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Biomass is one of the most feasible renewable alternatives to fossil fuels. Given this fact, this study aims to demonstrate that buriti fruit wastes (pits and husks) are a promising new feedstock for bioenergy production via thermochemical conversion. To evaluate the suitability of buriti pits and husks for bioenergy generation, their physicochemical properties, performance indices, and pyrolytic behavior were evaluated based on ultimate, proximate, and calorimetry analyses, emission factors, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM images), energy dispersive spectrometry (EDS), thermal analysis (TG/DTG/DSC curves), and devolatilization index (DI). In addition, the mineral and metal contents were quantified by inductively coupled plasma optical emission spectroscopy (ICP-OES). The buriti wastes exhibited low ash (< 3.2%) and moisture contents (< 13.0%), a high heating value (HHV) of 16.11–20.61 MJ kg−1, negligible nitrogen content (< 1.2%) and sulfur (non-detected), and lower carbon dioxide (1236–1244 g kg−1) and nitrogen oxides (3.32–3.95 g kg−1) emission factors than those of reference fuels. The physicochemical properties of buriti pits and husks were consistent with those of other agroforestry and agroindustrial biomasses. The DI of 1.47 and 5.27 × 10−8 mg min−1 °C−3 (or 0.35 and 1.17 ×10−6% min−1 °C−3) of buriti pits and husks, respectively, revealed the main difference between the thermal performance and suitability of buriti pits and husks for the partial or total replacement of fossil fuels. The buriti wastes displayed exceptional performance under direct combustion, and a comparison of buriti pits and husks highlighted the remarkable suitability of buriti pits for pyrolysis, probably due to the oleaginous nature of the material. • Buriti pits and husks were assessed for physicochemical and thermal properties. • Buriti wastes employment reduced 38.00% of gaseous emissions when compared to coal. • Buriti seeds presented a suitable pyrolytic behavior than reference fuels. • Buriti husks presented higher fixed carbon content compared to buriti pits. [ABSTRACT FROM AUTHOR]

Paper and pulp mills generate substantial quantities of cellulose-rich sludge materials that are disposed in landfills at a large scale. For sustainability purposes, sludge materials can be bioprocessed to produce renewable fuels and useful chemicals. The enzymatic hydrolysis of cellulose is the process bottleneck that affects the conversion economics directly by using zero-cost raw materials. In order to study and optimize the process, the characteristics of the sludge raw materials should be first evaluated. In this work, sludge samples were obtained from paper mills located at different locations in Wisconsin and Minnesota. Part of the sludge samples was washed (de-ashed) with hydrochloric acid while the other part remained unwashed. The samples were subjected to multiple spectroscopic analyses techniques to evaluate the morphological properties of cellulose fibers and to estimate the total structural carbohydrate content. The results showed that the de-ashing process changed some fiber characteristics and cellulose crystallinity structure in all sludge samples. Sludge sample A (obtained from Kraft pulp and recycled paper mill region) showed a high percentage of fiber, with crystalline cellulose, compared to the other two sludge samples suggesting that sludge A is a valuable source to make value-added products. Aspen Plus mass and energy calculations performed in view of the 'zero' cost and the reliable supply of sludge raw materials producing 2 mol H 2 /mol glucose. Moreover, the results showed that extracting crystalline cellulose from these sludge samples is more profitable than crystalline cellulose made from the other lignocellulosic feedstocks. The results reported here showed that the utilization of these sludge materials would be an economically attractive and promising alternative for the production of hydrogen. Image 1 • A new method for paper mill sludge (PMS) characterization as renewable feedstock. • The deashing step has a major effect on the bioconversion of the PMS. • Studying the crystalline cellulose of the PMS. • A relation between the characterization and potential sugar yield was established. [ABSTRACT FROM AUTHOR]

• Hydrothermal pretreatment improves the anaerobic digestion of pepper plant and eggplant. • The highest solubilization of C and N is obtained at 40 min of pretreatment. • Hydrothermal treatment improves methane production with an optimum of 84.5 mL STP CH 4 /g VS. Plant residues are an important source of organic matter that can be degraded by aerobic or anaerobic biological processes. However, due to the presence of lignocellulosic material, these residues are not easily biodegradable. Greenhouse crops, such as pepper and eggplant, generate large amounts of this type of waste after harvesting. In this study, a hydrothermal pretreatment was applied at 120 °C and different times to evaluate the enhancement of C and N solubilization in these residues. The highest solubilization of C was obtained at 40 min, as no significant increases were observed at higher times (100% and 68% for pepper plant [PP] and eggplant [EP], respectively). The solubilization of N shows a linear behavior (PP r2 = 0.9670 and EP r2 = 0.9395). Aerobic and anaerobic biodegradability were also evaluated, with better results found for the anaerobic digestion of the pretreated substrates. The nutrients balance with anaerobic co-digestion of both pretreated substrates (50:50% wt) improved methane production by 1.4 and 1.8 with respect to the substrates individually. [ABSTRACT FROM AUTHOR]

Highlights • N rate exhibited non-significant effects on biofuel feedstock quality indices but significantly improved TEY. • CP content and protein yield as forage quality increased with application of 60 kg N ha−1. • Late summer harvest provides best quality forage while early fall harvest supplied more TEY. • Soil NO 3 − content at early fall harvest increased with increasing N rate. • A lower N rate was suitable to produce quality forage or feedstock and to avoid NO 3 − leaching on sandy soil. Abstract Switchgrass (Panicum virgatum L.) is a perennial warm-season grass which has great potential as a forage or bioenergy crop in marginal land. This study was conducted to determine whether nitrogen (N) fertilization could affect biomass quality of switchgrass harvested in late summer and early fall. The effects of four N fertilizer application rates (0, 60, 120, and 240 kg N ha−1) and two harvest times (late summer and early fall) on the quality components of forage and biofuel feedstock and theoretical ethanol yield (TEY) were investigated on a sandy wasteland (Aridisol) in Inner Mongolia, China during the growing seasons of 2015 and 2016. Soil NO 3 − content was also examined in response to N application rates. Application of 60 kg N ha−1 significantly increased switchgrass crude protein (CP) content, protein yield, and TEY (p < 0.05), but did not affect other quality parameters of forage and biofuel feedstock. Compared with the late summer harvest, CP content and protein yield were significantly lower, while TEY was significantly higher in the early fall harvest (p < 0.05); however, cellulose, hemicellulose, and ash contents showed no significant differences between the two harvest times. Acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents were significantly lower for harvest in early fall than in late summer (p < 0.05). Soil NO 3 − content in early fall harvest increased significantly with increasing N application rate (p < 0.05), and was lower than that in the switchgrass green-up stage. These findings together with our results on biomass yield and apparent soil N balance suggest that a lower rate of N application appears sufficient to produce good quality forage as well as biomass without negatively affecting feedstock quality, while avoiding the risk of NO 3 − loss via leaching on a sandy soil. Switchgrass forage quality would be high during summer in terms of CP content, although delaying harvest until fall or even after a killing frost could provide better quality feedstock for bioenergy production. [ABSTRACT FROM AUTHOR]

Highlights • Cordgrass state average yields are 4.9 t/ha with break-even prices of $274/t. • Switchgrass state average yields are 5.8 t/ha with break-even prices of $271/ha. • Miscanthus yields average 4.0 t/ha with break-even prices of $272/t. • Average yields are lower than other parts of the U.S. and Canada. • Average break-even prices are expensive limiting investment attractiveness. Abstract Large scale industrial biomass efforts, whether in pursuit of cellulosic bioethanol, or combustion, will require amounts of feedstock in excess of available crop residues, leading to considerations of purpose grown agricultural biomass. This study determines the yields and break-even prices of perennial grass biomass crops in the state of North Dakota using bioeconomic GIS-based simulation modelling to address the uncertainty surrounding investments in biomass feedstock, particularly in northern climates and the Northern Great Plains. Cordgrass state average yields are 4.9 t/ha with break-even prices of $274/t. Switchgrass state average yields are 5.8 t/ha with break-even prices of $271/t. Miscanthus yields average 4.0 t/ha with break-even prices of $272/t. Average yields are lower than other parts of the United States and Canada, with Miscanthus suffering from significant potential winterkill. Average break-even prices are expensive, limiting the attractiveness of industrial scale investments in perennial grass biomass in the Northern Great Plains and other northerly climates. [ABSTRACT FROM AUTHOR]

Managed forests in southern U.S. are a potential source of lignocellulosic biomass for biofuel production. Changes in management practices to optimize biomass production may impact the quality of waters draining to nutrient-sensitive waters in coastal plain regions. We investigated shallow groundwater quality effects of intercropping switchgrass ( Panicum virgatum L.) with managed loblolly pine ( Pinus taeda L.) to produce bioenergy feedstock and quality sawtimber in a poorly drained soil of eastern North Carolina, U.S.A. Treatments included PINE (traditional pine production), PSWITCH (pine-switchgrass intercropped), SWITCH (switchgrass monoculture) and REF (mature loblolly pine stand). Each treatment was replicated three times on 0.8 ha plots drained by parallel-open ditches, 1.0–1.2 m deep and 100 m apart. Water samples were collected monthly or more frequently after fertilizer application. Water samples were analyzed for organic nitrogen (ON), ammonium N (NH 4 + - N), and nitrite+nitrate N (NO 3 − + NO 2 − - N), ortohophosphate phosphorus (OP), and total organic carbon (TOC). Overall, PSWITCH did not significantly affect shallow groundwater quality relative to PINE and SWITCH. ON, NO 3 − + NO 2 − - N, and TOC concentrations in PSWITCH, PINE and SWITCH were substantially elevated during the two years after tree harvest and site establishment. The elevated nutrient concentrations at the beginning of the study were likely caused by a combination of rapid organic matter decomposition of the abundant supply of post-harvest residues, warming of exposed soil surfaces and reduction of plant nutrient uptake that can occur after harvesting, and pre-plant fertilization. Nutrient concentrations returned to background levels observed in REF during the third year after harvest. [ABSTRACT FROM AUTHOR]

Pyrolysis temperature is known to affect the potential of biochar as a nutrient-holding soil amendment, but the mechanism is unclear. In this study, physiochemical properties of biochar derived from switchgrass, water oak and biosolid at different pyrolysis temperatures were characterized using multiple techniques. In addition, biochar sorption of nitrogen nutrients in forms of ammonium (NH 4 + ), nitrite (NO 2 − ) and nitrate (NO 3 − ) was investigated. The results indicated that the profound effects of pyrolysis temperature on biochar physiochemical properties were feedstock-specific. Similarly, biochar derived from different feedstocks at different temperatures exhibited different strengths to retain NH 4 + , NO 2 − and NO 3 − . The maximum NH 4 + retention capacities were found with the biochar of switchgrass produced at 800 °C (10.47 mg g −1 ), biochar of water oak at 400 °C (3.82 mg g −1 ), and raw biosolids (43.29 mg g −1 ). Meanwhile, biochar was found to have limited (switchgrass and water oak) and negative (biosolids) retention for NO 2 − and NO 3 − . The cation exchange capacity (CEC) and morphological characteristics (e.g., porosity) were found to be the predominant factors affecting biochar NH 4 + sorption. [ABSTRACT FROM AUTHOR]

Switchgrass is a promising bioenergy feedstock, but industrial-scale production may lead to negative environmental effects. This study considers one such potential consequence: the life cycle monetized damages to human health from air pollution. We estimate increases in mortality from long-term exposure to fine particulate matter (PM 2.5 ), which is emitted directly (“primary PM 2.5 ”) and forms in the atmosphere (“secondary PM 2.5 ”) from precursors of nitrogen oxides (NO x ), sulfur oxides (SO x ), ammonia (NH 3 ), and volatile organic compounds (VOCs). Changes in atmospheric concentrations of PM 2.5 (primary + secondary) from on-site production and supporting supply chain activities are considered at 2694 locations (counties in the Central and Eastern US), for two biomass yields (9 and 20 Mg ha −1 ), three nitrogen fertilizer rates (50, 100, and 150 kg ha −1 ), and two nitrogen fertilizer types (urea and urea ammonium nitrate). Results indicate that on-site processes dominate life-cycle emissions of NH 3 , NO x , primary PM 2.5 , and VOCs, whereas SO x is primarily emitted in upstream supply chain processes. Total air quality impacts of switchgrass production, which are dominated by NH 3 emissions from fertilizer application, range widely depending on location, from 2 to 553 $ Mg −1 (mean: 45) of dry switchgrass at a biomass yield of 20 Mg ha −1 and fertilizer application of 100 kg ha −1 N applied as urea. Switching to urea ammonium nitrate solution lowers damages to 2 to 329 $ Mg −1 (mean: 28). This work points to human health damage from air pollution as a potentially large social cost from switchgrass production and suggests means of mitigating that impact via strategic geographical deployment and management. Furthermore, by distinguishing the origin of atmospheric emissions, this paper advances the current emerging literature on ecosystem services and disservices from agricultural and bioenergy systems. [ABSTRACT FROM AUTHOR]

This research combines Geographic Information Systems (GIS) and Mixed Integer Programming (MIP) model to determine feedstock supply, preprocessing facility, and biorefinery locations at a highly resolved spatial scale with the objective of meeting a large-scale annual biofuel production and demand goal for Tennessee, USA. Simultaneous determination of this supply chain network using MIP is computationally expensive. Memory limitation of typical personal computers constrain the network problem. High Performance Computing environments may require days to solve, and without any assurance of a feasible solution. This paper proposes a two-stage optimization procedure to overcome these computational challenges while maintaining theoretical consistency with conventional firm location theory paradigms. The two-stage procedure assumes that firms first identify biorefinery locations with comparative advantage in terms of supplying biomass. Step two entails determining if costs can be lowered with the addition of preprocessing facilities, and their optimal location relative to the biorefinery sites. In contrast, a single step optimization procedure siting multiple biorefineries and concomitantly preprocessing units and biomass supply areas assumes a different strategy for a single firm. Results suggest that the two-stage optimization approach is able to identify a feasible solution of multiple feedstock areas, feedstock preprocessing and fuel production locations using high-resolution spatial layers over a relatively large geographic region in a fraction of the computer resources required to solve a single, simultaneous location problem. The optimal supply chain network solutions generated from the two-stage and single simultaneous approaches are different. The absolute difference in the smaller scaled models’ objective values is less than 1%. [ABSTRACT FROM AUTHOR]

Producing renewable fuel from dedicated energy crops, such as switchgrass, has the potential to generate localized environmental benefits. This study uses high-resolution spatial data for west Tennessee to quantify the effects of producing switchgrass for cellulosic ethanol on the grey water footprint (GWF), or the amount of freshwater needed to dilute nitrate leachate to a safe level, relative to existing agricultural production. In addition, the estimated cost and GWF are incorporated in a mixed-integer multi-objective optimization model to derive the efficient frontier of the feedstock supply chain and determine a switchgrass supply chain that achieves the greatest reduction in GWF at the lowest cost. Results suggest that background nitrate concentration in ambient water and the types of agricultural land converted to switchgrass production influence the extent of the GWF. The average GWF of switchgrass in the study area ranges between 131.8 L L −1 and 145.9 L L −1 of ethanol, which falls into the range of estimated GWF of other lignocellulosic biomass feedstock in the literature. Also, the average cost of reducing GWF from the feedstock supply chain identified by the compromise solution method is $0.94 m −3 in the region. A tradeoff between biofuel production costs and reduced nitrate loading in groundwater is driven by differences in the agricultural land converted to feedstock production. Our findings illustrate the energy-water-food nexus in the development of a local bioenergy sector and provide a management strategy associated with land use choices for the supply of energy crops. However, the water quality improvements associated with displacing crop with feedstock production in one region could be offset by expanded or more intensive agricultural production in other regions. [ABSTRACT FROM AUTHOR]

Environmental concerns and energy security have led to growing interest to second-generation biofuel production from non-edible feedstock such as switchgrass. In this article, sustainable and ecological indicators are introduced to evaluate the candidate locations efficiency for switchgrass cultivation. To optimize the candidate locations, a novel data envelopment analysis (DEA) cross-efficiency model is proposed which attempts to maximize output worst-cases of all candidate locations. Moreover, in order to consider both mean and standard deviation of candidate locations cross-efficiencies, a new ranking measure is presented. The performance of proposed model is investigated in comparison with several models through a real case study in Iran. The efficiency values of Iran provinces are calculated by several DEA cross-efficiency models. The numerical results show that proposed model manages to evaluate the candidate locations efficiency more moderate than other models. Besides, the standard deviation of cross-efficiencies for this model are lower than that of other models. The obtained findings from introduced DEA model reveal that based on the defined ranking measures, Khouzesan and Fars provinces are non-dominate locations for switchgrass cultivation. [ABSTRACT FROM AUTHOR]

Ongoing severe drought and increased demand for freshwater by municipal and industrial sectors have reduced the freshwater availability for agriculture in the far west Texas region. The region has enormous potential for developing alternative water sources for a bioenergy crop that requires less water and can grow on saline soils. In addition to improving farm income, this can help in producing 137 billion liters of bio-based transportation fuels goal set by the U.S. Congress by the year 2022. This study evaluated switchgrass ( Panicum virgatum L.) performance under treated urban wastewater irrigation on salt affected soils amended with gypsum and polymer using soil columns prepared from a salt affected land over six years under greenhouse conditions that mimicked the climatic conditions of the study region. Results indicated that switchgrass produced appreciable biomass even under highly saline and sodic conditions. Qualities of biomass under treated urban wastewater were comparable to that produced under freshwater irrigation. Expectedly, soil salinity increased with time at a greater rate under wastewater irrigation than freshwater. Soil SAR values were below threshold when adequate Ca was available to counter sodicity. In addition irrigation with treated wastewater improved nitrogen and potassium status in the root zone. This can reduce of cost of fertilization and increase farm profitability. [ABSTRACT FROM AUTHOR]

Perennial herbaceous biofeedstocks (PHB) have been proposed to confer multiple ecosystem services to agricultural lands. However, the role of PHBs to affect change in soil condition is not well documented, particularly for treatments with multiple species. The objective of this study was to quantify potential changes to soil properties resulting from PHB treatments in central and western North Dakota over a 5-yr period. Treatments with multiple perennial plant species were hypothesized to induce greater improvements in soil condition compared to monocultures. Soil properties were evaluated in seven PHB treatments (four monocultures, three mixtures) at five sites with sampling occurring immediately prior to treatment establishment in 2006 and again in 2011 across a 0 to 1.2 m depth. Perennial herbaceous biofeedstocks had minor and inconsistent effects on soil bulk density, electrical conductivity, and soil pH, and no effect on available P and soil organic C (SOC) in 2011. Contrasts between monoculture and mixtures in 2011 yielded no significant differences for any soil property at any site. However, PHB treatments did induce significant changes in soil properties between 2006 and 2011, with substantial declines in available P (> 10 kg P ha − 1 yr − 1 ) at sites with high initial P and modest increases in SOC (0.9–5.7 Mg C ha − 1 yr − 1 ) at sites with low initial SOC. Electrical conductivity decreased at two sites, though changes were minor (− 0.08 to − 0.18 dS m − 1 ). Soil pH did not change over the 5-yr study. Results from this study underscore the value of PHBs to remediate nutrient-laden and/or degraded soils, while concurrently resisting increased salinity and fertilizer-induced acidification. [ABSTRACT FROM AUTHOR]

This study assesses the supply of switchgrass and miscanthus, in Ontario, Canada, under different biomass prices and supply chain structures, using an integrated economic, biophysical and GIS model, to assess bioenergy policy. In a local, domestic supply chain, 4 million tonnes of baled biomass production per year becomes attractive for transport to the Nanticoke Generation Station at $69/t. For a larger scale export supply chain to Rotterdam in the form of biomass pellets aggregated on the farm, 20 million tonnes of production becomes attractive at approximately $198/t. For an export supply chain with aggregation at the major ports of Ontario, 20 million tonnes of baled biomass product is attractive for shipping to ports, with pellets subsequently transported to Rotterdam, at around $137/t. Higher bale transportation costs mean that agricultural lands closer to ports, but with lower yields, are preferred compared to the on-farm aggregation scenario. Given government incentives to ease the transition between annual and perennial crops and an actual realized demand from the Nanticoke Generation Station for biomass, this supply chain scenario is plausible. However, export scenarios are not attractive due to infrastructure constraints from current pellet processing capacity, and volatile international energy and commodity markets. [ABSTRACT FROM AUTHOR]

[Display omitted] • Herein, sustainable transformation of feedstock materials into high-value biodiesel is discussed. • Catalytic and non-catalytic transesterification of feedstock materials presents noteworthy benefits. • Biodiesel, as a low-emissions diesel, is noteworthy supernumerary fuel made from recyclable resources. As fossil fuels have been depleting, there is a need to develop an alternative fuel to meet the possible future energy shortage. Biodiesel is one of the most promising resources that has recently emerged. A thorough review has been conducted in this paper to highlight various aspects of the biodiesel, such as biodiesel feedstocks, production methods, properties and qualities of biodiesel, problems and potential solutions of using vegetable oil, advantages and disadvantages of biodiesel, the economic viability and finally the future of biodiesel. Various feedstock materials have been explored, such as non-edible oils like Jatropha curcas and Calophyllum inophyllum and, more recently, microalgae and genetically engineered plants such as poplar and switchgrass. Various production methods such as dilution, pyrolysis, microemulsion, and transesterification have been discussed, highlighting their merits and demerits. Out of these methods, the transesterification process is a better option for production and lowering production costs. The most sustainable way to produce biodiesel is via catalytic and non-catalytic transesterification processes. Various types of catalysts such as homogeneous & heterogeneous acid/basic, mixed, and enzymatic have been investigated to compare their catalytic potential in transesterification. [ABSTRACT FROM AUTHOR]

This study examined the effects of mild sodium carbonate (Na 2 CO 3 ) pretreatment on enzymatic hydrolysis of different feedstocks (i.e., corn stover, Miscanthus , and switchgrass). The results showed that sodium carbonate pretreatment markedly enhanced the sugar yields of the tested biomass feedstocks. The pretreated corn stover, Miscanthus , and switchgrass gave the glucose yields of 95.1%, 62.3%, and 81.3%, respectively, after enzymatic hydrolysis. The above glucose yields of pretreated feedstocks were 2–4 times that of untreated ones. The pretreatment also enhanced the xylose yields, 4 times for corn stover and 20 times for both Miscanthus and switchgrass. Sodium carbonate pretreatment removed 40–59% lignin from the tested feedstocks while preserving most of cellulose (<5% cellulose loss). Corn stover appeared to be least resistant to breakdown by Na 2 CO 3 and enzymatic hydrolysis. Our study indicated that mild sodium carbonate pretreatment was effective for reducing biomass recalcitrance and subsequently improving the digestibility of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Biofuel can be a potential supplement to fossil fuel and help in meeting increasing energy demand of the USA as well as rest of the world. However, it is important for the biofuel to be economically competitive and energy efficient to be established as a promising energy source. There has always been an argument about energy efficiency of biofuel production. Some studies have claimed that it requires more energy to produce ethanol then it actually produces as an output. The objective of the study is to determine energy efficiency of growing two potential cellulosic feedstock; switchgrass and Miscanthus and conversion them in to cellulosic ethanol. Energy efficiency was determined by calculating Net Energy Value (NEV), the difference between output energy obtained by ethanol and input energy used in producing ethanol. Input energy consisted of energy required to produce the cellulosic biomass, transporting it to the ethanol processing facility and processing cellulosic biomass in to ethanol. The analysis showed positive The NEV for both switchgrass and Miscanthus . NEV for Miscanthus (12.41 MJ/l of ethanol) was higher in compared to the switchgrass (7.90 MJ/l of ethanol). Monitory benefits of energy savings were also estimated to determine the impact of energy saving to the society. Results from this research showed both switchgrass and Miscanthus as potential biomass feedstock for cellulosic ethanol production. [ABSTRACT FROM AUTHOR]

Feedstock quality mainly depends upon the biomass composition and bioenergy conversion system being used. Higher cellulose and hemicellulose concentrations are desirable for biochemical conversion, whereas higher lignin is favored for thermochemical conversion. The efficiency of these conversion systems is influenced by the presence of high nitrogen and ash concentrations. Switchgrass ( Panicum virgatum L.) varieties are classified into two ecotypes based on their habitat preferences, i.e., upland and lowland. The objectives of this study were to quantify the chemical composition of switchgrass varieties as influenced by harvest management, and to determine if ecotypic differences exist among them. A field study was conducted near Ames, IA during 2012 and 2013. Upland (‘Cave-in-Rock’, ‘Trailblazer’ and ‘Blackwell’) and lowland switchgrass varieties (‘Kanlow’ and ‘Alamo’) were grown in a randomized block design with six replications. Six biomass harvests were collected at approximately 2-week intervals each year. In both years, delaying harvest increased cellulose, hemicellulose and lignin concentrations while decreasing nitrogen and ash concentrations in all varieties. On average, Kanlow had the highest cellulose and hemicellulose concentration (354 and 321 g kg −1 DM respectively), and Cave-in-Rock had the highest lignin concentration (33 g kg −1 DM). The lowest nitrogen and ash concentrations were observed in Kanlow (14 and 95 g kg −1 DM respectively). In general, our results indicate that delaying harvest until fall improves feedstock quality, and ecotypic differences do exist between varieties for important feedstock quality traits. These findings also demonstrate potential for developing improved switchgrass cultivars as bioenergy feedstock by intermating lowland and upland ecotypes. [ABSTRACT FROM AUTHOR]

Corn ( Zea mays L.) residues and perennial C 4 grasses are two Midwest bioenergy feedstock candidates due to their compatibility with agricultural infrastructure and potential for ecosystem service delivery. We validated the ecosystem process model AGRO-BGC by comparing model estimates with empirical observations from corn and perennial C 4 grass systems across Wisconsin and Illinois under no-tillage, nitrogen fertilized, and unfertilized management. Validation parameters included soil organic carbon (SOC), total soil nitrogen (N) to 1.2 m, aboveground net primary productivity (ANPP), net ecosystem productivity (NEP), and leaf area index (LAI). We parameterized AGRO-BGC to represent ecophysiological characteristics of corn and perennial prairie grasses, and constructed scenarios to represent corresponding edaphic, climate, and management conditions. Unfertilized annual model estimates had normalized mean average errors relative to field measurements of 0.3, 23, and 4 t ha −1 for ANPP, SOC, and N, respectively. Fertilized simulations erred from observations by 0.6, 29, 5 t ha −1 for ANPP, SOC, and N, respectively. We also estimated long-term implications of varying residue removal rates on SOC. Model estimates compared to field data tested the hypothesis that long-term increased residue removal decreases SOC. Field observations showed 0.17, 0.09, and a −0.17 t C ha −1 yr −1 change for control, harvest, and bare grass residue removal treatments, respectively. Simulated SOC loss was greatest for the most intensive residue removal scenarios (−0.48 and −0.68 t C ha −1 yr −1 for corn and grass, respectively), compared to no-harvest scenarios that increased SOC by 0.05 t C ha −1 yr −1 for both corn and grass. AGRO-BGC estimated a 0.07 t C ha −1 yr −1 loss under corn residue harvest, while estimating 0.09 t C ha −1 yr −1 loss for grass. Results suggest long-term increased corn and grass residue harvest (beyond grain) for biofuel feedstock will decrease SOC and soil productivity by approximately 15% in corn and 21% in grass systems over 47 years. [ABSTRACT FROM AUTHOR]

Switchgrass ( Panicum virgatum L.) intercropped with Loblolly pine ( Pinus taeda L.) has been proposed as a potential biomass feedstock for biofuel production in the southeastern United States. This study investigated effects of treatments (intercropping vs . grass only) on biomass increment processes and morphological properties of switchgrass at two experimental plots (Lenoir1) located in the coastal plain of North Carolina. We also evaluated effects of trimming lower tree branches of pine trees on switchgrass growth at another watershed-scale site (Carteret7) in the same region. Results showed that biomass yield of intercropped switchgrass was reduced by adjacent trees and negatively affected by relative position of grass to trees at the 6th year after planting at Lenoir1. Relative grass-to-tree position was also found to be a significant (p < 0.001) factor affecting grass growth at Carteret7 site with tree age of 5 years old, which is irrespective to the trimming practice. Trimming lower tree branches did not significantly (p = 0.57) improve biomass yield of switchgrass at Carteret7. We also observed intercropped switchgrass typically had higher specific leaf area and grew taller compared to grass-only plots. Stem-to-leaf ratios of switchgrass were significantly (p = 0.02) affected by trees at Lenoir1, but not by trimming lower branches in Carteret7 and relative position of grass to trees at both study sites. Findings from this study are important for evaluating the viability of producing biofuel feedstocks using this proposed intercropping system in the southeastern United States. [ABSTRACT FROM AUTHOR]

Currently we lack knowledge on how the soil microbial community responds to the transition from traditional grain production to cellulosic feedstock production systems with residue removal for biofuel production. Implementation of second-generation biofuel production systems could create a challenge in meeting the goal of providing cellulose biomass if the processes impact soil's function as part of ecosystem services. Our goal was to assess the transition period as we move from a grain harvest system with residue return into biomass production systems with both residue and grain removal. The existing traditional systems were continuous corn (CC) and corn–soybean rotations (corn–soybean–corn (R1) or soybean–corn–soybean (R2)). The biomass production systems include a previously established mixed tall grass prairie dominated by big bluestem ( Andropogon gerardii ; PR) where the above ground biomass is now harvested when it had been previously burned, corn–soybean rotations transitioned to residue recovery based on: Miscanthus × giganteus (MS), dual-purpose sorghum ( Sorghum bicolor ; SG), upland switchgrass ( Panicum virgatum ; c.v. Shawnee ; SW) and a tilled continuous corn changed to continuous no-till corn ( Zea mays ; CR) with the residue removed. Over a three-year transition period, biological indicators of soil health included microbial biomass and community structure profile using phospholipid fatty acid (PLFA) biochemical markers, and an assessment of the saprotrophic fungal diversity using denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction amplified ITS rRNA genetic marker. Over the course of the transition, bacterial biomass dominated soils in the annual systems of CC, R1, R2, CR and SG, and the perennial system of MS. While fungal biomass dominated soils under PR. Fungal PLFA signatures and ITS-DGGE profiles demonstrated similarity between PR and the transitioned SW system, and to a lesser extent SG. In contrast, MS did not statistically alter the microbial biomass, community structure or fungal diversity away from patterns observed in the corn–soybean system. Our findings support microbial community stability and resilience as we found no negative impacts in any of the biomass recovery systems (PR, MS, SG, SW and CR) relative to the traditional systems (CC, R1 and R2), as indicated by measures of soil health. We did find that the selection of the plant types used in the biomass system could have a significant impact on the structure of both bacterial and fungal communities. With respect to soil health indicators including the fungal community, our findings suggest the dual-purpose SG system provides an encouraging alternative to continuous maize when considering plant biomass production. The selection of this dedicated perennial biomass system offers an avenue to enhance indicators of soil health and associated ecosystem services while supporting the bioenergy economy. [ABSTRACT FROM AUTHOR]

The objective of this paper is to design two types of subsidies for biofuel feedstock production and water quality improvement and to analyze how each subsidy affects biomass supply and the abatement of nutrient runoff associated with the conversion of cropland to biomass production. Per-hectare (per-ha) subsidy was designed as a system that pays producers for each ha of cropland converted to switchgrass production and per-megagram (per-Mg) subsidy was a system that pays producers for each Mg of switchgrass produced. This study focuses on Oostanaula Creek watershed in East Tennessee. The analysis used a dynamic programming model coupled with a Soil and Water Assessment Tool (SWAT) simulation model to predict profit-maximizing fertilizer application rates, crop yields, and nitrogen (N) runoff for a biofuel feedstock (switchgrass) and a conventional crop (corn) across 28 different landscapes in the watershed. A Monte Carlo analysis was conducted to simulate the impact of stochastic N fertilizer and corn prices and yields on subsidies over a ten-year planning horizon. A per-ha subsidy system is more cost effective and feasible than a per-Mg system because the former has significantly lower subsidy than the latter for each kilogram (kg) of N reduction and for each Mg of switchgrass harvested. Converting all of the cropland from corn to switchgrass over ten years results in 124,084 dry Mg of switchgrass and 23% reduction in nitrogen runoff for the per-ha system and 122,347 dry Mg of switchgrass and 3% reduction for the per-Mg subsidy system. [ABSTRACT FROM AUTHOR]

In order to produce clean energy from renewable lignocellulosic biomass, the feedstock must be pretreated by means of one or combined cost-competitive methods to make the entire process economically feasible. Fungal cultivation may be one promising pretreatment approach, for which the effectiveness varies with different fungal strains in regard to biomass loss, sugar yield, enzyme loading, and co-product yield. Wild-type fungus might have a great potential in pretreating feedstock for both lowered enzyme loading and beneficial co-product enzyme production. In this study, 25 diverse fungal strains were screened for pretreatment of switchgrass biomass with regard to co-production of beneficial enzymes and the subsequent saccharification process, by examining switchgrass biomass loss, effectiveness of enzymatic hydrolysis, and ligninolytic activity. The most promising fungus was identified as an inedible mushroom, Agaricus molybdites (H4) with the highest saccharification efficiency and ligninolytic enzyme production. Additionally, eight accessory enzymes, e.g. pectinase, esterase, xylanase, β-glucosidase, chitinase, lipase, α-amylase, and laccase, were found to assist cellulase in enhancing saccharification of H4 pretreated switchgrass to varying degrees. Our experimental results suggest that pretreatment of switchgrass with an appropriate fungus, followed by exposure to cellulase and synergistic accessory enzymes can be an effective strategy for maximizing the process of saccharification. [ABSTRACT FROM AUTHOR]

Improper management of cattle manure and poultry litter from confined animal farming are usually source of water pollution. However, appropriate application of these products on switchgrass ( Panicum virgatum L.) field can enhance biomass yield and promote nutrient recycling. We evaluated the effects of harvest frequency and nutrient sources on yield and quality of switchgrass for biofuel feedstock. The experiment was carried out at Perkins and Lake Carl Blackwell, Oklahoma, from 2009 to 2011 using split plot design with four replications. The main plot treatments were two harvest frequencies single (June), and twice (June and November). The subplot treatments were nutrient sources: 1) cattle manure (CM), 2) poultry litter (PL), 3) urea (nitrogen at 150 kg ha −1 ), 4) combined chemical fertilizer (nitrogen-P 2 O 5 –K 2 O) with nitrogen at 150 kg ha −1 , P 2 O 5 at 40 kg ha −1 , and K 2 O at 20 kg ha −1 , 5) inter-seeded Crimson clover ( Trifolium incarnatum L.), and 6) control. Mean biomass yield was higher (12.4 Mg ha −1 ) in 2010 than other years possibly due to optimum moisture and temperature in 2010. At Perkins in 2010, application of CM and PL increased biomass yield significantly by 30 and 23% compared with combined chemical fertilizer (12.9 Mg ha −1 ). The effect of nutrient sources on cellulose, hemicellulose and lignin content was not significant at both locations. Cumulative biomass from twice harvest was similar to single harvest except in 2011 due to dry weather after the first cut. The cellulose and lignin content were significantly higher for single harvest compared with twice harvest at both locations. [ABSTRACT FROM AUTHOR]

Switchgrass ( Panicum virgatum L.) is a perennial warm-season grass identified as a model species for bioenergy feedstock production. Established switchgrass stands are very resilient to the environmental fluctuations; however, seed dormancy and weak seedling vigor make establishment difficult. Breaking seed dormancy of switchgrass is a first step to reduce risk of establishment failure and the costs associated with reseeding. Many studies have reported a myriad of methods to break seed dormancy of switchgrass, including chemical, mechanical, thermal, and hormonal seed treatments. Length of seed storage, storage conditions (e.g., temperature and humidity), and prior soil conditions (e.g., soil salinity and fertilizer rates) affect switchgrass seed dormancy. Strong interactions exist among germination, seedling emergence, and soil conditions; therefore, treated seeds tested in soil media will generate more accurate results following dormancy breaking techniques. This paper reviews the current methods used to break switchgrass seed dormancy. [ABSTRACT FROM AUTHOR]

The methane yield and microbial community resulting from co-digestion of dairy manure and switchgrass at different mixing ratios [4:0, 3:1, 2:2, 1:3, and 0:4 based on total solids (TS) content] were evaluated. The results indicated that switchgrass is an excellent feedstock for biogas production when co-digested with dairy manure. Mono-digestion of a high dose (>4% TS) of switchgrass led to volatile fatty acid accumulation and process failure, whereas co-digestion of switchgrass and dairy manure could increase the buffering capacity and improve the fermentation efficiency. The optimal mixture ratio of dairy manure and switchgrass was 2:2, with a methane yield that was 39% higher than that obtained by digestion of the individual substrates. The added amount of 8% TS at the 2:2 ratio achieved the highest methane yield of 158.6 mL/g VS, which corresponded to a 1.3-fold increase in the volumetric productivity of methane compared to mono-digestion of 4% TS switchgrass. Quantitative polymerase chain reaction and clone library analyses showed significant differences in the bacterial community resulting from the different co-substrate ratios. Planctomycetes (28%), Chloroflexi (24%), and Bacteroidetes (24%) were the dominant phyla in digesters with a co-substrate ratio of 2:2. [ABSTRACT FROM AUTHOR]

The goal of the study was to evaluate and compare the physical properties of control, pretreated and densified corn stover, switchgrass, and prairie cord grass samples. Ammonia Fiber Expansion (AFEX) pretreated switchgrass, corn stover, and prairie cord grass samples were densified by using the comPAKco device developed by Federal Machine Company of Fargo, ND. The densified biomass were referred as “PAKs” in this study. All feedstocks were ground into three different grind size of 2, 4 and 8 mm prior to AFEX pretreatment and the impact of grinding on pellet properties was studied. The results showed that the physical properties of AFEX-PAKed material were not influenced by the initial grind size of the feedstocks. The bulk density of the AFEX-PAKed biomass increased by 1.2–6 fold as compared to untreated and AFEX-pretreated materials. The durability of the AFEX-PAKed materials were between 78.25 and 95.2%, indicating that the AFEX-PAKed biomass can be transported easily. To understand the effect of storage on the physical properties of these materials, samples were stored in the ambient condition (20 ± 2 °C and 70 ± 5% relative humidity) for six months. After storage, thermal properties of the biomass did not change but glass transition temperature decreased. The water absorption index and water solubility index of AFEX-treated and AFEX-PAKed biomass showed mixed trends after storage. Moisture content decreased and durability increased upon storage. [ABSTRACT FROM AUTHOR]

Lignocellulosic biorefineries that plan to use switchgrass ( Panicum virgatum L.) biomass exclusively will encounter both temporal (across years) and spatial (across locations within a given year) variability in feedstock production. Long term land leases could be employed to facilitate feedstock availability for the expected life of the biorefinery. If the quantity of land leased is based on average yields, in some years more biomass will be produced than can be processed. In other years feedstock production on the leased land may be insufficient to prevent biorefinery downtime. An optimal strategy for identifying which land to lease and seed to switchgrass, while considering yield variability and the opportunity cost of biorefinery downtime, is the focus of the research. The objective is to determine for a given biorefinery location the least-cost quantity, quality, and location of land to lease for alternative estimates of biorefinery downtime cost due to variable switchgrass yields. Fifty years of weather data are used to simulate switchgrass yield distributions for a case study region. An innovative mathematical programming model is developed and used to reveal the cost-efficient D (Downtime Cost) L (Land to Lease) frontier for a 2 Gg d −1 biomass capacity biorefinery. If interyear storage is not permitted, 60,492 ha would be required to insure that the biorefinery run at full capacity every year given the estimated yield distributions. However, for some circumstances, it would be optimal to produce switchgrass on only 49,464 ha and idle the biorefinery for some days in low biomass production years. [ABSTRACT FROM AUTHOR]

To reduce the recalcitrance of lignocellulosic biomass for subsequent biological processing, we pretreated energy crop feedstocks with mild steam treatment (ST; 130 and 150 °C for 60 min) and wet disk milling (WDM). We tested two phylogenetically different, but typical energy crop feedstocks: Populus trichocarpa and switchgrass ( Panicum virgatum ). WDM after ST facilitated the fibrillation of both types of biomass, resulting in an increase of specific surface area, improved enzymatic saccharification yield, and decrease in cellulose crystallinity. After steam treatment at 150 °C followed by 17 cycles of WDM, enzymatic hydrolysis resulted in almost complete glucan to glucose conversion in both feedstocks. [ABSTRACT FROM AUTHOR]

Switchgrass is an attractive feedstock for biogas production via anaerobic digestion (AD). Many studies have used switchgrass for liquid anaerobic digestion (L-AD), but few have used switchgrass for solid-state anaerobic digestion (SS-AD). Limited air exposure to the reactor headspace has been adopted in commercial scale anaerobic digesters for different applications. However, little research has examined the effect of limited air exposure on biogas production during SS-AD. In this study, the effects of air exposure and total solids (TS) content on SS-AD performance were evaluated under mesophilic (36 ± 1 °C) and thermophilic (55 ± 0.3 °C) conditions. Limited air exposure did not significantly influence the methane yield during SS-AD. Thermophilic SS-AD had greater methane yields (102–145 L CH 4 kg −1 VS added ) than mesophilic SS-AD (88–113 L CH 4 kg −1 VS added ). Both mesophilic SS-AD (73–136 GJ) and thermophilic SS-AD (2–95 GJ) produced positive net energy based on a theoretical ‘garage-type’ SS-AD digester operating in a temperate climate. [ABSTRACT FROM AUTHOR]

Marginal and degraded lands are expected to be important resources in the production of biofuel feedstocks in order to avoid real or perceived competition with food, feed and fiber production. Globally, there are millions of hectares of salt-affected land available for lignocellulosic feedstock production. Greenhouse experiments determined the effects of irrigating with water having different levels of salinity and sodicity on seedling emergence, plant growth, and cation balance in plant tissues in several populations of switchgrass ( Panicum virgatum L.) and prairie cordgrass ( Spartina pectinata Link). The effect of salt stress on seedling emergence was more pronounced in switchgrass than prairie cordgrass with 31 and 15% reduction, respectively, compared with pure water. In a two-season greenhouse pot experiment, aboveground dry biomass production in control treatments was 8 and 21% higher in prairie cordgrass pc17-102 and pc17-109, respectively, than in EG 1102 switchgrass. Switchgrass EG 1102 produced greater biomass than prairie cordgrass populations when irrigated with moderately saline (5 dS m −1 ) water, although differences were not detected with highly saline water (10 dS m −1 ). Switchgrass EG 2101 emergence, plant growth and cation balance were severely affected by increasing levels of salinity. Overall, several prairie cordgrass populations and lowland switchgrass cultivars were found to have good emergence and high biomass production under moderate to high salt stress and may be good candidates for lignocellulosic feedstocks on salt-affected land. [ABSTRACT FROM AUTHOR]

The objective of this study was to estimate the storage dry matter (DM) losses for switchgrass bales that were preprocessed using an industrial baler technology prior to storage with three particles sizes of feedstock and two types of bale wraps. Mixed models were used to test difference in DM losses across the particle sizes, wrap materials, and storage days. Response functions were also estimated to determine DM losses for each particle size and wrap material at storage over time. DM losses were found to be different across particle size, wrap material, and storage period. Specifically, the DM losses were lower when the particle size of switchgrass baled decreased from full length to less than two centimeters. The results show switchgrass bales stored at the smallest particle size had lower DM losses than bales stored at the full length of feedstock. Also, applying additional film wrap that completely covers the net wrapped bale reduced DM losses relative to bales wrapped only in net. Furthermore, storage DM losses of preprocessed switchgrass bales increased linearly with days in storage. Our findings suggest that applying both net and film wrap to switchgrass bales composed by a particle size less than two centimeters can reduce DM losses during storage. Economic analysis indicates the price of switchgrass was also important in the choice of storage method for switchgrass. The results provide valuable insight into improving feedstock logistics and the feasibility of the advanced biofuels industry. [ABSTRACT FROM AUTHOR]

Lignin, isolated from switchgrass ( Panicum virgatum ) and tulip poplar ( Liriodendron tulipifera ) using organosolv fractionation is currently being explored for its potential use in the production of value-added chemicals and bio-based polymers. Taguchi Robust Product Design (TRPD) was applied to maximize lignin yield from the fractionation process. The following four controllable design factors were used in the TRPD: process temperature (120 °C, 140 °C and 160 °C), fractionation time (56 and 90 min), sulfuric acid concentration (0.025 M, 0.05 M and 0.1 M), and feedstock type (switchgrass/tulip poplar chip ratios of 10/90, 50/50 and 90/10). Process noise was induced in the experiment by using either the mass- or volume-based feedstock charges of switchgrass and tulip poplar chips. A maximum mean lignin yield of 78.63 wt% and signal-to-noise ratio of 37.90 was found at a 90 min runtime, a process temperature of 160 °C, a sulfuric acid concentration of 0.1 M, and a feedstock composition of 10% switchgrass and 90% tulip poplar. Process temperature was the most significant factor that influenced lignin yield. This study may provide a pathway for industrialists and researchers interested in maximizing lignin yield in the organosolv fractionation process. [ABSTRACT FROM AUTHOR]

Switchgrass is being evaluated as a potential feedstock source for cellulosic biofuels and is being cultivated in several regions of the United States. The recent availability of switchgrass land cover maps derived from the National Agricultural Statistics Service cropland data layer for the conterminous United States provides an opportunity to assess the environmental conditions of switchgrass over large areas and across different geographic locations. The main goal of this study is to develop a data-driven multiple regression switchgrass productivity model and identify the optimal climate and environment conditions for the highly productive switchgrass in the Great Plains (GP). Environmental and climate variables used in the study include elevation, soil organic carbon, available water capacity, climate, and seasonal weather. Satellite-derived growing season averaged Normalized Difference Vegetation Index (GSN) was used as a proxy for switchgrass productivity. Multiple regression analyses indicate that there are strong correlations between site environmental variables and switchgrass productivity ( r = 0.95). Sufficient precipitation and suitable temperature during the growing season (i.e., not too hot or too cold) are favorable for switchgrass growth. Elevation and soil characteristics (e.g., soil available water capacity) are also an important factor impacting switchgrass productivity. An anticipated switchgrass biomass productivity map for the entire GP based on site environmental and climate conditions and switchgrass productivity model was generated. Highly productive switchgrass areas are mainly located in the eastern part of the GP. Results from this study can help land managers and biofuel plant investors better understand the general environmental and climate conditions influencing switchgrass growth and make optimal land use decisions regarding switchgrass development in the GP. [ABSTRACT FROM AUTHOR]

High cost of technology is seen as the primary barrier to full commercialization of cellulosic biofuels. There is broad expectation that once conversion technology breakthroughs occur, policy support is only needed to accelerate cost reductions through “learning by doing” effects. In this study, we show that droughts pose a significant economic risk to biofuel producers and consumers regardless of the rate at which technology costs fall. We model a future switchgrass derived cellulosic biorefinery industry in Kansas based on spatially resolute historic (1996–2005) weather data, representing a rainfall regime that could reflect drought events predicted to occur throughout the U.S. Midwest by climatologists (Karl et al. (2009) U.S. Global Change Research Program USA). We find that droughts reduced modeled biorefinery capacity factors, on average, by 47%, raising biofuel production costs by 35% between a modeled dry and wet year. Interestingly, we find that two logical strategies to plan for drought; (1) building large biorefineries to source feedstock from a larger area and, (2) Storing switchgrass in good production years for use in drought years; are not very effective in reducing drought risks. Our findings should be of particular concern to low carbon fuel policies like California's Low Carbon Fuel Standard and the U.S. Second Renewable Fuel Standards (RFS2) whose costs of compliance may be much higher than expected. [ABSTRACT FROM AUTHOR]

Highlights: [•] We model field-to-biorefinery dedicated energy crop production and delivery cost. [•] We determine cost to produce and deliver switchgrass and forage sorghum biomass. [•] Estimated costs of delivering a flow of switchgrass is less than for forage sorghum. [•] The cost difference is primarily due to differences in harvest costs. [•] Harvest cost are influenced by the length of the harvest window. [ABSTRACT FROM AUTHOR]

Biofuel production from second-generation feedstock has become critical due to environmental concerns and the need for sustainable energy supply. This paper provides a unique optimization approach of quantifying and formulating the economic and environmental benefits of switchgrass production at the farm level. In particular, we propose a multi-objective mixed-integer programming model, which maximizes the revenue from harvested switchgrass biomass and the economic value obtained from the positive environmental impacts of switchgrass yield during a ten-year planning horizon. Environmental impacts include soil erosion prevention, sustainability of bird populations, carbon sequestration, and carbon emissions, while economic impacts are analyzed under various budget, yield, and sustainability scenarios. The proposed model is then applied to a case study in the state of Kansas. Results show that given the current market prices, switchgrass cultivation on grassland and cropland is highly profitable. The model results also suggest that if utilized by the government, conservation reserve program (CRP) incentives could make marginal land more favorable over cropland. We perform sensitivity analysis to address the uncertainty in budget, yield, and utilization of cropland, and present insights into the economic and environmental impacts of switchgrass production. This model can also be extended to biomass production from any other types of energy crops to identify the most efficient production planning strategies under various management scenarios. [ABSTRACT FROM AUTHOR]

Abstract: Limited information is available regarding the change in cost to deliver dedicated energy crop feedstock as the quantity of required feedstock increases. The objective is to determine the marginal cost to produce and deliver switchgrass feedstock to biorefineries. A mathematical programming model that includes 77 production regions (Oklahoma counties), monthly feedstock requirements, integer activities for harvest machines and integer activities for each of 16 potential biorefinery locations was constructed. The model was initially solved for a single biorefinery. The number of plants was incremented by one and the model resolved until nearly 10% of the cropland and improved pasture land was converted to switchgrass. The estimated cost to deliver 1.0 Mg of feedstock to a single 189 dam3 y−1 capacity biorefinery is 55 $. The cost to deliver feedstock increases as additional biorefineries are constructed and the cost for the ninth biorefinery of 87 $ Mg−1 is 58% greater than the cost to deliver to the first biorefinery. The cost difference is primarily due to differences in transportation cost. Initial cellulosic biorefineries will have an opportunity for establishing a feedstock cost advantage by carefully selecting land for conversion to switchgrass and by negotiating long term leases. [Copyright &y& Elsevier]

Highlights: [•] Switchgrass yields were generally not affected by the type of nitrogen fertilizer used. [•] Optimum N rates were variable for different locations, requiring site-specific recommendations. [•] Biomass yields and moisture content were reduced with progressively later harvest timing. [•] Quality of biomass as a bioenergy feedstock was optimized with a winter or spring harvest timing. [Copyright &y& Elsevier]

Abstract: Intercropping biofuel feedstocks in managed forests of the southeastern United States is a potentially sustainable source of renewable energy. Ecological effects of energy crops in forests are poorly understood, and it is unknown whether the ecological role of native rodents is influenced by alternative food resources. Therefore, we used a stable isotope analysis to compare diet and trophic responses of white-footed mice (Peromyscus leucopus) in 1) plots where switchgrass (Panicum virgatum), a C4 plant, was intercropped with loblolly pine (Pinus taeda), a C3 plant, 2) plots of loblolly pine, and 3) plots of monocropped switchgrass. We collected fur from live-trapped rodents and potential dietary sources in 2010. We predicted δ13C and δ15N values of mice in switchgrass plots would reflect a C4-based, granivorous, diet if there was an effect of intercropping on the functional role of mice. Del13C values of mouse fur in monocropped switchgrass, but not intercropped switchgrass plots, shifted more toward a C4 signal. However, δ15N values indicated that mice remained functionally omnivorous across treatments. Our results were supported by isotope values from invertebrates across guilds. Diet and trophic position of white-footed mice was not influenced by intercropping switchgrass in pine plantations indicating they maintained their functional role in this biofuels management regime. Future research should focus on individual and population responses of rodents to altered vegetation structure where biofuels feedstocks are grown and indirect effects on inter- and intra-species interactions. [Copyright &y& Elsevier]

Abstract: In this paper, we present a superstructure optimization approach for the integration of the simultaneous production of liquid fuels and hydrogen from switchgrass and shale gas. The process is based on Fischer-Tropsch technology in which the shale gas is reformed with steam, while the switchgrass is gasified and reformed (with steam or partial oxidation). The raw gas is cleaned up and its composition may be adjusted (using either water gas shift reaction or pressure swift adsorption). Next, the sour gases are removed before the liquid fuels are produced using an FT reactor. The heavy liquids are upgraded using hydrocracking to increase the yield towards FT-diesel. A sensitivity study on the raw material prices reveals that production costs for the biomass-shale gas facility are below $1/gal as long as biomass price is below $100/t and the price of the shale gas is not higher than $11.5/MMBTU. Furthermore, hydrogen is produced as long as the demand for liquid fuels can be met and there is enough shale gas available. [Copyright &y& Elsevier]

Abstract: Bioethanol produced from lignocellulosic feedstock show enormous potential as an economically and environmentally sustainable renewable energy source. Switchgrass (panicum virgatum) is considered as one of the best second generation feedstock for bioethanol production. In order to commercialize the production of switchgrass-based bioethanol, it is essential to design an efficient switchgrass-based bioethanol supply chain (SBSC) and effectively manage the logistics operation. This paper proposes an integrated mathematical model to determine the optimal comprehensive supply chain/logistics decisions to minimize the total SBSC cost by considering existing constraints. A case study based on North Dakota state (ND) in the United States illustrates the application of the proposed model. The results demonstrate that by using only 61% of the available marginal land for production of switchgrass feedstock, 100% of the annual gasoline energy equivalent requirement of ND can be economically and sustainably met from the produced bioethanol. Sensitivity analysis is conducted to provide insights for efficiently managing the entire SBSC and minimizing the total cost. [Copyright &y& Elsevier]

Abstract: Switchgrass was used as a lignocellulosic feedstock for second generation ethanol production, after pretreatment using sulfuric acid-catalyzed modified clean fractionation based on NREL’s (National Renewable Energy Laboratory) original procedure. Optimization of temperature, catalyst concentration and solvent composition was performed using Response Surface Methodology, and 59.03±7.01% lignin recovery, 84.85±1.34% glucose, and 44.11±3.44% aqueous fraction xylose yields were obtained at 140.00°C, 0.46% w/w catalyst concentration, 36.71% w/w ethyl acetate concentration, and 25.00% w/w ethanol concentration. The cellulose fraction did not inhibit the fermentation performance of Saccharomyces cerevisiae and resulted in an ethanol yield of 89.60±2.1%. [Copyright &y& Elsevier]

Abstract: Nitrogen-fixing bacteria (NFB) and other plant growth promoting rhizobacteria (PGPR) have been used to increase growth and yield of corn and sugarcane, two graminaceous crops utilized as bioenergy feedstocks. Switchgrass (SG, Panicum virgatum L.), a native perennial grass of North America, is also a desirable bioenergy crop because it can be grown on marginal lands and thus does not necessarily displace food production. Yet no investigations have been conducted on the use of NFB and/or PGPR as inoculants to increase SG growth and productivity. Studies reporting high biomass yields from SG with minimal to no fertilizer nitrogen (N) input prompted us to hypothesize that SG is obtaining part of its N from an alternative source, perhaps through biological nitrogen fixation from root/rhizome associated PGPR. We isolated bacteria from SG rhizomes that had not received fertilizer N input for over ten years and which increased plant growth in the absence of the fertilizer N under growth chamber conditions. The bacteria were identified as a strain of Paenibacillus polymyxa, a N2-fixing bacterium, and several other PGPR capable of solubilizing phosphate and/or producing auxins. Our objective was to test this PGPR inoculum under field conditions with low-N inputs. Here, we present the findings regarding SG productivity in the establishment year. Switchgrass seeds inoculated with the PGPR culture had greater tiller density, and taller tillers resulting in 40% higher yield than uninoculated plants. PGPR have the potential to be effectively utilized as inoculants to enhance SG yields in a low-N input production system. [Copyright &y& Elsevier]

Abstract: The U.S. Energy Independence and Security Act of 2007 mandates the use, if produced, of 6.06 × 1010 L of advanced biofuels by 2022. The objective of this study is to determine the ethanol price necessary for a biorefinery to breakeven when using switchgrass as the single feedstock to produce ethanol. A holistic model that encompasses acquisition of land use services, feedstock production, harvest, harvest machine investment, feedstock logistics (storage, transportation), biorefinery location and size, and biorefinery investment is constructed and used to determine breakeven ethanol price. The model was solved for each of three biomass to ethanol conversion rates (250, 334, and 417 L of ethanol Mg−1 of biomass) and each of three biorefinery investment cost estimates ($2, $4, and $6 × 108 for a biorefinery with annual capacity of 379 × 106 L). Breakeven ethanol prices ranged from $0.44 L−1 with a conversion rate of 417 L of ethanol Mg−1 and an investment cost of $2 × 108, to $0.72 L−1 with a conversion rate of 250 L Mg−1 and an investment cost of $6 × 108. Improving the efficiency of conversion from 250 to 334 L Mg−1 decreases the estimated breakeven cost by $0. 07 L−1. Improved conversion efficiency results in a reduction of the total quantity of feedstock required and in the cost to deliver feedstock. Most of the cost reduction follows from reductions in land required (rent), and biomass harvest, storage, and transportation costs. [Copyright &y& Elsevier]

Abstract: The production of cellulosic feedstocks for renewable fuels will increase over the coming decades. However, it is uncertain which feedstocks will be best suited for bioenergy production. A key factor dictating feedstock selection for a given region is water use efficiency (WUE), the trade-off between evapotranspiration (ET) and carbon uptake or productivity. Using an ecosystem model, two of the top candidate cellulosic feedstocks, Miscanthus × giganteus (miscanthus) and Panicum virgatum (switchgrass) were compared to Zea mays L. (maize), the existing dominant bioenergy feedstock, with 0 and 25% residue removal for the Midwest US. We determined productivity in three ways: harvested yield (HY), net ecosystem productivity (NEP) and net biome productivity (NBP). Evapotranspiration was compared against each of the three productivity metrics, respectively, to yield Harvest Water Use Efficiency (HWUE), Ecosystem Water Use Efficiency (EWUE) and Biome Water Use Efficiency (BWUE). Simulations indicated that, over the study domain, miscanthus had a significantly higher HWUE compared to switchgrass and maize, while maize and switchgrass were similar. When EWUE was compared miscanthus was higher than both maize and switchgrass, which were similar for most of the region. Biome WUE was similar for both of the perennials and higher compared to maize for most of the study domain with the exception of the driest regions where maize showed the highest BWUE. Removing 25% of maize residue slightly increased HWUE and greatly decreased BWUE throughout the domain, however only HWUE changes were statistically significant. These results indicate that the feedstock with the highest WUE varied based on the productivity metric, but BWUE for maize was consistently lower than the perennials. [Copyright &y& Elsevier]

Abstract: Switchgrass (Panicum virgatum L.) is being evaluated as a bioenergy crop for the northern Great Plains. Field measurements of CO2, CH4, and N2O flux are needed to estimate the net greenhouse gas (GHG) balance of this biofeedstock. The study objective was to determine effects of recommended Nitrogen (N) fertilization (67 kg ha−1 of N applied) and unfertilized switchgrass on growing season soil-atmosphere CO2, CH4, and N2O flux using static chamber methodology. Mean hourly CO2 flux was greatest during periods of active switchgrass growth and was similar between N fertilizer treatments (P = 0.09). Mean hourly N2O flux was consistently greater under N fertilization than without N throughout the growing season. Overall, N fertilization of switchgrass affected cumulative growing-season N2O flux (27.6 kg ha−1 ± 4.0 kg ha−1 vs. 86.3 kg ha−1 ± 14.3 kg ha−1 as CO2 equivalents (CO2eq) for 0 kg ha−1 and 67 kg ha−1 of N applied, respectively; P < 0.01), but not cumulative CO2 or CH4 flux (P = 0.08 and 0.51, respectively). Aboveground biomass production was greater with N application (6.8 Mg ha−1 ± 0.5 Mg ha−1 dry matter) than without N (3.2 Mg ha−1 ± 0.5 Mg ha−1) (P < 0.05). Net greenhouse gas intensity (GHGI; kg GHG flux kg− 1 harvest yield as CO2eq) for switchgrass production was similar between N treatments (0.71 vs. 0.44 for 0 kg ha−1 and 67 kg ha−1 of N applied, respectively; P = 0.18). [Copyright &y& Elsevier]

Abstract: To evaluate the potential of gamagrass as a feedstock for biofuels, seven gamagrass varieties were analyzed for their chemical composition and subjected to pretreatment at 121°C using 1% NaOH/H2SO4 (w/w) for 60min and enzymatic hydrolysis for fermentable sugar production. Based on total sugar yield, the varieties Eagle Point Devil Corn and Sun Devil were selected for NaOH and H2SO4 pretreatment, respectively. The investigation on pretreatment conditions showed that, the conditions applied in gamagrass variety screening (121°C, 1% NaOH/H2SO4, 60min) were sufficient to maximize sugar production, such that the total sugar yield of Eagle Point Devil Corn reached 479.6mgg−1 after NaOH pretreatment and that of Sun Devil reached 456.5mgg−1 raw biomass after H2SO4 pretreatment. Compared with other potential energy crops including switchgrass and Bermuda grass, gamagrass gave a higher sugar yield after NaOH pretreatment and a comparable sugar yield after H2SO4 pretreatment. [Copyright &y& Elsevier]

Abstract: We examined the impacts of increased biofuel feedstock production on regional water resource and water quality. We focused on the Upper Mississippi river basin, from which a majority of U.S. biofuel is produced at present. The production of biofuel from both conventional feedstock and cellulosic feedstock will potentially increase in the near future, and a significant portion of the cellulosic feedstock is expected to come from this region. In this work, we developed future scenarios of biofuel feedstock production in 2015 to assess the potential water quality and quantity changes associated with an increase in biofuel production through corn yield increase, harvesting a fraction of corn stover, and converting land to perennial grass (switchgrass). The estimates are accomplished by a watershed model SWAT. Results project a slight increase in phosphorus loading and decrease in nitrogen loading when corn yield is increased without cellulosic feedstock production. Harvesting a fraction of corn stover with improved management and efficient nitrogen use could lead to a decrease in nitrogen loading (up to 10%) and phosphorus loading (2%) when soil properties remain constant. Changes in sediment loadings are relatively minor. Growing switchgrass reduces soil erosion considerably and positively impacts nitrogen and phosphorus loadings at the projected yield and fertilizer input while switching from pasture to switchgrass would increase the water loss associated with ET (1% of total precipitation), decrease base flow (2%), and decrease the surface runoff flow to the basin. Major factors – including land use changes, feedstock types, fertilizer inputs, crop yield, and soil properties – were analyzed for their direct and composite impacts. [Copyright &y& Elsevier]

Abstract: To improve the cost-effectiveness of biomass-to-sugar conversion, sodium hydroxide (NaOH) pretreatment of switchgrass was carried out at 21°C using previously determined optimum conditions (2% NaOH (w/v), 6h), and the spent alkaline liquid (black liquor) was collected and used for pretreatment of corn stover, a feedstock exhibiting a higher susceptibility to NaOH attack, for improved enzymatic hydrolysis at a reduced cost. The results showed that, because of the high pH and the appreciable amount of carbohydrates in the black liquor, sugar production during enzymatic hydrolysis of corn stover pretreated with black liquor was comparable to that of biomass pretreated with 1% NaOH. After black liquor pretreatment at the best residence time (24h), the total reducing sugar, glucose, and xylose yields of corn stover reached 478.5, 287.7, and 145.3mg/g raw biomass, respectively, indicating the viability of this novel pretreatment technology. [Copyright &y& Elsevier]