The 2011 US Billion‐Ton Update 1 estimates that there are enough agricultural and forest resources to sustainably provide enough biomass to displace approximately 30% of the country's current petroleum consumption. A portion of these resources are inaccessible at current cost targets with conventional feedstock supply systems because of their remoteness or low yields. Reliable analyses and projections of US biofuels production depend on assumptions about the supply system and biorefinery capacity, which, in turn, depend on economics, feedstock logistics, and sustainability. A cross‐functional team has examined optimal combinations of advances in feedstock supply systems and biorefinery capacities with rigorous design information, improved crop yield and agronomic practices, and improved estimates of sustainable biomass availability. Biochemical‐conversion‐to‐ethanol is analyzed for conventional bale‐based system and advanced uniform‐format feedstock supply system designs. The latter involves ‘pre‐processing’ biomass into a higher‐density, aerobically stable, easily transportable format that can supply large‐scale biorefineries. Feedstock supply costs, logistics and processing costs are analyzed and compared, taking into account environmental sustainability metrics. © 2013 Society of Chemical Industry and John Wiley & Sons Ltd

Lignin by-products from biorefineries has the potential to provide a low-cost alternative to petroleum-based precursors to manufacture carbon fiber, which can be combined with a binding matrix to produce a structural material with much greater specific strength and specific stiffness than conventional materials such as steel and aluminum. The market for carbon fiber is universally projected to grow exponentially to fill the needs of clean energy technologies such as wind turbines and to improve the fuel economies in vehicles through lightweighting. In addition to cellulosic biofuel production, lignin-based carbon fiber production coupled with biorefineries may provide $2,400 to $3,600 added value dry Mg-1 of biomass for vehicle applications. Compared to producing ethanol alone, the addition of lignin-derived carbon fiber could increase biorefinery gross revenue by 30% to 300%. Using lignin-derived carbon fiber in 15 million vehicles per year in the US could reduce fossil fuel consumption by 2-5 billion liters year(-1), reduce CO2 emissions by about 6.7 million Mg year(-1), and realize fuel savings through vehicle lightweighting of $700 to $ 1,600 per Mg biomass processed. The value of fuel savings from vehicle lightweighting becomes economical at carbon fiber price of $6.60 kg(-1) under current fuel prices, or $13.20 kg(-1) under fuel prices of about $1.16 l(-1).

With the Earth's climate, flora, and fauna undergoing rapid change, understanding terrestrial ecosystem processes and their sensitivity to environmental and biotic conditions has become paramount. Many theories and models remain rudimentary due to sensor and environmental data inadequacies that persist despite rapid developments in sensor, computing, and networking technologies. This situation has prompted researchers to focus on the development of novel sensors to vastly improve our capability of capturing the high spatial and temporal variations within biogeochemical processes.

The economic availability of biomass resources is a critical component in evaluating the commercial viability of biofuels. To evaluate projected farmgate prices and grower payments needed to procure 295 million dry Mg (325 million dry tons) of biomass in the U.S. by 2022, this research employs POLYSYS, an economic model of the U.S. agriculture sector. A price-run simulation suggests that a farmgate price of $58.42Mg−1 ($53.00dryton−1) is needed to procure this supply, while a demand-run simulation suggests that prices of $34.56 and $71.61Mg−1 ($30.00 and $62.00dryton−1) in are needed in 2012 and 2022, respectively, to procure the same supply, under baseline yield assumptions. Grower payments are reported as farmgate price minus resource-specific harvest costs.

The report, Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply (generally referred to as the Billion-Ton Study or 2005 BTS), was an estimate of 'potential' biomass based on numerous assumptions about current and future inventory, production capacity, availability, and technology. The analysis was made to determine if conterminous U.S. agriculture and forestry resources had the capability to produce at least one billion dry tons of sustainable biomass annually to displace 30% or more of the nation's present petroleum consumption. An effort was made to use conservative estimates to assure confidence in having sufficient supply to reach the goal. The potential biomass was projected to be reasonably available around mid-century when large-scale biorefineries are likely to exist. The study emphasized primary sources of forest- and agriculture-derived biomass, such as logging residues, fuel treatment thinnings, crop residues, and perennially grown grasses and trees. These primary sources have the greatest potential to supply large, reliable, and sustainable quantities of biomass. While the primary sources were emphasized, estimates of secondary residue and tertiary waste resources of biomass were also provided. The original Billion-Ton Resource Assessment, published in 2005, was divided into two parts-forest-derived resources and agriculture-derived resources. The forest resources included residues produced during the harvesting of merchantable timber, forest residues, and small-diameter trees that could become available through initiatives to reduce fire hazards and improve forest health; forest residues from land conversion; fuelwood extracted from forests; residues generated at primary forest product processing mills; and urban wood wastes, municipal solid wastes (MSW), and construction and demolition (C&D) debris. For these forest resources, only residues, wastes, and small-diameter trees were considered. The 2005 BTS did not attempt to include any wood that would normally be used for higher-valued products (e.g., pulpwood) that could potentially shift to bioenergy applications. This would have required a separate economic analysis, which was not part of the 2005 BTS. The agriculture resources in the 2005 BTS included grains used for biofuels production; crop residues derived primarily from corn, wheat, and small grains; and animal manures and other residues. The cropland resource analysis also included estimates of perennial energy crops (e.g., herbaceous grasses, such as switchgrass, woody crops like hybrid poplar, as well as willow grown under short rotations and more intensive management than conventional plantation forests). Woody crops were included under cropland resources because it was assumed that they would be grown on a combination of cropland and pasture rather than forestland. In the 2005 BTS, current resource availability was estimated at 278 million dry tons annually from forestlands and slightly more than 194 million dry tons annually from croplands. These annual quantities increase to about 370 million dry tons from forestlands and to nearly 1 billion dry tons from croplands under scenario conditions of high-yield growth and large-scale plantings of perennial grasses and woody tree crops. This high-yield scenario reflects a mid-century timescale ({approx}2040-2050). Under conditions of lower-yield growth, estimated resource potential was projected to be about 320 and 580 million dry tons for forest and cropland biomass, respectively. As noted earlier, the 2005 BTS emphasized the primary resources (agricultural and forestry residues and energy crops) because they represent nearly 80% of the long-term resource potential. Since publication of the BTS in April 2005, there have been some rather dramatic changes in energy markets. In fact, just prior to the actual publication of the BTS, world oil prices started to increase as a result of a burgeoning worldwide demand and concerns about long-term supplies. By the end of the summer, oil prices topped $70 per barrel (bbl) and catastrophic hurricanes in the Gulf Coast shut down a significant fraction of U.S. refinery capacity. The following year, oil approached $80 per bbl due to supply concerns, as well as continued political tensions in the Middle East. The Energy Independence and Security Act of 2007 (EISA) was enacted in December of that year. By the end of December 2007, oil prices surpassed $100 per bbl for the first time, and by mid-summer 2008, prices approached $150 per bbl because of supply concerns, speculation, and weakness of the U.S. dollar. As fast as they skyrocketed, oil prices fell, and by the end of 2008, oil prices dropped below $50 per bbl, falling even more a month later due to the global economic recession. In 2009 and 2010, oil prices began to increase again as a result of a weak U.S. dollar and the rebounding of world economies.

Landscape implications of bioenergy feedstock choices are significant and depend on land-use practices and their environmental impacts. Although land-use changes and carbon emissions associated with bioenergy feedstock production are dynamic and complicated, lignocellulosic feedstocks may offer opportunities that enhance sustainability when compared to other transportation fuel alternatives. For bioenergy sustainability, major drivers and concerns revolve around energy security, food production, land productivity, soil carbon and erosion, greenhouse gas emissions, biodiversity, air quality, and water quantity and quality. The many implications of bioenergy feedstock choices require several indicators at multiple scales to provide a more complete accounting of effects. Ultimately, the long-term sustainability of bioenergy feedstock resources (as well as food supplies) throughout the world depends on land-use practices and landscape dynamics. Land-management decisions often invoke trade-offs among potential environmental effects and social and economic factors as well as future opportunities for resource use. The hypothesis being addressed in this paper is that sustainability of bioenergy feedstock production can be achieved via appropriately designed crop residue and perennial lignocellulosic systems. We find that decision makers need scientific advancements and adequate data that both provide quantitative and qualitative measures of the effects of bioenergy feedstock choices at different spatial and temporal scales and allow fair comparisons among available options for renewable liquid fuels.

Switchgrass (Panicum virgatum) is a perennial, warm-season grass that has been identified as a potential biofuel feedstock over a large part of North America. We examined above- and belowground responses to nitrogen fertilization in "Alamo" switchgrass grown in West Tennessee, USA. The fertilizer study included a spring and fall sampling of 5-year old switchgrass grown under annual applications of 0, 67, and 202 kg N ha(-1) (as ammonium nitrate). Fertilization changed switchgrass biomass allocation as indicated by root: shoot ratios. End-of-growing season root:shoot ratios (mean +/- SE) declined significantly (P <= 0.05) at the highest fertilizer nitrogen treatment (2.16 +/- 0.08, 2.02 +/- 0.18, and 0.88 +/- 0.14, respectively, at 0, 67, and 202 kg N ha(-1)). Fertilization also significantly increased above- and belowground nitrogen concentrations and decreased plant C:N ratios. Data are presented for coarse live roots, fine live roots, coarse dead roots, fine dead roots, and rhizomes. At the end of the growing season, there was more carbon and nitrogen stored in belowground biomass than aboveground biomass. Fertilization impacted switchgrass tissue chemistry and biomass allocation in ways that potentially impact soil carbon cycle processes and soil carbon storage. (C) 2010 Elsevier B.V. All rights reserved.

A wide range of energy technologies appears to be needed for the United States to meet its energy goals. A method is developed that relates the uncertainty of technological progress in eleven technology areas to the achievement of CO2 mitigation and reduced oil dependence. We conclude that to be confident of meeting both energy goals, each technology area must have a much better than 50/50 probability of success, that carbon capture and sequestration, biomass, battery electric or fuel cell vehicles, advanced fossil liquids, and energy efficiency technologies for buildings appear to be almost essential, and that the success of each one of the 11 technologies is important. These inferences are robust to moderate variations in assumptions.

Switchgrass is a potential bioenergy crop that could promote soil C sequestration in some environments. We compared four switchgrass cultivars on a well-drained Alfisol to test for differences in biomass, C, and N dynamics during the fourth growing season. There was no difference (P>0.05) among cultivars and no significant cultivar×time interaction in analyses of dry mass, C stocks, or N stocks in aboveground biomass and surface litter. At the end of the growing season, mean (±SE) aboveground biomass was 2.1±0.13kgm−2, and surface litter dry mass was approximately 50% of aboveground biomass. Prior to harvest, the live root:shoot biomass ratio was 0.77. There was no difference (P>0.05) among cultivars for total biomass, C, and N stocks belowground. Total belowground biomass (90cm soil depth) as well as coarse (≥1mm diameter) and fine (<1mm diameter) live root biomass increased from April to October. Dead roots were <10% of live root biomass to a depth of 90cm. Net production of total belowground biomass (505±132gm−2) occurred in the last half of the growing season. The increase in total live belowground biomass (426±139gm−2) was more or less evenly divided among rhizomes, coarse, and fine roots. The N budget for annual switchgrass production was closely balanced with 6.3gNm−2 removed by harvest of aboveground biomass and 6.7gNm−2 supplied by fertilization. At the location of our study in west Tennessee, intra-annual changes in biomass, C, and N stocks belowground were potentially important to crop management for soil C sequestration.

We present and apply a new method for analyzing the significance of advanced technology for achieving two important national energy goals: climate protection and energy security. Quantitative metrics for U.S. greenhouse gas emissions in 2050 and oil independence in 2030 are specified, and the impacts of 11 sets of energy technologies are analyzed using a model that employs the Kaya identity and incorporates the uncertainty of technological breakthroughs. The goals examined are a 50% to 80% reduction in CO2 emissions from energy use by 2050 and increased domestic hydrocarbon fuels supply and decreased demand that sum to 11 mmbd by 2030. The latter is intended to insure that the economic costs of oil dependence are not more than 1% of U.S. GDP with 95% probability by 2030. Perhaps the most important implication of the analysis is that meeting both energy goals requires a high probability of success (much greater than even odds) for all 11 technologies. Two technologies appear to be indispensable for accomplishment of both goals: carbon capture and storage, and advanced fossil liquid fuels. For reducing CO2 by more than 50% by 2050, biomass energy and electric drive (fuel cell or battery powered) vehicles also appear to be necessary. Every one of the 11 technologies has a powerful influence on the probability of achieving national energy goals. From the perspective of technology policy, conflict between the CO2 mitigation and energy security is negligible. These general results appear to be robust to a wide range of technology impact estimates; they are substantially unchanged by a Monte Carlo simulation that allows the impacts of technologies to vary by 20%.

Agricultural residues such as corn ( Zea mays L.) stover are a potential feedstock for bioenergy and bio‐based products that could reduce U.S. dependence on foreign oil. Collection of such residues must take into account concerns that residue removal could increase erosion, reduce crop productivity, and deplete soil carbon and nutrients. This article estimates where and how much corn stover can be collected sustainably in the USA using existing commercial equipment and estimates costs of that collection. Erosion constraints to collection were considered explicitly, and crop productivity and soil nutrient constraints were considered implicitly, by recognizing the value of residues for maintaining soil moisture and including the cost of fertilizer to replace nutrients removed. Possible soil carbon loss was not considered in the analysis. With an annual production of 196 million Mg of corn grain (∼9.2 billion bushels), the USA produces 196 million Mg of stover. Under current rotation and tillage practices, ∼30% of this stover could be collected for less than $33 Mg −1 , taking into consideration erosion and soil moisture concerns and nutrient replacement costs. Wind erosion is a major constraint to stover collection. Analysis suggests three regions of the country (central Illinois, northern Iowa/southern Minnesota, and along the Platte River in Nebraska) produce sufficient stover to support large biorefineries with one million Mg per year feedstock demands and that if farmers converted to universal no‐till production of corn, then over 100 million Mg of stover could be collected annually without causing erosion to exceed the tolerable soil loss.

Forecasting the magnitude of sustainable biofeedstock supplies is challenging because of 1) myriad potential feedstock types and their management; 2) the need to account for the spatial variation of both the supplies and their environmental and economic consequences; and 3) the inherent challenges of optimizing across economic and environmental considerations. Over the last two decades, US biomass forecasts have become increasingly complex and sensitive to environmental and economic considerations; however, more model development and research is needed. In particular, the landscape and regional tradeoffs of differing biofeedstock supplies need to be addressed, especially with regard to water quality concerns and wildlife/biodiversity. Feedstock assessments need to be done in the context of the direction of land-use change induced by biofeedstock production; they need to take into consideration both the starting environmental and economic conditions before the land was used to supply biofeedstocks and the probable future conditions that would result in the absence of biofeedstock production. To evaluate sustainability, process-oriented models need to be coupled or used to inform sector models and more work needs to be done on developing environmental metrics that are useful for evaluating economic and environmental tradeoffs. These challenges are exciting and worthwhile as they will enable the bioenergy industry to capture the environmental and social benefits of biofeedstock production and reduce risks. Published in 2007 by John Wiley and Sons, Ltd.

The U.S. Department of Energy (DOE) and the U.S. Department of Agriculture (USDA) are both strongly committed to expanding the role of biomass as an energy source. In particular, they support biomass fuels and products as a way to reduce the need for oil and gas imports; to support the growth of agriculture, forestry, and rural economies; and to foster major new domestic industries--biorefineries--making a variety of fuels, chemicals, and other products. As part of this effort, the Biomass R&D Technical Advisory Committee, a panel established by the Congress to guide the future direction of federally funded biomass R&D, envisioned a 30 percent replacement of the current U.S. petroleum consumption with biofuels by 2030. Biomass--all plant and plant-derived materials including animal manure, not just starch, sugar, oil crops already used for food and energy--has great potential to provide renewable energy for America's future. Biomass recently surpassed hydropower as the largest domestic source of renewable energy and currently provides over 3 percent of the total energy consumption in the United States. In addition to the many benefits common to renewable energy, biomass is particularly attractive because it is the only current renewable source of liquid transportation fuel. This, of course, makes it invaluable in reducing oil imports--one of our most pressing energy needs. A key question, however, is how large a role could biomass play in responding to the nation's energy demands. Assuming that economic and financial policies and advances in conversion technologies make biomass fuels and products more economically viable, could the biorefinery industry be large enough to have a significant impact on energy supply and oil imports? Any and all contributions are certainly needed, but would the biomass potential be sufficiently large to justify the necessary capital replacements in the fuels and automobile sectors? The purpose of this report is to determine whether the land resources of the United States are capable of producing a sustainable supply of biomass sufficient to displace 30 percent or more of the country's present petroleum consumption--the goal set by the Advisory Committee in their vision for biomass technologies. Accomplishing this goal would require approximately 1 billion dry tons of biomass feedstock per year.