Corn Stover Feedstock Research Articles

Enhancement of energy efficiency and economics of process designs for catalytic co-production of bioenergy and bio-based products from lignocellulosic biomass

Summary This study presents an integrated strategy for the co-production of bioenergy (biofuels: butene oligomers) and bio-based products (biomaterials: cyclopentanone (CPON) and alkylphenols) from hemicellulose (C5), cellulose (C6), and lignin fractions of lignocellulosic biomass based on experimental catalysis studies. To evaluate techno-economic feasibility of the strategy, we performed a system-level design study with three steps: process synthesis, energy analysis, and economic analysis. The results of process synthesis show that all biomass fractions are effectively converted with high numerical carbon yields (C6-to-butene oligomers: 52.5%, C5-to-CPON: 68.2%, and lignin-to-alkylphenols: 13.3%) but an efficient separation system for high recovery of bioenergy and bio-based products is crucial. Moreover, an efficient design of a heat exchanger network leads that the total energy requirements of the process are satisfied by the combustion of biomass degradation products (humins). Finally, an economic analysis is performed to estimate the minimum selling price of CPON as the highest energy material (201 Mt/day of CPON production using 2000 Mt/day of corn stover feedstock processing). This result shows that the process ($1.79/kg CPON) can be cost competitive with current petro-based production approaches. Copyright © 2017 John Wiley & Sons, Ltd.

Impact of six lignocellulosic biochars on C and N dynamics of two contrasting soils

AbstractBoth soil and biochar properties are known to influence greenhouse gas emissions from biochar‐amended soils, but poor understanding of underlying mechanisms challenges prediction and modeling. Here, we examine the effect of six lignocellulosic biochars produced from the pyrolysis of corn stover and wood feedstocks on CO2 and N2O emissions from soils collected from two bioenergy cropping systems. Effects of biochar on total accumulated CO2‐C emissions were minimal (<0.45 mg C g−1 soil; <10% of biochar C), consistent with mineralization and hydrolysis of small labile organic and inorganic C fractions in the studied biochars. Comparisons of soil CO2 emissions with emissions from microbially inoculated quartz–biochar mixtures (‘quartz controls’) provide evidence of soil and biochar‐specific negative priming. Five of six biochar amendments suppressed N2O emissions from at least one soil, and the magnitude of N2O emissions suppression varied with respect to both biochar and soil types. Biochar amendments consistently decreased final soil NO3− concentrations, while contrasting effects on pH, NH4+, and DOC highlighted the potential for formation of anaerobic microsites in biochar‐amended soils and consequential shifts in the soil redox environment. Thus, results implicated both reduced substrate availability and redox shifts as potential factors contributing to N2O emission suppression. More research is needed to confirm these mechanisms, but overall our results suggest that soil biochar amendments commonly reduce N2O emissions and have little effect on CO2 emissions beyond the mineralization and/or hydrolysis of labile biochar C fractions. Considering the large C credit for the biochar C, we conclude that biochar amendments can reduce greenhouse gas emissions and enhance the climate change mitigation potential of bioenergy cropping systems.

Fermentative production of high titer citric acid from corn stover feedstock after dry dilute acid pretreatment and biodetoxification

The aim of this work is to study the citric acid fermentation by a robust strain Aspergillus niger SIIM M288 using corn stover feedstock after dry dilute sulfuric acid pretreatment and biodetoxification. Citric acid at 100.04g/L with the yield of 94.11% was obtained, which are comparable to the starch or sucrose based citric acid fermentation. No free wastewater was generated in the overall process from the pretreatment to citric acid fermentation. Abundant divalent metal ions as well as high titer of potassium, phosphate, and nitrogen were found in corn stover hydrolysate. Further addition of extra nutrients showed no impact on increasing citric acid formation except minimum nitrogen source was required. Various fermentation parameters were tested and only minimum regulation was required during the fermentation. This study provided a biorefining process for citric acid fermentation from lignocellulose feedstock with the maximum citric acid titer and yield.

Characterization and quantification of biochar alkalinity

Lack of knowledge regarding the nature of biochar alkalis has hindered understanding of pH-sensitive biochar-soil interactions. Here we investigate the nature of biochar alkalinity and present a cohesive suite of methods for its quantification. Biochars produced from cellulose, corn stover and wood feedstocks had significant low-pKa organic structural (0.03–0.34 meq g−1), other organic (0–0.92 meq g−1), carbonate (0.02–1.5 meq g−1), and other inorganic (0–0.26 meq g−1) alkalinities. All four categories of biochar alkalinity contributed to total biochar alkalinity and are therefore relevant to pH-sensitive soil processes. Total biochar alkalinity was strongly correlated with base cation concentration, but biochar alkalinity was not a simple function of elemental composition, soluble ash, fixed carbon, or volatile matter content. More research is needed to characterize soluble biochar alkalis other than carbonates and to establish predictive relationships among biochar production parameters and the composition of biochar alkalis.

A bio-based ‘green’ process for catalytic adipic acid production from lignocellulosic biomass using cellulose and hemicellulose derived γ-valerolactone

A bio-based ‘green’ process is presented for the catalytic conversion of corn stover to adipic acid (ADA) based on experimental studies. ADA is used for biobased nylon 6.6 manufacturing from lignocellulosics as carbon and energy source. In this process, the cellulose and hemicellulose fractions are catalytically converted to γ-valerolactone (GVL), using cellulose and hemicellulose-derived GVL as a solvent, and subsequently upgrading to ADA. Experimental studies showed maximal carbon yields (biomass-to-GVL: 41% and GVL-to-ADA: 46%) at low concentrations (below 16wt% solids) using large volumes of GVL solvents while requiring efficient interstage separations and product recovery. This work presents an integrated process, including catalytic conversion and separation subsystems for GVL and ADA production and recovery, and designs a heat exchanger network to satisfy the total energy requirements of the integrated process via combustion of biomass residues (lignin and humins). Finally, an economic analysis shows that 2000 metric tonnes (Mt) per day of corn stover feedstock processing results in a minimum selling price of $633 per Mt if using the best possible parameters.

Fermentative production of high titer gluconic and xylonic acids from corn stover feedstock by Gluconobacter oxydans and techno-economic analysis

High titer gluconic acid and xylonic acid were simultaneously fermented by Gluconobacter oxydans DSM 2003 using corn stover feedstock after dry dilute sulfuric acid pretreatment, biodetoxification and high solids content hydrolysis. Maximum sodium gluconate and xylonate were produced at the titer of 132.46g/L and 38.86g/L with the overall yield of 97.12% from glucose and 90.02% from xylose, respectively. The drawbacks of filamentous fungus Aspergillus niger including weak inhibitor tolerance, large pellet formation and no xylose utilization were solved by using the bacterium strain G. oxydans. The obtained sodium gluconate/xylonate product was highly competitive as cement retarder additive to the commercial product from corn feedstock. The techno-economic analysis (TEA) based on the Aspen Plus modeling was performed and the minimum sodium gluconate/xylonate product selling price (MGSP) was calculated as $0.404/kg. This study provided a practical and economic competitive process of lignocellulose utilization for production of value-added biobased chemicals.

Comparative life cycle assessment of fossil and bio-based polyethylene terephthalate (PET) bottles

Both biofuels and bioplastics are often regarded as sustainable solutions to current environmental problems such as climate change, fossil depletion and acidification. However, both have been criticized for being economically costly, competing with other societally beneficial goods such as food, and offering limited environmental benefits compared to their fossil counterparts. This study provides a comparative environmental Life Cycle Analysis (LCA) for 100% bio-based polyethylene terephthalate (PET) bottles, versus fully fossil-based and partially bio-based PET bottles. An attributional life cycle assessment (aLCA) and sensitivity analysis of key assumptions is carried out to compare cradle-to-factory-gate impacts (i.e. feedstock extraction, component production and product manufacturing) of twelve PET bottle production scenarios. Results indicate that woody-biomass based PET bottles have 21% less global warming potential and require 22% less fossil fuel than their fossil based counterparts, but perform worse in other categories such as ecotoxicity and ozone depletion impacts. Results are sensitive to impact allocation assumptions as well as parameter input assumptions related to isobutanol production. In most categories, with avoided impact credits considered, forest residue feedstocks result in overall better environmental performance than corn stover feedstocks for bio-PET bottle production. The variability in avoided burdens could alter the relative environmental rankings for fossil and bio-PET bottles. Depending on the biomass feedstock, extraction and pre-processing are likely more emission-intensive than the corresponding fossil refinery processes due to the significant upstream emissions embodied in the application of fertilizers, and the significant chemical and energy inputs required to break recalcitrant lignocellulosic bonds.

A techno-environmental overview of a corn stover biomass feedstock supply chain for cellulosic biorefineries

ABSTRACTCorn stover is the primary feedstock choice of the first generation of cellulosic biorefineries in the Midwestern US due to its abundance in the region. The technically sound, economic and environment-friendly supply system of this feedstock is inevitable for the commercial success and proliferation of these biorefineries. Such supply systems involve different aspects of stover production, harvesting, collection, handling, transportation, storage and preprocessing. This review discusses the environmental concerns of stover collection for biofuels production, and provides an update on the technological status of the corn stover feedstock supply system. The major environmental concerns of corn stover collection discussed here include its impact on soil nitrogen availability and crop requirements, changes in crop productivity, soil erosion and change in soil organic carbon, soil fertility, carbon sequestration, nutrient emissions and disease pressures. The cellulosic biorefinery feedstock quality requirements and different supply chain components are also thoroughly discussed. This review concludes by presenting a perspective on near-term and future corn stover-based feedstock supply systems with the potential to be commercially implemented. Although the extent of stover removal from the field is highly debated, there is a consensus that some fraction of biomass removal would help lower both agronomic production cost and environmental impact.

Techno-Economic Analysis of Cellulosic Butanol Production from Corn Stover through Acetone–Butanol–Ethanol Fermentation

Biobutanol has fuel properties comparable to those of gasoline; however, its commercial production through acetone–butanol–ethanol (ABE) fermentation from lignocellulosic biomass is still encumbering due to low product yield, energy extensive recovery method, and butanol toxicity to microbes. Recent development of simultaneous saccharification, vacuum fermentation, and recovery technique has the potential to reduce these problems and improve butanol yield, which has gained significant attention as an emerging alternative way for ABE fermentation. Thus, the main objective of this study was to assess the techno-economic feasibility of commercial-scale ABE fermentation for a 113.4 million L/year (30 million gal/year) butanol production and identify operational targets for process improvement. Commercial dilute sulfuric acid pretreatment and corn stover feedstock were used in this study. Experimental data on the pretreatment of corn stover and the ABE fermentation and recovery were gathered from recent public...

A techno‐economic analysis of the corn stover feedstock supply system for cellulosic biorefineries

AbstractThe primary feedstock choice for most first‐generation commercial cellulosic biorefineries in the Midwest is corn stover. Their rated capacities are between 76 and 114 million liters per year (MLPY). For uninterrupted operation of these plants, a year‐round supply of corn stover needs to be secured, requiring a robust, efficient, and cost‐effective feedstock supply system. Thus, the main objective of this work is to stochastically analyze the techno‐economics of corn stover supply system for a 114 MLPY cellulosic biorefinery in the Midwest using production‐scale experimental field data collected in Iowa. This study analyzes the resources requirements (equipment, labor, fuel, and consumables) and costs of different components of the supply chain that include harvesting (windrowing and baling), in‐field bale collection and stacking at the field‐edge, handling and transportation of bales from the field‐edge to the distributed storage facilities and then to the biorefinery plant, storage, and finally the audit of nutrients removed during stover collection from the field. Additionally, this study identifies and ranks different supply chain parameters based on their relative influence on the overall resources and costs requirements. A 114 MLPY cellulosic biorefinery annually requires around 0.95 million corn stover bales supply, 250 000 hours equivalent of labor and 4.3 million L of diesel fuel. The average cost of biorefinery gate delivered corn stover is estimated to be 121.9 $‐std. t−1. This cost is identified to be the most sensitive to bale density followed by harvest rate, bale length, baler field efficiency, and annual harvest days. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

Process synthesis and analysis for catalytic conversion of lignocellulosic biomass to fuels: Separate conversion of cellulose and hemicellulose using 2-sec-butylphenol (SBP) solvent

We developed a strategy for the catalytic production of liquid hydrocarbon fuels (butene oligomers) from cellulose and hemicellulose, which are the major fractions of lignocellulosic biomass. In this strategy the cellulose and hemicellulose fractions are separated through a pretreatment step and then converted to levulinic acid (LA) by monophasic and biphasic reactions using 2-sec-butylphenol (SBP) solvent respectively. The LA is upgraded catalytically to γ-valerolactone (GVL), and subsequently to butene oligomers. To design the integrated strategy, we developed separation subsystems to satisfy the optimized feed concentration for catalytic conversions and to recycle solvents (SBP). To satisfy energy requirements for our process from combustion of biomass residues, we designed a heat exchanger network (HEN) for minimum energy consumption by maximizing heat recovery from the process streams. Our technoeconomic evaluation shows that the integrated strategy using corn stover feedstock results in a minimum selling price of $3.71 per gallon of gasoline equivalent for butene oligomers if using the best possible parameters.

Acetone-butanol-ethanol fermentation of corn stover: current production methods, economic viability and commercial use.

Biobutanol is a next-generation liquid biofuel with properties akin to those of gasoline. There is a widespread effort to commercialize biobutanol production from agricultural residues, such as corn stover, which do not compete with human and animal foods. This pursuit is backed by extensive government mandates to expand alternative energy sources. This review provides an overview of research on biobutanol production using corn stover feedstock. Structural composition, pretreatment, sugar yield (following pretreatment and hydrolysis) and generation of lignocellulose-derived microbial inhibitory compounds (LDMICs) from corn stover are discussed. The review also discusses different Clostridium species and strains employed for biobutanol production from corn stover-derived sugars with respect to solvent yields, tolerance to LDMICs and in situ solvent recovery (integrated fermentation). Further, the economics of cellulosic biobutanol production are highlighted and compared to corn starch-derived ethanol and gasoline. As discussed herein, the economic competitiveness of biobutanol production from corn stover largely depends on feedstock processing and fermentation process design.

Acceleration of biodetoxification on dilute acid pretreated lignocellulose feedstock by aeration and the consequent ethanol fermentation evaluation.

BackgroundBiodetoxification by the fungus Amorphotheca resinae ZN1 provides an effective way of inhibitor removal from pretreated lignocellulose feedstock and has been applied in the process of ethanol, biolipids, and lactic acid production. However, the long-time used and the consumption of considerable xylose in the pretreated materials reduced the process efficiency. The improvements of biodetoxification should be made to enhance the production of biochemical from lignocellulosic materials.ResultsThis study reported an acceleration method of A. resinae ZN1-based biodetoxification on the corn stover (CS) feedstock pretreated using dry dilute acid pretreatment. Under proper aeration and well-mixing condition, the conversion rate of furfural, 5-hydroxymethylfurfural (HMF), acetic acid, and typical phenolic compounds were significantly accelerated by more than twofolds faster, which resulted in the reduction of biodetoxification time from 96 h in the conventional process to 36 h. Simultaneous saccharification and ethanol fermentation assay on accelerated biodetoxification of the dry dilute acid pretreated CS feedstock achieved the similar ethanol titer (48.56 g/L of 36 h’ accelerated biodetoxification vs. 50.00 g/L of 4 days’ conventional biodetoxification) and yield (58.10 vs. 59.63 %). Substrate priority of inhibitors to sugars by A. resinae ZN1 was discovered and considerable xylose was reserved in the accelerated biodetoxification. Cell growth of A. resinae fungus in liquid medium and on pretreated CS solids revealed that the enhanced aeration enhanced the biodetoxification rate rather than the cell growth rate. Accelerated inhibitor conversion might come from the increased supply of cofactors of nicotinamide adenine dinucleotide or nicotinamide adenine dinucleotide phosphate from the step of aldehyde inhibitors to the corresponding acids, instead of cell mass increase.ConclusionAccelerated biodetoxification reduced the period of biodetoxification and retained the xylose components in the pretreated CS, which provided a practical method on improving process efficiency for cellulosic ethanol production from severe pretreated lignocellulose feedstock.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0438-9) contains supplementary material, which is available to authorized users.

Corn stover ethanol yield as affected by grain yield, Bt trait, and environment

Literature values for glucose release from corn stover are highly variable which would likely result in tremendous variability in bio-refinery ethanol yield from corn stover feedstock. A relatively recent change in United States corn genetics is the inclusion of the Bacillus thuringiensis (Bt) trait, which now accounts for three-fourths of all US planted corn acreage. The objective of this study was to evaluate the effect of corn grain yield, inclusion of the Bt trait, and location environment on corn stover quality for subsequent ethanol conversion. Two hybrid pairs (each having a Bt and non-Bt near-isoline) were analyzed giving a total of 4 hybrids. In 2010 and 2011, field plots were located in Michigan at four latitudinal differing locations in four replicated plots at each location. Stover composition and enzymatic digestibility was analyzed and estimated ethanol yield (g g−1) was calculated based on hydrolyzable glucan and xylan levels. Analysis showed that there were no significant differences in total glucose or xylose levels nor in enzymatically hydrolyzable glucan and xylan concentrations between Bt corn stover and the non-Bt stover isolines. Regression analyses between corn grain yield (Mg ha−1) and corn stover ethanol yield (g g−1) showed an inverse relationship indicative of a photosynthate source-sink relationship. Nevertheless, the quantity of stover produced was found to be more critical than the quality of stover produced in maximizing potential stover ethanol yield on a land area basis.

Engineering wild-type robust Pediococcus acidilactici strain for high titer l- and d-lactic acid production from corn stover feedstock

Pediococcus acidilactici TY112 producing l-lactic acid and P. acidilactici ZP26 producing d-lactic acid, were engineered from the wild-type P. acidilactici DQ2 by ldhD or ldh gene disruption, and the robustness of the wild-type strain to the inhibitors derived from lignocellulose pretreatment was maintained well. In simultaneous saccharification and fermentation (SSF), 77.66gL−1 of l-lactic acid and 76.76gL−1 of d-lactic acid were obtained at 25% (w/w) solids content of dry dilute acid pretreated and biodetoxified corn stover feedstock. l- and d-Lactic acid yield and productivity were highly dependent on the inhibitor removal extent due to the significant down-regulation on the expressions of ldh and ldhD encoding lactate dehydrogenase by inhibitor, especially syringaldehyde and vanillin at the low concentrations. This study provided a prototype of industrial process for high titer l- and d-lactic acid production from lignocellulose feedstock.

Long term storage of dilute acid pretreated corn stover feedstock and ethanol fermentability evaluation

This study reported a new solution of lignocellulose feedstock storage based on the distributed pretreatment concept. The dry dilute sulfuric acid pretreatment (DDAP) was conducted on corn stover feedstock, instead of ammonia fiber explosion pretreatment. Then the dry dilute acid pretreated corn stover was stored for three months during summer season with high temperature and humidity. No negative aspects were found on the physical property, composition, hydrolysis yield and ethanol fermentability of the long term stored pretreated corn stover, plus the additional merits including no chemicals recovery operation, anti-microbial contaminant environment from stronger acid and inhibitor contents, as well as the mild and slow hydrolysis in the storage. The new pretreatment method expanded the distributed pretreatment concept of feedstock storage with potential for practical application.

High titer l-lactic acid production from corn stover with minimum wastewater generation and techno-economic evaluation based on Aspen plus modeling

Technological potentials of l-lactic acid production from corn stover feedstock were investigated by experimental and techno-economic studies. An optimal performance with 104.5g/L in l-lactic acid titer and 71.5% in overall yield from cellulose in corn stover to l-lactic acid using an engineered Pediococcus acidilactici strain were obtained by overcoming several technical barriers. A rigorous Aspen plus model for l-lactic acid production starting from dry dilute acid pretreated and biodetoxified corn stover was developed. The techno-economic analysis shows that the minimum l-lactic acid selling price (MLSP) was $0.523perkg, which was close to that of the commercial l-lactic acid produced from starch feedstock, and 24% less expensive than that of ethanol from corn stover, even though the xylose utilization was not considered. The study provided a prototype of industrial application and an evaluation model for high titer l-lactic acid production from lignocellulose feedstock.

Corn Stover Nutrient Removal Estimates for Central Iowa, USA

One of the most frequent producer-asked questions to those persons striving to secure sustainable corn (Zea mays L.) stover feedstock supplies for Iowa’s new bioenergy conversion or other bio-product facilities is “what quantity of nutrients will be removed if I harvest my stover?” Our objective is to summarize six years of field research from central Iowa, U.S.A. where more than 600, 1.5 m2 samples were collected by hand and divided into four plant fractions: vegetative material from the ear shank upward (top), vegetative material from approximately 10 cm above the soil surface to just below the ear (bottom), cobs, and grain. Another 400 stover samples, representing the vegetative material collected directly from a single-pass combine harvesting system or from stover bales were also collected and analyzed. All samples were dried, ground, and analyzed to determine C, N, P, K, Ca, Mg, S, Al, B, Cu, Fe, Mn, and Zn concentrations. Mean concentration and dry matter estimates for each sample were used to calculate nutrient removal and estimate fertilizer replacement costs which averaged $25.06, $20.04, $16.62, $19.40, and $27.41 Mg−1 for top, bottom, cob, stover, and grain fractions, respectively. We then used the plant fraction estimates to compare various stover harvest scenarios and provide an answer to the producer question posed above.

High ethanol fermentation performance of the dry dilute acid pretreated corn stover by an evolutionarily adapted Saccharomyces cerevisiae strain

Ethanol fermentation was investigated at the high solids content of the dry dilute sulfuric acid pretreated corn stover feedstock using an evolutionary adapted Saccharomyces cerevisiae DQ1 strain. The evolutionary adaptation was conducted by successively transferring the S. cerevisiae DQ1 cells into the inhibitors containing corn stover hydrolysate every 12h and finally a stable yeast strain was obtained after 65days’ continuous adaptation. The ethanol fermentation performance using the adapted strain was significantly improved with the high ethanol titer of 71.40g/L and the high yield of 80.34% in the simultaneous saccharification and fermentation (SSF) at 30% solids content. No wastewater was generated from pretreatment to fermentation steps. The results were compared with the published cellulosic ethanol fermentation cases, and the obvious advantages of the present work were demonstrated not only at the high ethanol titer and yield, but also the significant reduction of wastewater generation and potential cost reduction.

Impact of Pretreatment Technologies on Saccharification and Isopentenol Fermentation of Mixed Lignocellulosic Feedstocks

In order to enable the large-scale production of biofuels or chemicals from lignocellulosic biomass, a consistent and affordable year-round supply of lignocellulosic feedstocks is essential. Feedstock blending and/or densification offers one promising solution to overcome current challenges on biomass supply, i.e., low energy and bulk densities and significant compositional variations. Therefore, it is imperative to develop conversion technologies that can process mixed pelleted biomass feedstocks with minimal negative impact in terms of overall performance of the relevant biorefinery unit operations: pretreatment, fermentable sugar production, and fuel titers. We processed the mixture of four feedstocks—corn stover, switchgrass, lodgepole pine, and eucalyptus (1:1:1:1 on dry weight basis)—in flour and pellet form using ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate, dilute sulfuric acid (DA), and soaking in aqueous ammonia (SAA) pretreatments. Commercial enzyme mixtures, including cellulases and hemicellulases, were then applied to these pretreated feedstocks at low to moderate enzyme loadings to determine hydrolysis efficiency. Results show significant variations on the chemical composition, crystallinity, and enzymatic digestibility of the pretreated feedstocks across the different pretreatment technologies studied. The advanced biofuel isopentenol was produced during simultaneous saccharification and fermentation (SSF) of pretreated feedstocks using an engineered Escherichia coli strain. Results show that IL pretreatment liberates the most sugar during enzymatic saccharification, and in turn led to the highest isopentenol titer as compared to DA and SAA pretreatments. This study provides insights on developing biorefinery technologies that produce advanced biofuels based on mixed feedstock streams.