Bioenergy technologies for carbon abatement

In this paper, bioenergy technologies (BETs) are presented as potential carbon abatement opportunities substituting fossil fuel or traditional (less efficient) biomass energy systems. Cost of energy (produced or saved) of BETs is compared with fossil fuel and traditional biomass energy systems to estimate the incremental cost (IC). The IC of carbon abatement for each of the selected BETs (in $ kWh⁻¹ or $ GJ⁻¹) is estimated using the carbon emission (tC kWh⁻¹ or tC GJ⁻¹) reduction obtained by substituting fossil fuel and traditional biomass alternatives. The abatement costs are estimated and compared for ten combinations of BETs (with seven technology alternatives) substituting conventional technologies. The analysis indicates that out of the ten project cases six have negative ICs in the range of −37 to −688 $ tC⁻¹ and four have positive ICs in the range of 52–162 $ tC⁻¹ mitigation. The negative ICs indicate that the suggested alternatives are cheaper than the original technologies. Thus, results indicate that the chosen BETs are cost-effective mitigation opportunities and are currently aggressive candidates under Clean Development Mechanism.     

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.     

The economical and environmental performance of miscanthus and switchgrass production and supply chains in a European setting

The purpose of this study is to analyse the economical and environmental performance of switchgrass and miscanthus production and supply chains in the European Union (EU25), for the years 2004 and 2030. The environmental performance refers to the greenhouse gas (GHG) emissions, the primary fossil energy use and to the impact on fresh water reserves, soil erosion and biodiversity. Analyses are carried out for regions in five countries. The lowest costs of producing (including storing and transporting across 100 km) in the year 2004 are calculated for Poland, Hungary and Lithuania at 43–64 € per oven dry tonne (odt) or 2.4–3.6 € GJ^?1 higher heating value. This cost level is roughly equivalent to the price of natural gas (3.1 € GJ^?1) and lower than the price of crude oil (4.6 € GJ^?1) in 2004, but higher than the price of coal (1.7 € GJ^?1) in 2004. The costs of biomass in Italy and the United Kingdom are somewhat higher (65–105 € odt^?1 or 3.6–5.8 € GJ^?1). The doubling of the price of crude oil and natural gas that is projected for the period 2004–2030, combined with nearly stable biomass production costs, makes the production of perennial grasses competitive with natural gas and fossil oil. The results also show that the substitution of fossil fuels by biomass from perennial grasses is a robust strategy to reduce fossil energy use and curb GHG emissions, provided that perennial grasses are grown on agricultural land (cropland or pastures). However, in such case deep percolation and runoff of water are reduced, which can lead to overexploitation of fresh water reservoirs. This can be avoided by selecting suitable locations (away from direct accessible fresh water reservoirs) and by limiting the size of the plantations. The impacts on biodiversity are generally favourable compared to conventional crops, but the location of the plantation compared to other vegetation types and the size and harvesting regime of the plantation are important variables.     

Performance of simulated flexible integrated gasification polygeneration facilities,Part B: Economic evaluation.

This paper investigates the economics of integrated gasification polygeneration (IG-PG) facilities and assesses under which market conditions flexible facilities outperform static facilities. In this study, the facilities use Eucalyptus wood pellets (EP), torrefied wood pellets (TOPS) and Illinois #6 coal as feedstock to produce electricity, FT-liquids, methanol and urea. All facilities incorporate CCS. The findings show production costs from static IG-PG facilities ranging between 12 and 21 €/GJ using coal, 19–33 €/GJ using TOPS and 22–38 €/GJ using EP, which is above the average market prices. IG-PG facilities can become competitive if capital costs drop by 10%–27% for coal based facilities. Biomass based facilities will need lower biomass pellet prices or higher CO₂ credit prices. Biomass becomes competitive with coal at a CO₂ credit price of 50–55 €/t CO₂. Variations in feedstock, CO₂ credit and electricity prices can be offset by operating a feedstock flexible IG-PG facility, which can switch between coal and TOPS, thereby altering its electricity production. The additional investment is around 0.5% of the capital costs of a dedicated coal based IG-PG facility. At 30 €/t CO₂, TOPS will be the preferred feedstock for 95% of the time at a feedstock price of 5.7 €/GJ. At these conditions, FT-liquids (gasoline/diesel) can be produced for 15.8 €/GJ (116 $/bbl). Historic records show price variations between 5.7 and 7.3 €/GJ for biomass pellet, 1.0–5.6 €/GJ for coal and 0–32 €/t CO₂. Within these price ranges, coal is generally the preferred feedstock, but occasionally biomass is preferred. Lower biomass prices will increase the frequency of switching feedstock preference from coal to biomass, raising the desire for flexibility. Of the three investigated chemicals, an IG-PG facility producing FT-liquids benefits the most from flexibility. Our study suggests that if the uncertainty in commodity prices is high, a small additional investment can make flexible IG-PG facilities attractive.     

The impact of feedstock cost on technology selection and optimum size

Development of biomass projects at optimum size and technology enhances the role that biomass can make in mitigating greenhouse gas. Optimum sized plants can be built when biomass resources are sufficient to meet feedstock demand; examples include wood and forest harvest residues from extensive forests, and grain straw and corn stover from large agricultural regions. The impact of feedstock cost on technology selection is evaluated by comparing the cost of power from the gasification and direct combustion of boreal forest wood chips. Optimum size is a function of plant cost and the distance variable cost (DVC, $ dry tonne⁻¹ km⁻¹) of the biomass fuel; distance fixed costs (DFC, $ dry tonne⁻¹) such as acquisition, harvesting, loading and unloading do not impact optimum size. At low values of DVC and DFC, as occur with wood chips sourced from the boreal forest, direct combustion has a lower power cost than gasification. At higher values of DVC and DFC, gasification has a lower power cost than direct combustion. This crossover in most economic technology will always arise when a more efficient technology with a higher capital cost per unit of output is compared to a less efficient technology with a lower capital cost per unit of output. In such cases technology selection cannot be separated from an analysis of feedstock cost.     

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.     

The potential biomass for energy production in the Czech Republic

Biomass production is a promising alternative for the Czech Republic's (CZ) agricultural sector. Biomass could cover the domestic bio-energy demand of 250 PJ a⁻¹ (predicted for 2030), and could be exported as bio-fuels to other EU countries. This study assesses the CZ's biomass production potential on a regional level and provides cost–supply curves for biomass from energy crops and agricultural and forestry residues. Agricultural productivity and the amount of land available for energy crop production are key variables in determining biomass potentials. Six scenarios for 2030 with different crop-yield levels, feed conversion efficiencies and land allocation procedures were built. The demand for food and fodder production was derived from FAO predictions for 2030. Biomass potential in the CZ is mainly determined by the development of food and fodder crop yields because the amount of land available for energy crop production increases with increasing productivity of food and fodder crops. In most scenarios the NUTS-3 regions CZ020, 31 and 32 provided the most land for energy-crop production and the highest biomass potentials. About 110 PJ a⁻¹, mostly from agricultural and forestry residues, can be provided from biomass when the present Czech agricultural productivity is maintained. About 195 PJ a⁻¹ (105 PJ from energy crops) can be provided when production systems are optimised with regard to fertilizer regimes and 365 PJ a⁻¹ (290 PJ from energy crops) when the yield level of Dutch agriculture is reached. Costs for woody biomass decrease with increasing plantation yield and range between 2.58 and 4.76 € GJ⁻¹. It was concluded that Czech agriculture could provide enough biomass for domestic demand and for export if agricultural productivity is increased.     

European biomass resource potential and costs

The objective of this study is to assess the European (EU27⁺ and Ukraine) cost and supply potential for biomass resources. Three methodological steps can be distinguished (partly based on studies explained elsewhere in this volume) (i) an evaluation of the available ‘surplus’ land, (ii) a modeled productivity and (iii) an economic assessment for 13 typical bioenergy crops. Results indicate that the total available land for bioenergy crop production – following a ‘food first’ paradigm – could amount to 900 000 km² by 2030. Three scenarios were constructed that take into account different development directions and rates of change, mainly for the agricultural productivity of food production. Feedstock supply of dedicated bioenergy crop estimates varies between 1.7 and 12.8 EJ y^?1. In addition, agricultural residues and forestry residues can potentially add to this 3.1–3.9 EJ y^?1 and 1.4–5.4 EJ y^?1 respectively. First generation feedstock supply is available at production costs of 5–15 € GJ^?1 compared to 1.5–4.5 € GJ^?1 for second generation feedstocks. Costs for agricultural residues are 1–7 € GJ^?1 and forestry residues 2–4 € GJ^?1. Large variation exists in biomass production potential and costs between European regions, 280 (NUTS2) regions specified. Regions that stand out with respect to high potential and low costs are large parts of Poland, the Baltic States, Romania, Bulgaria and Ukraine. In Western Europe, France, Spain and Italy are moderately attractive following the low cost high potential criterion.     

Assessing farmers' willingness to supply biomass as energy feedstock: Cereal straw in Apulia (Italy)

Cereal straw currently has end-uses such as animal bedding and feeding, but there are no official statistics regarding the fraction of straw that is not used. Although cereal straw is an abundant source of biomass still largely unexploited for energy purposes, the feedstock market interplay with current straw uses (e.g. animal bedding and feeding) and on-farm practices (e.g. chopped and incorporated) is still unknown. This research used farmers' stated preferences to assess the supply curve (i.e. amount and price) of cereal straw for bio-energy purposes. In addition, we performed an econometric regression on the straw price demanded by farmers (willingness to accept). A sample of data gathered in 2014 from 203 cereal growers in Apulia region (southern Italy) was used, and the results show that more than half of respondents would sell their cereal straw on the feedstock market, and that the preferred sales method is in-swath. The price requested would be higher (15.15 EUR ha^− 1) than that currently applied on the local straw market (12.00 EUR ha^− 1). Explanatory factors refer to farmers who currently burn stubble on-field, farmers involved in Agro-Environmental Schemes or contract provision, farmers with off-farm employment and farms with larger areas dedicated to cereals.     

Field-testing of SPRERI's open core gasifier for thermal application

One unit of Sardar Patel Renewable Energy Research Institute (SPRERI's) 1.25 GJ h⁻¹ capacity open core down draft gasifier burner system, suitable for thermal application was installed at M/s Dinesh Pharmaceutical Pvt. Ltd., Nandesari, for steam generation. Producer gas burner was used in dual fuel mode (60% LDO (light diesel oil)+40% producer gas). Gasifier consumed 78–80 kg h⁻¹ of wood, and replaced 40% (20 l h⁻¹) LDO. The system was tested for a cumulative period of 600 h using sawmill woody waste as feedstock in test runs of 15–18 h. Financial analysis of the gasifier system showed that user could save about Rs. 221.8 per hour by using dual fuel (60% LDO+40% producer gas) for steam generation. Economic analysis of the system tested in the field indicated the viability of the gasifier-based operation.     

Economics of switchgrass and miscanthus relative to coal as feedstock for generating electricity

Switchgrass (Panicum virgatum) serves as a model dedicated energy crop in the U.S.A. Miscanthus (Miscanthus x giganteus) has served a similar role in Europe. This study was conducted to determine the most economical species, harvest frequency, and carbon tax required for either of the two candidate feedstocks to be an economically viable alternative for cofiring with coal for electricity generation. Biomass yield and energy content data were obtained from a field experiment conducted near Stillwater, Oklahoma, U.S.A., in which both grasses were established in 2002. Plots were split to enable two harvest treatments (once and twice yr^?1). The switchgrass variety ‘Alamo’, with a single annual post-senescence harvest, produced more biomass (15.87 Mg ha^?1 yr^?1) than miscanthus (12.39 Mg ha^?1 yr^?1) and more energy (249.6 million kJ ha^?1 yr^?1 versus 199.7 million kJ ha^?1 yr^?1 for miscanthus). For the average yields obtained, the estimated cost to produce and deliver biomass an average distance of 50 km was $43.9 Mg^?1 for switchgrass and $51.7 Mg^?1 for miscanthus. Given a delivered coal price of $39.76 Mg^?1 and average energy content, a carbon tax of $7 Mg^?1 CO₂ would be required for switchgrass to be economically competitive. For the location and the environmental conditions that prevailed during the experiment, switchgrass with one harvest per year produced greater yields at a lower cost than miscanthus. In the absence of government intervention such as requiring biomass use or instituting a carbon tax, biomass is not an economically competitive feedstock for electricity generation in the region studied.     

Net carbon dioxide emissions from alternative firewood-production systems in Australia

The use of firewood for domestic heating has the potential to reduce fossil-fuel use and associated CO₂ emissions. The level of possible reductions depends upon the extent to which firewood off-sets the use of fossil fuels, the efficiency with which wood is burnt, and use of fossil fuels for collection and transport of firewood. Plantations grown for firewood also have a cost of emissions associated with their establishment. Applying the FullCAM model and additional calculations, these factors were examined for various management scenarios under three contrasting firewood production systems (native woodland, sustainably managed native forest, and newly established plantations) in low-medium rainfall (600–800 mm) regions of south-eastern Australia. Estimates of carbon dioxide emissions per unit of heat energy produced for all scenarios were lower than for non-renewable energy sources (which generally emit about 0.3–1.0 kg CO₂ kWh⁻¹). Amongst the scenarios, emissions were greatest when wood was periodically collected from dead wood in woodlands (0.11 kg CO₂ kWh⁻¹), and was much lower when obtained from harvest residues and dead wood in native forests (<0.03 kg CO₂ kWh⁻¹). When wood was obtained from plantations established on previously cleared agricultural land, use of firewood led to carbon sequestration equivalent to −0.06 kg CO₂ kWh⁻¹ for firewood obtained from a coppiced plantation, and −0.17 kg CO₂ kWh⁻¹ for firewood collected from thinnings, slash and other residue in a plantation grown for sawlog production. An uncertainty analysis, where inputs and assumptions were varied in relation to a plausible range of management practices, identified the most important influencing factors and an expected range in predicted net amount of CO₂ emitted per unit of heat energy produced from burning firewood.     

Ensilage performance of sorghum hybrids varying in extractable sugars

Renewable feedstock resources require novel storage technologies to optimize industrial use. Solid state fermentation of biomass feedstock may provide organic chemicals and fibers while reducing the risk of current dry-storage procedures. Here, we compare the chemical composition and fermentation of six sorghum hybrids (Sorghum bicolor L. Moench) following 1, 7, and 21 days of storage. Ensilage of 7 days resulted in a pH of 3.8 and declined further to 3.75 at day 21. Lactate increased during ensilage from 2.0 to 3.9 g 100 g⁻¹. Acetic acid increased between 1 and 7 days of ensiling but did not change until the end of the ensiling period. Total organic acids averaged 2.5 g 100 g⁻¹ after day 1 and increased to 4.2 and 4.7 g `100 g⁻¹ after days 7 and 21, respectively. Neutral detergent fiber ranged from 38 to 50 g 100 g⁻¹ among hybrids and total non-structural carbohydrates varied from 18 to 32 g 100 g⁻¹. Hemicellulose and cellulose ranged from 13 to 19 g 100 g⁻¹ and 20 and 28 g 100 g⁻¹, respectively. Genotypic variation in sorghum may offer designing dual-purpose hybrids for production of biomass and economically valuable byproducts.     

Biofuel production potentials in Europe: Sustainable use of cultivated land and pastures. Part I: Land productivity potentials

IIASA's agro-ecological zones modelling framework has been extended for biofuel productivity assessments distinguishing five main groups of feedstocks covering a wide range of agronomic conditions and energy production pathways, namely: woody lignocellulosic plants, herbaceous lignocellulosic plants, oil crops, starch crops and sugar crops. A uniform Pan-European land resources database was compiled at the spatial resolution of 1 km². Suitability and productivity assessments were carried out by matching climate characteristics with plant requirements, calculating annual biomass increments or yields including consideration of soil and terrain characteristics of each grid-cell.Potential biomass productivity and associated energy yields were calculated for each grid-cell. Spatial distributions of suitabilities of biofuel feedstocks in Europe were generated for each individual feedstock as well as for the five biofuel feedstock groups. Estimated agronomical attainable yields, both in terms of biomass (kg ha^?1) as well as biofuel energy equivalent (GJ ha^?1), were mapped and tabulated by agriculture and pasture land cover classes as derived from the CORINE land cover database. Results have been further aggregated by administrative units at NUTS 2 level.     

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.     

Outlook for advanced biofuels

To assess which biofuels have the better potential for the short-term or the longer term (2030), and what developments are necessary to improve the performance of biofuels, the production of four promising biofuels—methanol, ethanol, hydrogen, and synthetic diesel—is systematically analysed. This present paper summarises, normalises and compares earlier reported work. First, the key technologies for the production of these fuels, such as gasification, gas processing, synthesis, hydrolysis, and fermentation, and their improvement options are studied and modelled. Then, the production facility's technological and economic performance is analysed, applying variations in technology and scale. Finally, likely biofuels chains (including distribution to cars, and end-use) are compared on an equal economic basis, such as costs per kilometre driven. Production costs of these fuels range 16–22 €/GJ_HHV now, down to 9–13 €/GJ_HHV in future (2030). This performance assumes both certain technological developments as well as the availability of biomass at 3 €/GJ_HHV. The feedstock costs strongly influence the resulting biofuel costs by 2–3 €/GJ_fuel for each €/GJ_HHV feedstock difference. In biomass producing regions such as Latin America or the former USSR, the four fuels could be produced at 7–11 €/GJ_HHV compared to diesel and gasoline costs of 7 and 8 €/GJ (excluding distribution, excise and VAT; at crude oil prices of ∼35 €/bbl or 5.7 €/GJ). The uncertainties in the biofuels production costs of the four selected biofuels are 15–30%. When applied in cars, biofuels have driving costs in ICEVs of about 0.18–0.24 €/km now (fuel excise duty and VAT excluded) and may be about 0.18 in future. The cars’ contribution to these costs is much larger than the fuels’ contribution. Large-scale gasification, thorough gas cleaning, and micro-biological processes for hydrolysis and fermentation are key major fields for RD&D efforts, next to consistent market development and larger scale deployment of those technologies.     

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.     

A techno-economic evaluation of the effects of centralized cellulosic ethanol and co-products refinery options with sugarcane mill clustering

This work compares the calculated techno-economic performance for thermochemical and biochemical conversion of sugarcane residues, considering future conversion plants adjacent to sugarcane mills in Brazil. Process models developed by the National Renewable Energy Laboratory were adapted to reflect the Brazilian feedstock composition and used to estimate the cost and performance of these two conversion technologies. Models assumed that surplus bagasse from the mill would be used as the feedstock for conversion, while cane trash collected from the field would be used as supplementary fuel at the mill. The integration of the conversion technology to the mill enabled an additional ethanol production of 0.033 m³ per tonne of cane for the biochemical process and 0.025 m³ t^?1 of cane plus 0.004 m³ t^?1 of cane of higher alcohols for the thermochemical process. For both cases, electricity is an important co-product for the biorefinery, but especially for biochemical conversion, with surpluses of about 50 kWh t^?1 of cane. The economic performance of the two technologies is quite similar in terms of the minimum ethanol selling price (MESP), at 318 $ m^?3 (United States 2007 dollars) for biochemical conversion and 329 $ m^?3 for thermochemical conversion.     

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.     

Wood ash effects on plant and soil in a willow bioenergy plantation

Intensive management for biomass production results in high rates of nutrient removal by harvesting. We tested whether wood ash generated when burning wood for energy could be used to ameliorate negative soil effects of short-rotation harvesting practices. We measured the temporal and spatial dynamics of soil nutrient properties after wood ash applications in a willow plantation in central New York State and determined the influence of wood ash application on willow growth. Wood ash was applied annually for 3 years at the rates of 10 and 20 Mg ha⁻¹ to coppiced willow, Salix purpurea, clone SP3. Wood ash application significantly increased soil pH in the 0–10 cm soil layer from 6.1 in the control to 6.9 and 7.1 in the 10 and 20 Mg ha⁻¹ treated plots. Wood ash application significantly increased soil extractable phosphorus, potassium, calcium, and magnesium concentrations. Potassium was the element most affected by wood ash treatment at all soil depths. Wood ash had no significant effect on nutrient concentrations of foliar, litter, and stem tissue. Wood ash did not affect either individual plant growth or plot biomass production, which declined over the course of the study; it did increase the size of stems, but this effect was balanced by a decrease in the number of stems. Applying nitrogen as well as wood ash might be required to maintain the productivity of this SRIC system.