Showing papers in "Bioenergy Research in 2016"

Sources of Biomass Feedstock Variability and the Potential Impact on Biofuels Production

Abstract: Terrestrial lignocellulosic biomass has the potential to be a carbon neutral and domestic source of fuels and chemicals. However, the innate variability of biomass resources, such as herbaceous and woody materials, and the inconsistency within a single resource due to disparate growth and harvesting conditions, presents challenges for downstream processes which often require materials that are physically and chemically consistent. Intrinsic biomass characteristics, including moisture content, carbohydrate and ash compositions, bulk density, and particle size/shape distributions are highly variable and can impact the economics of transforming biomass into value-added products. For instance, ash content increases by an order of magnitude between woody and herbaceous feedstocks (from ∼0.5 to 5 %, respectively) while lignin content drops by a factor of two (from ∼30 to 15 %, respectively). This increase in ash and reduction in lignin leads to biofuel conversion consequences, such as reduced pyrolysis oil yields for herbaceous products as compared to woody material. In this review, the sources of variability for key biomass characteristics are presented for multiple types of biomass. Additionally, this review investigates the major impacts of the variability in biomass composition on four conversion processes: fermentation, hydrothermal liquefaction, pyrolysis, and direct combustion. Finally, future research processes aimed at reducing the detrimental impacts of biomass variability on conversion to fuels and chemicals are proposed. © 2015 Battelle Energy Alliance, LLC, contract manager for Idaho National Laboratory.

Nitrogen Use Efficiency for Sugarcane-Biofuel Production: What Is Next?

Abstract: Land area devoted to sugarcane (Saccharum spp.) production in Brazil has increased from 2 million to 10 million ha over the past four decades. Studies have shown that, from an environmental perspective, the transformation of nitrogen (N) fertilizers into N2O gases can offset the advantages gained by replacing fossil fuels with biofuels. Our objectives here were to review recent developments in N management for sugarcane-biofuel production and assess estimates of N use efficiency (NUE) and N losses based on future scenarios, as well as for life-cycle assessments of bioenergy production. Approximately 60 % of N-based fertilizer applied to sugarcane fields in Brazil is recovered by plants and soils, whereas N losses to leaching and N2O emissions can average 5.6 and 1.84 % of the total applied N, respectively. Maintenance of trash, rotation with N-fixing legume species, and optimization of byproducts usage have potential for reducing the N requirements of sugarcane cultivation in Brazil. Moreover, the development of sugarcane genotypes with higher NUEs, along with management systems that consider soil capacity of mineralization, is required for improving the NUE of sugarcane. Strategies to maintain N as NH4 + in sugarcane-cropped soils also have the potential to reduce N losses and enhance NUE. The development of second-generation biofuels is important for increasing biofuel production while simultaneously maintaining N rates and improving NUE, and sugarcane systems in Brazil show potential for sustainable biofuel production with low N rates and limited N2O losses. Reducing N rates in sugarcane fields is thus necessary for improving sugarcane-based biofuel production and reducing its environmental impacts.

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

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

Ecosystem Services of Woody Crop Production Systems

Abstract: Short-rotation woody crops are an integral component of regional and national energy portfolios, as well as providing essential ecosystem services such as biomass supplies, carbon sinks, clean water, and healthy soils. We review recent USDA Forest Service Research and Development efforts from the USDA Biomass Research Centers on the provisioning of these ecosystem services from woody crop production systems. For biomass, we highlight productivity and yield potential, pest susceptibility, and bioenergy siting applications. We describe carbon storage in aboveground woody biomass and studies assessing the provision of clean and plentiful water. Soil protection and wildlife habitat are also mentioned, in the context of converting lands from traditional row-crop agriculture to woody production systems.

Mixed Feedstock Approach to Lignocellulosic Ethanol Production—Prospects and Limitations

Abstract: Lignocellulosic ethanol is a promising alternative to fossil-derived fuels because lignocellulosic biomass is abundant, cheap and its use is environmentally friendly. However, the high costs of feedstock supply and the expensive processing requirements of lignocellulosic biomass hinder the development of the lignocellulosic biorefinery. Lignocellulosic ethanol production so far, has been based mainly on single feedstocks while the use of mixed feedstocks has been poorly explored. Previous studies from alternative applications of mixed lignocellulosic biomass (MLB) have shown that their use can bring about significant cost savings when compared to single feedstocks. Although laboratory-scale evaluations have demonstrated that mixed feedstocks give comparable or even higher ethanol yields compared to single feedstocks, more empirical studies are needed to establish the possibility of achieving significant cost savings in terms of pre-biorefinery logistics. In this review, some potential benefits of the use of MLB for ethanol production are highlighted. Some anticipated limitations of this approach have been identified and ways to surmount them have been suggested. The outlook for ethanol production from MLB is promising provided that revolutionary measures are taken to ensure the sustainability of the industry.

Feasibility of Manufacturing Cellulose Nanocrystals from the Solid Residues of Second-Generation Ethanol Production from Sugarcane Bagasse

Abstract: The reuse of the solid residues generated in the production of second-generation (2G) ethanol to obtain high-value products is a potential strategy for improving the economic and environmental viability of the overall process. This study evaluated the feasibility of using the residual solids remaining after the enzymatic hydrolysis of sugarcane bagasse for the production of cellulose nanocrystals (CNC), a valuable bionanomaterial. To this end, sugarcane bagasse subjected to steam explosion (SEB) or liquid hot water (LHWB) pretreatment was hydrolysed using different loadings of a commercial cellulase cocktail. Samples of SEB and LHWB were hydrolysed enzymatically, resulting in glucose releases close to 40 g/L, which would be suitable for producing 2G ethanol by microbial fermentation. The solid residues after the enzymatic hydrolysis step presented cellulose contents of up to 54 %, indicating that a significant amount of recalcitrant crystalline cellulose remained available for subsequent use. These solid residues were purified and submitted to acid hydrolysis, resulting in the successful formation of CNC with crystallinity close to 80 %, lengths of 193–246 nm and diameters of 14–18 nm. The CNC produced presented morphology, dimensions, physical-chemical characteristics, thermal stability and crystallinity within the ranges reported for this type of material. Moreover, the enzyme loading or the type of hydrothermal pretreatment process employed here showed no significant effects on the CNC obtained, indicating that these variables could be flexibly adjusted according to specific interests.

Lipid Yield and Composition of Azolla filiculoides and the Implications for Biodiesel Production

Abstract: The aquatic fern Azolla is one of the fastest-growing nitrogen-fixing plants on Earth and therefore considered as a potential source of biomass for bioenergy production. The lipid fraction from Azolla filiculoides was analyzed to investigate whether it suited biodiesel production. Since the productivity of Azolla is further increased at higher CO2 concentrations, A. filiculoides biomass was produced at 800 ppm CO2 mimicking a cultivation system utilizing CO2 waste from industry. The harvested biomass contained 7.92 ± 0.14 % dry weight (dw) crude lipids. Drying conditions did not significantly affect lipid composition or yields, indicating that drying conditions may be energetically optimized without the risk of product loss. Total lipid extracts contained 4.2 ± 0.38 % free fatty acids. Of the crude lipid fraction, 41 ± 13 % consisted of fatty acids that were converted into fatty acid methyl esters upon saponification in methanol. Unique mid-chain (di)hydroxy compounds constituted 7.2 ± 2.8 % of the crude lipids. Based on the fatty acid profile, it was estimated that Azolla biodiesel meets requirements set by the EN14214 standard on fuel density, cetane number, and iodine value. The cold filter plugging point (CFPP), however, is expected to be too high due to relatively high concentrations of lignoceric acid and the presence of the mid-chain (di)hydroxy compounds. To produce high-quality biodiesel from Azolla lipids, therefore, a fractionation step will be required removing these compounds. As an advantage, the long-chain alcohols and (di)hydroxy fatty acids obtained after fractionation may provide a valuable secondary product stream with applications to chemical industry and nutrition.

Soil Health, Crop Productivity, Microbial Transport, and Mine Spoil Response to Biochars

Abstract: Biochars vary widely in pH, surface area, nutrient concentration, porosity, and metal binding capacity due to the assortment of feedstock materials and thermal conversion conditions under which it is formed. The wide variety of chemical and physical characteristics have resulted in biochar being used as an amendment to rebuild soil health, improve crop yields, increase soil water storage, and restore soils/spoils impacted by mining. Meta-analysis of the biochar literature has shown mixed results when using biochar as a soil amendment to improve crop productivity. For example, in one meta-analysis, biochar increased crop yield by approximately 10 %, while in another, approximately 50 % of the studies reported minimal to no crop yield increases. In spite of the mixed crop yield reports, biochars have properties that can improve soil health characteristics, by increasing carbon (C) sequestration and nutrient and water retention. Biochars also have the ability to bind enteric microbes and enhance metal binding in soils impacted by mining. In this review, we present examples of both effective and ineffective uses of biochar to improve soil health for agricultural functions and reclamation of degraded mine spoils. Biochars are expensive to manufacture and cannot be purged from soil after application, so for efficient use, they should be targeted for specific uses in agricultural and environmental sectors. Thus, we introduce the designer biochar concept as an alternate paradigm stating that biochars should be designed with properties that are tailored to specific soil deficiencies or problems. We then demonstrate how careful selection of biochars can increase their effectiveness as a soil amendment.

Understanding the Physicochemical Characteristics and the Improved Enzymatic Saccharification of Corn Stover Pretreated with Aqueous and Gaseous Ammonia

Abstract: Physicochemical characteristics of corn stover pretreated by soaking in aqueous ammonia (SAA) and low-moisture anhydrous ammonia (LMAA) were compared and investigated The glucan digestibility of the treated biomass reached 90 % (SAA) and 84 % (LMAA) The LMAA pretreatment enhanced the digestibility by cleaving cross-linkages between cell wall components, whereas the SAA pretreatment additionally improved the digestibility by efficiently removing a major portion of the lignin under mild reaction conditions without significant loss of carbohydrates Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) revealed the structural and chemical transformations of lignin during the pretreatments Both pretreatments effectively cleaved ferulate cell wall cross-linking that is associated with the recalcitrance of grass lignocellulosics toward enzymatic saccharification Extracted lignin from SAA pretreatment was extensively depolymerized but retained “native” character, as evidenced by the retention of β-ether linkages

Sixteen-year biomass yield and soil carbon storage of giant reed (Arundo donax L.) grown under variable nitrogen fertilization rates.

Abstract: High and stable biomass yields for long periods (15–20 years) are indispensable for the successful establishment of a well-developed bioenergy sector. However, the effects of management practices, particularly nitrogen fertilization, on productivity and soil organic carbon (SOC) are difficult to understand, especially when considering that continuous harvesting cycles may have cumulative effects on the crop and its resources use capacity. The objective of this study was to evaluate the effects of different N fertilization levels on biomass production and SOC accumulation of giant reed over 16 years. Every year, starting from the second one, two N fertilization rates were applied: 80 (N80) and 160 (N160) kg N ha−1. The control treatment (N0) was unfertilized. Nitrogen content and use capacity, and SOC gains were determined. Mean 16-year biomass yields were 16.2, 17.1, and 19.5 Mg ha−1 in the N0, N80, and N160 treatments, respectively. Variable yielding phases were observed in the N160 treatment with declining yields towards the last sampling season, whereas the N0 was characterized by increasing yields up to the fourth growing season; thereafter, declining yields were observed. Nitrogen concentration and removed N in the aboveground harvested biomass increased from N0 to N160 and as the stand become older. Mean total SOC stock gains were 1.0 and 0.6 Mg C ha−1 year−1 in the N160 and N0 treatments, respectively. The largest SOC stocks were found in the topsoil, with the largest amount (12 Mg C ha−1 in 16 years) in the N160 treatment. In conclusion, long-term high N fertilization rates result in marginal increments in biomass productivity (about 3 Mg ha−1 year−1), but in substantial increments in SOC, especially in surface soil layers. A farmer might prefer to grow giant reed without the burdens of fertilization despite the seemingly benefits on SOC and lower yields of unfertilized plots.

Policy implications of allocation methods in the life cycle analysis of integrated corn and corn stover ethanol production

Abstract: A biorefinery may produce multiple fuels from more than one feedstock. The ability of these fuels to qualify as one of the four types of biofuels under the US Renewable Fuel Standard and to achieve a low carbon intensity score under California’s Low Carbon Fuel Standard can be strongly influenced by the approach taken to their life cycle analysis (LCA). For example, in facilities that may co-produce corn grain and corn stover ethanol, the ethanol production processes can share the combined heat and power (CHP) that is produced from the lignin and liquid residues from stover ethanol production. We examine different LCA approaches to corn grain and stover ethanol production considering different approaches to CHP treatment. In the baseline scenario, CHP meets the energy demands of stover ethanol production first, with additional heat and electricity generated sent to grain ethanol production. The resulting greenhouse gas (GHG) emissions for grain and stover ethanol are 57 and 25 g-CO2eq/MJ, respectively, corresponding to a 40 and 74 % reduction compared to the GHG emissions of gasoline. We illustrate that emissions depend on allocation of burdens of CHP production and corn farming, along with the facility capacities. Co-product handling techniques can strongly influence LCA results and should therefore be transparently documented.

Laccase-Mediator Pretreatment of Wheat Straw Degrades Lignin and Improves Saccharification

Abstract: Agricultural by-products such as wheat straw are attractive feedstocks for the production of second-generation bioethanol due to their high abundance. However, the presence of lignin in these lignocellulosic materials hinders the enzymatic hydrolysis of cellulose. The purposes of this work are to study the ability of a laccase-mediator system to remove lignin improving saccharification, as a pretreatment of wheat straw, and to analyze the chemical modifications produced in the remaining lignin moiety. Up to 48 % lignin removal from ground wheat straw was attained by pretreatment with Pycnoporus cinnabarinus laccase and 1-hydroxybenzotriazole (HBT) as mediator, followed by alkaline peroxide extraction. The lignin removal directly correlated with increases (∼60 %) in glucose yields after enzymatic saccharification. The pretreatment using laccase alone (without mediator) removed up to 18 % of lignin from wheat straw. Substantial lignin removal (37 %) was also produced when the enzyme-mediator pretreatment was not combined with the alkaline peroxide extraction. Two-dimensional nuclear magnetic resonance (2D NMR) analysis of the whole pretreated wheat straw material swollen in dimethylsulfoxide-d 6 revealed modifications of the lignin polymer, including the lower number of aliphatic side chains involved in main β-O-4′ and β-5′ inter-unit linkages per aromatic lignin unit. Simultaneously, the removal of p-hydroxyphenyl, guaiacyl, and syringyl lignin units and of p-coumaric and ferulic acids, as well as a moderate decrease of tricin units, was observed without a substantial change in the wood polysaccharide signals. Especially noteworthy was the formation of Cα-oxidized lignin units during the enzymatic treatment.

Influence of Willow Biochar Amendment on Soil Nitrogen Availability and Greenhouse Gas Production in Two Fertilized Temperate Prairie Soils

Abstract: The potential of biochar to improve numerous soil physical, chemical and biological properties is well known However, previous research has concentrated on old and highly weathered tropical soils with poor fertility, while reports regarding the influence of biochar application on relatively young and fertile temperate prairie soils are limited Furthermore, the mechanism(s) underlying biochar-induced effects on the plant availability of inorganic nitrogen (N) fertilizers and their relationship to greenhouse gas production is not well understood The objective of this study was to determine the effect of a biochar soil amendment, produced by slow pyrolysis using shrub willow (Salix spp) bioenergy feedstock, on CO2, N2O and CH4 fluxes by two contrasting marginal soils from Saskatchewan, Canada with and without added urea, over a 6-week incubation period Biochar decreased soil N availability after 6 weeks only in the lower organic matter (Brown) soil, with no effect on the Black soil, regardless of fertilizer N addition, which was attributed to soil N immobilization by heterotrophs mineralizing the labile biochar-carbon There appeared to be a synergistic effect when combining biochar and urea, evidenced by enhanced urease activity and higher initial nitrification rates compared to biochar or fertilization alone The accelerated urea hydrolysis in the presence of biochar may increase NH3 volatilization losses associated with urea fertilization and, therefore, warrants further investigation The decreased N2O emissions following biochar addition, with (both soils) or without (Black soil) fertilizer N, could be due to decreased ammonium and nitrate availability, along with changes in denitrification potential as related to improved aeration Biochar significantly reduced the water-filled pore space, which concurrently increased CH4 consumption in both soils The lack of biochar effect on CO2 emissions from either soil, with or without fertilizer N, suggests enhanced CO2 consumption by autotrophic nitrifiers Biochar application appears to be an effective management approach for improving N2O and CH4 fluxes in temperate prairie soils

Anaerobic Co-digestion of Swine Manure and Microalgae Chlorella sp.: Experimental Studies and Energy Analysis

Abstract: Integration of algae production with livestock waste management has the potential to recover energy and nutrients from animal manure, while reducing discharges of organic matter, pathogens, and nutrients to the environment. In this study, microalgae Chlorella sp. were grown on centrate from anaerobically digested swine manure. The algae were harvested for mesophilic anaerobic digestion (AD) with swine manure for bioenergy production. Low biogas yields were observed in batch AD studies with algae alone, or when algae were co-digested with swine manure at ≥43 % algae (based on volatile solids [VS]). However, co-digestion of 6–16 % algae with swine manure produced similar biogas yields as digestion of swine manure alone. An average methane yield of 190 mL/g VSfed was achieved in long-term semi-continuous co-digestion studies with 10 ± 3 % algae with swine manure. Data from the experimental studies were used in an energy analysis assuming the process was scaled up to a concentrated animal feeding operation (CAFO) with 7000 pigs with integrated algae-based treatment of centrate and co-digestion of manure and the harvested algae. The average net energy production for the system was estimated at 1027 kWh per day. A mass balance indicated that 58 % of nitrogen (N) and 98 % of phosphorus (P) in the system were removed in the biosolids. A major advantage of the proposed process is the reduction in nutrient discharges compared with AD of swine waste without algae production.

Impact of Different Lignin Fractions on Saccharification Efficiency in Diverse Species of the Bioenergy Crop Miscanthus

Abstract: Lignin is a key factor limiting saccharification of lignocellulosic feedstocks. In this comparative study, various lignin methods—including acetyl bromide lignin (ABL), acid detergent lignin (ADL), Klason lignin (KL), and modified ADL and KL determination methods—were evaluated for their potential to assess saccharification efficiency. Six diverse accessions of the bioenergy crop miscanthus were used for this analysis, which included accessions of Miscanthus sinensis, Miscanthus sacchariflorus, and hybrid species. Accessions showed large variation in lignin content. Lignin estimates were different between methods, but (highly) correlated to each other (0.54 ≤ r ≤ 0.94). The strength of negative correlations to saccharification efficiency following either alkaline or dilute acid pretreatment differed between lignin estimates. The strongest and most consistent correlations (−0.48 ≤ r ≤ −0.85) were obtained with a modified Klason lignin method. This method is suitable for high throughput analysis and was the most effective in detecting differences in lignin content (p < 0.001) between accessions.

Environmental technologies of woody crop production systems

Abstract: Soil erosion, loss of productivity potential, biodiversity loss, water shortage, and soil and water pollution are ongoing processes that decrease or degrade provisioning (e.g., biomass, freshwater) and regulating (e.g., carbon sequestration, soil quality) ecosystem services. Therefore, developing environmental technologies that maximize these services is essential for the continued support of rural and urban populations. Genotype selection is a key component of these technologies, and characteristics of the species used in short rotation woody biomass systems, as well as the silvicultural techniques developed for short rotation woody crops are readily adapted to environmental applications. Here, we describe the development of such woody crop production systems for the advancement of environmental technologies including phytoremediation, urban afforestation, forest restoration, and mine reclamation. The primary goal of these collective efforts is to develop systems and tools that can help to mitigate ecological degradation and thereby sustain healthy ecosystems across the rural to urban continuum.

Dry Matter Losses and Greenhouse Gas Emissions From Outside Storage of Short Rotation Coppice Willow Chip

Abstract: This study examined the dry matter losses and the greenhouse gas (GHG) concentrations within two short rotation coppice (SRC) willow wood chip storage heaps. One heap was built on a grassland area (East Midlands) and the other (Rothamsted) on a concrete hard standing. A series of 1- and 3-m probes were embedded in the heaps in order to retrieve gas samples for analysis, and pre-weighed net bags were positioned in the core of the heap to detect dry matter losses. The bagged samples showed dry matter losses of 18 and 19 % in the East Midlands and Rothamsted heaps after 210 and 97 days storage, respectively. The Rothamsted heap showed a whole-heap dry matter loss of 21 %. During this time, the wood chips dried from 54 to 39 % moisture content in the East Midlands heap and 50 to 43 % at Rothamsted. The results from analysing the whole Rothamsted heap indicated an overall loss of 1.5 GJ per tonne stored, although measurements from bagged samples in the core suggested that the chips dried sufficiently to have a minimal energy loss from storage. The process of mixing the heap, however, led to incorporation of wet outer layers and hence the average moisture content was higher in an average sample of chip. After establishment of the heaps, the temperature rose rapidly and this correlated with a peak in carbon dioxide (CO2) concentration within the heap. A peak in methane (CH4) concentration was also detected in both heaps, though more noticeably in the East Midlands heap after around 55 days. In both instances, the peak CH4 concentration occurred as CO2 concentrations dropped, suggesting that after an active period of aerobic decomposition in the first 2 months of storage, the conditions in the heap became anaerobic. The results from this study suggest that outside wood chip storage is not an efficient method of storing biomass, though this may be location-specific as there are some studies showing lower dry matter losses. It is necessary to explore other methods of harvesting SRC to minimise losses and optimise land use efficiency. Further research is required to detect whether there are fugitive emissions of CH4 from wood chip heaps, as this will compromise the net GHG savings from utilising the biomass stored in this way.

An Olive Tree Pruning Biorefinery for Co-Producing High Value-Added Bioproducts and Biofuels: Economic and Energy Efficiency Analysis

Abstract: This work presents a conceptual design of an integrated biorefinery using olive tree pruning as feedstock. The biorefinery combines a state-of-the-art thermochemical technology for producing high value-added antioxidants with an energy self-sufficient biochemical platform for lignocellulosic ethanol production. These plants are integrated by exchanging energy and feedstock. The process and design parameters employed in the plant designs are based on the authors’ own lab and pilot-scale data. The paper discusses the economic dilemma of using this feedstock for producing high value-added products in small amounts versus producing large amounts of low-profit biofuels. The feasibility of this production strategy at medium scale is demonstrated via a techno-economic analysis based on total production cost for each co-product. Each plant is energy integrated, and the energy performance of the bioethanol plant is assessed by calculating the end-use-energy ratio. Both analyses are parameterized with respect to plant capacity (100–1500 t dry weight (dw)/day) and raw material price (20–100 €/ton dry weight).

Effects of Sewage Sludge Application on Biomass Production and Concentrations of Cd, Pb and Zn in Shoots of Salix and Populus Clones: Improvement of Phytoremediation Efficiency in Contaminated Soils

Abstract: Fast-growing clones of Salix and Populus species have been studied for phytoremediation of soils contaminated by risk elements (REs) using short-rotation coppice plantations. Biomass yield, accumulation and removal of RE (Cd, Pb and Zn) by highly productive willow (S1—(Salix schwerinii × Salix viminalis) × S. viminalis, S2—Salix × smithiana) and poplar (P1—Populus maximowiczii × Populus nigra, P2—P. nigra) clones were investigated with and without sewage sludge (SS) application. The precise field experiment was established in April 2008 on moderately Cd-, Pb- and Zn-contaminated soil. Initially, shoots were harvested after four seasons in February 2012 and then after two more seasons in February 2014. The application of SS limited plant growth during the first years of the experiment in the majority of treatments, mainly due to weed competition and higher concentrations of available soil nutrients causing lower yields than those of control (C) treatments. Well-developed roots were able to take advantage of SS applications, and shoot yield was mainly higher in SS treatments in the second harvest, reaching up to 15 t dry matter (DM) ha−1. Willows performed better than poplars. Application of SS reduced RE shoot concentrations compared to the C treatment. The removal of RE was significantly higher in the second harvest for all clones and elements (except the P2 clone), and the biomass yield was the major driving force for the amount of RE removed by shoots. Well-developed plantations of fast-growing trees showed better suitability for the phytoextraction of moderately contaminated soils for Cd and partly for Zn but not for Pb, which was less available to plants. From the four tested clones, S2 showed the best removal of Cd (up to 0.94 %) and Zn (up to 0.34 %) of the total soil element content, respectively, and this clone is a good candidate for phytoextraction. SS can be a suitable source of nutrients for Salix clones without any threat to the food chain in terms of biomass contamination, but its application to the soil can result in an increased incidence of some weeds during the first years of plantation.

Compositional Analysis of Biomass Reference Materials: Results from an Interlaboratory Study

Abstract: Biomass compositional methods are used to compare different lignocellulosic feedstocks, to measure component balances around unit operations and to determine process yields and therefore the economic viability of biomass-to-biofuel processes. Four biomass reference materials (RMs NIST 8491–8494) were prepared and characterized, via an interlaboratory comparison exercise in the early 1990s to evaluate biomass summative compositional methods, analysts, and laboratories. Having common, uniform, and stable biomass reference materials gives the opportunity to assess compositional data compared to other analysts, to other labs, and to a known compositional value. The expiration date for the original characterization of these RMs was reached and an effort to assess their stability and recharacterize the reference values for the remaining material using more current methods of analysis was initiated. We sent samples of the four biomass RMs to 11 academic, industrial, and government laboratories, familiar with sulfuric acid compositional methods, for recharacterization of the component reference values. In this work, we have used an expanded suite of analytical methods that are more appropriate for herbaceous feedstocks, to recharacterize the RMs’ compositions. We report the median values and the expanded uncertainty values for the four RMs on a dry-mass, whole-biomass basis. The original characterization data has been recalculated using median statistics to facilitate comparisons with this data. We found improved total component closures for three out of the four RMs compared to the original characterization, and the total component closures were near 100 %, which suggests that most components were accurately measured and little double counting occurred. The major components were not statistically different in the recharacterization which suggests that the biomass materials are stable during storage and that additional components, not seen in the original characterization, were quantified here.

Life Cycle Assessment of New Willow Cultivars Grown as Feedstock for Integrated Biorefineries

Abstract: The fossil fuel resources which power the chemical and energy industries are shrinking or becoming increasingly expensive. Moreover, their excavation and consumption have a negative impact on the environment, including global warming. For these reasons, new, cleaner, resources are being sought to replace them, such as lignocellulosic biomass. The aim of this study was to determine the environmental impact of the production of seven new cultivars of willow grown in a commercial plantation for use in an integrated biorefinery. The characteristics of the production and transport of 1 tonne of dry willow chips for the minimum (cultivar UWM 155), maximum (cultivar UWM 006) and average yield have shown that the cultivar with the lowest yield has the highest impact on the environment for all the selected categories of impact (CML 2 baseline 2000 method). For the average yield across all the cultivars, at a transportation distance of 25 km, this study found a high environmental impact of mineral NPK fertilisation, biomass harvest and road transport. The stage of normalisation for the average yield showed that freshwater toxicity had the greatest impact on the environment of all the categories under study. The effect of the other categories was 22–76 % lower for abiotic depletion and global warming, respectively. GHG emission amounted to 36 kg CO2 eq. per 1 Mg of dry willow chips transported for 25 km, and it increased with an increase in the transport distance by 24 and 71 % for 50 and 100 km, respectively. The lowest GHG emission per 1 Mg of dry chips was achieved for the production of the high-yielding biomass cultivars UWM 006 and UWM 043. Their chips could be transported for longer distances, i.e. 50 and 100 km, because their impact on global warming was much lower than the low-yielding cultivars UWM 155, Tur and UWM 035.

Novel Biomass Pretreatment Using Alkaline Organic Solvents: A Green Approach for Biomass Fractionation and 2,3-Butanediol Production

Abstract: Valorization of each component of lignocellulosic biomass is critical for sustainability of biorefinery industries. Current biorefineries are confined to ethanol-centric processes and focus only on the carbohydrate-derived sugar using energy-intensive pretreatment methods, leading to deteriorated lignin quality for high-value applications. Organosolv fractionation is an effective method to improve hydrolysis efficiency of cellulose and extract a good quality lignin stream; however, hemicelluloses recovery is challenging if an acid catalyst is used. An alkali catalyst in the organosolv process, therefore, could be a promising alternative approach. We evaluated various organic solvents (glycerol, 2,3-butanediol, dimethyl sulfoxide, ethanol, butanol, isopropanol, acetonitrile, and water) for pretreatment of different biomass feedstocks, including corn stover (grass), poplar (hardwood), and Douglas fir (softwood) using sodium hydroxide as a catalyst. Results showed that an ethanol and isopropanol mixture led to 18 % more sugar released per gram of biomass than the control (conventional aqueous alkali pretreatment) for corn stover; a mixture of ethanol, butanol, and water was the next most effective solvent. For pretreatment of poplar biomass, glycerol and 2,3-butanediol were the most efficient solvents; glycerol pretreatment offers further process improvement opportunities. The organic solvents used in this experiment were not effective for Douglas fir. The quality of released sugars was statistically equal to that of synthetic sugars for 2,3-butanediol fermentation using Klebsiella oxytoca. This study opened up a promising route for high value application for all biomass components. Further research is needed to characterize the extracted lignin for quality evaluation.

Financial Risk Assessment and Optimal Planning of Biofuels Supply Chains under Uncertainty

Abstract: Biofuels provide an attractive alternative for satisfying energy demands in a more sustainable way than fossil fuels. To establish a biorefinery, an optimal plan must be implemented for the entire associated supply chain, covering such aspects as selection of feedstocks, location, and capacity of biorefineries, selection of processing technologies, production amounts and transportation flows. In this context, there are several parameters, including the availability of biomass, product demand, and product prices, which are difficult to predict because they might change drastically over the different seasons of the year as well as across years. To address this challenge, this work presents a mathematical programming model for the optimal planning of a distributed system of biorefineries that considers explicitly the uncertainty associated with the supply chain operation as well as the associated risk. The potential of the proposed approach is demonstrated through its application to the production of biofuels in Mexico, considering multiple raw materials and products.

Sorghum and Switchgrass as Biofuel Feedstocks on Marginal Lands in Northern China

Abstract: To avoid food versus fuel conflicts in China, the production of bioenergy crops requires the evaluation of marginal lands under arid and semiarid conditions. We conducted field experiments with sorghum (Sorghum bicolor (L.) Moench) and switchgrass (Panicum virgatum L.) in Northern China. The biomass yield and nutrient (N, P, and K) accumulation of sorghum (leaves and stalks) and switchgrass (aboveground portion) were examined in 2012 and 2013. The soil organic carbon (SOC) content at depths of 0–30 cm was quantified at sorghum, switchgrass, and native grassland sites. The aboveground biomass yield of sorghum averaged 13.9 t ha−1 (14.2 and 13.6 t ha−1 in 2012 and 2013, respectively), while the switchgrass yield had a higher variability (14.8 versus 8.1 t ha−1 in 2012 and 2013, respectively) and averaged 11.5 t ha−1. The removals of N, P, and K averaged 56, 10, and 160 kg ha−1, respectively, for sorghum and 41, 11, and 89 kg ha−1, respectively, for switchgrass. To attain maximum biomass yield with minimum nutrient removal and the lowest transportation costs (due to the moisture content), the switchgrass harvest should be delayed until approximately 160 days after regrowth (DAR) in this region, whereas sorghum, which matures earlier, can be harvested as early as 120 days after sowing (DAS). Earlier harvests would increase the flexibility for large-scale ethanol production facilities. The SOC content within the 0–15-cm layer averaged 15.8 and 11.6 g C kg−1 before and 3 years after the establishment of the switchgrass culture, respectively, although the SOC increased with the culture age. In contrast, the SOC content of the 15–30-cm layer did not differ between the adjacent native grassland and the switchgrass planting. Under sorghum, the SOC content was reduced although it did not differ significantly from that of the native grassland at a significance level of p < 0.05. We conclude that high biomass yields can be obtained from the two crops under natural rainfall in the arid and semiarid conditions of Northern China. To address nutrient removal and SOC reduction, the leaves of sorghum should be returned to the field to increase the input of organic materials into the soil and reduce nutrient removal, which enhances soil fertility and sustainable production.

Biorefinery Developments for Advanced Biofuels from a Sustainable Array of Biomass Feedstocks: Survey of Recent Biomass Conversion Research from Agricultural Research Service

Abstract: When the USA passed the Renewable Fuel Standards (RFS) of 2007 into law, it mandated that, by the year 2022, 36 billion gallons of biofuels be produced annually in the USA to displace petroleum. This targeted quota, which required that at least half of domestic transportation fuel be “advanced biofuels” either produced from lignocellulosic feedstocks or be a sustainable liquid fuel other than corn ethanol or biodiesel from vegetable oils, will not likely be met due to the difficulty in commercializing alternative biofuels. The number one cost to a biorefinery is the biomass feedstock cost. Thus, it is important that research into biorefinery strategies be closely coupled to advances in crop science that account for crop yield and crop quality. To reach the RFS targets, stepwise progress in biorefinery technology is needed, as the industry moves from corn ethanol toward utilizing a wider array of lignocellulose-based biomass feedstocks. In 2010, the US Department of Agriculture created five Regional Biomass Research Centers to optimize production, collection, and conversion of crops to bioenergy, thus building a network that fosters collaboration among researchers to improve the biorefinery industry. An important component of the five Regional Biomass Research Centers is the four USDA Agricultural Research Service (ARS) regional utilization laboratories located across the country. These USDA ARS labs were originally set up by their commodities, whereby, in broad terms, the Northern Lab, now NCAUR, focused on corn and soy; the Eastern Lab on oils, leather, dairy, and meats; the Southern Lab on cotton, sugars, and fibers; and the Western Lab on other grains, including wheat and specialty crops. Each lab’s traditional expertise in these respective core commodity crops has been maintained as biofuel research came to the fore, but with the addition of new crops and biotechnological expertise, these labs often collaborate with each other, as will be revealed below. This review outlines some of the recent advances from the ARS labs in developing new bioprocessing strategies required to develop bioenergy from new crop sources.

Change in Yield Between First and Second Rotations in Willow (Salix spp.) Biomass Crops is Strongly Related to the Level of First Rotation Yield

Abstract: Yield is a critical factor in the development and understanding of willow biomass crops which experience multiple harvests after planting. Small changes in yield can have substantial impacts on economic and environmental assessments. Studies have reported increases between first rotation yield (FRY) and second rotation yield (SRY); however, there is minimal agreement on the variation of this increase. This study analyzes FRYs and SRYs of commercial willow cultivars in 360 research plots across five sites in the Northeast and North Central USA. Mean FRYs were 9.6 Mg ha−1 year−1 and mean SRYs were 7.9 % greater at 10.3 Mg ha−1 year−1. The relative change in yield between rotations was high for plots with low FRYs, but decreased as FRY increased and was negative when FRYs were highest. Therefore, applying a single yield increase factor to all willow crops may result in errors. Linear and logistic regression modeling were used to predict the magnitude of yield change across the range of FRYs and the probability for increasing/constant yields. Results showed that FRY alone predicts yield change with an R 2 of 0.635, and adding cultivar and site/management factors increases R 2 to 0.697. One study limitation is that many plots with the highest FRYs came from a drought influenced site. A meta-analysis of literature data revealed that this pattern of decreasing relative gains as FRYs increase is widespread though not previously addressed. Acknowledging this pattern should provide more accurate yield estimates over multiple rotations.

Synthesis and Application of Bifunctional Porous Polymers Bearing Chloride and Sulfonic Acid as Cellulase-Mimetic Solid Acids for Cellulose Hydrolysis

Abstract: A two-step strategy was demonstrated to synthesize porous polymeric solid acids with bifunctionality (chloride and sulfonic acid) to mimic cellulase for hydrolyzing cellulose. The solid acids were synthesized from aromatic monomers bearing chloride through Friedel-Crafts polymerization and then sulfonated with fuming sulfuric acid to introduce sulfonic acid. The chloride and sulfonic acid were expected to function as the cellulose-binding group (CBG) and the cellulose-hydrolytic group (CHG), respectively. It was found that the synthesized cellulase-mimetic solid acids were more effective in hydrolyzing microcrystalline cellulose (Avicel) than non-cellulase-mimetic solid acid (Amberlyst 15) and sulfuric acid at the same acid loading. Ball-milled Avicel could be hydrolyzed by up to 84.9 % by the cellulase-mimetic solid acids. The performance of the solid acids was supposedly attributed to the synergetic roles of the CBG and the CHG and the porous structure of the synthesized solid acids.

Bioenergy Potential, Energy Crops, and Biofuel Production in Mexico

Abstract: The negative impact of burning fossil fuels on the global climate, uncertainty over the long-term price of fossil fuels— caused in part by geopolitics and pending decisions on the exploration of oil shale and gas, tar sands and arctic oil reserves, and in part by uncertainty over future regulations on greenhouse gas emissions—and the increasing global demand for energy resulting from population growth and economic development drive the need to deploy renewable energy on a large scale. Mexico is a promising country in the development of renewable energy due to its warm and sunny climate, which supports solar energy generation and crop cultivation throughout the year, and its relative abundance of agricultural land that is suitable for energy crops, but not for food crops, thus minimizing competition between food and energy production. With a well developed infrastructure of roads, ports, and industrial centers, and a relatively low cost of labor, Mexico is among the most relevant emerging bioeconomies. In a recent study, Alemán-Nava et al. [1] reported the current use and future potential of renewable sources in the production of renewable energy, which included solar, hydroelectric, geothermal and wind energy, and bioenergy. However, these alternative sources of energy have not yet been fully exploited in Mexico. According to the Mexican Ministry of Energy (SENER) and the National Energy Balance databases [2], in 2014, Mexico produced 8826 PetaJoule (PJ = 10 J) of energy from the following sources: fossil fuels 91.31% (crude oil 63.42%, natural gas 23.56%, coal 3.44%, and condensates from natural gas production 0.89%), nuclear energy 1.14%, and renewables 7.56% (hydroelectric 1.59%, geothermal 1.47%, solar 0.10%, wind 0.26%, biomass 4.12%, and biogas 0.02%); these statistics indicate that fossil fuels still dominate, and that biomass represents only a small proportion of the total. While there are multiple renewable alternatives for the generation of electricity, biofuels are currently the only alternative source of liquid transportation fuels, and while the market share of electric cars is expected to increase, airplanes and ships will continue to require liquid fuels. Biomass is among the most promising feedstocks for the production of biofuels in Mexico, since the net emissions of CO2 are substantially lower compared to the use of both fossil and first-generation biofuels, there is an abundance of biomass, and large-scale biomass production and processing has potential to generate opportunities in different commercial sectors and can contribute to sustainable regional economic development [3, 4]. Furthermore, in recent years, Mexico has made significant changes in public policies to enhance its development of renewable energies. For example, in 2005, the Law on the * Héctor A. Ruiz hector_ruiz_leza@uadec.edu.mx

Sweet Sorghum Juice and Bagasse as Feedstocks for the Production of Optically Pure Lactic Acid by Native and Engineered Bacillus coagulans Strains

Abstract: Sweet sorghum is a bioenergy crop that produces large amounts of soluble sugars in its stems (3–7 Mg ha−1) and generates significant amounts of bagasse (15–20 Mg ha−1) as a lignocellulosic feedstock. These sugars can be fermented not only to biofuels but also to bio-based chemicals. The market potential of the latter may be higher given the current prices of petroleum and natural gas. The yield and rate of production of optically pure d-(−)- and l-(+)-lactic acid as precursors for the biodegradable plastic polylactide was optimized for two thermotolerant Bacillus coagulans strains. Strain 36D1 fermented the sugars in unsterilized sweet sorghum juice at 50 °C to l-(+)-lactic acid (∼150 g L−1; productivity, 7.2 g L−1 h−1). B. coagulans strain QZ19-2 was used to ferment sorghum juice to d-(−)-lactic acid (∼125 g L−1; productivity, 5 g L−1 h−1). Carbohydrates in the sorghum bagasse were also fermented after pretreatment with 0.5 % phosphoric acid at 190 °C for 5 min. Simultaneous saccharification and co-fermentation of all the sugars (SScF) by B. coagulans resulted in a conversion of 80 % of available carbohydrates to optically pure lactic acid depending on the B. coagulans strain used as the microbial biocatalyst. Liquefaction of pretreated bagasse with cellulases before SScF (L + SScF) increased the productivity of lactic acid. These results show that B. coagulans is an effective biocatalyst for fermentation of all the sugars present in sweet sorghum juice and bagasse to optically pure lactic acid at high titer and productivity as feedstock for bio-based plastics.

Biochemical Conversion of Torrefied Norway Spruce After Pretreatment with Acid or Ionic Liquid

Abstract: The chemical effects of torrefaction and the possibility to combine torrefaction with biochemical conversion were explored in experiments with five preparations of wood of Norway spruce that had be ...