Switchgrass Feedstock Research Articles

A Spatially Explicit Evaluation of the Economic Performance of a Perennial Energy Crop on the Marginal Land of the Loess Plateau and China

The Loess Plateau, with a large area of marginal land, holds the potential to produce 62–106 Tg per year of switchgrass biomass; however, the economic feasibility of producing bioenergy in the region is unclear. The farm-gate feedstock production (FGFP) cost of switchgrass was calculated in a spatially explicit way by taking the geographic variation in crop yield, soil properties, land quality, and input costs into consideration in order to evaluate the economic performance of bioenergy production. Cost–supply curves were constructed to explore the energy supply potential of switchgrass feedstock. The calculations were conducted using ArcGIS in a 1 km grid and all the evaluations were conducted under different agricultural management practice (AMP) scenarios in parallel. The FGFP costs showed significant spatial variation ranging from 95 to 7373 CNY (Chinese Yuan) per tonne−1 and that the most economically desirable areas are scattered in the south and southeast region. The weighted average FGFP costs are 710, 1125, and 1596 CNY per tonne−1 for small bale (SB), large bale (LB), and chipping (CP) harvest methods, respectively. The projected energy supply potential is 1927 PJ (Petajoules) per year−1, of which 30–93% can be supplied below the market prices of different fossil fuels according to feedstock formats. Compared to current biomass residual pricing, 50–66 Tg (Teragrams) switchgrass feedstock is competitive. The results demonstrated that the Loess Plateau holds the potential to produce bioenergy that is economically feasible. This study provides a methodological framework for spatially explicit evaluation of the economic performance of perennial energy crops. Detailed information obtained from this study can be used to select the optimal locations and AMPs to produce feedstock production at minimum cost.

Predicting productivity: A trait-based analysis of variability in biomass yield among switchgrass feedstock cultivars

Plant trait variation in bioenergy crops is hypothesized to affect crop biomass production. The extent of this trait variation and its relationship to production should be explored to inform cultivar selection in different environments and with environmental change. Switchgrass (Panicum virgatum L.) is an important prospective bioenergy crop in North America because it has the potential for high productivity, a wide geographic range, and distinct ecotypes that differ in a number of traits likely to be associated with production. Commercial cultivars of switchgrass have been developed for specific traits, but few studies have assessed if variation in multiple distinct traits relates to productivity and if this relationship differs with environmental conditions. To determine how trait variation affects biomass production in switchgrass we sampled a field trial of 12 switchgrass cultivars of two ecotypes (eight upland, four lowland) being grown in a common garden at the W.K. Kellogg Biological Station, Michigan State University, Michigan, USA. Yield was measured annually for eight years (2010–2017). Between 2014 and 2016, we measured physiological, morphological, and system-level (weed suppression and recovery from drought) traits of these cultivars in the common garden. We used principal components analysis to summarize these traits into composite trait variables and developed linear models to assess the relationship between composite traits and yield across and within years. The 12 cultivars exhibited considerable trait variation that did not align entirely with ecotype. Composite trait axes representing height, phenology, and leaf nitrogen content were strong predictors of yield during stand establishment (years one to three) and in drought years, but were less predictive after stand maturation. Variation in yield across the eight years of the study was better explained by traits than growing season precipitation or drought severity. Interestingly, despite differences in traits, overall ecotype was not a strong predictor of interannual variation in yield especially during stand establishment. The results suggest that traits should be incorporated into agronomic decisions for planting and managing switchgrass cultivars in bioenergy production.

Heteroexpression of Osa-miR319b improved switchgrass biomass yield and feedstock quality by repression of PvPCF5

BackgroundSwitchgrass (Panicum virgatum L.), a C4 perennial grass, has been recognized as one of the most potentially important lignocellulose biofuel crops. MicroRNA319 (miR319) plays a key role in plant development, abiotic resistance, and cell wall biosynthesis by repressing expression of its target TCP genes. We hypothesized miR319–TCP pathway could play important roles in switchgrass feedstock characteristics for biofuel production, and produced switchgrass transgenic plants overexpressing miR319 (by ectopic expressing Osa-MIR319b gene), blocking miR319 (by overexpressing a target mimicry of miR319/MIM319) and repression of miR319 target gene PvPCF5. Plant phenotype, biomass yield, and feedstock quality of transgenic plants were analyzed.ResultsOverexpression of miR319 in switchgrass promoted leaf elongation and expansion of transgenic plants, increased plant height, stem diameter, and resulted in a significant increase in plant biomass yield. Transgenic plants overexpressing of miR319 reduced lignin content, showed significantly higher enzymatic hydrolysis efficiency compared to the wild type plant. However, opposite results were observed in the MIM319 plants. Furthermore, suppression of miR319 target gene PvPCF5 activity also reduced lignin content, increased lignin monomer S/G ratio and the proportion of β-O-4 linkages, while significantly improving the sugar production per plant. Quantitative real-time (qRT-PCR) analysis indicated that expression of PvMYB58/63B and PvHCT with predicted TCP binding sites in their promoter regions was negatively regulated by miR319–PvPCF5 module.ConclusionsMiR319–PvPCF5 module plays positive roles in regulating biomass yield and quality of switchgrass. It can be utilized as a candidate molecular tool in regulating biomass yield and feedstock quality. The finding could also be transferred to other grasses for forage quality improvement through genetic manipulation.

The effect of feedstock composition on fast pyrolysis and upgrading to transportation fuels: Techno-economic analysis and greenhouse gas life cycle analysis

Process economics and greenhouse gas (GHG) emissions are evaluated for the conversion of eleven (11) biomass feedstocks to produce transportation fuels via fast pyrolysis and then pyrolysis oil upgrading via hydrodeoxygenation. The biomass consists of six (6) pure feeds (pine, tulip poplar, hybrid poplar, switchgrass, corn stover, oriented strand board) and five (5) blends. Feedstock blends combine pine, tulip poplar, hybrid poplar, switchgrass, and oriented strand board in various ratios. The assumptions used in this analysis are based on a unique experimental data set. They are “field to wheel” data generated from a multistep experiment that started from biomass preparation and was followed by biomass feedstock conversion to pyrolysis oil, and then finished by pyrolysis oil upgrading to produce hydrocarbon liquid fuel. Process economic results are reported in US dollars per gasoline gallon equivalent (gge) at the minimum fuel selling price (MFSP). For all eleven feedstocks, the largest cost contribution to MFSP is capital-related costs, which is approximately 30%–40% of the MFSP and includes capital depreciation, income tax, and return on investment. Feedstock cost (approximately 30% of MFSP), hydrotreating catalyst cost (13%–18% of MFSP) and labor cost (12%–15% of MFSP) also contribute significant cost to MFSP. Final fuel product yield is one of the most significant parameters affecting the process economics. The highest product yield is from pine feedstock, while switchgrass feedstock gives the lowest yield. Using blends (woody mixed with herbaceous), with which the product yield is still reasonable, may further improve process economics compared to pure feedstocks because of the lower feedstock price for blends. Blend feedstocks cost less than pure feedstock because of greater diversity in feedstock choices, lower risk, and lower transportation costs. GHG reduction does not necessarily align with favorable economics. Process parameters that most significantly affect the life cycle GHG emissions (from feedstock production to vehicle operation) are (1) natural gas used for hydrogen production and electricity usage in fast pyrolysis and pyrolysis oil upgrading, (2) energy usage in the feedstock harvesting, transport, and preprocessing operations, and (3) nitrogen fertilizer usage for growing biomass.

Pre-treatment of biomasses using magnetised sulfonic acid catalysts

There is a significant interest in employing solid acid catalysts for pre-treatment of biomasses for subsequent hydrolysis into sugars, because solid acid catalysts facilitate reusability, high activity, and easier separation. Hence the present research investigated pretreatment of four lignocellulosic biomasses, namely Switchgrass (Panicum virgatum L ‘Alamo’), Gamagrass (Tripsacum dactyloides), Miscanthus (Miscanthus × giganteus) and Triticale hay (Triticale hexaploide Lart.) at 90°C for 2 h using three carbon-supported sulfonic acid catalysts. The catalysts were synthesized via impregnating p-Toluenesulfonic acid on carbon (regular) and further impregnated with iron nitrate via two methods to obtain magnetic A and magnetic B catalysts. When tested as pre-treatment agents, a maximum total lignin reduction of 17.73±0.63% was observed for Triticale hay treated with magnetic A catalyst. Furthermore, maximum glucose yield after enzymatic hydrolysis was observed to be 203.47±5.09 mg g–1 (conversion of 65.07±1.63%) from Switchgrass treated with magnetic A catalyst. When reusability of magnetised catalysts were tested, it was observed that magnetic A catalyst was consistent for Gamagrass, Miscanthus × Giganteus and Triticale hay, while magnetic B catalyst was found to maintain consistent yield for switchgrass feedstock. Our results suggested that magnetised solid acid catalyst could pre-treat various biomass stocks and also can potentially reduce the use of harsh chemicals and make bioenergy processes environment friendly.

Microbial communities and diazotrophic activity differ in the root‐zone of Alamo and Dacotah switchgrass feedstocks

AbstractNitrogen (N) bioavailability is a primary limiting nutrient for crop and feedstock productivity. Associative nitrogen fixation (ANF) by diazotrophic bacteria in root‐zone soil microbial communities have been shown to provide significant amounts of N to some tropical grasses, but this potential in switchgrass, a warm‐season, temperate, US native, perennial tallgrass has not been widely studied. ‘Alamo’ and ‘Dacotah’ are cultivars of switchgrass, adapted to the southern and northern regions of the United States, respectively, and offer an opportunity to better describe this plant–bacterial association. The nitrogenase enzyme activity, microbial communities, and amino acid profiles in the root‐zones of the two ecotypes were studied at three different plant growth stages. Differences in the nitrogenase enzyme activity and free soluble amino acid profiles indicated the potential for greater nitrogen fixation in the high productivity Alamo compared with the lower productivity Dacotah. Changes in the amino acid profiles and microbial community structure (rRNA genes) of the root‐zone suggest different plant–bacterial interactions can help to explain differences in nitrogenase activity. PICRUSt analysis revealed functional differences, especially nitrogen metabolism, that supported ecotype differences in root‐zone nitrogenase enzyme activity. It is thought that the greater productivity of Alamo increased the belowground flow of carbon into roots and root‐zone habitats, which in turn support the high energy demands needed to support nitrogen fixation. Further research is thus needed to understand plant ecotype and cultivar trait differences that can be used to breed or genetically modify crop plants to support root‐zone associations with diazotrophs.

Evaluation of Sugars and Bio-oil Production Using Lead Contaminated Switchgrass Feedstock

A combination of biochemical and thermochemical process to produce sugars and bio-oil by using switchgrass which was grown in lead contaminated soil was studied. Four different process routes which involve fast pyrolysis, enzymatic hydrolysis, acid hydrolysis, and their combinations were investigated. The impact of lead content in the switchgrass feedstock used for the production of sugars and bio-oil along with the recovery of lead through the above mentioned routes were evaluated. The yields of sugars from acid hydrolysis and enzymatic hydrolysis did not seem to be affected by the lead contained in the switchgrass. The chemical product distribution in bio-oil produced from pyrolysis of lead-containing switchgrass and regular switchgrass showed slight differences. The highest overall yields of the liquid products were obtained from the fourth route which utilized all the three process steps, resulting in the lowest yield of bio-char byproduct which had the lowest content lead (2 mg/kg).

Global gene expression profiling of two switchgrass cultivars following inoculation with Burkholderia phytofirmans strain PsJN.

Improvement and year-to-year stabilization of biomass yields are primary objectives for the development of a low-input switchgrass feedstock production system using microbial endophytes. An earlier investigation of the effect of Burkholderia phytofirmans strain PsJN on switchgrass germplasm demonstrated differential responses between genotypes. PsJN inoculation of cv. Alamo (lowland ecotype) increased the plant root system, shoot length, and biomass yields, whereas it had no beneficial effect on cv. Cave-in-Rock (upland ecotype). To understand the gene networks governing plant growth promotion responses triggered by PsJN, the gene expression profiles were analysed in these two hosts, following seedling inoculation. The Affymetrix platform switchgrass expressed sequence tag (EST) microarray chip representing 122 972 probe sets, developed by the DOE BioEnergy Science Center, was employed to assess transcript abundance at 0.5, 2, 4, and 8 DAI (days after PsJN inoculation). Approximately 20 000 switchgrass probe sets showed significant responses in either cultivar. Switchgrass identifiers were used to map 19 421 genes in MapMan software. There were apparent differences in gene expression profiling between responsive and non-responsive cultivars after PsJN inoculation. Overall, there were 14 984 and 9691 genes affected by PsJN inoculation in Alamo and Cave-in-Rock, respectively. Of these, 394 are annotated as pathogenesis-related genes. In the responsive cv. Alamo, 68 pathogenesis-related genes were affected, compared with only 10 in the non-responsive cv. Cave-in-Rock. At the very early stage at 0.5 DAI, both cultivars exhibited similar recognition and defence responses, such as genes in signalling and proteolysis, after which the defence reaction in the responsive cv. Alamo became weaker while it was sustained in non-responsive cv. Cave-in-Rock.

Investigating the impact of biomass quality on near-infrared models for switchgrass feedstocks

The aim of this study was to determine the impact of incorporating switchgrass samples that have been in long term storage on the development of near-infrared (NIR) multivariate calibration models and their predictive capabilities. Stored material contains more variation in their respective spectral signatures due to chemical changes in the bales with storage time. Partial least squares (PLS) regression models constructed using NIR spectra of stored switchgrass possessed an instability that interfered with the correlation between the spectral data and measured chemical composition. The models were improved using calibration sample sets of equal parts stored and fresh switchgrass to more accurately predict the chemical composition of stored switchgrass. Acceptable correlation values (r calibration ) were obtained using a calibration sample set composed of 25 stored samples and 25 samples of fresh switchgrass for cellulose (0.91), hemicellulose (0.74), total carbohydrates (0.76), lignin (0.98), extractives (0.92), and ash (0.87). Increasing the calibration sample set to 100 samples of equal parts stored to senesced material resulted in statistically increased ( p = 0.05) correlations for total carbohydrates (0.89) and ash (0.96). When these models were applied to a separate validation set (equal to 10% of the calibration sample set), high correlation coefficients (r) for predicted versus measured constituent content were observed for cellulose (0.94), total carbohydrates (0.98), lignin (0.91), extractives (0.97), and ash (0.90). For optimization of processing economics, the impact of feedstock storage must be investigated for implementation in conversion processes. While NIR is a well-known high-throughput technique for characterization of senesced switchgrass, the selection of appropriate calibration samples and consequent multivariate models must be taken into careful consideration for NIR application in a biomass storage facility for rapid chemical compositional determination.

Environmental impact assessment of regional switchgrass feedstock production comparing nitrogen input scenarios and legume-intercropping systems

Abstract As the use of second-generation biofuel crops increases, so do questions about sustainability, particularly their potential to affect fossil energy consumption and greenhouse gas emissions. This study used a life-cycle approach to compare environmental impacts associated with three switchgrass (Panicum virgatum L.) production scenarios: i) regional production from a pool of Tennessee farmers based on in-field inputs and biomass yield; ii) varying nitrogen (N)-input levels from a replicated field study for 8-yrs i.e., a 100% and 9% decrease, and an 81% and 172% increase from 'baseline levels' of N inputs used under objective i; and, iii) a legume-intercrop system compared to baseline levels in order to determine effects of displacing synthetic-N with legumes. When compared across all agricultural inputs, nitrogen fertilizer production and breakdown resulted in the greatest environmental impacts. Although fertilization increased lignocellulosic yields, a 100% reduction in N-inputs from baseline levels reduced the formation of carbon, methane, and nitrous oxides per unit of production, (or dry tonne of biomass over 10-yrs) compared to a 172% increase. Switchgrass yield response indicated a 'less is more' scenario, as inputs beyond the current recommended input level (67 kg N ha−1) are not environmentally remunerating. During switchgrass biomass production, inputs with lesser impacts included phosphorus, herbicides, pesticides, and diesel fuel. Legume-intercropping reduced greenhouse gas emissions and groundwater acidification (5% and 27% reduction in global warming potential and formation of acidifying species, respectively) compared with the 67 kg N ha−1rate. Although N-fertilizers impact environmental sustainability of regional switchgrass feedstock production, environmental consequences can be reduced under proper N-management i.e., ≤67 kg N ha−1 or legume intercropping. However, given that the aim of second-generation feedstocks is to reduce the current reliance on fossil fuels, their production still requires fossil energy-based inputs. Consequently, greenhouse gas reductions and the extent of cleaner feedstock production during the agricultural biofuel supply chain is contingent upon input management and optimizing synthetic fertilizer usage.

Switchgrass Field Performance on Two Soils as Affected by Bacterization of Seedlings with Burkholderia phytofirmans Strain PsJN

Switchgrass (Panicum virgatum L.) is a perennial warm season grass capable of growth on marginal lands without major inputs of water and fertilizers. However, full utilization of its agronomic potential as a bioenergy crop requires improvement of its stand establishment, disease resistance, and prevention of the biomass yield variation from year to year. Our program focuses on the utilization of beneficial bacterial endophytes to enhance switchgrass performance under a low-input production system on marginal lands. We demonstrated earlier that inoculation of switchgrass cv. Alamo with a growth promoting endophyte, Burkholderia phytofirmans strain PsJN (PsJN), can significantly enhance seedling vigor and plant growth under both in vitro and greenhouse conditions. In this study, we tested the effects of PsJN bacterization of switchgrass seedlings on stand establishment, plant growth, and biomass yield in three field experiments conducted over 2 years on highly fertile prime land, and on a former tobacco farm with low fertility soil. PsJN bacterization improved growth and development of switchgrass seedlings, significantly stimulated plant root and shoot growth, and tiller number on the low fertility soil (p < 0.001), and enhanced biomass accumulation on both poor (p < 0.001) and rich (p < 0.05) soils, with more effective stimulation of plant growth in low fertility soil than in high fertility soil. The study indicates the potential for the use of PsJN and/or other beneficial bacterial endophytes in the development of low-input switchgrass feedstock production systems.

Marginal cost of delivering switchgrass feedstock and producing cellulosic ethanol at multiple biorefineries

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.

The value of native, warm-season perennial grasses grown for pasture or biofuel in the southern Great Plains, USA

The Renewable Fuel Standard under the Energy Independence and Security Act of 2007 mandated the production of 60.5 GL (1 GL = 1 × 109 L) of cellulosic biofuel by 2022. Switchgrass (Panicum virgatum) has been identified as a primary feedstock because it is a perennial adapted to a wide environmental range and produces high yields. Development of the cellulosic biofuel industry has been slow, one reason being a lack of available feedstock driven by lack of a developed market. Rather than considering it only as a dedicated biofuel feedstock, we examined switchgrass potential for both grazing and biofuel feedstock. In a series of experiments testing dry matter yield, grazing preference and animal bodyweight gain, switchgrass (cv. Alamo) was found to produce greater total yield (17.7 kg ha–1) than 15 other warm-season perennial grasses, was the most preferred by stocker cattle in a grazing preference study, and produced good average daily gains in a grazing study (0.84–1.05 kg head–1). These results demonstrate the potential of switchgrass for both grazing and biofuel feedstock. However, the feedstock price would need to increase above US$83 Mg–1 before the economics of dedicated switchgrass feedstock production would surpass that of a combination of switchgrass grazing and feedstock production.

Impacts of Feedstock Composition on Alcohol Yields and Greenhouse Gas Emissions from the NREL Thermochemical Ethanol Conversion Process

There has been great attention focused on the effects of first and second generation biofuels on global warming. The Energy Independence and Security Act (EISA) and the Renewable Fuel Standard (RFS) have mandated production levels and performance criteria of biofuels in the United States. The thermochemical conversion of biomass to ethanol shows potential as a biofuel production pathway. The objective of this research was to examine the alcohol yields and GHG emissions from the thermochemical conversion process for six different feedstocks on a gate-to-gate basis. GHG analyses and life cycle assessments were performed for natural hardwood, loblolly pine, eucalyptus, miscanthus, corn stover, and switchgrass feedstocks using a NREL thermochemical model and SimaPro. Alcohol yield and GHG emission for the hybrid poplar baseline feedstock conversion were 105,400 L dry metric ton−1 and 2.8 kg CO2 eq. per liter, respectively. Compared with the baseline, loblolly pine produced the highest alcohol yields, an 8.5% increase, and the lowest GHG emissions per liter of ethanol, a 9.1% decrease. Corn stover, due to its high ash content, had the lowest yields and the highest GHG emissions per liter of ethanol. The results were highly sensitive to the ash and water content of the biomass, indicating that biomass properties can significantly affect the environmental impact of the thermochemical ethanol conversion process.

Screening for novel bacteria from the bioenergy feedstock switchgrass (Panicum virgatum L.)

Switchgrass is considered as a good candidate for biofuel, especially ethanol production due to its huge biomass output and high cellulose content. In a search for novel microorganisms capable of using and degrading switchgrass to produce sugars and ethanol, enrichment experiments were established to screen for microorganisms from soil samples obtained at the University of Tennessee Agricultural Research Station, Jackson, Tennessee. Three enrichments were prepared and incubated at different pH and temperatures: (1) 30°C, pH 5, (2) 30°C, pH 8 and (3) 60°C, pH5. Bulk community DNA was directly extracted from the enrichments. Microbial community structures were determined by phylogenetic analysis of 16S rRNA gene sequences retrieved from the enrichment cultures containing switchgrass as the carbon source. The mesophilic enrichments were dominated by Sarcina, Anaerobacter, and Clostrium, which were not found in the thermophilic enrichment. The thermophilic enrichment selected for two types of bacteria belonging to the class Bacilli (Geobacillus and Saccharococcus). The thermophilic enrichments were dominated by the Geobacillus spp. (Firmicutes, class Bacilli), and Saccharococcus (Firmicutes, class Bacilli); both containing thermophilic microorganisms with some cellulolytic members. Enzymatic assays detected the presence of enzymes involved in cellulose (β-glucosidase and cellobiohydrolase) and hemicellulose degradations (β-xylosidase); and the activity tends to be higher in the enrichments incubated at 30°C.

Do Yield and Quality of Big Bluestem and Switchgrass Feedstock Decline over Winter?

Switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerdardii Vitman) are potential perennial bioenergy feedstocks. Feedstock storage limitations, labor constraints for harvest, and environmental benefits provided by perennials are rationales for developing localized perennial feedstock as an alternative or in conjunction with annual feedstocks (i.e., crop residues). Little information is available on yield, mineral, and thermochemical properties of native species as related to harvest time. The study’s objectives were to compare the feedstock quantity and quality between grasses harvested in the fall or the following spring. It was hypothesized that biomass yield may decline, but translocation and/or leaching of minerals from the feedstock would improve feedstock quality. Feedstock yield did not differ by crop, harvest time, or their interactions. Both grasses averaged 6.0 Mg ha−1 (fall) and 5.4 Mg ha−1 (spring) with similar high heating value (17.7 MJ kg−1). The K/(Ca + Mg) ratio, used as a quality indicator declined to below a 0.5 threshold, but energy yield (Megajoule per kilogram) decreased 13 % by delaying harvest until spring. Only once during the four study-years were conditions ideal for early spring harvest, in contrast during another spring, very muddy conditions resulted in excessive soil contamination. Early spring harvest may be hampered by late snow, lodging, and muddy conditions that may delay or prevent harvest, and result in soil contamination of the feedstock. However, reducing slagging/fouling potential and the mass of mineral nutrients removed from the field without a dramatic loss in biomass or caloric content are reasons to delay harvest until spring.

Analyses using Cell Wall Glycan-directed Monoclonal Antibodies Reveal Xylan-degradation by Two Microbial Glycosyl Hydrolases in Cell Walls from Poplar and Switchgrass Biomass

Plant biomass represents the major source for renewable bio-fuels. Cell walls constitute the major portion of plant biomass. The main challenge in sustainable production of ligno-cellulosic biofuel is overcoming the cell wall recalcitrance barrier. A number of cell wall components including lignin and hemicelluloses have been shown to contribute to this cell wall recalcitrance. Thus, removing or reducing the proportion of wall components that contribute to cell wall recalcitrance of ligno-cellulosic biomass is a key step in sustainable ligno-cellulosic biofuel production. We have demonstrated the use of a comprehensive array of cell wall glycan-directed monoclonal antibodies to study the hydrolytic activities of two xylan-degrading microbial glycosyl hydrolases, CjXyl10B (a representative member of the GH10 family) and NpXyl11A (a representative member of the GH11 family) on cell wall extracts and cell walls from poplar and switchgrass biomass. Depletion of xylan epitopes, as monitored by the antibodies, in base extracts generated from raw poplar and switchgrass biomass that are treated with CjXyl10B or NpXyl11A confirmed the xylanase activity of these hydrolases, and demonstrates the utility of the antibody-based approach for screening for enzymes active on native biomass. Base extracts isolated from raw biomass treated with these enzymes prior to extraction also exhibited reduced xylan content. Further, prior removal of lignin significantly increased the efficiency of the xylan degradation in raw poplar and switchgrass biomass by the CjXyl10B and NpXyl11A enzymes. These results, thus hint that these two xylanases could potentially be used, in combination with lignin reduction, as efficient xylan-removing agents, while processing poplar and switchgrass feed stocks for biofuel production.

An integrated optimization model for switchgrass-based bioethanol supply chain

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.

Growth promotion and colonization of switchgrass (Panicum virgatum) cv. Alamo by bacterial endophyte Burkholderia phytofirmans strain PsJN

BackgroundSwitchgrass is one of the most promising bioenergy crop candidates for the US. It gives relatively high biomass yield and can grow on marginal lands. However, its yields vary from year to year and from location to location. Thus it is imperative to develop a low input and sustainable switchgrass feedstock production system. One of the most feasible ways to increase biomass yields is to harness benefits of microbial endophytes.ResultsWe demonstrate that one of the most studied plant growth promoting bacterial endophytes, Burkholderia phytofirmans strain PsJN, is able to colonize and significantly promote growth of switchgrass cv. Alamo under in vitro, growth chamber, and greenhouse conditions. In several in vitro experiments, the average fresh weight of PsJN-inoculated plants was approximately 50% higher than non-inoculated plants. When one-month-old seedlings were grown in a growth chamber for 30 days, the PsJN-inoculated Alamo plants had significantly higher shoot and root biomass compared to controls. Biomass yield (dry weight) averaged from five experiments was 54.1% higher in the inoculated treatment compared to non-inoculated control. Similar results were obtained in greenhouse experiments with transplants grown in 4-gallon pots for two months. The inoculated plants exhibited more early tillers and persistent growth vigor with 48.6% higher biomass than controls. We also found that PsJN could significantly promote growth of switchgrass cv. Alamo under sub-optimal conditions. However, PsJN-mediated growth promotion in switchgrass is genotype specific.ConclusionsOur results show B. phytofirmans strain PsJN significantly promotes growth of switchgrass cv. Alamo under different conditions, especially in the early growth stages leading to enhanced production of tillers. This phenomenon may benefit switchgrass establishment in the first year. Moreover, PsJN significantly stimulated growth of switchgrass cv. Alamo under sub-optimal conditions, indicating that the use of the beneficial bacterial endophytes may boost switchgrass growth on marginal lands and significantly contribute to the development of a low input and sustainable feedstock production system.

Tennessee case study in full-scale development and integration of switchgrass feedstocks with biorefinery operations: Genera Energy and UT Biofuels Initiative

Industrial BiotechnologyVol. 7, No. 5 COMMENTARYTennessee case study in full-scale development and integration of switchgrass feedstocks with biorefinery operations: Genera Energy and UT Biofuels InitiativeKelly TillerKelly TillerSearch for more papers by this authorPublished Online:24 Oct 2011https://doi.org/10.1089/ind.2011.7.357AboutSectionsPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail FiguresReferencesRelatedDetailsCited byHigh-Resolution Multiobjective Optimization of Sustainable Supply Chains for a Large-Scale Lignocellulosic Biofuel Industry4 March 2021Effect of land use change for bioenergy production on feedstock cost and water qualityApplied Energy, Vol. 210Multi‐attribute uncertainty analysis of the life cycle of lignocellulosic feedstock for biofuel production13 December 2016 | Biofuels, Bioproducts and Biorefining, Vol. 11, No. 2Normalization in sustainability assessment: Methods and implicationsEcological Economics, Vol. 130Assessing multimetric aspects of sustainability: Application to a bioenergy crop production system in East Tennessee26 February 2016 | Ecosphere, Vol. 7, No. 2Economic analysis of alternative logistics systems for Tennessee-produced switchgrass to penetrate energy marketsBiomass and Bioenergy, Vol. 85Assessing Sustainable Bioenergy Feedstock Production Potential by Integrated Geospatial Analysis of Land Use and Land Quality3 May 2015 | BioEnergy Research, Vol. 8, No. 4Sustainable Production of Bioenergy Feedstock from the Industrial Forest: Potential and Challenges of Operational Scale Implementation1 December 2015 | Current Sustainable/Renewable Energy Reports, Vol. 2, No. 4Multifunctional landscapes: Site characterization and field-scale design to incorporate biomass production into an agricultural systemBiomass and Bioenergy, Vol. 80Conversion of switchgrass to ethanol using dilute ammonium hydroxide pretreatment: influence of ecotype and harvest maturityEnvironmental Technology, Vol. 34, No. 13-14 Volume 7Issue 5Oct 2011 InformationCopyright 2011, Mary Ann Liebert, Inc.To cite this article:Kelly Tiller.Tennessee case study in full-scale development and integration of switchgrass feedstocks with biorefinery operations: Genera Energy and UT Biofuels Initiative.Industrial Biotechnology.Oct 2011.357-364.http://doi.org/10.1089/ind.2011.7.357Published in Volume: 7 Issue 5: October 24, 2011PDF download