Pretreated Straw Research Articles

Attributional and consequential life cycle perspectives of second-generation polylactic acid: The benefits of integrating a recycling strategy

The climate crisis calls for a shift from petrochemicals to bio-based products to reduce environmental consequences. Polylactic acid (PLA) is one of the most widely used biopolymers, due to its mechanical properties and renewable origin, to produce bio-based compostable plastic for food packaging. The objective of this study is to determine the environmental feasibility of a second-generation PLA production based on wheat straw; and the role of a chemical recycling plant on the environmental performance of a bioproduct at an early design stage. A holistic assessment was performed through the Life Cycle Assessment (LCA) methodology considering both attributional and consequential perspectives, through a cradle-to-grave approach. The attributional LCA results show that lactic acid production was the main contributor due to the wheat straw pre-treatment and downstream separation and purification (DSP) processes. The integration of a recycling plant leads to a significant reduction of burdens, ranging from 1.38 to 0.44 kg CO2eq in the Global Warming category. Furthermore, consequential LCA results shows that the increased demand for substitute products for activities such as feeding, fertilisation and energy generation and the indirect emissions from land use change related to the conversion of land for the cultivation of raw materials are relevant factors in the environmental effects associated with the possible implementation of straw-based bioPLA production system.

Magnetic solid acid catalyst derived from different alkaline pretreatment of rice straw for hydrolysis of microcrystalline cellulose

Magnetic solid acid catalyst derived from different alkaline pretreatment of rice straw for hydrolysis of microcrystalline cellulose

Effects of cold isostatic press pretreatment of rice straw on microstructure and efficiency of anaerobic digestion for methane production

In this study, rice straw was pretreated using by cold isostatic pressure to disrupt its microstructure and improve the performance of anaerobic digestion, and the optimal process parameters were optimized using the response surface methodology. The results showed that cold isostatic pressure pretreatment under optimal conditions (pressure of 400 MPa and holding time of 9 min) was effective in disrupting the structure of rice straw and improving its biodegradability. The cumulative methane production of the cold isostatic pressure pretreatment group increased by 76% compared to the untreated group. In addition, microbial community analysis showed that the relative abundance of Firmicutes, Halobacterota, DMER64 and Methanosaeta was higher in groups pretreated with cold isostatic pressure than in untreated groups. This study demonstrated the potential of pretreatment of rice straw with cold isostatic pressure to increase methane production during anaerobic digestion.

Green and chemical-free pretreatment of corn straw using cold isostatic pressure for methane production

In this study, the effect of cold isostatic pressure (CIP) pretreatment on the physicochemical properties and subsequent anaerobic digestion (AD) performance of corn straw (CS) was explored. The CS was subjected to CIP pretreatment by pressures of 200, 400 and 600 MPa, respectively, while AD was carried out at medium temperature (35 ± 2 °C). The results showed that CIP pretreatment disrupted the dense structure of the CS and altered the crystallinity index and surface hydrophobicity of the CS, thereby affecting the AD process. The presence of CIP pretreatment increased the initial reducing sugar concentration by 0.11–0.27 g/L and increased the maximum volatile fatty acids content by 112.82–436.64 mg/L, which facilitated the process of acidification and hydrolysis of the AD. It was also observed that the CIP pretreatment maintained the pH in the range of 6.37–7.30, maintaining the stability of the overall system. Moreover, the cumulative methane production in the CIP pretreatment group increased by 27.17 %–64.90 % compared to the control group. Analysis of the microbial results showed that CIP pretreatment increased the abundance of cellulose degrading bacteria Ruminofilibacter from 21.50 % to 27.53 % and acetoclastic methanogen Methanosaeta from 45.48 % to 56.92 %, thus facilitating the hydrolysis and methanogenic stages. The energy conversion analysis showed that CIP is a green and non-polluting pretreatment strategy for the efficient AD of CS to methane.

Greater Importance of Structural Changes Over Lignin Removal in Impacting the Enzymatic Hydrolysis of Crop Straws.

The importance of structural changes and lignin removal in influencing the enzymatic hydrolysis of crop straws was investigated. Alkaline pretreatment of corn stover (CS) and rice straw (RS) was conducted to remove lignin. It was found that alkaline pretreatment caused more lignin removal from CS than RS under the same condition, and CS and RS treated at 40 °C (CS40 and RS40) attained less lignin removal than those treated at 80 °C (CS80 and RS80). However, CS40 achieved glucan conversion efficiency of 70.77% which was 11.85% less than that of RS40, and similar glucan conversion efficiencies were obtained for RS 40 and RS80. Structural observation showed that the connection among single fiber bundle of CS40 was tighter than that of RS40, while those of RS40 and RS80 were loose. It meant that structural changes might be more important than lignin removal to influence enzymatic hydrolysis of crop straws.

Evaluation of locally-available agricultural and industrial waste materials as effective carriers for bacterial inocula in freshwater bioremediation

The pollution of freshwater is a pressing global environmental concern, necessitating effective management strategies for polluted aquatic environments. Bioremediation has emerged as a highly promising environmentally friendly approach. However, the selection of suitable candidates capable of effectively degrading or removing pollutants remains a challenging task. The introduction of live candidates, particularly bacteria, into natural environments also poses its own set of difficulties. To address these challenges, immobilizing bacteria within carrier materials has emerged as a leading option. In this study, we meticulously assessed the suitability of four locally-available and low-cost agricultural and industrial waste materials as carriers to transport bacteria into water bodies. The selection criteria encompassed bacteria immobilization capacity, viability, and the resulting water quality after treatment. In order to facilitate comparison, the widely-used sodium alginate was included as a benchmark, and Escherichia coli was employed as the model bacterial inoculum. Our findings revealed that alkaline pre-treatment of corn husk, rice husk, rice straw, and sugarcane bagasse significantly enhanced the bacteria immobilization capacity of these materials. Notably, the viability of bacteria in carrier materials, including sodium alginate, exhibited remarkable resilience, with a count of 107 CFU/g material even after 49 days of storage at room temperature. Moreover, upon determining the quality parameters of the receiving water, the introduction of rice husk and sodium alginate materials demonstrated no significant adverse impact. The quality parameters were well within the acceptable range defined by the World Health Organization standards for drinking water and the Sri Lankan ambient water quality standards for various purposes. Based on the overall performance evaluation, we advocate for the application of rice husk and sodium alginate as superior carriers for delivering bacterial inocula to aquatic environments, particularly in polluted water bodies targeted for bioremediation efforts. Nonetheless, we recommend the collection of carrier materials only after the establishment of bio inoculum in the receiving water, as a precautionary measure to minimize any potential impact on the chemical oxygen demand of the water.

The feasibility of sodium hydroxide pretreatment of rice straw for solid substrate preparation to enhance laccase production by solid state fermentation

BackgroundCurrently, broad industrial application of laccases is commonly restricted by the high-cost related production. Solid state fermentation (SSF) using agricultural waste is an attractively economic strategy for laccase production, yet its efficiency is low. Pretreatment of cellulosic substrate might be a vital breakpoint to solve the problem in solid state fermentation (SSF). In this study, sodium hydroxide pretreatment was involved to prepare solid substrates from rice straw. Fermentability of solid substrates in terms of carbon resource supply, accessibility and water retention value, and their influence on performance of SSF were analyzed.ResultsThe results showed that sodium hydroxide pretreatment provided desirable solid substrates with higher enzymatic digestibility and optimal water retention value, which further facilitated the homogeneity of mycelium growth, laccase distribution and nutrition utilization during SSF. The pretreated rice straw (1 h) with diameter less than 0.085 cm gave the maximum laccase production of 2912.34 U/g, which was 7.72 times higher than the control.ConclusionHence, we proposed that enough balance between nutrition accessibility and structure support was a must for rational design and preparation of solid substrate. Additionally, sodium hydroxide pretreatment of lignocellulosic waste might be an ideal step to enhance the efficiency and lower the production cost in SSF.

Application of Ammoniation Pretreatment in Anaerobic Digestion of Straw

Straw is a widely available and highly renewable biomass resource with good utilization value. However, its dense structure is not conducive to methane production during anaerobic fermentation and requires pretreatment. To achieve high-value conversion, pretreatment technologies can effectively destroy the rank structure of straw and increase gas production. Ammoniation pretreatment has unique advantages in pretreating straws. This article reviews the ammoniation pretreatment mechanism, the impact of ammoniation pretreatment parameters on anaerobic fermentation, and ammoniation pretreatment technology, providing a reference for the ammoniation pretreatment of straw.

Sodium Hydroxide Hydrothermal Extraction of Lignin from Rice Straw Residue and Fermentation to Biomethane

The purpose of the NaOH pretreatment of rice straw with a recycling strategy was to enhance the economic efficiency of producing biomethane. Anaerobic digestion is used for converting rice straw into biogas. In this work, 5% NaOH and rice straw mixed samples were autoclaved at 121 °C for 20 min for lignin removal. The NaOH black liquor was separated using filtration for the subsequent treatment cycle. The NaOH liquor was utilized in one more subsequent recycling procedure to test its ability to remove lignin from the rice straw. The 5% NaOH treatment results in a reduction in rice straw (RC) lignin of 73.6%. The lignin content of the recycled NaOH-filtrated rice straw samples (RCF1) was reduced by 55.5%. The 5% NaOH-treated rice straw sample yields a total cumulative biogas of 1452.4 mL/gVS, whereas the recycled NaOH-filtered (RCF1) samples generate 1125.2 mL/gVS after 30 days of incubation. However, after 30 days of incubation, the untreated rice straw (RCC) bottle produced a total of 285.5 mL/gVS of biogas. The total increase in methane output after NaOH treatment is 6–8 times greater, and the biogas yield improves by 80–124%. We show here that the recycled NaOH black solution has still the effectiveness to be used for successive pretreatment cycles to remove lignin and generate methane. In the meantime, the NaOH black solution contains useful materials (lignin, sugars, potassium, and nitrogen) that could be purified for commercial purposes, and more importantly recycling the NaOH solution decrease the chances of environmental pollution. Thus, recycling NaOH decreased chemical consumption, which would provide net benefits instead of using fresh NaOH solution, had a lower water consumption, and provided the prospect of producing an optimum yield of methane in anaerobic digestion. This method will decrease the chemical treatment costs for biomass pretreatment prior to anaerobic digestion. Recycling of NaOH solution and the integration of pretreatment reactors could be a novel bioprocessing addition to the current technology.

Enhancing enzymatic hydrolysis of waste sunflower straw by clean hydrothermal pretreatment

Hydrothermal pretreatment is an effective way to change the lignocellulose structure and improve its saccharification. An efficient hydrothermal pretreatment of sunflower straw was conducted when the severity factor (LogR0) was 4.1. 58.8% of xylan and 33.5% of lignin were removed at 180 °C for 120 min with a solid-to-liquid ratio of 1:15. A series of characterizations (such as X-ray diffraction, Fourier Transform infrared spectroscopy, scanning electron microscopy, chemical component analysis, cellulase accessibility) proved that hydrothermal pretreatment destroyed sunflower straw surface structure, enlarged its pores, and enhanced the accessibility to cellulase (371.2 mg/g). After the enzymatic saccharification of treated sunflower straw for 72 h, 68.0% yield of reducing sugar and 61.8% yield of glucose were achieved, and 3.2 g/L xylo-oligosaccharide was obtained in the filtrate. Overall, this easy-to-operate and green hydrothermal pretreatment could effectively destroy the surface barrier of lignocellulose, help remove lignin and xylan, and increase the enzymatic hydrolysis efficiency.

Ultrasound‐assisted formic acid–choline chloride deep eutectic solvent pretreatment of cotton straw to extracted lignin

AbstractDeep eutectic solvent (DES) is a new type of green solvent that can be used for the separation of lignocellulosic components. In this study, ultrasound‐assisted DES pretreatment was used to treat cotton straw, which could retain most of the cellulose in cotton straw and separate hemicellulose and lignin at the same time. Here, DESs with different molar ratios were prepared using choline chloride as hydrogen bond acceptor and formic acid as hydrogen bond donor. Simultaneously changing the ultrasonic frequency and DESs synergistic extraction of lignin. Results show that the ultrasonic power is 32 kHz (room temperature), ultrasound 30 min, oil bath heat 3 h under the best conditions can significantly extract lignin, and the yield of lignin is 87.7% and the purity reached 97.3%. The characteristic peaks of FT‐IR confirmed the extraction of lignin. The structural characteristics of 2D‐HSQC also confirmed the effective separation of lignin, and x‐ray diffraction (XRD) and scanning electron microscope (SEM) confirmed the effect of ultrasound‐assisted DES pretreatment on lignocellulose structure. In short, this study provides a feasible method for the separation of lignocellulose.

Correction to: Pretreatment of finger millet straw (Eleusine coracana) for enzymatic hydrolysis towards bioethanol production

Correction to: Pretreatment of finger millet straw (Eleusine coracana) for enzymatic hydrolysis towards bioethanol production

In vitro ruminal degradability of wheat straw cultivated with white-rot fungi adapted to mushroom farming conditions

Biological treatment of cereal straw for ruminant nutrition purposes might present an environmentally friendly option of valorizing a widely available by-product of grain production for farming systems with low external input. Several strains of white-rot fungi have been selected in the past under mostly controlled laboratory conditions for their capacity of lignin degradation. The study adapted to conditions on farm for upscaling purposes. The development of the in vitro straw digestibility with two different moistening pre-treatments and inoculated with three different fungi species, namely Pleurotus ostreatus, Ceriporiopsis subvermispora and Volvariella volvacea, was determined up to 42 days of fermentation with five sampling times. The effect of physical straw pre-treatments on nutritional parameters was evaluated. The neutral detergent fiber digestibility (NDFD30h), enzymatically soluble organic substance (ELOS) and the gas production (Hohenheim Feed value Test, HFT) as indicators for in vitro ruminal degradability decreased over time independent of the fungus: HFT, ELOS and NDFD30h by up to 50, 35 and 30% of the original straw. Remoistening and autoclaving the straw increased the gas production significantly by 2.6 mL/200 g dry matter (DM), and ELOS and NDFD30h by 45 and 51 g/kg DM compared to the original straw (34.9 mL/200 mg DM, 342 g/kg DM, 313 g/kg NDF).

Recovery of mixture of hydroxyethylammonium carboxylate protic ionic liquids from sugarcane pretreatment liquor using activated carbon in a fixed bed column

Integrated strategies using fixed bed columns can facilitate the recovery of protic ionic liquids (PILs) used in the pretreatment of lignocellulosic biomass. In this study, we investigated the adsorption of 2-hydroxyethylammonium acetate [Mea][Ac] and 2-hydroxyethylammonium hexanoate [Mea][Hex] on activated carbon in a fixed bed column for recovering the PILs mixture present in the liquor of the pretreatment. Breakthrough curves were determined experimentally. Breakthrough time (tb), exhaustion time (te), difference between tb and te, adsorption efficiency (ϕads), column efficiency (ϕcol) and qe equilibrium capacity were evaluated as a function of simultaneous variations in superficial velocity (vs) and temperature (T) using a central composite rotatable design. The optimum conditions for PIL purification were vs = 1.66 cm/min (Q = 1.3 mL/min) and T = 20 °C. After selection of optimum operating conditions, PILs separation was evaluated in a model solution and sugarcane pretreatment liquor, with similar intervals for recover of PILs. This is the first study to develop a successful proof of concept of mixture PILs [Mea][Ac]/[Mea][Hex] recovery from sugarcane straw pretreatment liquor in a fixed-bed column of activated carbon. The results indicate that the method has great potential for industrial application.

Acid/alkali-catalyzed deep eutectic solvent pretreatment of corn straw for enhanced biohydrogen production

Lignocellulose is considered as a potential source for biohydrogen production, however, the tough and rigid structure endow the lignin with high resistance to biodegradation. In this work, choline chloride/1,4-butanediol deep eutectic solvent (DES) pretreatment aiding with AlCl3/NaOH was developed to dissociate the lignin macromolecular structure of corn straw for promoting biohydrogen production. The results showed that alkali-catalyzed DES pretreatment reached a yield of biohydrogen production of 117.4 mL/g total solids (TS) in comparison with that of acid-catalyzed DES pretreatment (100.5 mL/g TS) at 100 °C for 3 h with 4.0 wt% alkali/acid dosage. The enhanced biohydrogen production was mainly ascribed to the higher lignin removal rate (81.3%) of alkali-catalyzed DES pretreatment, which facilitated subsequent enzymatic saccharification and dark fermentation of carbohydrate. Moreover, the recovered lignin obtained from this pretreatment displayed well-preserved β-O-4′ linkages (44.4/100Ar) with an appropriate molecular weight (1540 g/mol) and regular spherical particles. The new insights of this work may provide guidance for designing novel DES pretreatment toward bio-energy production from lignocellulose fractionation and component valorization.

Efficient delignification of wheat straw for microbial lipid production enabled by a novel ternary deep eutectic solvent containing ethylene glycol

Lignocellulose pretreatment often faces the problem of lignin condensation with less attention to biofuel production from total sugars, which significantly hinders biomass fractionation and energy utilization efficiency. The aim of this work was to design a novel ternary deep eutectic solvent (DES) (citric acid: choline chloride: ethylene glycol in a molar ratio of 1:1:2) for pretreatment of wheat straw with a solid/liquid ratio (S/L) of 1:20 (w/w) to achieve non-condensed lignin and high-yield fermentable sugars at 100 °C for 12 h. The introduction of ethylene glycol into ternary DES could capture the formed benzyl carbocation to protect lignin structure, inhibit excessive degradation of hemicellulose but to fermentable sugars (e.g., xylose), and improve the enzymatic digestibility of cellulose (98.73%, w/w). The mechanisms of both lignin fractionation and the in-situ lignin protection during the pretreatment of wheat straw enabled by ternary DES were systematically elucidated. Importantly, Trichosporon cutaneum cultivated in undetoxified DES waste liquid (hemicellulose-rich) and residue hydrolysate (cellulose-rich) could totally afford 8.7 g microbial lipid per 100 g wheat straw, which is superior to previous reports. This green in-situ lignin protection and fractionation strategy provides a new avenue for upgrading lignocellulose to microbial lipids.

Efficient Pretreatment of Corn Straw with Ionic Liquid Composite System

Efficient Pretreatment of Corn Straw with Ionic Liquid Composite System

Modeling the microbial pretreatment of camelina straw and switchgrass by Trametes versicolor and Phanerochaete chrysosporium via solid-state fermentation process: A growth kinetic sub-model in the context of biomass-based biorefineries.

Advancing microbial pretreatment of lignocellulose has the potential not only to reduce the carbon footprint and environmental impacts of the pretreatment processes from cradle-to-grave, but also increase biomass valorization, support agricultural growers, and boost the bioeconomy. Mathematical modeling of microbial pretreatment of lignocellulose provides insights into the metabolic activities of the microorganisms as responses to substrate and environment and provides baseline targets for the design, development, and optimization of solid-state-fermentation (SSF) bioreactors, including substrate concentrations, heat and mass transfer. In this study, the growth of Trametes versicolor 52J (TV52J), Trametes versicolor m4D (TVm4D), and Phanerochaete chrysosporium (PC) on camelina straw (CS) and switchgrass (SG) during an SSF process was examined. While TV52J illustrated the highest specific growth rate and maximum cell concentration, a mutant strain deficient in cellulose catabolism, TVm4D, performed best in terms of holocellulose preservation and delignification. The hybrid logistic-Monod equation along with holocellulose consumption and delignification models described well the growth kinetics. The oxygen uptake rate and carbon dioxide production rate were directly correlated to the fungal biomass concentration; however, a more sophisticated non-linear relationship might explain those correlations better than a linear model. This study provides an informative baseline for developing SSF systems to integrate fungal pretreatment into a large-scale, on-farm, wet-storage process for the utilization of agricultural residues as feedstocks for biofuel production.

Emerging technologies of employing algae and microorganisms to promote the return-to-field of crop straws: A mini-review.

As an agricultural waste, crop straw enriched with a variety of nutrients is regarded as an important fertilizer resource. In the past, crop straw return-to-field played a key role in the sustainability of agricultural environment, but some problems, such as ammonia loss in ammoniation, low rate of straw decomposition, and high carbon footprint, attracted researchers' attentions. In this paper, we propose three technical routes, including cyanobacteria-based ammonia assimilation, microorganisms-based crop straw pretreatment, and microalgae-based carbon capture, to address the aforementioned problems. Besides, challenges which may hinder the practical application of these technical routes as well as the potential solutions are discussed in detail. It is expected that this paper could provide new ideas to the practical application of crop straw return-to-field.

Effects of Ammonification–Steam Explosion Pretreatment on the Production of True Protein from Rice Straw during Solid-State Fermentation

It is difficult to obtain high-protein contents from rice straw using direct fermentation due to its low nitrogen content. This study investigates the effects of ammonification–steam explosion pretreatment of rice straw on the protein content after solid-state fermentation (SSF). The pretreatment is carried out under multi-strain inoculation conditions. The samples of rice straw after ammonification (TA), steam explosion (TSE), and ammonification and steam explosion (TA-SE) were compared to the control group (TC). The results indicate that both ammonification and steam explosion could disintegrate rice straw’s lignocellulosic structure, releasing nutrients that can be used for microbial reproduction. In addition, amino compounds are formed along with depolymerization products, thus effectively promoting the true protein content. Post-fermentation, total crude protein contents of TA, TSE, and TA-SE samples were 2.56, 1.83, and 4.37 times higher than that of Tc samples, respectively, and true protein contents were 2.52, 1.83, and 5.03 times higher. This study shows that the true protein content by combined ammonification and steam explosion pretreatment of rice straw during 96 h of solid-state fermentation was 46.7% of its total matter, rendering it a suitable alternative to high-protein animal feed.