Four harvest scenarios (low cut, high-cut top, high-cut bottom, and normal cut) were evaluated and are expressed as collected stover harvest indices (CSHI). High-cut top and high-cut bottom samples were obtained from the same plot in separate operations. Chemical composition, dilute acid pretreatment response, ethanol conversion yield and efficiency, and thermochemical conversion for each scenario were determined. Mean grain yield in this study (10.1 Mg ha⁻¹ dry weight) was representative of the average yield (10.0 Mg ha⁻¹) for the area (Story County, IA) and year (2005). The four harvest scenarios removed 6.7, 4.9, 1.7, and 5.1 Mg ha⁻¹ of dry matter, respectively, or 0.60 for low cut, 0.66 for normal cut, and 0.61 for the total high-cut (top+bottom) scenarios when expressed as CSHI values. The macro-nutrient replacement value for the normal harvest scenario was $57.36 ha⁻¹ or $11.27 Mg⁻¹. Harvesting stalk bottoms increased stover water content, risk of combine damage, estimated transportation costs, and left insufficient soil cover, while also producing a problematic feedstock. These preliminary results indicate harvesting stover (including the cobs) at a height of approximately 40 cm would be best for farmers and ethanol producers because of faster harvest speed and higher quality ethanol feedstock.     

Economics of willow growing in Northern Ireland

This paper reviews the e economics of short rotation coppice willow as an energy crop in Northern Ireland. Gross margins are presented for willow production and compared with, in the particular circumstances of Northern Ireland, equivalent outputs from grain production, lowland sheep and suckler cow production. The model used indicated a gross margin of £45 ha⁻¹ yr⁻¹ for a 12 tDM ha⁻¹ annual coppice crop without subsidies where the crop value was placed at £40 t⁻¹. This was equivalent to a 7 t winter wheat crop at £70 t⁻¹ and compared favourably with both lowland sheep and suckler cows.Currently the industry in Northern Ireland is at a very early stage of development and this imposes cost penalties on the pioneer growers. This situation is compared with the situation in Sweden where there is an established industry of 15,000 ha, where costs are significantly lower. Gross margin for the pioneer grower in Northern Ireland is about £100 ha⁻¹ yr⁻¹ less than for Swedish willow growers.     

Above-ground biomass estimation in ten tropical dry evergreen forest sites of peninsular India

The present study aims to estimate the above-ground biomass (AGB) distribution in ten 1-ha permanent plots, established in five sites each in inland and coastal tropical dry evergreen forests of peninsular India. Two linear regression equations, one using basal area (BA, Method 1) and the other using BA and height (Method 2) were followed. On using method 1, the AGB varied from 39.69 to 170.02 Mg ha⁻¹ and by method 2, it varied from 73.06 to 173.10 Mg ha⁻¹. The relationship between BA and AGB yielded a positive correlation for all the five sites of inland and coastal areas. The basic wood specific gravity of 41 tree species determined by oven-dry weight by volume, ranged from 0.46 to 0.92 g cm⁻³ for inland sites and 0.47 to 0.89 g cm⁻³ for the coastal sites. The AGB estimation obtained in this study represents a more realistic picture of biomass of tropical dry evergreen forests, because a relatively large area was sampled.     

Utilization of summer legumes as bioenergy feedstocks

Sunn hemp (Crotolaria juncea), is a fast growing, high biomass yielding tropical legume that may be a possible southeastern bioenergy crop. When comparing this legume to a commonly grown summer legume – cowpeas (Vigna unguiculata), sunn hemp was superior in biomass yield (kg ha^?1) and subsequent energy yield (GJ ha^?1). In one year of the study after 12 weeks of growth, sunn hemp had 10.7 Mg ha^?1 of biomass with an energy content of 19.0 Mg ha^?1. This resulted in an energy yield of 204 GJ ha^?1. The energy content was 6% greater than that of cowpeas. Eventhough sunn hemp had a greater amount of ash, plant mineral concentrations were lower in some cases of minerals (K, Ca, Mg, S) known to reduce thermochemical conversion process efficiency. Pyrolytic degradation of both legumes revealed that sunn hemp began to degrade at higher temperatures as well as release greater amounts of volatile matter at a faster rate.     

Above-ground biomass production and nutrient accumulation in young stands of silver birch on abandoned agricultural land

During the last decade, more than 400 000 ha of agricultural land was abandoned in Estonia. Such areas are often characterized by rapid natural afforestation with silver birch, which has led to an increase both in the woodland area and in the area of silver birch stands. However, many bioenergetic aspects related to birch stands growing on arable land are still poorly understood. The main aim of the present study was to investigate the above-ground biomass production, nutrient (NPK) accumulation, and foliar characteristics of young silver birch stands on abandoned agricultural land. Five 8-year-old stands of silver birch growing on different soil types were included in the study.The density of the studied stands varied from 3060 to 36 200 trees per ha and their above-ground biomass varied from 6.0 to 22.9 t DM ha⁻¹. The largest share in the above-ground biomass of the birches (59–80%) was from the stems. The mean stem mass of the birches ranged from 0.29 to 1.79 kg, and the mean total above-ground biomass ranged from 0.36 to 3.03 kg. The leaf area index for the studied stands varied from 1.21 to 4.64 m² m⁻², being the highest for the stand of medium density. Mean single leaf area varied from 9.4±0.2 to 15.4±0.3 cm², leaf weight per area varied from 61.1±0.4 to 77.5±0.5 g m², and specific leaf area varied from 13.2±0.1 to 16.8±0.1 m² kg⁻¹. However, no significant differences were found between stand density and the foliar characteristics. There was a strong positive correlation between soil nitrogen concentration and leaf nitrogen concentration (R=0.92); regarding phosphorus concentration, the corresponding correlation was weak (R=0.52) and regarding potassium concentration, no significant correlation was found. The amount of nitrogen accumulated in the above-ground part of the silver birch stands varied between 42.4 and 145.8 kg ha⁻¹, the amount of phosphorus, between 5.9 and 27.9 kg ha⁻¹, and the amount of potassium, between 7.2 and 78.6 kg ha⁻¹. The N:P:K ratios for the foliage were comparable. It is evident that the proportion of nitrogen and phosphorus are close to optimum, while the N:K ratio was lower than optimum value in all cases.     

Yield and composition of herbaceous biomass harvested from naturalized grassland in southern Iowa

Much of the land area in southern Iowa is used for perennial pastures that are dominated by cool-season grass species. These species are well adapted to the soils and climate and have become naturalized within the region. Biomass produced from these pastures might potentially be used as a feedstock for cofiring with coal to supplement supplies of dedicated energy crops such as switchgrass (Panicum virgatum L.). While much is known about the use of these pasture species for forage production, relatively little information is available on their use as a bioenergy feedstock. This research was conducted to assess the potential of harvesting cool-season pastures for cofiring with coal. Ten representative sites located in south central Iowa were evaluated. Across all sites, 26 plant species were identified, with individual sites having between 5 and 14 species. Biomass yield was determined at several sampling locations within each site. Yields ranged from 0.75 to 8.24 t ha⁻¹ over all sites. Mean yield across all sites was 4.20 t ha⁻¹. Fuel characteristics of the cool-season species were evaluated for burning qualities. Concentrations of ash, chlorine and sulfur are important for determining suitability in a biofuel. Ash content ranged from 58.5–118.1 g kg⁻¹ DM across all sites. Chlorine ranged from 0.8–7.6 g kg⁻¹ DM and sulfur content ranged from 0.7–3.4 g kg⁻¹ DM. Highest heating value (HHV) ranged from 17.69–19.46 MJ kg⁻¹. These results indicate that cool-season grassland in southern Iowa can produce biomass of sufficient yield and quality to supplement other sources for cofiring with coal to generate electricity.     

Aboveground tree biomass in a recovering tropical sal (Shorea robusta Gaertn. f.) forest of Eastern Ghats,India

Aboveground biomass of individual tree species by component and total biomass per unit area for four different stages of a recovering tropical dry deciduous forest stands, dominated by sal (Shorea robusta Gaertn. f.) of the Eastern Ghats, India were investigated during 2001–2002. Different periods of recovering (2, 4, 6, and 10-year) forest stands (84°13′E, 20°29′N) were selected in the Kandhamal district of Orissa, India and sample trees of all species were harvested. Tree species diversity was 23, 23, 21 and 22 in 2, 4, 6, and 10-year recovering stands, respectively. Species-wise Ixora pavetta showed the highest biomass in 2 and 4-year stands while Shorea robusta in 6 and 10-year stands. Component-wise, in all species, bole–wood contribution ranged between 22.6% and 60.9%. Aboveground tree biomass, in all the stands, was dominated by Shorea robusta, which ranged between 12.68 and 231.91 Mg ha⁻¹. Total aboveground tree biomass was 30.12, 49.21, 107.54 and 261.08 Mg ha⁻¹ in 2, 4, 6 and 10-year stands, respectively.     

Biomass yield,nitrogen response,and nutrient uptake of perennial bioenergy grasses in North Carolina

Although perennial grasses show considerable potential as candidates for lignocellulosic bioenergy production, these crops exhibit considerable variation in regional adaptability and yield. Giant miscanthus (Miscanthus × giganteus Greef & Deuter), Miscanthus sinensis Anderss. ‘Gracillimus’ and MH2006, plume grass (Saccharum arundinaceum Retz.), ravenna grass (Saccharum ravennae (L.) L.), switchgrass (Panicum virgatum L. ‘Alamo’), and giant reed (Arundo donax L.) field plots were established in 2008, treated with four nitrogen (N) fertilizer rates (0, 34, 67, 134 kg ha⁻¹ y⁻¹), and harvested annually in winter from 2008 to 2011. Giant reed, ‘Gracillimus’, switchgrass, MH2006, giant miscanthus and ravenna grass at the Mountain site produced mean dry matter yields of 22.8, 21.3, 20.9, 19.3, 18.4, and 10.0 Mg ha⁻¹ y−¹, respectively (averaged over the last two years). Dry matter yields at the Coastal site for giant reed, giant miscanthus, switchgrass, ravenna grass, and ‘Gracillimus’ were 27.4, 20.8, 20.1, 14.3, and 9.4 Mg ha⁻¹ y⁻¹, respectively (averaged over the last two years). Increasing N rates up to 134 kg N ha⁻¹ did not have a consistent significant effect on biomass production. High yields coupled with high mortality for plume grass at both sites indicates its potential as a bioenergy crop and need for continued improvement. Overall, the perennial grasses in this study had low nutrient removal, although giant reed and plume grass often removed significantly more N, P, K and S compared with Miscanthus spp. and switchgrass. Our results indicate that giant reed, giant miscanthus, and switchgrass are productive bioenergy crops across geographic regions of North Carolina.     

Runoff,sediment, nitrogen,and phosphorus losses from agricultural land converted to sweetgum and switchgrass bioenergy feedstock production in north Alabama

Renewable energy sources such as bioenergy crops have significant potential as alternatives to fossil fuels. Potential environmental problems arising from soil sediment and nutrient losses in runoff water from bioenergy crops need to be evaluated in order to determine the sustainability and overall feasibility of implementing bioenergy development strategies. This paper discusses runoff, sediment, N, and total P losses from agricultural land (continuous cotton (Gossypium hirsutum L.)) converted to short-rotation sweetgum (Liquidamber styraciflua L.) plantations with and without fescue (Festuca elatior L.) and switchgrass (Panicum virgatum L.) bioenergy crops, compared to corn (Zea mays L.), on a Decatur silt loam soil in north Alabama, from 1995 to 1999. Runoff volume was significantly correlated to total rainfall and sediment yield in each year, but treatment differences were not significant. Sweetgum plots produced the highest mean sediment yield of up to 800 kg ha⁻¹compared to corn and switchgrass plots, which averaged less than 200 kg ha⁻¹. Runoff NH₄⁺ N losses averaged over treatments and years for spring season (3.1 kg ha⁻¹) were three to five times those for summer, fall, and winter seasons. Runoff NO₃⁻ N for no-till corn and switchgrass plots in spring and summer were five to ten times that for sweetgum plots. No-till corn and switchgrass treatments had 2.4 and 2.1 kg ha⁻¹ average runoff total P, respectively, which were two to three times that for sweetgum treatments. Growing sweetgum with a fescue cover crop provides significantly lower risk of water pollution from sediment, runoff NH₄⁺ N, and NO₃⁻ N.     

Short-rotation forestry of birch,maple, poplar and willow in Flanders (Belgium) I—Biomass production after 4 years of tree growth

During the last three decades, oil crises, agricultural surpluses and global climate change enhanced the interest in short-rotation forestry (SRF). In this study, the biomass production of birch (Betula pendula Roth), maple (Acer pseudoplatanus L.—Tintigny), poplar (Populus trichocarpa × deltoides—Hoogvorst) and willow (Salix viminalis—Orm) growing under a short-rotation (SR) management system were compared after a 4 years period. The plantation was established on former agricultural land. The sandy soil had a mean pH of 4.5 and a mean carbon content of 1.0%. Survival rates after 4 years were 75.8%, 96.8%, 86.3% and 97.6% for birch, maple, poplar and willow, respectively. The mean actual annual biomass production for these four species amounted to 2.6, 1.2, 3.5 and 3.4 t DM ha⁻¹ yr⁻¹, respectively. The large variation in biomass production at the different plots of the plantation could not be explained by the measured soil parameters. Biomass production results found here were in the lower range of values reported in literature. However, in contrast to most other studies, no weed control, fertilisation or irrigation was applied in this experiment. As marginal agricultural soils are suboptimal for the growth of poplar and willow, birch can be considered as a very interesting alternative for the establishment of SR plantations in Flanders.     

Estimation of woody biomass production from a short-rotation bio-energy system in semi-arid Australia

Short, 3–5 year, rotations of trees have been proposed as a method of regaining hydrological control of dryland farming systems (300–600 mm annual rainfall) in southern Australia and thus alleviating salinization of land and water. At the termination of the rotation, the trees will be removed and used as a bioenergy feedstock. In the absence of any tree growth data in this region, allometric relationships were developed for three prospective short-rotation species (Eucalyptus globulus, Eucalyptus occidentalis and Pinus radiata), for 3-year-old trees, at a site with a mean annual rainfall of 365 mm. Equations that related stem diameter over bark at 10 cm (D₁₀) and tree height (ht) to total tree biomass (above and below ground), leaves, stems (stemwood and bark) and roots were developed, by combining data from different planting densities (500, 1000, 2000 and 4000 stem ha⁻¹) and landscape positions (upper-slope, mid-slope and lower-slope).Mean oven-dry yields of the three species, in the high planting density treatment were not significantly different and ranged from 12 to 14 t ha⁻¹ (3 years)⁻¹. There were consistent increases in biomass yield with planting density, with this generally being greatest with the 4000 stem ha⁻¹ treatment. There were marked differences in productivity with slope position. For E. globulus and E. occidentalis the best yields were obtained in lower landscape positions with initial planting densities of 4000 stem ha⁻¹, with 16.6 and 22.2 t ha⁻¹ (3 years)⁻¹, total biomass produced, respectively. The best yield of P. radiata was 15.4 t ha⁻¹ (3 years)⁻¹ from an initial planting density of 4000 stem ha⁻¹ in an upper landscape position. These differences partly reflected site hydrology, with water accumulating in downslope positions. Partitioning of tree components was variable between species, with root:shoot (R:S) ratio being significantly (P<0.0001) higher for E. occidentalis (0.5) compared with the other two species (0.3). Results suggest that biomass productivity can be optimized in this region by using high initial planting densities and recognizing the interaction of different species with site hydrology.     

Evaluating the impact of three incentive programs on the economics of cofiring willow biomass with coal in New York State

Plantations of fast-growing willow shrubs are being promoted as a source quality biomass feedstock for bioenergy and bioproducts in New York State (NY). In the near-term, cofiring of the feedstock—in combination with other woody biomass—with coal in existing utility power boilers is considered to be the most promising conversion method for energy generation. Despite the clear technological viability and associated environmental benefits, cofiring of willow has not been widely adopted. The relatively high production cost of the willow feedstock, which is over twice that of coal, is the primary reason for this lack of interest. Taxes that account for some of the social costs of using coal and/or incentives that appropriate value for some of the social benefits of using willow are essential for eliminating most or the entire current price differential. This paper presents an integrated analysis of the economics of power generation from cofiring willow biomass feedstock with coal, from the perspective of the grower, aggregator and the power plant. Emphasis is placed on analyzing the relative impact of a green premium price, a closed-loop biomass tax credit, and payments to growers under the proposed Conservation Reserve Program (CRP) harvesting exemption policy. The CRP payments reduced the delivered cost of willow by 36–35%, to $1.90 GJ⁻¹ and $1.70 GJ⁻¹, under current and increased yield conditions, respectively. These prices are still high, relative to coal. Other incentives are required to ensure commercial viability. The required levels of green premium price (0.4–1.0 cents kWh⁻¹) and biomass tax credit (0.75–2.4 cents kWh⁻¹) vary depending on whether the incentives were being applied by themselves or in combination, and whether current yield or potential increased yields were being considered. In the near term, cofiring willow biomass and coal can be an economically viable option for power generation in NY if the expected overall beneficial effects associated with the production and use of the biomass is accounted for.     

Biomass production and soil nutrients in organic and inorganic fertilized willow biomass production systems

The use of organic waste materials as nutrient sources for willow biomass production is an attractive means to decrease fertilization costs, increase biomass production and reduce greenhouse gas emissions associated with the system. In this study, changes in soil nutrients and biomass production of two willow varieties (Salix miyabeana–SX64 and Salix purpurea–9882-34) in organic and synthetic fertilized systems were compared at three locations in Northeastern U.S.A: Middlebury VT (MID), Delhi NY (DEL) and Fredonia NY (FRE). A 150 and 200 kg available N ha⁻¹ of urea as commercial fertilizer (CF), biosolid compost (BC) and digested dairy manure (DM) and a control (CT0) treatments were applied in June 2008 to the willow which was re-sprouting after coppice. There was no significant difference (p > 0.05) in biomass production among the fertilization treatments at any of the three sites and for either of the varieties. First rotation biomass production of 9882-34 ranged from 9.0 to 11.6 Mg ha⁻¹ yr⁻¹ at DEL, 3.4–8.8 Mg ha⁻¹ yr⁻¹ at MID and 3.5–7.7 Mg ha⁻¹ yr⁻¹ at FRE. For SX64, biomass production ranged from 13.2 to 19.0 Mg ha⁻¹ yr⁻¹ at DEL, 9.0–15.0 Mg ha⁻¹ yr⁻¹ at Mid and 5.5–9.3 Mg ha⁻¹ yr⁻¹ at FRE. SX64 deployed small numbers of large stems and produced more biomass than 9882-34 which deployed large numbers of small stems. Application of BC significantly increased soil N and P levels at MID in both 2008 and 2009 (p < 0.05). At DEL, BC and DM treatments increased soil N, Ca, Mg and OM levels in both 2008 and 2009 (p < 0.05). The fertilization treatments had no significant effect on any soil nutrients at FRE. This study indicates that willow biomass can be produced without fertilizer additions in the first rotation across this range of sites due to the nutrient status of these sites and high internal nutrient cycling in these systems.     

Biomass production from traditional coppice management in northern Italy

Traditional coppice stands cover millions of hectares throughout Europe and offer large amounts of biomass. The study analyzed 10 commercial coppice harvesting operations in northwestern Italy, where modern machines were deployed. Removals, prices, work, revenues and costs were carefully determined. Firewood was the main product, representing between 70% and 100% of the total product mass and value. Traditional coppice stands often yield over 200 m³ of energy biomass per hectare, at the time of cut. Cable yarding operations were better organized than ground-based operations, which explained why they incurred the same harvesting cost, despite the more challenging site conditions under which they were deployed. Mean harvesting cost was 45 € m⁻³, of which about 10% was needed for felling, 70% for extraction and processing, and the remaining 20% for loading and transportation. All operations accrued some profit, which varied between 13 and 43 € m⁻³ or between 1600 and 8600 € ha⁻¹, depending on operational efficiency, value recovery and stand yield.     

Long-term yield potential of switchgrass-for-biofuel systems

Limited information is available regarding biomass production potential of long-term (>5- yr-old) switchgrass (Panicum virgatum L.) stands. Variables of interest in biomass production systems include cultivar selection, site/environment effects, and the impacts of fertility and harvest management on productivity and stand life. We studied biomass production of two upland and two lowland cultivars under two different managements at eight sites in the upper southeastern USA during 1999–2001. (Sites had been planted in 1992 and continuously managed for biomass production.) Switchgrass plots under lower-input management received 50 kg N ha⁻¹ yr⁻¹ and were harvested once, at the end of the season. Plots under higher-input management received 100 kg N ha⁻¹ (in two applications) and were harvested twice, in midsummer and at the end of the season. Management effects on yield, N removal, and stand density were evaluated. Annual biomass production across years, sites, cultivars, and managements averaged 14.2 Mg ha⁻¹. Across years and sites, a large (28%) yield response to increased inputs was observed for upland cultivars; but the potential value of higher-input management for lowland cultivars was masked overall by large site×management interactions. Nitrogen removal was greater under the higher-input system largely due to greater N concentrations in the midsummer harvests. Management recommendations (cultivar, fertilization, and harvest frequency), ideally, should be site and cultivar dependent, given the variable responses reported here.     

A comparative analysis of woody biomass and coal for electricity generation under various CO2 emission reductions and taxes

Mitigating global climate change via CO₂ emission control and taxation is likely to enhance the economic potential of bioenergy production and utilization. This study investigated the cost competitiveness of woody biomass for electricity production in the US under alternative CO₂ emission reductions and taxes. We first simulated changes in the price of coal for electricity production due to CO₂ emission reductions and taxation using a computable general equilibrium model. Then, the costs of electricity generation fueled by energy crops (hybrid poplar), logging residues, and coal were estimated using the capital budgeting method. Our results indicate that logging residues would be competitive with coal if emissions were taxed at about US$25 Mg⁻¹ CO₂, while an emission tax US$100 Mg⁻¹ CO₂ or higher would be needed for hybrid poplar plantations at a yield of 11.21 dry Mg ha⁻¹ yr⁻¹ (5 dry tons ac⁻¹ yr⁻¹) to compete with coal in electricity production. Reaching the CO₂ emission targets committed under the Kyoto Protocol would only slightly increase the price of fossil fuels, generating little impact on the competitiveness of woody biomass. However, the price of coal used for electricity production would significantly increase if global CO₂ emissions were curtailed by 20% or more. Logging residues would become a competitive fuel source for electricity production if current global CO₂ emissions were cut by 20–30%. Hybrid poplar plantations would not be able to compete with coal until emissions were reduced by 40% or more.     

Using modified foragers to harvest short-rotation poplar plantations

In Italy, short rotation coppice (SRC) has become very popular in recent years, with over 4000 ha already planted – almost exclusively with clonal poplar. Commercial harvesting operations are dominated by modified foragers, equipped with dedicated SRC headers. At present, contractors use two main header types: German Claas HS-2 and Italian GBE. The former fits smaller foragers with a power below 300 kW, the latter is used on larger harvest units. This study models the performance of modified foragers on a range of short-rotation poplar plantations. Data were collected from 45 operations, covering a total of 118 ha and producing over 4400 green tonnes of wood chips. The average yield of the fields harvested during the trials was about 23 gt ha^?1 year^?1 (at a moisture content of 59%), and machine productivity ranged from 9 to 70 green tonnes per scheduled machine hour (gt SMH^?1), with an average value of 35 gt SMH^?1. A model was developed to predict harvesting performance and cost, showing that harvesting cost can be maintained below the 15 € gt^?1 (2 € GJ^?1) level, if field stocking exceeds 40 gt ha^?1.