Corn Residue Supply in the Irrigated Corn Belt

The present study quantifies the profit-maximizing supply of corn stover per unit of land under alternative crop rotations in irrigated cropland with and without limits to irrigation. The model is parameterized based on growing conditions in Nebraska, USA. Our analysis quantifies a trilemma between stover supply, groundwater consumption, and food/feed supply per unit of land. In the absence of water conservation policies, higher stover prices are associated with higher supply and increased irrigation application. If an upper limit is imposed on irrigation at the baseline level (for groundwater conservation purposes), an increase in net revenue from stover sale from $15 to $25/metric ton is associated with an increase in stover supply of 5 metric tons/ha and a 2-metric ton reduction in corn yield under continuous corn. Under corn/soybean rotation, such an increase in net revenue is associated with an increase in stover supply of 10 metric tons/ha, and reductions of 0.5 metric tons in corn yield and 0.7 metric tons in soybean yield.     

Switchgrass (Panicum vigratum, L.) delivery to a biorefinery using integrated biomass supply analysis and logistics (IBSAL) model

This study develops cost, energy input and carbon emissions for a number of switchgrass supply options. The Integrated Biomass Supply Analysis and Logistics (IBSAL) model developed at Oak Ridge National Laboratory is used to evaluate the delivery systems. Three biomass collection systems: baling, loafing and ensiling are evaluated. The number and operational performance of equipment are specified to complete collection operations within 120 days of harvest after August 1. Bales are stacked and tarped on the farm side. The transport of biomass from the farm side to a biorefinery takes place over a full year cycle, i.e. 365 days. Supply quantities range from 454 to 4540 dry tonnes/day (500-5000 dry tons/day). Delivered costs to a biorefinery with capacity of 1814 dry tonnes/day (2000 dry tons/day) are: 44-47 dollars/dry tonne for delivered bales (round and square); 37 dollars/dry tonne for delivered loafs (size 2.4 m x 3.6 m x 6 m); 40 dollars/dry tonne for chopped biomass; and 48 dollars/dry tonne for ensiled chops. These costs do not include any payment to the farmers or switchgrass farming cost. Based on the data from literature, the switchgrass farming cost can range from 30 to 36 dollars/dry tonne. These costs would be additional to the switchgrass collection and transportation cost. Switchgrass collection is generally less expensive than collection of straw or corn stover because of the assumed high yield of 11 dry tonnes/ha and a denser biomass. Energy consumption for delivery systems at this capacity ranges from 4.8% to 6.3% of the energy content of switchgrass. Additional 1% of the energy content of switchgrass is consumed in its farming. At 1814 dry tonnes/day (2000 dry tons/day) capacity, greenhouse gas emissions ranges from 75 to 100 kg of CO2/dry tonne of switchgrass delivered.     

Integrated Economic and Environmental Assessment of Cellulosic Biofuel Production in an Agricultural Watershed

SWAT watershed model simulated biomass yield and pollutant loadings were integrated with associated economic costs of farm production and transport to study two dedicated energy crops, switchgrass and Miscanthus, and corn stover, as feedstocks for a cellulosic biorefinery. A multi-level spatial optimization (MLSOPT) framework was employed to get spatially explicit cropping plans for a watershed under the assumption that the watershed supplies biomass to a hypothetical biorefinery considering both the biochemical and the thermochemical conversion pathways. Consistent with previous studies, the perennial grasses had higher biomass yield than corn stover, with considerably lower sediment, nitrogen, and phosphorus loadings, but their costs were higher. New insights were related to the tradeoffs between cost, feedstock production, and the level and form of environmental quality society faces as it implements the Renewable Fuel Standard. Economically, this involved calculating the farthest distance a biorefinery would be willing to drive to source corn residue before procuring a single unit of perennial grasses from productive agricultural soils.     

The Feasibility of Producing Adequate Feedstock for Year-Round Cellulosic Ethanol Production in an Intensive Agricultural Fuelshed

To date, cellulosic ethanol production has not been commercialized in the United States. However, government mandates aimed at increasing second-generation biofuel production could spur exploratory development in the cellulosic ethanol industry. We conducted an in-depth analysis of the fuelshed surrounding a starch-based ethanol plant near York, Nebraska that has the potential for cellulosic ethanol production. To assess the feasibility of supplying adequate biomass for year-round cellulosic ethanol production from residual maize (Zea mays) stover and bioenergy switchgrass (Panicum virgatum) within a 40-km road network service area of the existing ethanol plant, we identified ～14,000 ha of marginally productive cropland within the service area suitable for conversion from annual rowcrops to switchgrass and ～132,000 ha of maize-enrolled cropland from which maize stover could be collected. Annual maize stover and switchgrass biomass supplies within the 40-km service area could range between 429,000 and 752,000 metric tons (mT). Approximately 140–250 million liters (l) of cellulosic ethanol could be produced, rivaling the current 208 million l annual starch-based ethanol production capacity of the plant. We conclude that sufficient quantities of biomass could be produced from maize stover and switchgrass near the plant to support year-round cellulosic ethanol production at current feedstock yields, sustainable removal rates and bioconversion efficiencies. Modifying existing starch-based ethanol plants in intensive agricultural fuelsheds could increase ethanol output, return marginally productive cropland to perennial vegetation, and remove maize stover from productive cropland to meet feedstock demand.     

Raw materials evaluation and process development studies for conversion of biomass to sugars and ethanol

A range of cellulosic raw materials in the form of agricultural crop residue was analyzed for chemical composition and assessed for potential yields of sugars through chemical pretreatment and enzymatic hydrolysis of these materials. Corn stover was used as a representative raw material for a preliminary process design and economic assessment of the production of sugars and ethanol. With the process as presently developed, 24 gal ethanol can be obtained per ton of corn stover at a processing cost of about $1.80/gal exclusive of by-product credits. The analysis shows the cost of ethanol to be highly dependent upon: (1) the cost of the biomass, (2) the extent of conversion to glucose, (3) enzyme recovery and production cost, and (4) potential utilization of xylose. Significant cost reduction appears possible through further research in these directions.     

Supply of cellulosic biomass in Illinois and implications for the Conservation Reserve Program

We developed a mathematical programming model to estimate the supply of cellulosic biomass in Illinois at various biomass prices and examine the implications of biomass production for the maintenance costs of the Conservation Reserve Program (CRP). We find that Illinois has the potential to produce about 38.4–54.5 million dry metric tons (MT) of biomass in 2020 at a biomass price of $150/MT, depending on the production costs of cellulosic feedstocks, residue collection technology, and rates of yield increases of conventional crops. Corn stover will account for more than 65% of the total biomass production across biomass prices and the scenarios considered, while the roles of wheat straw and energy crops are quite limited. Given biomass prices of $50/MT‐$150/MT, many landowners would convert their expiring CRP lands to croplands. To maintain the size of the CRP during the 2007–2020 period at the 2007 levels in Illinois, total program maintenance costs would be $104.6–176.5 million at a biomass price of $50/MT, depending on biomass production conditions and crop yields on CRP lands. This would increase to $155.2–245.4 million at a biomass price of $150/MT.     

Economic Analysis of the Potential of Cellulosic Biomass Available in France from Agricultural Residue and Energy Crops

The objective of this research is to evaluate the feasibility and locations of using cellulosic biomass both from crop residues and from dedicated energy crops to supply 200-million-liter-biodiesel plants in France. The estimation of the potential amount of agricultural residue available in 2015 in each region of France is calculated. The residues considered in this study come from cereal straw and corn stover. Results show that eight out of the twenty one French regions have enough agricultural residues available to supply at least one 200 million liter biofuel plant. Region Centre has the largest potential, with enough residues to supply three to five plants. Finally, cost of supplying one biodiesel plant of 200 million liters in the region Centre is estimated. Results show that collection of biomass will be effective in an area with a radius of 58 Km to 168 Km depending of the raw material considered and its abundance. The cost of supplying a plant with miscanthus is much higher than with residues only. Thus, crop residues appear to offer a lower cost to produce biodiesel in the near term compared to a dedicated crop. Results show that production of biofuel from cellulosic biomass should not be limited by the supply of raw material, but costs of conversion to liquid fuels clearly will play a key role in the development of cellulosic biofuels. Energy prices and policies will have a significant impact on second generation biofuel development.     

Chemical and morphological characterization of sugarcane bagasse submitted to a delignification process for enhanced enzymatic digestibility

Background

While advantages of biofuel have been widely reported, studies also highlight the challenges in large scale production of biofuel. Cost of ethanol and process energy use in cellulosic ethanol plants are dependent on technologies used for conversion of feedstock. Process modeling can aid in identifying techno-economic bottlenecks in a production process. A comprehensive techno-economic analysis was performed for conversion of cellulosic feedstock to ethanol using some of the common pretreatment technologies: dilute acid, dilute alkali, hot water and steam explosion. Detailed process models incorporating feedstock handling, pretreatment, simultaneous saccharification and co-fermentation, ethanol recovery and downstream processing were developed using SuperPro Designer. Tall Fescue (Festuca arundinacea Schreb) was used as a model feedstock.

Results

Projected ethanol yields were 252.62, 255.80, 255.27 and 230.23 L/dry metric ton biomass for conversion process using dilute acid, dilute alkali, hot water and steam explosion pretreatment technologies respectively. Price of feedstock and cellulose enzymes were assumed as $50/metric ton and 0.517/kg broth (10% protein in broth, 600 FPU/g protein) respectively. Capital cost of ethanol plants processing 250,000 metric tons of feedstock/year was $1.92, $1.73, $1.72 and $1.70/L ethanol for process using dilute acid, dilute alkali, hot water and steam explosion pretreatment respectively. Ethanol production cost of $0.83, $0.88, $0.81 and $0.85/L ethanol was estimated for production process using dilute acid, dilute alkali, hot water and steam explosion pretreatment respectively. Water use in the production process using dilute acid, dilute alkali, hot water and steam explosion pretreatment was estimated 5.96, 6.07, 5.84 and 4.36 kg/L ethanol respectively.

Conclusions

Ethanol price and energy use were highly dependent on process conditions used in the ethanol production plant. Potential for significant ethanol cost reductions exist in increasing pentose fermentation efficiency and reducing biomass and enzyme costs. The results demonstrated the importance of addressing the tradeoffs in capital costs, pretreatment and downstream processing technologies.     

Economics and Energy of Ethanol Production from Alfalfa, Corn, and Switchgrass in the Upper Midwest, USA

In the USA, biomass crop systems will be needed to meet future ethanol production goals. We estimated production costs, profits, and energy budgets for three potential crop systems for the Upper Midwest: continuous corn with stover harvest, an alfalfa–corn rotation with stover harvest, and switchgrass. Production costs, profits, and on-farm energy use were greatest for continuous corn, less for alfalfa–corn, and least for switchgrass. Energy to transport crops was similar for all crop systems. Both energy used to produce ethanol and energy output in ethanol was greatest for continuous corn, less for alfalfa–corn, and least for switchgrass. Co-product energy output was 32% greater for alfalfa–corn than continuous corn and 42% greater than switchgrass. Net energy produced (outputs–inputs) was greatest for switchgrass, followed by continuous corn, and then alfalfa–corn. Efficiency of energy production (outputs/inputs) was greatest for switchgrass, followed by alfalfa–corn, and then continuous corn. Our analysis emphasizes tradeoffs among crop systems. Corn may produce high rates of ethanol and net energy, but will do so least efficiently and with the greatest erosion and N leaching. Corn may have the greatest production costs, but return the greatest profit. Comparatively, alfalfa–corn will produce less ethanol and net energy, but will do so more efficiently, and with less erosion and little N leaching. Production costs, but also profits, may be less for alfalfa–corn than continuous corn. Switchgrass may produce the most net energy and will do so most efficiently and with the least erosion, but will also yield the least ethanol. Nitrogen leaching will be less for switchgrass than corn, but greater than alfalfa–corn. Switchgrass may be the least expensive to produce, but may return a profit only if selling prices or yields are high.     

Biomass feedstock preprocessing and long‐distance transportation logistics

Biomass‐based biofuels have gained attention because they are renewable energy sources that could facilitate energy independence and improve rural economic development. As biomass supply and biofuel demand areas are generally not geographically contiguous, the design of an efficient and effective biomass supply chain from biomass provision to biofuel distribution is critical to facilitate large‐scale biofuel development. This study compared the costs of supplying biomass using three alternative biomass preprocessing and densification technologies (pelletizing, briquetting, and grinding) and two alternative transportation modes (trucking and rail) for the design of a four‐stage biomass–biofuel supply chain in which biomass produced in Illinois is used to meet biofuel demands in either California or Illinois. The BioScope optimization model was applied to evaluate a four‐stage biomass–biofuel supply chain that includes biomass supply, centralized storage and preprocessing (CSP), biorefinery, and ethanol distribution. We examined the cost of 15 scenarios that included a combination of three biomass preprocessing technologies and five supply chain configurations. The findings suggested that the transportation costs for biomass would generally follow the pattern of coal transportation. Converting biomass to ethanol locally and shipping ethanol over long distances is most economical, similar to the existing grain‐based biofuel system. For the Illinois–California supply chain, moving ethanol is Biomass‐based biofuels have gained attention because they are renewable energy sources that could facilitate energy independence and improve rural economic development. As biomass supply and biofuel demand areas are generally not geographically contiguous, the design of an efficient and effective biomass supply chain from biomass provision to biofuel distribution is critical to facilitate large‐scale biofuel development. This study compared the costs of supplying biomass using three alternative biomass preprocessing and densification technologies (pelletizing, briquetting, and grinding) and two alternative transportation modes (trucking and rail) for the design of a four‐stage biomass–biofuel supply chain in which biomass produced in Illinois is used to meet biofuel demands in either California or Illinois. The BioScope optimization model was applied to evaluate a four‐stage biomass–biofuel supply chain that includes biomass supply, centralized storage and preprocessing (CSP), biorefinery, and ethanol distribution. We examined the cost of 15 scenarios that included a combination of three biomass preprocessing technologies and five supply chain configurations. The findings suggested that the transportation costs for biomass would generally follow the pattern of coal transportation. Converting biomass to ethanol locally and shipping ethanol over long distances is most economical, similar to the existing grain‐based biofuel system. For the Illinois–California supply chain, moving ethanol is $0.24 gal^?1 less costly than moving biomass even in densified form over long distances. The use of biomass pellets leads to lower overall costs of biofuel production for long‐distance transportation but to higher costs if used for short‐distance movement due to its high capital and processing costs. Supported by the supply chain optimization modeling, the cellulosic‐ethanol production and distribution costs of using Illinois feedstock to meet California demand are $0.08 gal^?1 higher than that for meeting local Illinois demand.     

Farmers’ Supply Response, Price of Corn Residue, and Its Economic Viability as an Energy Feedstock

Previous economic analyses of energy from corn stover assumed yield reductions from residue removal (without nutrient replacement) and limited or no supply response by farmers to changes in the price of stover. We exploit agronomic and cost information from a randomized block design experiment to model and quantify farmers’ supply response to changes in relative prices of corn stover, corn grain, and soybean. We then couple this supply response with a model of a cost-minimizing processing plant. Results suggest that stover-based energy may be closer to economic viability than previously found. In addition, in areas where reductions in corn yield due to corn monoculture are small, processing plants may find optimal to pay a higher price for stover to induce farmers to adopt continuous corn because it reduces transportation cost. This suggests that such areas may experience changes in their land cover configuration if stover-based energy does become commercially viable.     

Determining Switchgrass Breakeven Prices in a Landscape Design System

Precision agriculture technologies allow producers to identify areas of fields that are underperforming and unprofitable. If these less productive parts of the field could be converted to a bioenergy crop through subfield management strategies (landscape design), there may be potential gains to farmer revenue, biomass availability, and reduced adverse environmental impacts. Switchgrass is considered as a potential energy crop due its ability to thrive in marginal conditions. Previous studies have examined switchgrass production and breakeven costs, but have not looked at how production costs may change when produced in a landscape design situation. Adapting costs to the partial field situation, this paper determines the switchgrass breakeven prices ($ ton^?1) which equate producers’ net revenues in a base case (all corn) and landscape design case. That breakeven price is the price at which the farmer would be indifferent between the base and landscape design cases. We examine the case of a general, 100-acre field in Iowa, with 15 acres converted to switchgrass production, as well as 11 actual fields in Central Iowa where unprofitable subfields are assumed to be converted to switchgrass production, and the remaining portion of the field remains in corn. We find an average switchgrass breakeven price of $173 ton^?1 when land costs are included, and an average of $114 ton^?1 when no land costs are considered. A stochastic analysis to obtain a distribution of switchgrass breakeven prices under uncertainty is performed, producing distributions of switchgrass breakeven prices of $65–$266 ton^?1 and $108– $432 ton^?1 with and without land costs, respectively.     

Managing Feedstock Supply Risk for the Development of a US Stover Biofuel Industry

Feedstock supply risk is one of the key concerns limiting cellulosic biofuel expansion. We use an economic model of corn stover-based ethanol production to investigate strategies to manage stover supply uncertainty, including three contract arrangements that vary according to risk-sharing between the processor and farmers. Applying this model to corn stover-based ethanol in the USA, we find that a greater quantity of biofuel is supplied at lower cost under right-of-access contracts than a delivered quantity contract. The processor can manage some of the risk borne under the right-of-access contracts by contracting excess acreage and, if available, by purchasing deficit stover from a spot market. Contracting excess acreage increases the expected biofuel cost but results in lower uncertainty surrounding cellulosic biofuel supply. A biomass spot market provides a source of biomass during low yielding years, but can also create competition for the processor as an alternative outlet for farmers to supply stover under favorable spot market prices. In general, farmers’ contract preferences are responsive to the basic structure of incentives, which could provide flexibility to processors as the industry develops and market uncertainties change.     

Direct measures of mechanical energy for knife mill size reduction of switchgrass, wheat straw, and corn stover

Lengthy straw/stalk of biomass may not be directly fed into grinders such as hammer mills and disc refiners. Hence, biomass needs to be preprocessed using coarse grinders like a knife mill to allow for efficient feeding in refiner mills without bridging and choking. Size reduction mechanical energy was directly measured for switchgrass (Panicum virgatum L.), wheat straw (Triticum aestivum L.), and corn stover (Zea mays L.) in an instrumented knife mill. Direct power inputs were determined for different knife mill screen openings from 12.7 to 50.8 mm, rotor speeds between 250 and 500 rpm, and mass feed rates from 1 to 11 kg/min. Overall accuracy of power measurement was calculated to be ±0.003 kW. Total specific energy (kWh/Mg) was defined as size reduction energy to operate mill with biomass. Effective specific energy was defined as the energy that can be assumed to reach the biomass. The difference is parasitic or no-load energy of mill. Total specific energy for switchgrass, wheat straw, and corn stover chopping increased with knife mill speed, whereas, effective specific energy decreased marginally for switchgrass and increased for wheat straw and corn stover. Total and effective specific energy decreased with an increase in screen size for all the crops studied. Total specific energy decreased with increase in mass feed rate, but effective specific energy increased for switchgrass and wheat straw, and decreased for corn stover at increased feed rate. For knife mill screen size of 25.4 mm and optimum speed of 250 rpm, optimum feed rates were 7.6, 5.8, and 4.5 kg/min for switchgrass, wheat straw, and corn stover, respectively, and the corresponding total specific energies were 7.57, 10.53, and 8.87 kWh/Mg and effective specific energies were 1.27, 1.50, and 0.24 kWh/Mg for switchgrass, wheat straw, and corn stover, respectively. Energy utilization ratios were calculated as 16.8%, 14.3%, and 2.8% for switchgrass, wheat straw, and corn stover, respectively. These data will be useful for preparing the feed material for subsequent fine grinding operations and designing new mills.     

Modeling the effects of pelleting on the logistics of distillers grains shipping

The energy security needs of energy importing nations continue to escalate. It is clear that biofuels can help meet some of the increasing need for energy. Theoretically, these can be produced from a variety of biological materials, including agricultural residues (such as corn stover and wheat straw), perennial grasses, legumes, algae, and other biological materials. Currently, however, the most heavily utilized material is corn starch. Industrial fuel ethanol production in the US primarily uses corn, because it is readily converted into fuel at a relatively low cost compared to other biomass sources. The production of corn-based ethanol in the US is dramatically increasing. As the industry continues to grow, the amount of byproducts and coproducts also increases. At the moment, the nonfermentable residues (which are dried and sold as distillers dried grains with solubles – DDGS) are utilized only as livestock feed. The sale of coproducts provides ethanol processors with a substantial revenue source and significantly increases the profitability of the production process. Even though these materials are used to feed animals in local markets, as the size and scope of the industry continues to grow, the need to ship large quantities of coproducts grows as well. This includes both domestic as well as international transportation. Value-added processing options offer the potential to increase the sustainability of each ethanol plant, and thus the industry overall. However, implementation of new technologies will be dependent upon how their costs interact with current processing costs and the logistics of coproduct deliveries. The objective of this study was to examine some of these issues by developing a computer model to determine potential cost ramifications of using various alternative technologies during ethanol processing. This paper focuses specifically on adding a densification unit operation (i.e., pelleting) to produce value-added DDGS at a fuel ethanol manufacturing plant. We have examined the economic implications of pelleting DDGS for varying DDGS production rates (100–1000 tons/d) and pelleting rates (0–100%), for a series of DDGS sales prices ($50–$200/ton). As the proportion of pelleting increases, the cost of transporting DDGS to distant markets drastically declines, because the rail cars can be filled to capacity. For example, at a DDGS sales price of $50/ton, 100% pelleting will reduce shipping costs (both direct and indirect) by 89% compared to shipping the DDGS in bulk form (i.e., no pelleting), whereas at a DDGS sales price of $200/ton, it will reduce costs by over 96%. It is clear that the sustainability of the ethanol industry can be improved by implementing pelleting technology for the coproducts, especially at those plants that ship their DDGS via rail.     

Evaluating Local Crop Residue Biomass Supply: Economic and Environmental Impacts

The increasing interest in energy production from biomass requires a better understanding of potential local production and environmental impacts. This information is needed by local producers, biomass industry, and other stakeholders, and for larger scale analyses. This study models biomass production decisions at the field level using a case example of a biomass gasification facility constructed at the University of Minnesota??Morris (UMM). This institutional-scale application has an anticipated feedstock demand of about 8,000?Mg?year^?1. The model includes spatial impacts due to sub-field variation in soil characteristics and transportation costs. Results show that the amount of biomass producers could profitably supply within a 32.2-km radius of UMM increases as plant-gate biomass price increases from $59 to $84?Mg^?1, with 588,000?Mg annual biomass supply at $84?Mg^?1. Results also show that the most profitable tillage and crop rotation practices shift in response to increasing biomass price with producers shifting from a corn-soybean rotation toward continuous corn. While biomass harvest is conducive to increased soil erosion rates and reduced soil organic carbon levels, changes in crop production practices are shown to at least partially offset these impacts. Transportation costs tend to concentrate and intensify biomass production near the biomass facility, which also tends to concentrate environmental impacts near the facility.     

Biomass transportation model and optimum plant size for the production of ethanol

A detailed model based on a non-dimensional transportation factor is developed to assess the economics of biomass collection, transportation, and storage. The optimum plant size for bio-refineries is investigated; ethanol production from corn stover via dilute acid hydrolysis is presented as a case study. The conversion of straight-line, farm-to-plant distances to road distances via a winding factor leads to a shift in the distribution of transportation distances towards shorter hauls. The capital investment scaling exponent was calculated using the model developed at the National Renewable Energy Laboratory (Aden et al., NREL/TP-510-32438, 2002) and found to be 0.7. The cost of the delivered corn stover is proportional to the square root of the inverse of the farmer participation; as a consequence, bio-fuel producers intending to use agricultural residues as feedstock should work towards a farmer participation of fifty percent. Costs associated with storage represent a significant portion of the production cost.     

Natural binders and solid bridge type binding mechanisms in briquettes and pellets made from corn stover and switchgrass

Corn stover and switchgrass are two important feedstocks considered for producing renewable fuels and energy in the US. Densification of these biomass feedstocks into briquettes/pellets would help reduce the problems and costs of bulk transportation, handling, and storage of biomass feedstocks. In this study, the role of the natural binders in corn stover and switchgrass to make durable particle–particle bonding in briquettes/pellets was investigated by micro-structural analyses. Scanning Electron Microscopy (SEM) images of briquettes made by using a uniaxial piston-cylinder densification apparatus in the laboratory, briquettes made by using a pilot-scale roll-press briquetting machine, and pellets made by using a pilot-scale conventional ring-die pelleting machine were analysed. The SEM images showed that the bonding between particles was created mainly through solid bridges. The solid bridges between particles were made by natural binders in the biomass expressed during the densification process. UV auto-fluorescence images of briquettes and pellets further confirmed that the solid bridges were made mainly by natural binders such as lignin and protein. It was found that activating (softening) the natural binders using moisture and temperature in the range of glass transition is important to make durable particle–particle bonding.     

Farm-Scale Production Cost of Switchgrass for Biomass

The economic potential of cellulosic biomass from switchgrass has heretofore been evaluated using estimates of farm costs based on extrapolation from experimental data and budget estimates. The objective of the project reported here was to estimate the cost of production that would be experienced by farmers on commercial production situations. Switchgrass was produced as a biomass crop on commercial-scale fields by ten contracting farmers located from northern North Dakota to southern Nebraska. Results showed a wide range of yields and costs across the five production years and ten sites, with an overall average cost of $65.86 Mg^?1 of biomass dry matter, and annualized yield of 5.0 Mg ha^?1. The low-cost half of the producers were able to produce at an average cost of $51.95 Mg^?1over the 5-year period. When projected to a full 10-year rotation, their cost fell further to $46.26 Mg^?1. We conclude that substantial quantities of biomass feedstock could have been produced in this region at a cost of about $50 Mg^?1 at the farm gate, which translates to about $0.13/l of ethanol. These results provide a more reliable benchmark for current commercial production costs as compared to other estimates, which range from $25 to $100 Mg^?1.     

An integrated biogeochemical and economic analysis of bioenergy crops in the Midwestern United States

This study integrates a biophysical model with a county‐specific economic analysis of breakeven prices of bioenergy crop production to assess the biophysical and economic potential of biofuel production in the Midwestern United States. The bioenergy crops considered in this study include a genotype of Miscanthus, Miscanthus×giganteus, and the Cave‐in‐Rock breed of switchgrass (Panicum virgatum). The estimated average peak biomass yield for miscanthus in the Midwestern states ranges between 7 and 48 metric tons dry matter per hectare per year ( t DM ha^?1 yr^?1), while that for switchgrass is between 10 and 16 t DM ha^?1 yr^?1. With the exception of Minnesota and Wisconsin, where miscanthus yields are likely to be low due to cold soil temperatures, the yield of miscanthus is on average more than two times higher than yield of switchgrass. We find that the breakeven price, which includes the cost of producing the crop and the opportunity cost of land, of producing miscanthus ranges from $53 t^?1 DM in Missouri to $153 t^?1 DM in Minnesota in the low‐cost scenario. Corresponding costs for switchgrass are $88 t^?1 DM in Missouri to $144 t^?1 DM in Minnesota. In the high‐cost scenario, the lowest cost for miscanthus is $85 t^?1 DM and for switchgrass is $118 t^?1 DM, both in Missouri. These two scenarios differ in their assumptions about ease of establishing the perennial crops, nutrient requirements and harvesting costs and losses. The differences in the breakeven prices across states and across crops are mainly driven by bioenergy and row crop yields per hectare. Our results suggest that while high yields per unit of land of bioenergy crops are critical for the competitiveness of bioenergy feedstocks, the yields of the row crops they seek to displace are also an important consideration. Even high yielding crops, such as miscanthus, are likely to be economically attractive only in some locations in the Midwest given the high yields of corn and soybean in the region.