Untreated Feedstock Research Articles

Effect of manure co-digestion on methane production, carbon retention, and fertilizer value of digestate

Anaerobic digestion can provide benefits not only from the perspective of renewable energy production but also in the form of fertilization effect and increased retention of C in soils after digestate application. This study consisted of two phases, where the first phase assessed the suitability of carbon-rich co-feedstocks for methane production via laboratory testing. The second phase assessed the balance and stability of C before and after anaerobic digestion by systematic digestate characterization, and by evaluating its carbon retention potential using a modeling approach. The results indicated that pyrolysis chars had a negligible effect on the methane production potential of cattle manure, while wheat straw expectedly increased methane production. Thus, a mixture of cattle manure and wheat straw was digested in pilot-scale leach-bed reactors and compared with undigested manure and straw. Although the total amount of C in the digestate was lower than in the untreated feedstocks, the digestion process stabilized C and was modeled to be more effective in retaining C in the soil than untreated cattle manure and wheat straw. In addition, digestion converted 23–27 % of the C into valuable methane, increasing the valorization of the total C in the feedstock. Considering anaerobic digestion processes as a strategy to optimize both carbon and nutrient valorization provides a more holistic approach to addressing climate change and improving soil health.

Unleashing synergistic potential of microbially enhanced anaerobic co-digestion of petroleum refinery biosludge and yard waste: Impact of nutrient balance and microbial diversity

Petroleum refinery sludge, an egregious solid residue generated from the wastewater treatment plants poses an environmental hazard owing to its intricate hydrocarbon composition, necessitating competent treatment for secure disposal. The study proposes a green solution through anaerobic co-digestion of nitrogen-rich petroleum refinery sludge (PS) with carbon-rich yard waste (YW), balancing the nutrients and moisture content for efficient microbial proliferation. Using Central Composite Design-Response Surface Methodology, 1 L batch experiments were conducted with varying carbon/nitrogen (C/N) ratios and pH to achieve maximum biogas yield within 50 days of co-digestion. However, the sluggish biogas recovery (40%) indicated a slow rate-limiting hydrolysis, necessitating pretreatment. Feedstock incubation with Bacillus subtilis IH1 strain, isolated from the microbially-enriched PS, at 108 colony forming units (CFU) per mL for 5 days maximized the soluble chemical oxygen demand and volatile fatty acids by 2.2 and 1.4 folds respectively compared to untreated feedstock. Scale-up Bacillus subtilis aided co-digestion studies further augmented biogas by 76% against untreated monodigestion of PS with significant total petroleum hydrocarbons, emulsions, and lignocellulosic degradation. Further identification of major organic pollutants in the batch digestate revealed significant degradation of the toxic organic hydrocarbon pollutants apotheosizing the efficacy of the synergistic sustainable technique for the management of PS. Environmental implicationThe effluent treatment plants (ETPs) of petroleum refining industries generate sludge which is a complex mixture of petroleum hydrocarbons, oil–water (O/W) emulsions and heavy metals. These petroleum hydrocarbon constituents can be linear/cyclic alkanes, polyaromatics, resins and asphaltenes, whose intricate composition is reportedly carcinogenic, cytogenic and mutagenic, classifying it as hazardous waste. Biological treatment of these sludge through anaerobic digestion leads to utilization of petroleum hydrocarbons with subsequent energy recovery. Co-digestion of these sludge with competent co-substrates leads to nutrient balance, diverse microbial proliferation and toxicant dilution. Microbially aided co-digestion further augments methane rendering a digestate with utmost pollutant degradation.

Optimization of Biomethane Yield of Xyris capensis Grass Using Oxidative Pretreatment

Biogas production from lignocellulose feedstocks has become an acceptable energy source globally due to their availability and economy. Lignocellulose materials have a complex arrangement that hinders digestion during the process. Therefore, applying the pretreatment process to lower the recalcitrant properties is required to utilize the full potential of the feedstock. This study, therefore, examines the influence of the oxidative pretreatment on the microstructural arrangement and biomethane yield of Xyris capensis. Piranha solution was prepared using H2O2 and H2SO4 at 100, 95:5, 85:15, and 75:25% of H2O2:H2SO4, respectively, and Xyris capensis grass was soaked in the prepared solution. The pretreated and untreated feedstocks were examined under the scanning electron microscope (SEM) to study the effect of the pretreatment on the microstructural arrangement. The effect of the pretreatment on biomethane yield was investigated during anaerobic digestion in a laboratory-scale batch digester at a mesophilic temperature (37 °C). The SEM analysis shows that the oxidative pretreatment method significantly affects the substrate’s microstructure, and the pretreatment’s severity depends on the percentage of H2SO4 added. A biomethane yield of 174.41, 188.61, 192.23, 207.51, and 139.71 mL CH4/g VSadded was observed, and the yield was increased by between 24.84 and 48.52% compared to the untreated substrate. Therefore, applying oxidative pretreatment using low-cost H2O2 is a clear method of improving the biomethane yield of lignocellulose feedstocks.

Instant catapult steam explosion: An efficient preprocessing step for the robust and cost-effective chemical pretreatment of lignocellulosic biomass

The biorefinery based on lignocellulosic biomass requires an efficient preprocessing step to address problems regarding with the high cost of biomass transportation and the low cost-effectiveness of subsequent chemical pretreatment . In this study, the instant catapult steam explosion (ICSE) was investigated as an alternative preprocessing method to treat corn stalk feedstocks , and compared with conventional milling preprocessing. Besides reducing the particle size, ICSE can modify the microstructure and improve enzymatic degradability of the corn stalks as well. These preprocessed feedstocks were further pretreated by moderate chemical pretreatment methods, including dilute acid, dilute alkali, acid and alkali, organosolv, and ionic liquid. The ICSE-treated feedstocks showed 3-fold to 7-fold increase in enzymatic saccharification when compared with milled and untreated feedstocks. Meanwhile, its energy consumption only accounted for 5%–20% of the milling process, thereby resulting in an 80%–85% of energy savings. Therefore, the ICSE-based preprocessing can potentially be integrated with the supply chain of lignocellulosic biomass and enhance the economic efficiency of biorefinery. • Instant catapult steam explosion (ICSE) as a preprocess is superior to milling for the downward chemical pretreatment. • ICSE, modifying lignocellulose's structure and composition, prompts the chemical pretreatment and subsequent enzymatic hydrolysis. • The energy consumption of ICSE is significantly lower than the traditional milling process. • ICSE facility can be adopted by the regional biomass preprocessing center to improve the cost-effectiveness of biorefinery.

Enhancing Glucose Recovery from Hibiscus cannabinus L. through Phosphoric Acid Pretreatment

Non-food lignocellulosic biomass is an attractive source owing to its abundance as a renewable resource and cost-effectiveness. Hibiscus cannabinus L., commonly known as kenaf, is a fiber-producing plant with high cellulose yield and non-food biomass. This study aimed to enhance the glucose recovery (GR) of kenaf biomass (KB). The bark and core fibers of KB are rich in glucan content and low in lignin content. Based on its glucan and lignin contents, KB has considerable potential as a feedstock for synthesizing monomer sugars, which can produce biofuel and high-value compounds. Therefore, the bark and core fibers were treated at a moderate temperature with various concentrations of phosphoric acid, followed by enzymatic hydrolysis. After pretreatment, the chemical composition of both feedstocks was changed. Phosphoric acid substantially affected the elimination of partial lignin and hemicellulose, which led to enhanced enzymatic hydrolysis. The maximum hydrolysis efficiency (HE) and GR of bark and core fibers were achieved when both feedstocks were treated with 75% phosphoric acid. Compared with untreated feedstocks, HE increased by approximately 5.6 times for bark and 4.7 times for core fibers. However, GR was enhanced approximately 4.9-fold for bark and 4.3-fold for core fibers.

Improving Fast Pyrolysis Bio-Oil Yield and Quality by Alkali Removal from Feedstock.

Alkali removal from forest residues, eucalyptus residues, and wheat straw was studied by water and dilute nitric acid leaching. Leaching parameters were optimized for each feedstock in laboratory-scale experiments. After the optimization of leaching on the laboratory scale, nitric acid-leached and untreated feedstocks were pyrolyzed in a bench-scale bubbling fluidized bed unit. In the case of eucalyptus residues and wheat straw, nitric acid leaching was found to increase the organic liquid yield compared to untreated feedstock. In addition, the sugar content of the fast pyrolysis bio-oils was increased, and the alkali content reduced. On the other hand, the pyrolysis experiments with acid-leached forest residues were unsuccessful due to the bed agglomeration. These problems are expected to be a result of the lack of catalytically active elements in biomass which enhance especially the cracking reactions of lignin. Finally, the results were demonstrated in the pilot-scale unit where nitric acid-leached oat straw was pyrolyzed with high organic liquid yield.

Biological production of hydrogen and acetone- butanol-ethanol from sugarcane bagasse and rice straw using co-culture of Enterobacter aerogenes and Clostridium acetobutylicum

Production of hydrogen and acetone-butanol-ethanol (ABE) from hydrolysates of sugarcane bagasse (SCB) and rice-straw (RS) was carried out via dark fermentation using co-culture of Enterobacter aerogenes and Clostridium acetobutylicum. The best improvement in the yield of hydrogen and total ABE production were observed for alkaline pretreated RS at 100 °C for 60 min obtained from the highest total reducing sugars concentration of 40.7 g L−1 after the enzymatic hydrolysis. The hydrolysates of alkaline pretreated samples at 100 °C were efficiently converted to H2 by co-culture of Enterobacter aerogenes and Clostridium acetobutylicum with the highest hydrogen yield of 136.3 and 149.9 mL H2 g−1-VS of SCB and RS, representing 3.4 and 1.5-fold enhancement in the hydrogen production yield over that obtained from the pure cultures of Enterobacter aerogenes and Clostridium acetobutylicum, respectively. Mass balance and energy generation analysis indicate that the highest specific ABE and total energy production yields per gram untreated feedstock reached 0.12 g ABE and 5.5 kJ for SCB and 0.08 g ABE and 6.6 kJ for RS.

Effects of harvest time and desalination of feedstock on Spartina alterniflora biochar and its efficiency for Cd2+ removal from aqueous solution

Cadmium (Cd2+), as the primary contaminant in Chinese soils, is dangerous to human health and ecological security. Invasive plant Spartina alterniflora in Chinese coastal wetlands presents a promising feedstock for biochar, which is an efficient adsorbent for heavy metal removal. S. alterniflora harvested in summer, autumn and winter were pyrolyzed to produce biochars. We analyzed the effects of harvest time and desalination of feedstock on biochar properties and Cd2+ adsorption capacity in aqueous solution. Biochars were characterized by pH probe, elemental analyzer, SEM, BJH, BET, and FTIR, and the Cd2+ concentrations were measured using AAS. Except pH (9.85–10.95) and nitrogen contents (0.71–1.59%), other biochar properties had no linear correlations with harvest time. Biochars produced from feedstock harvested in autumn had the highest carbon contents (73.25%) and lowest functional groups diversity (CC and –CHx). The pH and carbon contents (64.44–73.25%) were increased by desalination treatment. The surface area (0.48–2.27 m2/g), total pore volume (0.0015–0.0055 mL/g), mesopore volume (0.0015–0.0052 mL/g), and Cd2+ adsorption capacities (16.29–32.34 mg/g) were affected by desalination treatment, and the effects varied with harvest time. Biochars produced from desalted feedstock harvested in summer and untreated feedstock harvested in winter showed higher surface area, porosity, and Cd2+ adsorption capacity. Moderate salt contents (1.5–3.0% in chloride content) in feedstock promote the formation of biochars with higher surface area and porosity.

Impact of Pretreatment on Hydrothermally Carbonized Spruce

Upgrading biomass waste streams can improve economics in wood industries by adding value to the process. This work considers use of a hydrothermal carbonization (HTC) process for the residual feedstock after lignin and hemicelluloses extraction. Batch experiments were performed at 200–240 °C temperatures and three hours residence time with an 8:1 biomass to water ratio for two feedstocks: Raw spruce and spruce after lignin extraction. The proximate analysis and heating value showed similar results for both feedstocks, indicating that the thermochemical conversion is not impacted by the removal of lignin and hemicelluloses; the pretreatment processing slightly increases the heating value of the treated feedstock, but the HTC conversion process produces a consistent upgrading trend for both the treated and untreated feedstocks. The energy yield was 9.7 percentage points higher for the treated wood on average across the range temperatures due to the higher mass yield in the treated experiments. The energy densification ratio and the mass yield were strongly correlated with reaction temperature, while the energy yield was not. Lignocellulosic composition of the solid HTC product is mainly affected by HTC treatment, the effect of lignin extraction is negligible.

A sustainable bioenergy conversion strategy for textile waste with self-catalysts using mini-pyrolysis plant

Based on the current economic and environmental analysis of the textile waste streams, textile waste alone can be a promising source of renewable energy. To realize that, catalyst-supported pyrolysis was used in the present research to treat textile waste and convert it into value-added energy carriers while attempting to minimize consumption of consumable chemicals (catalysts) and pyrolysis time and maximize the yield of valuable bio-oil and gases (Methane and Hydrogen). Pyrolysis was conducted on waste jeans (a major fraction of textile waste, rich in cellulose/cotton) with different dye colors (black and blue) and dye-originating heavy metals (used as a self-catalysts). Waste jeans of both colors were pyrolyzed in original condition and after acid leaching to remove the heavy metals for comparison. Also, the pyrolysis experiments were performed according to Technology Readiness Levels (TRL) concept, particularly in laboratory and pilot scale phases. At the first phase, Differential thermal analysis/Thermogravimetric analysis/3D-Fourier-Transform Infrared spectroscopy was employed to simulate the pyrolysis on a lab scale (fundamental level of TRL) and study the thermal and chemical decomposition of the selected samples up to 800 °C. At the second stage, a pilot pyrolysis plant was built (based on the fundamental results received from lab scale) to simulate the industrial energy conversion conditions and obtain the data needed to apply the developed approach at industrial scale. The developed plant consisted of four units: pyrolysis reactor (capacity 300 g, Nitrogen ambient, and max. temp. 800 °C), gas purification unit, instantaneous gas composition analysis unit (to study the effect of pyrolysis temperature on the generated Oxygen, Nitrogen, Carbon Monoxide, Carbon dioxide, Methane, and Hydrogen gases), and gas products collection unit. The pyrolysis products were analyzed using Gas Chromatography–Mass Spectrometry, Fourier-Transform Infrared Spectroscopy, elemental analysis, and Scanning Electron Microscope- Energy-dispersive X-ray Spectroscopy. The results showed that the developed technology successfully converted more than 82% of the feedstock into liquid-gas products and that the untreated feedstock had effective bio-oil yield 36–37.6% (depending on the composition of self-catalysts), which was ∼20% higher compared to the treated batches; 18% reduction in pyrolysis time of untreated feedstock was achieved as well.

Organics in soda-anthraquinone black liquors from hot-water-extracted non-wood feedstocks

ABSTRACT The chemical compositions of black liquors (BLs) obtained from the soda-anthraquinone (AQ) pulping of untreated and hot-water-extracted non-wood feedstocks (okra stalk, miscanthus stalk, and wheat straw) were determined. These under-utilized renewable and widely available feedstocks could provide a cheaper source for producing fiber and precursors for manufacturing green chemicals. These BLs were mainly characterized in terms of carbohydrate-derived volatile carboxylic acids (acetic and formic acids) and non-volatile carboxylic acids (hydroxy acids) as well as lignin. Additionally, in each case, the average molar mass and molar mass distribution of the dissolved lignin were measured. Results indicated typical effects of hot-water extraction; for example, in the case of hot-water-extracted feedstocks, compared to untreated feedstocks, more aliphatic carboxylic acids were formed, whereas in both cases the removal of lignin was similar. The maximum total amounts of aliphatic carboxylic acids were in the following order: okra/150 °C/P200 (39 g L−1) > miscanthus/150 °C/P200 (31 g L−1) > wheat/150 °C/P200 (15 g L−1). On the other hand, the total dissolved lignin was in the following order: wheat/150 °C/P200 (45 g L−1) > miscanthus/150 °C/P200 (35 g L−1) ≈ okra/140 °C/P50 (35 g L−1). The hot-water extraction also affected weight average molar mass (w) values of the dissolved lignin in BLs. When the pre-treatment conditions became harsher, the w values increased; the lowest value detected was 4160 g mol−1 for lignin in the okra BL from the untreated feedstock, and the highest value, 8730 g mol−1, was obtained for lignin in the wheat BL from pre-treated feedstock (150 °C/P200). All the data obtained are of importance when planning the overall strategy for recovering the non-wood-derived aliphatic carboxylic acids and lignin formed in this kind of integrated biorefinery approach.

Increased biogas production from wheat straw by chemical pretreatments

Abstract This work investigated the effect of three different chemical pretreatment methods on the biogas production from the anaerobic digestion of wheat straw. The lignocellulosic material was separately pretreated using i) the organic solvent N-methylmorpholine N-oxide (NMMO) at 120 °C for 3 h, ii) the organosolv method, employing ethanol as the organic solvent at 180 °C for 1 h and iii) using an alkaline pretreatment with NaOH at 30 °C for 24 h. All the pretreatments were effective in increasing the biomethane production yield of wheat straw. In particular, the cumulative biomethane production yield of 274 mL CH4/g VS obtained with the untreated feedstock was enhanced by 11% by the NMMO pretreatment and by 15% by both the organosolv and alkaline pretreatment. The three pretreatment methods had a different impact on the chemical composition of the straw. NMMO hardly changed the amount of carbohydrates and lignin present in the original feedstock. Organosolv had a major impact on dissolving the hemicellulose component, whereas the alkaline pretreatment was the most effective in removing the lignin fraction. In addition to the increased biogas yields, the applied pretreatments enhanced the kinetics of biomethane production.

Microstructural Evolution in Solution Heat Treatment of Gas-Atomized Al Alloy (7075) Powder for Cold Spray

Cold gas dynamic spray is being explored as a repair technique for high-value metallic components, given its potential to produce pore and oxide-free deposits of between several micrometers and several millimeters thick with good levels of adhesion and mechanical strength. However, feedstock powders for cold spray experience rapid solidification if manufactured by gas atomization and hence can exhibit non-equilibrium microstructures and localized segregation of alloying elements. Here, we used sealed quartz tube solution heat treatment of a precipitation hardenable 7075 aluminum alloy feedstock to yield a consistent and homogeneous powder phase composition and microstructure prior to cold spraying, aiming for a more controllable heat treatment response of the cold spray deposits. It was shown that the dendritic microstructure and solute segregation in the gas-atomized powders were altered, such that the heat-treated powder exhibits a homogeneous distribution of solute atoms. Micro-indentation testing revealed that the heat-treated powder exhibited a mean hardness decrease of nearly 25% compared to the as-received powder. Deformation of the powder particles was enhanced by heat treatment, resulting in an improved coating with higher thickness (~ 300 μm compared to ~ 40 μm for untreated feedstock). Improved particle–substrate bonding was evidenced by formation of jets at the particle boundaries.

Assessing the potential of biofuel (biochar) production from food wastes through thermal treatment

This work primarily investigated the feasibility of generating high quality biochar from food wastes (FW) torrefaction. The thermal behavior of FW torrefaction was studied between 225 and 300°C for 1 and 3h at a fixed heating rate of 15°C/min. Torrefaction upgraded the energy density, calorific value and carbon content of FW compared to the untreated feedstock. Mass loss constituted a good measure of the reactivity and ease of degradation of FW based on the cumulative effect of time and temperature. The fuel properties of torrefied FW approached those of coal whilst their high energy yields confirmed their use as potential coal substitutes in thermal conversion systems. Torrefaction at 275°C at both residence times were optimal while severe torrefaction at 300°C for 3h was energetically inefficient. FTIR analysis and the increased HHV of bio-oil fractions revealed that bio-oil could be used to produce value-added chemicals and biofuels upon upgrading.

Effect of N-methylmorpholine-N-oxide Pretreatment on Biogas Production from Rice Straw, Cocoa Shell, and Hazelnut Skin

Abstract This study investigated effects of chemical pretreatment with N-methylmorpholine-N-oxide (NMMO) on methane yields of rice straw, cocoa bean shell, and hazelnut skin. Three lignocellulosic materials were separately pretreated with NMMO at 120°C for 3 h. Subsequently, batch biomethane production tests were performed under mesophilic (37°C ± 2°C) conditions, also with the untreated feedstocks, to provide methane production baseline data. Pretreatment was particularly effective for rice straw, with an 82% increased biomethane production yield from 206 mL CH4/g volatile solids (VS) obtained with the untreated substrate. A lower enhancement of the biomethane yield from 199 to 226 mL CH4/g VS (i.e., 14% increase) was observed for cocoa shell. For hazelnut skin, NMMO pretreatment resulted in a faster digestion rate in the initial 7 days, increasing the biomethane yield from 17 to 27 mL CH4/g VS·day. However, the cumulative biomethane yield after 40 days was not affected by NMMO pretreatment.

Understanding the Impacts of AFEX™ Pretreatment and Densification on the Fast Pyrolysis of Corn Stover, Prairie Cord Grass, and Switchgrass.

Lignocellulosic feedstocks corn stover, prairie cord grass, and switchgrass were subjected to ammonia fiber expansion (AFEX™) pretreatment and densified using extrusion pelleting and ComPAKco densification technique. The effects of AFEX™ pretreatment and densification were studied on the fast pyrolysis product yields. Feedstocks were milled in a hammer mill using three different screen sizes (2, 4, and 8mm) and were subjected to AFEX™ pretreatment. The untreated and AFEX™-pretreated feedstocks were moisture adjusted at three levels (5, 10, and 15% wb) and were extruded using a lab-scale single screw extruder. The barrel temperature of the extruder was maintained at 75, 100, and 125°C. Durability of the extruded pellets made from AFEX™-pretreated corn stover, prairie cord grass, and switchgrass varied from 94.5 to 99.2, 94.3 to 98.7, and 90.1 to 97.5%, respectively. Results of the thermogravimetric analysis showed the decrease in the decomposition temperature of the all the feedstocks after AFEX™ pretreatment indicating the increase in thermal stability. Loose and densified feedstocks were subjected to fast pyrolysis in a lab-scale reactor, and the yields (bio-oil and bio-char) were measured. Bio-char obtained from the AFEX™-pretreated feedstocks exhibited increased bulk and particle density compared to the untreated feedstocks. The properties of the bio-oil were statistically similar for the untreated, AFEX™-pretreated, and AFEX™-pretreated densified feedstocks. Based on the bio-char and bio-oil yields, the AFEX™-pretreated feedstocks and the densified AFEX™-pretreated feedstocks (pellets and PAKs) exhibited similar behavior. Hence, it can be concluded that densifying the AFEX™-pretreated feedstocks could be a viable option in the biomass-processing depots to reduce the transportation costs and the logistical impediments without affecting the product yields.

Batch Fermentation Options for High Titer Bioethanol Production from a SPORL Pretreated Douglas-Fir Forest Residue without Detoxification

This study evaluated batch fermentation modes, namely, separate hydrolysis and fermentation (SHF), quasi-simultaneous saccharification and fermentation (Q-SSF), and simultaneous saccharification and fermentation (SSF), and fermentation conditions, i.e., enzyme and yeast loadings, nutrient supplementation and sterilization, on high titer bioethanol production from SPORL-pretreated Douglas-fir forest residue without detoxification. The results indicated that Q-SSF and SSF were obviously superior to SHF operation in terms of ethanol yield. Enzyme loading had a strong positive correlation with ethanol yield in the range studied. Nutrient supplementation and sterility were not necessary for ethanol production from SPORL-pretreated Douglas-fir. Yeast loading had no substantial influence on ethanol yield for typical SSF conditions. After 96 h fermentation at 38 °C on shake flask at 150 rpm, terminal ethanol titer of 43.2 g/L, or 75.1% theoretical based on untreated feedstock glucan, mannan, and xylan content was achieved, when SSF was conducted at whole slurry solids loading of 15% with enzyme and yeast loading of 20 FPU/g glucan and 1.8 g/kg (wet), respectively, without nutrition supplementation and sterilization. It is believed that with mechanical mixing, enzyme loading can be reduced without reducing ethanol yield with extended fermentation duration.

Combustion Properties of Birch (Betula pendula) Black Liquors From Sulfur-Free Pulping

Sulfur-free pulping has an environmental advantage over the traditional kraft process. This article describes the combustion properties of the black liquors produced from silver birch (Betula pendula) sawdust using three different cooking processes: two sulfur-free cooks (soda-anthraquinone and oxygen-alkali), and one reference kraft cook. It also considers the corresponding black liquors from an integrated forest biorefinery, in which a hot-water pretreatment of feedstock was performed prior to pulping. With the same cooking time, the total burning times for the sulfur-free black liquors were higher (15–55%) than those for the conventional kraft black liquors. However, no significant differences were noted between the total burning times for black liquors from pretreated feedstock and those from untreated feedstock. Especially in the case of untreated feedstock, the results showed that the kraft black liquors typically swelled more (25–45%) than the sulfur-free black liquors. It was further observed that the kraft and soda-anthraquinone black liquors from the untreated feedstock swelled more than those from the pretreated feedstock, while the oxygen-alkali black liquors swelled less.

Liquid hot water pretreatment of multi feedstocks and enzymatic hydrolysis of solids obtained thereof

Agricultural feedstocks (brewers’ spent grain – BSG, corncob – CC, corn husk – CH, wheat straw – WS and Luffa sponge – LS) were pretreated by liquid hot water (LHW) in order to increase cellulose recovery and enzymatic saccharification. LHW-pretreatment resulted in hemicellulose solubilization, and solids enriched in cellulose. Chemical analysis showed different susceptibilities of the feedstocks to LHW-pretreatment and enzymatic hydrolysis. Pretreated feedstocks presented higher crystallinity (determined through X-ray diffraction) and thermal stability (determined through thermogravimetric analysis) than untreated feedstocks. SEM images confirmed the effect of LHW-pretreatment on structural changes. Moreover, enzymatic hydrolysis and cellulose conversion to glucose (CCG) were improved for pretreated feedstocks, with exception of LS. CCG (in relation to glucose potential on solids) followed the order: BSG>CH>WS>CC>LS. LHW-pretreatment showed to be a good technology to pretreat multi feedstocks and for improving the enzymatic hydrolysis of recalcitrant agricultural feedstocks to sugars, which can be further converted to ethanol-fuel and other value-added chemicals.

Impact of AFEX™ Pretreatment and Extrusion Pelleting on Pellet Physical Properties and Sugar Recovery from Corn Stover, Prairie Cord Grass, and Switchgrass.

The effects of AFEX™ pretreatment, feedstock moisture content (5,10, and 15% wb), particle size (screen sizes of 2, 4, and 8mm), and extrusion temperature (75, 100, and 125°C) on pellet bulk density, pellet hardness, and sugar recovery from corn stover, prairie cord grass, and switchgrass were investigated. Pellets were produced from untreated and AFEX™ pretreated feedstocks using a laboratory-scale extruder. AFEX™ pretreatment increased subsequent pellet bulk density from 453.0 to 650.6kgm(-3) for corn stover from 463.2 to 680.1kgm(-3) for prairie cord grass, and from 433.9 to 627.7kgm(-3) for switchgrass. Maximum pellet hardness of 2342.8, 2424.3, and 1298.6N was recorded for AFEX™ pretreated corn stover, prairie cord grass, and switchgrass, respectively. Glucose yields of AFEX™ corn stover pellets, prairie cord grass, and switchgrass pellets varied from 88.9 to 94.9%, 90.1 to 94.9%, and 87.0 to 92.9%, respectively. Glucose and xylose yields of AFEX™ pellets were not affected by the extruder barrel temperature and the hammer mill screen size. The results obtained showed that low temperature and large particle size during the extrusion pelleting process can be employed for AFEX™-treated biomass without compromising sugar yields.