Black Locust as a Bioenergy Feedstock: a Review

Short rotation woody bioenergy crops (SRWC) could contribute a substantial portion of the biomass required to meet federal mandates and offset carbon emissions. One SRWC with strong bioenergy potential is black locust (Robinia pseudoacacia L.), planted extensively for wood and energy applications globally, but under-studied in its native US. This member of the Fabaceae family can fix nitrogen, tolerate stress, and sequester carbon while generating biomass yields up to 14 Mg ha^-1 yr^-1. This article offers a comprehensive state-of-the-art review of production practices, biomass and energy yield estimates, environmental risks and benefits, and economic considerations for this promising feedstock.     

Reporting on Marginal Lands for Bioenergy Feedstock Production: a Modest Proposal

Growing bioenergy feedstocks can provide a long-term sustainable production system for marginal land resources and is essential for minimizing food vs. fuel competition for prime croplands. However, the term “marginal” is too often used in research reports without being defined. We here suggest that clearly specifying the biophysical factors and agroeconomic context contributing to marginality will greatly enhance the utility and comparability of published research.     

Feedstock Crop Production Costs and Biofuel Feedstock Input Costs Associated with the Production of Energy Cane and Sweet Sorghum in the Southeastern USA

Concentration of biofuel feedstock crop production in specific regions of the USA is dependent on the relative comparative advantage of production in a specific region based on several agronomic and economic factors. For the southeastern region of the USA, energy cane and sweet sorghum have been identified as two feedstock crops with the greatest potential for further development of production. This study utilized field trial data from yield studies in Louisiana to develop estimates of feedstock crop production costs and biofuel feedstock input costs for these two crops. Results indicated that feedstock production costs on a harvest yield basis, as well as the related dry matter basis, were heavily dependent on yield level. Economic research from this study indicated that energy cane had a slight cost advantage compared with sweet sorghum, although production of sorghum in certain periods during the growing season was very cost competitive with energy cane.     

Simulation of Biomass Yield and Soil Organic Carbon under Bioenergy Sorghum Production

Developing sustainable management practices including appropriate residue removal and nitrogen (N) fertilization for bioenergy sorghum is critical. However, the effects of residue removal and N fertilization associated with bioenergy sorghum production on soil organic carbon (SOC) are less studied compared to other crops. The objective of our research was to assess the impacts of residue removal and N fertilization on biomass yield and SOC under biomass sorghum production. Field measurements were used to calibrate the DNDC model, then verified the model by comparing simulated results with measured results using the field management practices as agronomic inputs. Both residue removal and N fertilization affected bioenergy sorghum yields in some years. The average measured SOC at 0–50 cm across the treatments and the time-frame ranged from 47.5 to 78.7 Mg C ha⁻¹, while the simulated SOC was from 56.3 to 67.3 Mg C ha⁻¹. The high correlation coefficients (0.65 to 0.99) and low root mean square error (3 to 18) between measured and simulated values indicate the DNDC model accurately simulated the effects of residue removal with N fertilization on bioenergy sorghum production and SOC. The model predictions revealed that there is, in the long term, a trend for higher SOC under bioenergy sorghum production regardless of residue management.     

Assessing the Soil Carbon,Biomass Production,and Nitrous Oxide Emission Impact of Corn Stover Management for Bioenergy Feedstock Production Using DAYCENT

Harvesting crop residue needs to be managed to protect agroecosystem health and productivity. DAYCENT, a process-based modeling tool, may be suited to accommodate region-specific factors and provide regional predictions for a broad array of agroecosystem impacts associated with corn stover harvest. Grain yield, soil C, and N₂O emission data collected at Corn Stover Regional Partnership experimental sites were used to test DAYCENT performance modeling the impacts of corn stover removal. DAYCENT estimations of stover yields were correlated and reasonably accurate (adjusted r ²?=?0.53, slope?=?1.18, p?<<?0.001, intercept?=?0.36, p?=?0.11). Measured and simulated average grain yields across sites did not differ as a function of residue removal, but the model tended to underestimate average measured grain yields. Modeled and measured soil organic carbon (SOC) change for all sites were correlated (adjusted r ²?=?0.54, p?<<?0.001), but DAYCENT overestimated SOC loss with conventional tillage. Simulated and measured SOC change did not vary by residue removal rate. DAYCENT simulated annual N₂O flux more accurately at low rates (≤2-kg N₂O-N ha^?1 year^?1) but underestimated when emission rates were >3-kg N₂O-N ha^?1 year^?1. Overall, DAYCENT performed well at simulating stover yields and low N₂O emission rates, reasonably well when simulating the effects of management practices on average grain yields and SOC change, and poorly when estimating high N₂O emissions. These biases should be considered when DAYCENT is used as a decision support tool for recommending sustainable corn stover removal practices to advance bioenergy industry based on corn stover feedstock material.     

Biomass Production and Composition of Perennial Grasses Grown for Bioenergy in a Subtropical Climate Across Florida, USA

Carbohydrate and lignin composition of feedstock materials are major factors in determining their bioenergy potential. This study was conducted to quantify dry biomass yield and the carbohydrate and lignin composition of six potential biofuel grasses (elephantgrass, energycane, sweetcane, giant reed, giant miscanthus, and sugarcane) across three sites in Florida for plant (2009) and first ratoon (2010) crops. Dry biomass yields ranged from about 30 to 50 Mg ha^?1 and were generally greatest for elephantgrass, energycane, sweetcane, and sugarcane. Accordingly, total plant carbohydrate yields (20 to 25 Mg ha^?1) were comparable among sugarcane, energycane, sweetcane, and elephantgrass, but were generally less for giant reed and even less for giant miscanthus. However, the contribution of total extractable carbohydrates and total fiber carbohydrates to total plant carbohydrate yields differed among species. Sugarcane had the highest concentrations of extractable carbohydrates (219 to 356 mg g^?1), followed by energycane, then sweetcane, elephantgrass, and giant reed, with giant miscanthus having the lowest. Energycane and elephantgrass tended to have significantly more fiber glucose, and elephantgrass less xylose, than other species. Variability in total lignin concentrations on a fiber basis was relatively modest (250 to 285 mg g^?1) across species, but was generally highest in sweetcane and giant reed. Overall, elephantgrass and energycane were prime regional candidates for cellulosic conversion using fermentation processes due to high yields and favorable fiber characteristics, although energycane tended to have higher extractable carbohydrates.     

Global Potential of Rice Husk as a Renewable Feedstock for Ethanol Biofuel Production

The production of ethanol for the energy market has traditionally been from corn and sugar cane biomass. The use of such biomass as energy feedstocks has recently been criticised as ill-fated due to competitive threat against food supplies. At the same time, ethanol production from cellulosic biomass is becoming increasingly popular. In this paper, we analyse rice husk (RH) as a cellulosic feedstock for ethanol biofuel production on the ground of its abundance. The global potential production of bioethanol from RH is estimated herein and found to be in the order of 20.9 to 24.3 GL per annum, potentially satisfying around one fifth of the global ethanol biofuel demand for a 10% gasohol fuel blend. Furthermore, we show that this is especially advantageous for Asia, in particular, India and China, where economic growth and demand for energy are exploding.     

Economics of Alternative Fertilizer Supply Systems for Switchgrass Produced in Phosphorus-Deficient Soils for Bioenergy Feedstock

Limited information is available explaining the economics of supplying N and P fertilizers on established stands of switchgrass growing in phosphorus-deficient soils. The objective of this study was to determine the most economical fertilizer supply system for producing feedstock in phosphorus-deficient soil in the southern Great Plains. Data collected from field trials conducted at two locations in south-central Oklahoma along with prices quoted by local input suppliers and custom service providers and assumptions about the farm-gate price of feedstock were used to estimate expected values for production costs, gross revenue and net return to owner's labor, management, and overhead for eight fertilizer supply systems. The systems included a zero fertilizer check system (0/0), three P systems (0/34, 0/67, and 0/101), one N system (135/0), and three N and P systems (135/34, 135/67, and 135/101). Random-effects mixed ANOVA models were used to determine the effects of fertilizer system on the values of total cost and net return. For the base-case price scenario (feedstock, N and P prices of $110 Mg^?1 and $1.28 and 1.17 kg^?1, respectively), the 135/0 system was the most profitable system, producing 10.2 Mg of feedstock and $263 of net return per hectare. Economic results were most sensitive to the prices of feedstock, N and P. Net return was negative for all eight systems for the scenario where the farm-gate price of feedstock was relatively low ($55 Mg^?1) and prices for N and P were relatively high ($2.20 kg^?1).     

Selenium Content in Blood Fractions and Liver of Beef Heifers Is Greater with a Mix of Inorganic/Organic or Organic Versus Inorganic Supplemental Selenium but the Time Required for Maximal Assimilation Is Tissue-Specific

Selenium (Se) content of feedstuffs is dependent on the Se level of the soil. Even though Se in grass and forage crops is primarily present in organic forms, Se is commonly supplemented in cattle diets in an inorganic (sodium selenite) form in geographic regions where Se soil concentrations are low. The purpose of this study was to answer two important questions about inorganic (ISe) vs organic (OSe) forms of dietary supplementation of Se (3?mg/day) to growing beef heifers (0.5?kg/day): (1) what would the effect of supplementing Se with an equal blend of ISe:OSe (Mix) have on Se tissue concentrations and (2) how long does it take for the greater assimilation with OSE to occur and stabilize? A long-term (224?day) Se dietary supplementation trial was conducted with serial sampling performed (days?28, 56, 112, and 224) to determine the length of time required to achieve Se supplement (OSE, Mix, and ISe)-dependent changes in Se assimilation in blood fractions and liver tissue. Forty maturing Angus heifers were fed a corn silage-based diet for 98?days with no Se supplementation, and then a cracked corn/cottonseed hull-based diet (basal diet) without Se supplementation for 74?days. Liver biopsies were taken for Se analysis, and heifers were fed the same diet for another 14?days. Heifers were assigned (n?=?10) to one of four Se treatment groups such that basal liver Se contents were stratified among groups, and then fed enough of the basal diet (0.08?mg Se per day) and a mineral-vitamin mix that provided 0.16 (control) or 3.0?mg Se per day in ISe (sodium selenite), OSe (Sel-Plex(?)), or Mix (1:1 ISe:OSe) form to support 0.5?kg/day growth for 224?days. More Se was found in whole blood, red blood cells, serum, and liver of Mix and OSe heifers than ISe heifers, and all were greater than control. Se content either increased until day?56 then was stable (liver and plasma), or was stable until day?56 (whole blood) or day?112 (red blood cells) and then increased steadily through day?224, for all supplemental Se treatments. These data indicate that a 1:1 mix (1.5?mg Se:1.5?mg Se) of supplemental ISe and OSe is equal to 3?mg/day OSe supplementation and greater than 3?mg/day ISe supplementation. The data also indicate that Se levels stabilized in liver and plasma by 56 to 112?days whereas whole blood and red blood cell concentrations were still increasing through 224?days of supplementation, regardless of the form of supplemental Se.     

Microalgal-Bacterial Consortia as Future Prospect in Wastewater Bioremediation,Environmental Management and Bioenergy Production

In the recent years, microalgae have captured researchers’ attention as the alternative feedstock for various bioenergy production such as biodiesel, biohydrogen, and bioethanol. Cultivating microalgae in wastewaters to simultaneously bioremediate the nutrient-rich wastewater and maintain a high biomass yield is a more economical and environmentally friendly approach. The incorporation of algal–bacterial interaction reveals the mutual relationship of microorganisms where algae are primary producers of organic compounds from CO₂, and heterotrophic bacteria are secondary consumers decomposing the organic compounds produced from algae. This review would provide an insight on the challenges and future development of algal–bacterial consortium and its contribution in promoting a sustainable route to greener industry. It is believed that microalgal-bacterial consortia will be implemented in the near-future for sub-sequential treatment of wastewater bioremediation, bioenergy production and CO₂ fixation, promoting sustainability and making extraordinary advancement in life sciences sectors.     

Optimizing Sweet Sorghum Production for Biofuel in the Southeastern USA Through Nitrogen Fertilization and Top Removal

Sustainable bioenergy cropping systems require not only high yields but also efficient use of inputs. Management practices optimizing production of sweet sorghum [Sorghum bicolor (L.) Moench] for bioenergy use are needed. The effects of N rate (45, 90, 135, and 180?kg N?ha^?1) and top removal (at boot stage, anthesis, and none) on biomass, brix, estimated sugar yield, and N and P recovery of sweet sorghum cv. M-81E were investigated in Florida at two sites differing in soil type. Across all data, dry biomass yields averaged 17.7 Mg?ha^?1 and were not affected by N fertilization rate at either site (P?>?0.10). Mean brix values ranged from 131 to 151?mg?g^?1 and were negatively related to N rate. Top removal, either at boot stage or anthesis, resulted in greater brix values and 13% greater sugar yields at both locations. Whole plant N recovery was positively and linearly related to N rate and ranged from 78 to 166?kg N?ha^?1, approximately two thirds of which was in leaf and grain tissues. Based on yield and nutrient recovery responses, optimal nutrient requirements were 90 to 110?kg N?ha^?1 and 15 to 20?kg P?ha^?1. Higher N fertilization led to greater N recovery, but little to modest gain in sugar yield. Thus, proper nutrient and harvest management will be needed to optimize sugar yields of sweet sorghum for production of biofuels and bio-based products. Further research is needed to refine management practices of sweet sorghum for bioenergy production, especially with regard to the use of leaf and grain tissues.     

Bioenergy Traits of Ten Switchgrass Populations Grown in the Northeastern/Mid-Atlantic USA

Although switchgrass (Panicum virgatum L.) has emerged as a bioenergy crop throughout the midwestern and southern USA, little evaluation has been conducted on the performance of switchgrass as a bioenergy crop in the Northeast/Mid-Atlantic. The objectives of this study were to evaluate biomass characteristics of ten switchgrass populations grown in New Jersey and to determine which populations are best for use in biomass production. Ten populations of switchgrass were planted in a spaced-plant nursery in Freehold, NJ and evaluated for: winter injury, anthracnose disease caused by Colletotrichum navitas, lodging, tiller density, height, heading and anthesis date, and biomass yield as well as cellulose, hemicellulose, lignin, ash, chlorine, calcium, magnesium, phosphorous, and potassium in 2007 and 2008. Eastern upland populations 9064202 (Cape May Plant Materials Center accession #9064202), High Tide, and Carthage showed the least amount of winter injury, while southern lowland populations Alamo and Cimarron showed the most winter injury. Lowland populations were less susceptible to anthracnose than upland ecotypes and were taller and later maturing with higher cellulose contents. Lowland populations NSL, Cimarron, and Timber showed the least amount of lodging, and upland populations had the highest tiller densities. Lowland populations Cimarron and Timber had the highest biomass yields of 906.9 and 803.6 kg dry matter plant^?1, respectively. Lignocellulosic and mineral contents did not differ greatly among cultivars and generally did not show trends with respect to cytotype. Timber, an eastern lowland ecotype, exhibited the best combination of characteristics and is a promising population for biomass production in the Northeast/Mid-Atlantic region of the USA.     

Inorganic Nitrogen Leaching from Organic and Conventional Rice Production on a Newly Claimed Calciustoll in Central Asia

Characterizing the dynamics of nitrogen (N) leaching from organic and conventional paddy fields is necessary to optimize fertilization and to evaluate the impact of these contrasting farming systems on water bodies. We assessed N leaching in organic versus conventional rice production systems of the Ili River Valley, a representative aquatic ecosystem of Central Asia. The N leaching and overall performance of these systems were measured during 2009, using a randomized block experiment with five treatments. PVC pipes were installed at soil depths of 50 and 180 cm to collect percolation water from flooded organic and conventional paddies, and inorganic N (NH₄-N+NO₃-N) was analyzed. Two high-concentration peaks of NH₄-N were observed in all treatments: one during early tillering and a second during flowering. A third peak at the mid-tillering stage was observed only under conventional fertilization. NO₃-N concentrations were highest at transplant and then declined until harvest. At the 50 cm soil depth, NO₃-N concentration was 21–42% higher than NH₄-N in percolation water from organic paddies, while NH₄-N and NO₃-N concentrations were similar for the conventional and control treatments. At the depth of 180 cm, NH₄-N and NO₃-N were the predominant inorganic N for organic and conventional paddies, respectively. Inorganic N concentrations decreased with soil depth, but this attenuation was more marked in organic than in conventional paddies. Conventional paddies leached a higher percentage of applied N (0.78%) than did organic treatments (0.32–0.60%), but the two farming systems leached a similar amount of inorganic N per unit yield (0.21–0.34 kg N Mg⁻¹ rice grains). Conventional production showed higher N utilization efficiency compared to fertilized organic treatments. These results suggest that organic rice production in the Ili River Valley is unlikely to reduce inorganic N leaching, if high crop yields similar to conventional rice production are to be maintained.     

Organic Carbon Composition and Oxygen Metabolism across a Gradient of Seasonally Inundated Limesink and Riparian Wetlands in the Southeast Coastal Plain,USA

A set of three relatively pristine seasonally inundated limesink wetlands and one riparian wetland was studied over a 4–6 month long inundation period in 2001. Patterns in organic matter properties and oxygen consumption in the water column followed a previously documented ecological gradient based on soil composition, vegetation type, and canopy cover. The full canopy, cypress-gum swamp had the highest mean concentrations of dissolved organic carbon (DOC; 26.2 mg/l) and dissolved lignin (sum 6; 299 μg/l) with lower concentrations observed in the partial canopy, cypress savanna (22.0 mg/l DOC; 252 μg/l sum 6) and the open marsh savanna (20.6 mg/l DOC; 135 μg/l sum 6), respectively. During the inundation period, DOC increased in concentration, dissolved lignin decreased, and δ¹³C shifted to more positive values which collectively indicate a large reduction in the percentage of aromatic carbon during the inundation period. All wetlands had very high concentrations of organic matter, yet microbial oxygen consumption was almost always stimulated by the addition of glucose rather than inorganic nutrients. Stimulation by glucose suggests that there were very small pools of highly bioavailable forms of DOC in the wetlands. A larger pool of moderately bioavailable organic matter had the capacity to sustain microbial oxygen consumption rates under dark conditions for at least 15 d. During the inundation period, the cypress-gum swamp had the lowest average rates of whole water oxygen consumption (1.0 μM/h) with increasing rates observed in the cypress savanna (1.3 μM/h), marsh savanna (1.6 μM/h), and riparian wetland (1.9 μM/h), respectively. The lignin compositional fingerprint varied across the gradient of limesink wetlands, and was useful for identifying different sources of vascular plant-derived DOM. Vascular plant production, algal production, microbial respiration, and UV degradation are all important drivers of DOM cycling, and the consistencies observed in this initial assessment of seasonally inundated limesink wetlands suggest they vary in predictable ways across the ecological gradient.     

Switchgrass Response to Nitrogen Fertilizer Across Diverse Environments in the USA: a Regional Feedstock Partnership Report

The Regional Feedstock Partnership is a collaborative effort between the Sun Grant Initiative (through Land Grant Universities), the US Department of Energy, and the US Department of Agriculture. One segment of this partnership is the field-scale evaluation of switchgrass (Panicum virgatum L.) in diverse sites across the USA. Switchgrass was planted (11.2 kg PLS ha^?1) in replicated plots in New York, Oklahoma, South Dakota, and Virginia in 2008 and in Iowa in 2009. Adapted switchgrass cultivars were selected for each location and baseline soil samples collected before planting. Nitrogen fertilizer (0, 56, and 112 kg N ha^?1) was applied each spring beginning the year after planting, and switchgrass was harvested once annually after senescence. Establishment, management, and harvest operations were completed using field-scale equipment. Switchgrass production ranged from 2 to 11.5 Mg ha^?1 across locations and years. Yields were lowest the first year after establishment. Switchgrass responded positively to N in 6 of 19 location/year combinations and there was one location/year combination (NY in Year 2) where a significant negative response was noted. Initial soil N levels were lowest in SD and VA (significant N response) and highest at the other three locations (no N response). Although N rate affected some measures of biomass quality (N and hemicellulose), location and year had greater overall effects on all quality parameters evaluated. These results demonstrate the importance of local field-scale research and of proper N management in order to reduce unnecessary expense and potential environmental impacts of switchgrass grown for bioenergy.     

C_4 Plants as Biofuel Feedstocks: Optimising Biomass Production and Feedstock Quality from a Lignocellulosic Perspective

The main feedstocks for bioethanol are sugarcane (Saccharum officinarum) and maize (Zea mays),both of which are C4 grasses,highly efficient at converting solar energy into chemical energy,and both are food crops.As the systems for lignocellulosic bioethanol production become more efficient and cost effective,plant biomass from any source may be used as a feedstock for bioethanol production.Thus,a move away from using food plants to make fuel is possible,and sources of biomass such as wood from forestry and ...     

Effect of Inorganic and Organic Ligands on the Bioavailability of Methylmercury as Determined by Using a mer-lux Bioreporter

A mer-lux bioreporter was constructed to assess the bioavailability of methylmercury [CH₃Hg(II)] in Escherichia coli. The bioreporter was shown to be sensitive, with a detection limit of 2.5 nM CH₃Hg(II), and was used to investigate the effects of chlorides, humic acids, and thiols on the bioavailability of CH₃Hg(II) in E. coli. It was found that increasing the concentration of chlorides resulted in an increase in CH₃Hg(II) bioavailability, suggesting that there was passive diffusion of the neutral complex (CH₃HgCl⁰). Humic acids were found to reduce the bioavailability of CH₃Hg(II) in varying degrees. Complexation with cysteine resulted in increased bioavailability of CH₃Hg(II), while assays with equivalent concentrations of methionine and leucine had little or no effect on bioavailability. The mechanism of uptake of the mercurial-cysteine complexes is likely not passive diffusion but could result from the activities of a cysteine transport system. The bioavailability of CH₃Hg(II) decreased with increasing glutathione concentrations.     

Dedicated Energy Crops and Crop Residues for Bioenergy Feedstocks in the Central and Eastern USA

Dedicated energy crops and crop residues will meet herbaceous feedstock demands for the new bioeconomy in the Central and Eastern USA. Perennial warm-season grasses and corn stover are well-suited to the eastern half of the USA and provide opportunities for expanding agricultural operations in the region. A suite of warm-season grasses and associated management practices have been developed by researchers from the Agricultural Research Service of the US Department of Agriculture (USDA) and collaborators associated with USDA Regional Biomass Research Centers. Second generation biofuel feedstocks provide an opportunity to increase the production of transportation fuels from recently fixed plant carbon rather than from fossil fuels. Although there is no “one-size-fits-all” bioenergy feedstock, crop residues like corn (Zea mays L.) stover are the most readily available bioenergy feedstocks. However, on marginally productive cropland, perennial grasses provide a feedstock supply while enhancing ecosystem services. Twenty-five years of research has demonstrated that perennial grasses like switchgrass (Panicum virgatum L.) are profitable and environmentally sustainable on marginally productive cropland in the western Corn Belt and Southeastern USA.     

Effects of Management on Economic Profitability of Forest Biomass Production and Carbon Neutrality of Bioenergy Use in Norway Spruce Stands Under the Changing Climate

We analyzed the effects of management on the economic profitability of forest biomass production and carbon neutrality of bioenergy use in Norway spruce (Picea abies L. Karst) stands under the changing climate. We employed a forest ecosystem model and life cycle assessment tool. In particular, we studied the effects of thinning, nitrogen fertilization, and rotation length on: (1) the production of timber and energy biomass, and its economic profitability (net present value), (2) carbon stock in the forest ecosystem and carbon balance in forestry, and (3) carbon dioxide (CO₂) emissions from the use of biomass in energy production. Results showed that the current Finnish baseline management with and without nitrogen fertilization resulted in the highest mean annual timber production and net present value (NPV) for long rotations (60 to 80 years), regardless of climate scenario. Mean annual production of energy biomass was enhanced by increasing stocking by 20–30 % compared to the baseline management, and/or use of nitrogen fertilization. Such management gave lower CO₂ emissions per unit of energy compared to the baseline management, as the carbon stock in the forest ecosystem and the carbon balance in forestry increased. Overall, the carbon neutrality and net present value were, on average, the highest in the baseline management or with a 20 % increase in stocking, with nitrogen fertilization and 60- to 80-year rotation lengths, regardless of the climate applied. However, it was not possible to simultaneously maximize the NPV of forest biomass production and the carbon neutrality of bioenergy use.     

Combination Effects of Organic and Inorganic Chromium on Production Performance,Reproductive Response,Immune Status,and Maternal Antibody Transmission in Breeder Quails Under Heat Stress

Biological Trace Element Research - This experiment was carried out to investigate the combination effects of organic and inorganic chromium (Cr) on egg production, egg quality, reproductive...