Crop residue crucially contributes in running the essential agro-environment services. The modernization in crop production with high yielding varieties substantially increased the crop residue and its management challenges. The critical window period between two crops like in wheat sowing after rice and sugarcane harvest and poor suitability of some crop residues for animal feed pushed the malpractice of crop residue burning especially in developing countries like India. In long-term, the practice of residue burning along with climate change phenomenon puts the serious challenges in maintaining the quality of natural resources and sustainable crop production system. The precious elements retained in the crop residue are lost upon burning and converted to harmful air pollutants which otherwise can run the essential services in soil-plant system and find industrial applications as feedstock if managed in a sustainable way. The present review article provides critical insights on the current status of residue production and in-situ management of crop residue via different routes using suitable machinery package along with relative advantages and challenges. The prospective of crop residue to derive the soil ameliorants through composting and thermal decomposition approaches are critically discussed in the present review study. Moreover, a brief account is presented on residue derived energy generation (liquid and gaseous fuels) through thermo-chemical and thermal decomposition processes, which can ease the burden of fossil fuels on environment as well as economy of the country. The review article also explores cutting-edge industrial application of crop residue, present challenges and future thrust areas to overcome such issues in the sustainable crop residue management. 

Crop residue management challenges, opportunities and way forward for sustainable food-energy security in India: A review

Most by-product wastes of the coffee industry are underutilized, including a fibrous husk that covers the coffee seeds, known as parchment. The present work aims to characterize the parchment fiber and to study the influence of alkaline treatment followed by a steam explosion process assisted by mechanical high shearing to obtain microfibrillated cellulose. The first step of this study was to quantify, using a three-steps methodology, the lignocellulosic constituents present in the parchment. Cellulose, hemicellulose and lignin were identified by Fourier transform infrared spectrophotometry (FTIR) and thermogravimetric analysis (TGA). From these results it was quantified around 22% of cellulose in the parchment. In sequence, alkaline treatment and steam explosion were performed to raise the cellulose content. The novelty of this work was to perform the steam explosion under relatively milder conditions, in order to produce microfibrillated cellulose with a high aspect ratio. It was observed by TGA an improvement in thermal stability and by X-ray diffraction (XRD) an increasing in the crystallinity. Finally, from scanning electron microscopy (SEM) it was verified that cellulose fibrils became more exposed, with diameters reaching micro and nanometric sizes. This ensures a potential for composite reinforcement with microfibrillated cellulose.

Characterization of coffee parchment and innovative steam explosion treatment to obtain microfibrillated cellulose as potential composite reinforcement

Pulp and Paper Processing

Rice (Oryza sativa L.) is a major cereal crop used for human nutrition worldwide. Harvesting and processing of rice generates huge amounts of lignocellulosic by-products such as rice husks and straw, which present important lignin contents that can be used to produce chemicals and materials. In this work, the structural characteristics of the lignins from rice husks and straw have been studied in detail. For this, whole cell walls of rice husks and straw and their isolated lignin preparations were thoroughly analyzed by an array of analytical techniques, including pyrolysis coupled to gas chromatography-mass spectrometry (Py-GC/MS), nuclear magnetic resonance (NMR), and derivatization followed by reductive cleavage (DFRC). The analyses revealed that both lignins, particularly the lignin from rice husks, were highly enriched in guaiacyl (G) units, and depleted in p-hydroxyphenyl (H) and syringyl (S) units, with H:G:S compositions of 7:81:12 (for rice husks) and 5:71:24 (for rice straw). These compositions were reflected in the relative abundances of the different interunit linkages. Hence, the lignin from rice husks were depleted in β-O-4' alkyl-aryl ether units (representing 65% of all inter-unit linkages), but presented important amounts of β-5' (phenylcoumarans, 23%) and other condensed units. On the other hand, the lignin from rice straw presented higher levels of β-O-4' alkyl-aryl ethers (78%) but lower levels of phenylcoumarans (β-5', 12%) and other condensed linkages, consistent with a lignin with a slightly higher S/G ratio. In addition, both lignins were partially acylated at the γ-OH of the side-chain (ca. 10-12% acylation degree) with p-coumarates, which overwhelmingly occurred over S-units. Finally, important amounts of the flavone tricin were also found incorporated into these lignins, being particularly abundant in the lignin of rice straw.

/pdf/structural-characteristics-of-the-guaiacyl-rich-lignins-from-13pnfvc97m.pdf

Structural Characteristics of the Guaiacyl-Rich Lignins From Rice (Oryza sativa L.) Husks and Straw.

Rice (Oryza sativa L.) straw is a highly abundant, widely available, and low cost agricultural waste that can be used as a source to extract valuable phytochemicals of industrial interest. Hence, in the present work, the chemical composition of the lipophilic compounds present in rice straw was thoroughly characterized by gas chromatography and mass spectrometry using medium-length high-temperature capillary columns, which allowed the identification of a wide range of lipophilic compounds, from low molecular weight fatty acids to high molecular weight sterols esters, sterol glucosides, or triglycerides in the same chromatogram. The most abundant lipophilic compounds in rice straw were fatty acids, which accounted for up to 6,400 mg/kg (41.0% of all identified compounds), followed by free sterols (1,600 mg/kg; 10.2%), sterol glucosides (1,380 mg/kg; 8.8%), fatty alcohols (1,150 mg/kg; 7.4%), and triglycerides (1,140 mg/kg; 7.3%), along with lower amounts of high molecular weight wax esters (900 mg/kg; 5.8%), steroid ketones (900 mg/kg; 5.8%), monoglycerides (600 mg/kg; 3.8%), alkanes (400 mg/kg; 2.6%), diglycerides (380 mg/kg; 2.4%), sterol esters (380 mg/kg; 2.4%), tocopherols (340 mg/kg; 2.2%), and steroid hydrocarbons (60 mg/kg; 0.4%). This information is of great use for the valorization of rice straw to obtain valuable lipophilic compounds of interest for the nutraceutical, pharmaceutical, cosmetic, and chemical industries. Moreover, this knowledge is also useful for other industrial uses of rice straw, as in pulp and papermaking, since some lipophilic compounds are at the origin of the so-called pitch deposits during pulping.

/pdf/chemical-composition-of-lipophilic-compounds-from-rice-oryza-3qiok99x.pdf

Chemical Composition of Lipophilic Compounds From Rice (Oryza sativa) Straw: An Attractive Feedstock for Obtaining Valuable Phytochemicals

Separation of cellulose from agricultural straw is one of the key bottlenecks hindering the application of such kind of biomass resources. In this chapter, we provide three environmental-friendly ways for separation of cellulose from agricultural straw pretreated with steam explosion, which include delignification with recyclable water-polar aprotic organic solvent, selective bio-degradation of the lignin component, and extraction of cellulose with imidazolium-based ionic liquids from the steam-exploded rice straw. The isolated rice straw celluloses have been adopted as an enhancement for all-cellulose composites (ACCs) and cellulose/cement composites. Ultra-high tensile strength (650.2 MPa) can be achieved for the ACCs containing the activated straw cellulose fiber (A-SCF). The cellulose/cement composites show a significant promotion in the flexural strength and fracture toughness. The new nonderivative solvent for cellulose, tetrabutylammonium hydroxide (TBAH) aqueous solution with urea as additives has been proved to be manipulable for dissolving cellulose.

/pdf/environmentally-friendly-method-for-the-separation-of-4cjxdnqk4m.pdf

Environmentally Friendly Method for the Separation of Cellulose from Steam-Exploded Rice Straw and Its High-Value Applications

The invention discloses a process method for improving the dissolving property of cellulose in a tetrabutyl ammonium hydroxide aqueous solution. According to the process method, the tetrabutyl ammonium hydroxide aqueous solution is treated at three different temperature periods, so as to obtain a relatively high and good cellulose dissolution effect. The process method specifically comprises the following steps: 1) adding cellulose into the 35-50% tetrabutyl ammonium hydroxide aqueous solution, and stirring to dissolve at relatively high temperature; 2) stirring to dissolve the solution obtained in the step 1) at relatively low temperature; 3) leaving the solution obtained in the step 2) to stand at secondary high temperature. By only reducing the temperature, dissolution of cellulose in the tetrabutyl ammonium hydroxide aqueous solution is promoted in the temperature reduction process.

Process method for improving dissolving property of cellulose in tetrabutyl ammonium hydroxide aqueous solution

The invention discloses a method for preparing a cellulose solution.According to the basic technical principle of the method, the wetting property of a solvent on natural cellulose crystals is improved with the amphipathicity of the cellulose solvent so that dissolution of cellulose can be promoted.Based on the principle, the invention provides a room-temperature mild dissolution technical method for cellulose.The method has the advantages that the technology is simple, room-temperature dissolution is achieved, and the method is environmentally friendly and not sensitive to the moisture content of a system.The cellulose solvent is prepared from, by weight, 5-70% of organic base, 2-90% of an assistant and 1-65% of water.Cellulose and the cellulose solvent are blended to form a blend, stirring is carried out until complete dissolution, and the target cellulose solution is obtained.The cellulose solution prepared with the method is used for manufacturing regenerated cellulose membranes or regenerated cellulose fibers or cellulose-base composites.

Method for preparing cellulose solution

The invention discloses a process of preparing cellulose nanocrystalline dispersion liquid on the basis of controllable dissolution. The process includes: adopting a cellulose solvent as an organic alkali/urea/water mixed system, wherein concentration of organic alkali is 30-45 wt%, concentration of urea is 1-24 wt%, the balance is water, and concentration of cellulose is 0.1-35.0 wt%. On the basis of a principle of regulating bi-philic characteristics of the cellulose solvent and inducing the same to generate differential dissolubility in different crystallization degree areas of cellulose, controllable selective dissolution technology is provided; the cellulose nanocrystalline dispersion liquid is prepared through controllable selective dissolution of the cellulose solvent to noncrystalline areas and semi-crystalline areas in a cellulose material, and pure cellulose nanocrystals can be obtained through further conventional treatment. The cellulose nanocrystals prepared have chemical structure of natural cellulose. The process is simple, mild in condition, low in equipment requirement, free of environment pollution in the preparation process, suitable for industrialized production and wide in application prospect.

Process of preparing cellulose nanocrystalline dispersion liquid on basis of controllable dissolution

The invention discloses a batched preparation method of interlayer in-situ polymerization of graphene/polymer foams. The method mainly comprises the following steps of 1, preparing a graphitic layer compound, wherein an oxidizing agent and concentrated sulfuric acid are mixed and added into graphite, after standing is performed, solid parts are separated out, and dilute sulfuric acid is used for washing repeatedly; 2, performing monomer interlayer in-situ polymerization, wherein the graphitic layer compound obtained in step 1 and monomers are mixed and react with each other under the proper temperature; 3, cleaning and drying the product, wherein the product obtained in step 2 is subjected to water and alcohol repeated washing and dried under the temperature of 30-200 DEG C, and graphene/polymer foams are obtained. The preparation process is simple, safe and controllable, graphene in the product is dispersed uniformly, and the method has the advantages that the preparation flow is short, little time and energy are consumed, control is easy, and the cost is low.

Batched preparation method of interlayer in-situ polymerization of graphene/polymer foams

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