Converting Eucalyptus biomass into ethanol: Financial and sensitivity analysis in a co-current dilute acid process. Part II

The technical and financial performance of high yield Eucalyptus biomass in a co-current dilute acid pretreatment followed by enzymatic hydrolysis process was simulated using WinGEMS^® and Excel^®. Average ethanol yield per dry Mg of Eucalyptus biomass was approximately 347.6 L of ethanol (with average carbohydrate content in the biomass around 66.1%) at a cost of $0.49 L⁻¹ of ethanol, cash cost of ∼ $0.46 L⁻¹ and CAPEX of $1.03 L⁻¹ of ethanol. The main cost drivers are: biomass, enzyme, tax, fuel (gasoline), depreciation and labor. Profitability of the process is very sensitive to biomass cost, carbohydrate content (%) in biomass and enzyme cost. Biomass delivered cost was simulated and financially evaluated in Part I; here in Part II the conversion of this raw material into cellulosic ethanol using the dilute acid process is evaluated.     

An analysis of the feasibility for increasing woody biomass production from pine plantations in the southern United States

In the near future, wood from the 130 000 km² of pine plantations in the southern United States could provide much of the feedstock for emerging bioenergy industries. Research and operational experience show that total plantation biomass productivity exceeding 22.4 Mg ha^?1 y^?1 green weight basis with rotations less than 25 years are biologically possible, financially attractive, and environmentally sustainable. These gains become possible when intensively managed forest plantations are treated as agro-ecosystems where both the crop trees and the soil are managed to optimize productivity and value. Intensive management of southern US pine plantations could significantly increase the amount of biomass available to supply bioenergy firms. Results from growth and yield simulations using models and a financial analysis suggest that if the 130 000 km² of cutover pine plantations and an additional 20 000 km² of planted idle farmland are intensively managed in the most profitable regimes, up to 77.5 Tg green weight basis of woody biomass could be produced annually. However, questions exist about the extent to which intensive management for biomass production can improve financial returns to owners and whether they would adopt these systems. The financial analysis suggests providing biomass for energy from pine plantations on cutover sites is most profitable when intensive management is used to produce a mixture of traditional forest products and biomass for energy. Returns from dedicated biomass plantations on cutover sites and idle farmland will be lower than integrated product plantations unless prices for biomass increase or subsidies are available.     

The financial feasibility of delivering forest treatment residues to bioenergy facilities over a range of diesel fuel and delivered biomass prices

Forest treatments have the potential to produce significant quantities of forest residue biomass, which includes the tops and limbs from merchantable trees and smaller trees removed to meet management objectives. We spatially analyzed the sensitivity of financially feasible biomass volumes for delivery to a bioenergy facility across 16 combinations of delivered biomass and diesel prices for a 515,900 ha area in western Montana. At the lowest delivered biomass price analyzed, $31.52 per oven dried tonne (ODT), 28% of the potential volume was financially feasible at the lowest diesel price, $0.053 L⁻¹, dropping off to 6% of the volume at the highest diesel price analyzed, $1.32 L⁻¹. With a 50% increase in delivered biomass price to $47.28 ODT⁻¹, feasibility increased to 88% at the $0.53 L⁻¹ diesel price, dropping to 36% of the volume at the $1.32 L⁻¹ diesel price. Another 50% increase in delivered biomass price to $63.05 ODT⁻¹ resulted in the feasible volume converging on the total potential volume at the lower diesel prices, and at the highest delivered price, $78.81 ODT⁻¹, nearly all potentially available biomass is financially feasible even at the highest diesel fuel price analyzed. Haul was almost entirely restricted to paved roads closest to the bioenergy facility at the lowest delivered biomass price. As delivered price increased, feasible volume expanded further into areas accessed by unpaved roads as well as paved roads further from the bioenergy facility. Results show that financial feasibility is much more sensitive to changes in delivered biomass prices than diesel prices.     

Input-output analysis of energy requirements for short rotation, intensive culture, woody biomass

A production model for short rotation, intensive culture (SRIC) plantations was developed to determine the energy and financial costs of woody biomass. The model was based on hybrid poplars planted on good quality agricultural sites at a density of 2100 cuttings ha⁻¹, with average annual growth forecast at 16 metric tonne, oven dry (Mg(OD)). Energy and financial analyses showed preharvest costs of 4381 megajoules (MJ) Mg⁻¹ (OD) and $16 (U.S.) Mg⁻¹ (OD). Harvesting and transportation requirements increased the total costs to 6130 MJ Mg⁻¹ (OD) and $39 Mg⁻¹ (OD) for the delivered material. On an energy cost basis, the principal input was land, whereas on a financial basis, costs were more uniformly distributed among equipment, land, labor, and materials and fuel.     

Trends and productivity improvements from commercial willow plantations in Sweden during the period 1986-2000

The production trends of commercial willow plantations for bioenergy in Southern and Central Sweden were studied for the period 1986-2000 based on harvest records of the first cutting cycle after the establishment of 1512 plantations. The trends were modelled by using a mixed model in order to include the variability of management options by the growers, which were grouped into four classes according to their performance. The spatial variability of the productivity is included using an agro-climatic index based on the official estimates of oat yields. Results of the study show average yield increments of 2.06 odt ha⁻¹ yr⁻¹ per decade. Areas with high productivity have significantly increased the yields of willow during the period studied, from 1.3 to 5.4 odt ha⁻¹ yr⁻¹. Regarding management, the best growers group shows a national average increment of 2.75 odt ha⁻¹ yr⁻¹ per decade, and the latest plantings reach an average of 6 odt ha⁻¹ yr⁻¹. This group is formed by farmers with previous experience growing willow, who tend to have significantly higher yields. In addition, experienced farmers increased their yields an average of 0.34 odt ha⁻¹ yr⁻¹ regardless of the group they were classified in. It is expected that future improvements of the willow varieties will result in a significant increase in the mean yields in the near future.     

Cost estimates of post harvest forest biomass supply for Canada

This study estimates the potential physical amounts and financial costs of post-harvest forest residue biomass supply in Canada. The analyses incorporate the locations of harvest activities in Canada, the geographical variation of forest productivity patterns and the costs associated with the extraction and transportation of residue feedstock to bioenergy facilities. We estimated the availability of harvest residues within the extent of industrial forest management operations in Canadian forests. Our analyses focused on the extraction of biomass from roadside harvest residues that involve four major cost components: pre-piling and aggregation, loading, chipping and transportation. The estimates of residue extraction costs also included representation of basic ecological sustainability and technical accessibility constraints. Annual supply of harvestable residual biomass with these ecological sustainability constraints were estimated to be approximately 19.2–23.3 Tg_*year⁻¹ and 16.5–20.0 Tg_*year⁻¹ in scenarios that included both ecological and technical accessibility limitations. These estimates appear to be less than other similar studies, due to the higher level of spatial details on inventories and ecological and operational constraints in our analyses. The amount of residual biomass available in baseline scenarios at a supply cost of $60 ODT⁻¹ and $80 ODT⁻¹ were 1.08 and 1.38 Tg year⁻¹ and 7.82 and 10.14 Tg year⁻¹ respectively. Decreasing residue extraction costs by 35% increased the amount of residues available at a $60 ODT⁻¹ and $80 ODT⁻¹ supply price by ∼5.5–5.7 and ∼1.5–1.6 times respectively. The assessment methodology is generic and could be extended to examine residue supplies for specialized biomass markets such as lignocellulosic ethanol production.     

Exploration of regional and global cost–supply curves of biomass energy from short-rotation crops at abandoned cropland and rest land under four IPCC SRES land-use scenarios

We explored the production cost of energy crops at abandoned agricultural land and at rest land at a regional and a global level to the year 2050 using four different land-use scenarios. The estimations were based on grid cell data on the productivity of short-rotation crops on the available land over time and assumptions regarding the capital and the labour input required to reach these productivity levels. It was concluded that large amounts of grown biomass at abandoned agricultural land and rest land, 130–270 EJ yr^?1 (about 40–70% of the present energy consumption) may be produced at costs below $2 GJ^?1 by 2050 (present lower limit of cost of coal). Interesting regions because of their low production cost and significant potentials are the Former USSR, Oceania, Eastern and Western Africa and East Asia. Such low costs presume significant land productivity improvements over time and cost reductions due to learning and capital-labour substitution. An assessment of biomass fuel cost, using the primary biomass energy costs, showed that the future costs of biomass liquid fuels may be in the same order of the present diesel production costs, although this may change in the long term. Biomass-derived electricity costs are at present slightly higher than electricity baseload costs and may directly compete with estimated future production costs of fossil fuel electricity with CO₂ sequestration. The present world electricity consumption of around 20 PWh yr^?1 may be generated in 2050 at costs below $45 MWh^?1 in A1 and B1 and below $55 MWh^?1 in A2 and B2. At costs of $60 MWh^?1, about 18 (A2) to 53 (A1) PWh yr^?1 can be produced.     

Optimization of bioenergy yield from cultivated land in Denmark

A cost minimization model for supply of starch, oil, sugar, grassy and woody biomass for bioenergy in Denmark was developed using linear programming. The model includes biomass supply from annual crops on arable land, short rotation forestry (willow) and plantation forestry. Crop area distributions were simulated using cost data for year 2005. Five scenarios with different constraints, e.g. on food and feed supply and on nitrogen balance were considered focusing on: a) constraints as the year 2005, b) landscape aesthetics and biodiversity c) groundwater protection, d) maintaining current food and feed production, or e) on site carbon sequestration. In addition, two oil price levels were considered. The crop area distributions differed between scenarios and were affected by changing fossil oil prices up to index 300 (using 55$ per barrel in 2005 as index = 100). The bioenergy supply (district heating, electric power, biogas, RME or bioethanol) varied between 56 PJ in the “2005” scenario at oil index 100 and 158 PJ at oil index 300 in the groundwater scenario. Our simple model demonstrates the effect of prioritizing multiple uses of land resources for food, feed or bioenergy, while maintaining a low nitrogen load to the environment. In conclusion, even after drastic landuse changes the bioenergy supply as final energy will not exceed 184 PJ annually (including 26 PJ processed biowaste sources) by far lower than the annual domestic total energy consumption ranging between 800 and 850 PJ yr^?1.     

Nitrogen fertilization of switchgrass increases biomass yield and improves net greenhouse gas balance in northern Michigan, U.S.A

Nitrogen (N) fertilization can increase bioenergy crop production; however, fertilizer production and application can contribute to greenhouse gas (GHG) emissions, potentially undermining the GHG benefits of bioenergy crops. The objective of this study was to evaluate the effects of N fertilization on GHG emissions and biomass production of switchgrass bioenergy crop, in northern Michigan. Nitrogen fertilization treatments included 0 kg ha⁻¹ (control), 56 kg ha⁻¹ (low) and 112 kg ha⁻¹ (high) of N applied as urea. Soil fluxes of CO₂, N₂O and CH₄ were measured every two weeks using static chambers. Indirect GHG emissions associated with field activities, manufacturing and transport of fertilizer and pesticides were derived from the literature. Switchgrass aboveground biomass yield was evaluated at the end of the growing season. Nitrogen fertilization contributed little to soil GHG emissions; relative to the control, there were additional global warming potential of 0.7 Mg ha⁻¹ y⁻¹ and 1.5 Mg ha⁻¹ y⁻¹ as CO₂ equivalents (CO₂eq), calculated using the IPCC values, in the low and high N fertilization treatments, respectively. However, N fertilization greatly stimulated CO₂ uptake by switchgrass, resulting in 1.5- and 2.5-fold increases in biomass yield in the low and high N fertilization treatments, respectively. Nitrogen amendments improved the net GHG benefits by 2.6 Mg ha⁻¹ y⁻¹ and 9.4 Mg ha⁻¹ y⁻¹ as CO₂eq relative to the control. Results suggest that N fertilization of switchgrass in this region could reduce (15-50%) the land base needed for bioenergy production and decrease pressure on land for food and forage crop production.     

Process mechanization models for improved Eucalyptus plantation management in Southern China based on the analysis of currently applied semi-mechanized harvesting operations

Within the last decades ecological and environmental dimensions were in the focus of Chinese forestry and forest research, but forest operations were much less studied. However, a sustainable, efficient, and continuous forest biomass supply is crucial for a socio-economic development in rural areas, and will contribute to national forest management aims. Today, high supply costs and insufficient biomass supply are bottlenecks for bioenergy and wood processing industry in the P.R. China.The aim of this study was (1) to characterize, and obtain process data of the current harvesting operations in forest plantations in Southern China, (2) to develop a harvesting productivity model based on the current performance, and (3) to develop applicable models for improved mechanized operations. The study was conducted in Eucalyptus (Eucalyptus grandis x urophylla) and Mytilaria (Mytilaria laosensis) plantations in steep terrain (8.5–27.5°; respectively 15–52%) in Guangxi province, with a tree diameter at 1.3 m height ranging from 9.8 to 15.4 cm. Via conducting time and motion studies, 237.8 h were recorded and 121.5 m³ were harvested between October 2008 and May 2010.The clear cut operations are characterized by basic manual work, except motor-manual work for tree felling and cross-cutting. The overall time consumption for harvesting and extraction was 115.07 min m⁻³, respectively the productivity was 0.58 m³ h⁻¹. Manual hauling of the logs was identified as the most time consuming activity. Therefore, priority should be given to extraction activities when trying to improve productivity and work safety through mechanization.     

A bottom-up assessment and review of global bio-energy potentials to 2050

In this article, a model for estimating bioenergy production potentials in 2050, called the Quickscan model, is presented. In addition, a review of existing studies is carried out, using results from the Quickscan model as a starting point. The Quickscan model uses a bottom-up approach and its development is based on an evaluation of data and studies on relevant factors such as population growth, per capita food consumption and the efficiency of food production. Three types of biomass energy sources are included: dedicated bioenergy crops, agricultural and forestry residues and waste, and forest growth. The bioenergy potential in a region is limited by various factors, such as the demand for food, industrial roundwood, traditional woodfuel, and the need to maintain existing forests for the protection of biodiversity. Special attention is given to the technical potential to reduce the area of land needed for food production by increasing the efficiency of food production. Thus, only the surplus area of agricultural land is included as a source for bioenergy crop production. A reference scenario was composed to analyze the demand for food. Four levels of advancement of agricultural technology in the year 2050 were assumed that vary with respect to the efficiency of food production. Results indicated that the application of very efficient agricultural systems combined with the geographic optimization of land use patterns could reduce the area of land needed to cover the global food demand in 2050 by as much as 72% of the present area. A key factor was the area of land suitable for crop production, but that is presently used for permanent grazing. Another key factor is the efficiency of the production of animal products. The bioenergy potential on surplus agricultural land (i.e. land not needed for the production of food and feed) equaled 215–1272 EJ yr⁻¹, depending on the level of advancement of agricultural technology. The bulk of this potential is found in South America and Caribbean (47–221 EJ yr⁻¹), sub-Saharan Africa (31–317 EJ yr⁻¹) and the C.I.S. and Baltic States (45–199 EJ yr⁻¹). Also Oceania and North America had considerable potentials: 20–174 and 38–102 EJ yr⁻¹, respectively. However, realization of these (technical) potentials requires significant increases in the efficiency of food production, whereby the most robust potential is found in the C.I.S. and Baltic States and East Europe. Existing scenario studies indicated that such increases in productivity may be unrealistically high, although these studies generally excluded the impact of large scale bioenergy crop production. The global potential of bioenergy production from agricultural and forestry residues and wastes was calculated to be 76–96 EJ yr⁻¹ in the year 2050. The potential of bioenergy production from surplus forest growth (forest growth not required for the production of industrial roundwood and traditional woodfuel) was calculated to be 74 EJ yr⁻¹ in the year 2050.     

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 system model estimates of short-rotation hardwood production in Hawaii

By coupling a short-rotation, intensive-culture (SRIC) biomass production model with a geographical information system and database, potential biomass supply (dry Mg) and delivered cost ($(dry Mg)⁻¹) of three promising tropical hardwoods, Eucalyptus grandis, E. saligna, and Leucaena leucocephala, were estimated at all locations identified as potentially available for tree plantations on the island of Maui. Analyses were performed at two scales-island-wide (10⁵ ha order of magnitude) for general land-use planning, and specific-site (10² ha order of magnitude) for field-level recommendations. The results are presented as yield and delivered cost maps and biomass supply curves for the entire island, and as management strategies depicted graphically as functions of growing space and rotation age that provide least-cost biomass feedstocks delivered from two specific field sites to a designated bioconversion facility on Maui. The methodology is a cost- and time-efficient means to provide useful information to land owners and other decision makers contemplating SRIC forestry as an alternative land use.     

Economic and energy efficiency of salvaging biomass from wildfire burnt areas for bioenergy production in northwestern Ontario: A case study

Wildfire burnt forest biomass can be salvaged as feedstock for bioenergy power generating stations. Despite availability of such forest biomass in northwestern Ontario, its procurement has generally been considered uneconomic and no studies have looked into the cost of harvesting, processing, and transporting the burnt material for bioenergy production. In order to meet the demand of biomass for proposed and existing power generating stations using renewable fuels, a standard costing model is used to determine the feasibility of procuring biomass from burnt areas using a full-tree to roadside, roadside grinder to mill system. The case-study was conducted at the Hogarth Plantations near Thunder Bay, Ontario, Canada. The total cost incurred for processing and delivery of biomass from wildfire burnt area with a hauling distance of 7 km and total trip cycle time of 2.55 h was found to be $29.65 gt^?1, with net energy content of 11.4 GJ gt^?1. The total procurement cost depends on the hauling distance and a linear relationship between the two was established. The energy analysis found a net energy output to input ratio of 35:1 for the operation.     

The economic feasibility of sugar beet biofuel production in central North Dakota

This study examines the financial feasibility of producing ethanol biofuel from sugar beets in central North Dakota. Under the Energy Independence and Security Act (EISA) of 2007, biofuel from sugar beets uniquely qualifies as an “advanced biofuel”. EISA mandates production of 21 billion gallons of advanced biofuels annually by 2022. A stochastic simulation financial model was calibrated with irrigated sugar beet data from central North Dakota to determine economic feasibility and risks of production for 0.038 hm³y⁻¹ (or 10 MGY (Million Gallon per Year) and 0.076 hm³y⁻¹ (or 20 MGY) ethanol plants. Study results indicate that feedstock costs, which include sugar beets and beet molasses, account for more than 70 percent of total production expenses. The estimated breakeven ethanol price for the 0.076 hm³y⁻¹ plant is $400 m⁻³ ($1.52 per gallon) and $450 m⁻³ ($1.71 per gallon) for the 0.038 hm³y⁻¹ plant. Breakeven prices for feedstocks are also estimated and show that the 0.076 hm³y⁻¹ plant can tolerate greater ethanol and feedstock price risks than the 0.038 hm³y⁻¹ plant. Our results also show that one of the most important factors that affect investment success is the price of ethanol. At an ethanol price of $484.21 m⁻³ ($1.84 per gallon), and assuming other factors remain unchanged, the estimated net present value (NPV) for the 0.076 hm³y⁻¹ plant is $41.54 million. By comparison, the estimated NPV for the 0.038 hm³y⁻¹ plant is only $8.30 million. Other factors such as changes in prices of co-products and utilities have a relatively minor effect on investment viability.     

Greenhouse gas balances and mitigation costs of 70 modern Germany-focused and 4 traditional biomass pathways including land-use change effects

With Germany as the point of energy end-use, 70 current and future modern pathways plus 4 traditional biomass pathways for heat, power and transport have been compiled and examined in one single greenhouse gas (GHG) balancing assessment. This is needed to broaden the narrow focus on biofuels for transport and identify the role of bioenergy in GHG mitigation. Sensitivity analysis for land-use changes and fossil reference systems are included. Co-firing of woody biomass and fermentation of waste biomass are the most cost-efficient and effective biomass applications for GHG emission reduction in modern pathways. Replacing traditional biomass with modern biomass applications offers an underestimated economic potential of GHG emission reduction. The range of maximum CO₂ equivalent GHG reduction potential of bioenergy is identified in a range of 2.5-16 Gt a⁻¹ in 2050 (5-33% of today’s global GHG emissions), and has an economic bioenergy potential of 150 EJ a⁻¹.     

Using an inventory control model to establish biomass harvesting policies

The financial performance of a biomass-dependent production system was evaluated using an inventory control model. Dynamic programming was employed to examine the constraints and capabilities of producing ethanol from various biomass crops. In particular, the model evaluated the plantation, harvest, and manufacturing components of a woody biomass supply system. Using inventory control to establish biomass harvesting policies is one way of achieving a cost efficient operation. The optimum wood to ethanol production scheme could produce 38 million 1 of ethanol in any given harvest year, a 13.6 million 1 increase over the least optimal policy. Delivered cost was $0.38 l⁻¹ consistent with the unit costs from other studies. Nearly 60% of the cost was from the manufacturing component of the system. The remaining costs were attributed to growing biomass (14%), harvest and shipment of the crop (18%), storage of the raw material and finished product (7%), and “lost sales” (2%). Inventory control, in all phases of production, could influence total delivered costs of ethanol by as much as 62%. A comparison between the least costly wood system and alternative systems further illustrated the benefits of inventory control.     

Techno-economic analysis of fuel cell auxiliary power units as alternative to idling

This paper presents a techno-economic analysis of fuel-cell-based auxiliary power units (APUs), with emphasis on applications in the trucking industry and the military. The APU system is intended to reduce the need for discretionary idling of diesel engines or gas turbines. The analysis considers the options for on-board fuel processing of diesel and compares the two leading fuel cell contenders for automotive APU applications: proton exchange membrane fuel cell and solid oxide fuel cell. As options for on-board diesel reforming, partial oxidation and auto-thermal reforming are considered. Finally, using estimated and projected efficiency data, fuel consumption patterns, capital investment, and operating costs of fuel-cell APUs, an economic evaluation of diesel-based APUs is presented, with emphasis on break-even periods as a function of fuel cost, investment cost, idling time, and idling efficiency. The analysis shows that within the range of parameters studied, there are many conditions where deployment of an SOFC-based APU is economically viable. Our analysis indicates that at an APU system cost of $ 100 kW⁻¹, the economic break-even period is within 1 year for almost the entire range of conditions. At $ 500 kW⁻¹ investment cost, a 2-year break-even period is possible except for the lowest end of the fuel consumption range considered. However, if the APU investment cost is $ 3000 kW⁻¹, break-even would only be possible at the highest fuel consumption scenarios. For Abram tanks, even at typical land delivered fuel costs, a 2-year break-even period is possible for APU investment costs as high as $ 1100 kW⁻¹.     

A novel approach to simulate growth of multi-stem willow in bioenergy production systems with a simple process-based model (3PG)

An important requirement for commercialization of willow biomass production in short-rotation crop (SRC) plantations is the reliable and cost-efficient estimation of biomass yield. Predictions and simulations of willow stand biomass have been problematic due to issues with modeling the multi-stem growth form of willow. The aim of this paper was to develop a new approach for managing allometric measurements from multi-stemmed willow for stand growth simulations. The 3PG model (Physiological Principles in Predicting Growth) was parameterized for willow and was used for biomass yield simulation for an entire 22-yr cycle (seven 3-yr rotations) of willow in SRC plantations. The multi-stemmed growth form was transformed into a single-stem modeling form by deriving whole plant willow allometric relationships using detailed stem-level measurements of basal area, stem biomass and volume. 3PG model predictions for plant diameter, height, biomass, and stand biomass and volume were within the 95% confidence range of mean plot values. Model simulations showed that after seven 3-yr rotations only 20% of planted cuttings would survive (a decrease from 15,152 to 3022 plants ha⁻¹), but stand volume would increase continuously with each subsequent rotation. 3PG predictions for cumulative (for 22 yr) aboveground biomass was 272 Mg ha⁻¹ and mean annual yield was 12 Mg ha⁻¹ yr⁻¹, comparing favorably with other findings. To our knowledge, this work is the first where the 3PG model was calibrated and used for willow species. Once parameterized for a specific willow clone, 3PG can predict biomass accumulation for any agricultural land in North America using only available soil and climate data.     

Modeling the profitability of power production from short-rotation woody crops in Sub-Saharan Africa

Increasing electricity supply in Sub-Saharan Africa is a prerequisite to enable economic development and reduce poverty. Renewable sources such as wood-fueled power plants are being promoted for social, environmental and economic reasons. We analyzed an economic model of a vertically integrated system of short-rotation woody crops (SRWC) plantations coupled with a combined heat and power (CHP) plant under Sub-Saharan African conditions. We analyzed a 5 MW (electric) base-case scenario under Ugandan conditions with a 2870 ha Eucalyptus grandis plantation and a productivity of 12 t ha⁻¹ y⁻¹ (oven dry basis) under a 5-year rotation. Plant construction and maintenance constituted 27% and 41% of total costs, respectively. Plantation productivity, carbon credit sales as well as land, fuel, labor & transport costs played an economic minor role. Highly influential variables included plant efficiency & construction costs, plantation design (spacing and rotation length) and harvest technologies. We conclude that growing 12–24 t ha⁻¹ y⁻¹ at a five year rotation can produce IRR's of 16 and 19% over 30-years, respectively. Reducing rotation length significantly reduced short-term financial risk related to frontloaded costs and relatively late revenues from electricity sales. Long-term feed-in tariffs and availability of a heat market played a significant economic role. The base-case scenario's 30-year IRR dropped from 16% to 9% when a heat market was absent. Results suggest a leveling-off of economies-of-scale effects above 20 MW (electric) installations. Implementation-related research needs for pilot activities should focus on SRWC productivity and energy life cycle analysis.