Practical Considerations in Developing Bioenergy Crops

Biofuels represent a significant challenge and opportunity for agriculture. Producing liquid fuels from cellulosic biomass affords a number of potential environmental benefits. Biofuels result in lower greenhouse gas emissions than fuels derived from petroleum. Growing perennial biomass crops reduces soil erosion and sequesters more carbon than annual crops grown for grain or biomass. Corn and sorghum are crops that have high near-term potential as annual biomass crops. Dedicated biomass crops with very high yields will produce more fuel per acre, helping to balance land for food and fuel. Switchgrass and Miscanthus are perennial species that have been broadly evaluated as potential biomass crops, but will benefit from further development for widespread use. New crops and cropping systems developed specifically for bioenergy production will be necessary to meet biofuel production targets. Bioenergy crops should be developed that use inputs efficiently, have high and stable productivity, have positive environment impact, and are compatible with existing cropping systems. Most importantly, biomass crop portfolios must be developed that allow for sustained energy supply throughout the year

Potential for Sorghum Genotypes in a Double-cropping System

The majority of the ethanol currently produced in the United States is derived from the hydrolysis and fermentation of starch provided from corn (Zea mays) grain. Although this is a suitable temporary solution, there are some long-term issues associated with continued use of corn grain as an ethanol feedstock. It has been estimated that if the entire U.S. corn crop was used for ethanol production, it would only meet approximately 15 to 25% of the U.S. transportation fuel need. Thus ethanol produced from biomass is expected to help meet the energy needs that grain ethanol may not provide

Convergence of Agriculture and Energy: II. Producing Cellulosic Biomass for Biofuels

Global energy demand is increasing as known global petroleum supplies are decreas¬ing. Calls to supplement or replace the current fossil-based energy system with new, envi¬ronmentally and economically sustainable strategies continue to increase, especially in light of more expensive traditional energy sources. Various governmental agencies and working groups have set aggressive targets and timelines for decreasing fossil fuel consumption by substituting bio-based energy (Bush 2007; Foust et al. 2007; Perlack et al. 2005; Smith et al. 2004). The alignment and continuity of these goals is illustrated in Figure 1. Current biofuel production in the United States relies primarily on corn grain conver¬sion to ethanol, but future systems are expected to depend more intensively on plant biomass than on grain as a feedstock for production of ethanol and other biofuels. In addition, current cropping systems generally are designed to optimize grain production and are not designed to harvest all the aboveground portion of the plant for cellulose-containing biomass. Significant, immediate national investments are needed, along with changes in policy, to address chal¬lenges limiting the sustainable production and efficient use of cellulosic biomass as a fuel feedstock to meet anticipated U.S. demand. The Bush Administration outlined a portfolio of recommended technologies, pro¬cesses, and practices for bio-based energy production that targets improved rates of feedstock conversion and greater efficiency in energy use. The plan also states that a significant portion of the nation’s 2017 energy supply, especially transportation fuel, will come from conversion of biomass feedstock to liquid fuels. Considering just the biomass-derived fuels contribution, roughly 250 million tons or more of grain and cellulosic biomass per year will be needed to reach the 10-year goal, and 650 to 700 million tons per year of biomass to reach the 2025 goal (Figure 1)

Book Review: \u3ci\u3eA Biomass Future for the North American Great Plains: Toward Sustainable Land Use and Mitigation of Greenhouse Warming\u3c/i\u3e By Norman J. Rosenberg

This book presents a comprehensive, thoroughly researched, and timely treatment of the topic. Interpretive summaries at the end of each chapter emphasize salient points and are very helpful to the reader. Illustrations (including color plates in end materials) are useful, but a number have poor resolution, making them difficult to interpret. The book is appropriate for upper-level students and other individuals interested in sustainable agriculture, agroecology, bioenergy, and related topics

EFFECTS OF MATURITY AND ENVIRONMENT ON THE AMOUNT, COMPOSITION, AND IN VITRO DISAPPEARANCE OF HEMICELLULOSE IN TALL FESCUE

The purpose of this study was to determine the extent to which environmental conditions during growth influence the amount, chemical composition and in vitro disappearance of tall fescue hemicellulose and its constituents. First growth was sampled and cut on May 16, June 14, and July 19. Regrowth was sampled at weekly intervals following each cutting. Samples were extracted with neutral detergent and the neutral detergent fiber (NDF) was treated with 1.0 N H(,2)SO(,4) to hydrolyze hemicellulose (HC). A high performance liquid chromatography (HPLC) technique, using cation exchange resins and water as the sole eluent, was adapted to measure concentrations of xylose and arabinose in the HC hydrolyzates. The remaining portion of HC was assumed to consist primarily of glucuronic acid. Selected samples were incubated in rumen fluid to determine the in vitro digestibility of the various cell wall constituents. Neutral detergent fiber in first growth leaf tissue increased 10.2 percentage units of dry matter between May 16 and June 14, and increased 5.3 additional units between June 14 and July 19. Acid fiber (AF) percentage increased 7.3 units and hemicellulose (HC) increased 3.9 units between May 16 and June 14. Between June 14 and July 19, AF and HC increased by 2.2 and 3.2 percentage units respectively. Xylose percent of dry matter increased 5.1 units between May 16 and June 14, and increased 2.0 units between June 14 and July 19, while arabinose percentage remained about the same during the entire period. Between May 16 and July 19, the in vitro disappearance of NDF decreased from 37.9 percent to 22.4 percent, AF disappearance decreased from 27.1 percent to 9.2 percent, and HC disappearance decreased from 50.1 percent to 39.4 percent. Xylose in vitro disappearance decreased from 40.8 percent to 36.5 percent, arabinose disappearance decreased from 78.1 percent to 53.8 percent, and glucuronic acid disappearance decreased from 50.0 percent to 39.1 percent. Second growth NDF increased over time from May 16 (early summer growth) and from June 14 (mid-summer growth), but it decreased in regrowth from July 19 (late summer growth). The trends if AF paralled the NDF trends, but HC trends were opposite. Xylose percentage in HC followed the NDF trends more closely than the HC trends, while arabinose showed little variation. In vitro NDF disappearance in second growth decreased over time during all three periods, and was related more to AF disappearance than HC disappearance, suggesting that the effect of time was greater on cellulose than on hemicellulose. Decreases in HC in vitro disappearance were related to decreases in both xylose and glucuronic acid disappearance. The effect of environment on fiber digestibility was indicated because NDF disappearance in three week-old regrowth was higher in mid-summer growth than in the same age material from the other two periods. When calculations were made to estimate changes that occurred in the composition of newly synthesized cell wall, the magnitude of differences was much greater than indicated by the original data, although the trends were similar. Differences were associated more with time of season than with tissue age (weeks). No consistent trends were found linking amounts of cell wall constituents to temperature. However, concentrations of NDF, AF, and xylose increased during the period of increasing daylength and decreased during the period of decreasing daylength. These results suggest that changes in the amount and composition of newly synthesized fiber may have been influenced by photoperiod

Practical Considerations in Developing Bioenergy Crops

Biofuels represent a significant challenge and opportunity for agriculture. Producing liquid fuels from cellulosic biomass affords a number of potential environmental benefits. Biofuels result in lower greenhouse gas emissions than fuels derived from petroleum. Growing perennial biomass crops reduces soil erosion and sequesters more carbon than annual crops grown for grain or biomass. Corn and sorghum are crops that have high near-term potential as annual biomass crops. Dedicated biomass crops with very high yields will produce more fuel per acre, helping to balance land for food and fuel. Switchgrass and Miscanthus are perennial species that have been broadly evaluated as potential biomass crops, but will benefit from further development for widespread use. New crops and cropping systems developed specifically for bioenergy production will be necessary to meet biofuel production targets. Bioenergy crops should be developed that use inputs efficiently, have high and stable productivity, have positive environment impact, and are compatible with existing cropping systems. Most importantly, biomass crop portfolios must be developed that allow for sustained energy supply throughout the year.</p

Potential for Sorghum Genotypes in a Double-cropping System

The majority of the ethanol currently produced in the United States is derived from the hydrolysis and fermentation of starch provided from corn (Zea mays) grain. Although this is a suitable temporary solution, there are some long-term issues associated with continued use of corn grain as an ethanol feedstock. It has been estimated that if the entire U.S. corn crop was used for ethanol production, it would only meet approximately 15 to 25% of the U.S. transportation fuel need. Thus ethanol produced from biomass is expected to help meet the energy needs that grain ethanol may not provide.</p

The Relationship Between Species Diversity and Productivity of Cool-Season Grassland

Iowa grasslands consist mainly of introduced cool-season grasses and forbs. Many of these species are well adapted and have become naturalised. Most of these grasslands are located on marginal sites with heterogeneous soils and topography. Consequently, there is significant variation in the botanical composition and biomass productivity within and across grassland sites. This experiment aimed to evaluate the botanical composition and biomass productivity of representative grasslands and to determine if there was a relationship between grassland species diversity and biomass production across sites