Among the most abundantly available bioresources, lignocellulosic biomass offers a ‘green renewable’ alternative resource for producing high-value biomaterials suitable for acoustical applications. In this study, a systemic process is developed to fabricate sound absorbing material using refined cellulosic microfibrils generated from natural deep eutectic solvent (NADES) pretreated rice straw. Physico-chemical characterization using FTIR and FESEM analysis confirmed substantial removal of the hemicellulose and lignin from the extracted cellulosic microfibrils. Moreover, the surface area after NADES pretreatment increased to 12.55 m2/g from 2.18 m2/g of raw rice straw, suggesting the enhanced potential of sound dissipation within the biomaterial. The noise reduction coefficient (NRC) of the NADES pretreated rice straw is increased to 0.55 compared to 0.41 with untreated rice straw. Sound absorption performance shows an increasing trend with the increase in sample thickness (25 mm to 50 mm); however, no significant improvement in sound absorption is observed with an air gap of more than 20 mm. Overall, the tested biomaterial shows comparable NRC to commercially available synthetic sound absorbing materials.
Research Article
Targeted Functionalization of Waste Lignocellulosic Biomass to Produce Sound Absorbing Materials
https://doi.org/10.21203/rs.3.rs-3349333/v1
This work is licensed under a CC BY 4.0 License
Journal Publication
published 12 Jun, 2024
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NADES pretreatment
Rice straw
Sound absorption coefficient
Air gap effect
Lignocellulosic biomass is an alternative renewable resource for materials [1–4] and energy products [3, 5]. Often the technologies for biomass valorization have focused on converting the biomass resources to either fuels or high-value chemicals [6–9]. In this regard, pretreatment and directed transformation of biomass constituents to products remain challenging due to the involvement of multistep bio- or chemo-catalytic processes [10–13]. Following this, the large-scale availability of waste lignocellulosic biomass, such as agricultural residues, remains a task to tackle. For example, in India, around 900 million tons (MT) of agricultural residues, and specifically about ~ 165 MT of rice straw, are generated annually, often disposed of by burning in the open environment, creating hazardous air pollution to an alarming level [14–16]. Clearly, the technologies to convert biomass into valorized fuels or chemicals available today are not economically viable options for consideration [17–19], calling for an economical alternative for waste biomass utilization. Herein, we demonstrate an easy and economically viable sustainable protocol to produce bio-renewable sound absorbing materials from rice straw, which may be used in various appliances and building acoustical applications. The market for acoustical materials has grown significantly in the last few decades, and it is expected to reach ~ $20 billion by 2028 [20].
The transformation of agricultural residues such as rice straw to bio-based materials requires a pretreatment step due to the recalcitrance nature of biomass [21–23]. Mechanical, chemical, physico-chemical, and biological pretreatment techniques are employed [21, 24–32], out of which chemical pretreatment is considered most effective in the delignification of biomass [33]. However, large-scale use of toxic chemicals in pretreatment processes necessitates an environmentally benign process [34, 35]. Recent utilization of ionic liquids and deep eutectic solvents as green solvents in biomass pretreatment offers a ray of hope to develop such an environmentally benign process [29, 35–37]. Among the two available options, the preparation of deep eutectic solvents is relatively cheaper and easily recyclable [29, 36, 37]. For rice straw, deep eutectic solvents are applied for pretreatment[38, 39], while some reports have mentioned bio-renewable lactic acid as an option to synthesize natural deep eutectic solvents (NADES) to develop a more sustainable process for biomass pretreatment[37, 39, 40]. For the first time, in this study, we demonstrate a practical application of NADES in preparing high-quality cellulose micro-fibrils to develop sound absorbing materials, which may find commonplace application in buildings, automobiles, machinery, etc [41, 42].
Synthetic materials such as glass wool, melamine foam, and polyurethane foam are mainly employed for sound absorption applications. The highly porous structure (> 90% porosity) of these materials assists in the transformation of sound energy into thermal energy, ultimately leading to high dissipation of sound within the material. As an alternative, synthesizing sound absorbing materials from waste biomass has intrigued researchers in the past [41–46]. Yang et al. examined the sound absorption of rice straw-wood particle boards using urea formaldehyde resin as a binder. However, all the developed materials showed noise reduction coefficient (NRC) ≤ 0.3 due to the unavailability of porous structure [47]. Huang et al. investigated sound absorption of nonwoven composite boards made from coconut and polyester fibers through a needle punching technique. The compact structure and presence of voids lead to a high sound absorption coefficient (SAC) at medium to high frequencies (more than 3000 Hz); however, the NRC values are not mentioned in the report[48]. Sakthive et al. studied the sound absorption of sugarcane bagasse and bamboo charcoal-based fiber composites developed using compression molding techniques for automotive applications. The SAC of the developed composites is within 0.4, even at 4000Hz frequency (NRC < 0.4) [49]. While all these attempts are encouraging, none has led to any systematic development of a bio-based sound absorbing material with comparable NRC values to commercial synthetic materials by correlating the microstructural properties of the material with its acoustical properties. This study presents a primer for such a material development.
Rice straw is collected from the agricultural fields of Ghaziabad, India. Analytical grade lactic acid and choline chloride are procured from Sisco Research Laboratory Private Limited Delhi and Central Drug House Private Limited Delhi, India. The collected rice straw is washed with tap water to remove any soil particles and dried at 105ºC for 24hr until the moisture content reduced to < 5%. Then the rice straw is milled to a fine powder using a grinder (Sujata, 900W) and sieved to 35 mesh size to ensure uniform particle size. The sieved rice straw is stored at room temperature in a dark place to avoid photodegradation. NADES reagent is prepared following our earlier reports with few modifications [40, 50]. In brief, lactic acid, choline chloride, and water are mixed in a 9:1:0.11 ratio, and the final mixture is subjected to agitation at 80ºC for 30–40 min until a clear solution is formed. Rice straw pretreatment is performed at 10 wt% solid loading for 60–180 min at 120–140ºC using NADES. The cellulosic pulp obtained after pretreatment is washed with water till neutrality (pH ~ 7.0) and dried at 55ºC for 48hr.
The dried cellulosic pulp is used as a feedstock to fabricate sound absorbing material (Fig. 1). The dried pulp is filled in a 3-D printed poly lactic acid cavity (25 mm thickness with 29 mm and 100 mm diameter). Afterward, the cavity is covered with jute fabric from both ends for normal incidence SAC testing in a two-microphone impedance tube set-up. Complete details are mentioned in the supplementary (S-1).
The physico-chemical characterizations are performed to examine the effectiveness of NADES pretreatment on the functional, structural, and morphological properties of the developed biomaterial. Fourier Transform Infrared Spectroscopy (FTIR, Thermo Scientific Nicolet iS50 FT-IR) in attenuated total reflection (ATR) mode is conducted to investigate the presence of functional groups associated with cellulose, hemicellulose, and lignin in spectral range 4000 − 500 cm− 1 with a scanning rate of 4 cm− 1 considering 128 scans. X-ray Diffraction (XRD, Rikagu Miniflex 600) is carried out to determine the crystallinity of raw and pretreated rice straw samples. The scanning rate is kept at 2°/min with a step increment of 0.04° at 2θ scan range 10–40°.
Thermogravimetric Analysis (TGA) of raw and pretreated rice straw samples is performed with Simultaneous Thermal Analyser (TA Instruments SDT 650) in the nitrogen environment at a ramp rate of 20°/min in the temperature range from 25°C to 750°C. The surface area of the samples is measured using Brunauer -Emmett-Teller (BET, MicrotracBEL Corp Belsorp Max) analyzer. All samples are degassed for 6hr at 120°C before the measurement. Field emission scanning electron microscopy (FESEM, FEI Quanta 200F) is utilized to analyze the morphology of the raw and pretreated rice straw samples. Energy Dispersive X-ray Spectroscopy (EDX, Zeiss EVO18) is employed to determine the elemental composition of raw and pretreated rice straw samples.
Properties related to sound absorption, such as density, porosity, tortuosity, and normal incidence SAC of raw and pretreated rice straw samples, are measured to assess the effect of NADES pretreatment. Density is measured through a weighing balance (Mettler Toledo, ME155DU) method using ethanol as a solvent. The final density is calculated according to Eq. 1:
Where ρsample (in kg/m3) is the density of raw and pretreated rice straw samples, ρliquid is the density of the liquid (ethanol) ρliquid = 0.789 g/cm3, Wair is the weight of raw and pretreated rice straw samples in the air, and Wliquid is the weight of sample fully submerged in the liquid (ethanol). Moreover, the porosity and tortuosity of the raw and pretreated rice straw samples are estimated using the following empirical formula from density values [46].
Where \(\varnothing\) is the porosity of the sample in %, ρs is the density of the sample, and ρf is the density of fibers.
Where a∞ is the tortuosity of the sample, L is the sound wave path without obstruction, and L´ is the path traveled by sound wave in the presence of fibers (S -2).
Normal incidence SAC of the developed biomaterial is measured using a two-microphone impedance tube set-up (Brüel & Kjær, Type 4206-T) according to ASTM E1050-19[51]. All the samples are tested in a frequency range of 63 Hz to 6300 Hz at 24°C and 80% relative humidity. Moreover, the effect of air gap on the sound absorption performance of the developed biomaterial is examined at 10 mm, 20 mm, and 30 mm air gaps between the sample and backplate (S-1). All samples are measured three times, and average values are reported.
The FTIR spectra of the raw and NADES pretreated rice straw provide insights into the modification in the functional groups associated with macromolecules, viz. cellulose, hemicellulose, and lignin (Fig. 2). Cellulose fraction can be assigned to absorbance bands 893 cm− 1 (linked to glycosidic C-H deformation), 1158 cm− 1 (C-O-C stretching), 2910 cm− 1 (stretching vibrations of C-H group), and 3443 cm− 1 (attributed to O-H vibrations)[52, 53]. Deviation in the hemicellulose absorbance band at 1730 cm− 1 is attributed to the C = O stretching of acetyl acid [53]. Altercation in lignin content from the straw cell wall can be observed from the absorbance band at 1465 cm− 1 assigned to bending vibrations in C-H3 functionality. However, the C = C stretching of the aromatic ring of lignin is assigned at 1510 cm− 1, 1598 cm− 1, and 1635 cm− 1 [33, 53]. The FTIR spectra indicate that the fraction of lignin and hemicellulose decreases after pretreatment, which could be caused due to the weakening/breakage of the straw cell wall, leading to the formation of crakes and cavities.
Lignin is present in the complex composition of high and low molecular weight constituents in the straw cell wall [54]. It is observed that lignin removed from the straw cell wall after pretreatment remains in soluble (low molecular weight fraction) and insoluble (high molecular weight fraction) form in the pretreated residue [53]. Noticeably, the removal of lignin and hemicellulose ultimately results in enhancing the accessibility of cellulosic fraction in the pretreated pulp. Furthermore, the frequency band around 1080 cm− 1 can be designated to the Si-O-Si functionality of silica [55]. Silica is present in rice straw ranging from 5 to 14 wt % [56]. However, continuous stirring of pretreatment media can be attributed to the movement of some of the silica to inner layers from straw cell wall, causing variation in the silica absorbance band in pretreated rice straw samples. EDX data also confirms the presence of silica in the inner layers of pretreated samples (S-3). The presence of silica in the pretreated pulp improves the flame-retardant property, which may be useful in end-use acoustical applications [57, 58].
XRD analysis is performed to investigate the variation in the degree of crystallinity in raw and pretreated rice straw samples. Due to its amorphous structure, rice straw does not show sharp peaks; however, two broad peaks around 22.6 degrees (200 plane) and 16–18 degrees (110 plane) are observed in raw and pretreated rice straw samples [33] (Fig. 3). The peak around 22.6 degrees could be attributed to crystalline cellulose Iα and Iβ, whereas the peak around 16–18 degrees is linked with amorphous cellulose [33]. On pretreatment, an increase in the peak area around the (200) and (110) planes suggests enhancement in the crystalline fraction with an increase in pretreatment duration and time. The degree of crystallinity is generally measured by crystallinity index through peak area and peak height methods [59]. It is observed that, after a certain point, the ratio of (I200 -IAmp)/I200 in the peak height method remains almost constant (S-4), leading to similar crystallinity index values in pretreated rice straw samples [1hr (RS 140°C), 3hr (120°C), and 3hr (140°C)]. The results through the peak area method indicate that the crystallinity index of raw rice straw (45.72%) is increased to 56.70 %, 59.43%, 2.48–67.85% after pretreating for 1hr (120°C), 1hr (140°C), 3hr (120°C) and 3hr (140°C), respectively. An increase in crystallinity index suggests enhancement in the cellulosic fraction after NADES pretreatment and reduction in the amorphous lignin and hemicellulose content which is also exhibited in FTIR spectroscopy. A similar increase in the crystallinity index of the rice straw on pretreatment with different methods is observed in many other reports [33, 56, 60–62].
Thermogravimetric analysis (TGA) provides insight into the thermal stability of raw and pretreated rice straw samples. The TGA curve in Fig. 4 can be divided into three stages 25°C- 250°C (stage 1), 250°C-400°C (stage 2), and 400–750°C (stage 3). Weight loss in stages 1, 2, and 3 are measured around 10%, 55%, and 13%, respectively, indicating the largest weight loss in stage 2. Weight loss due to the removal of moisture and hemicellulose is predominant in stage 1; however, the decomposition of hemicellulose and low molecular weight organic compounds led to weight loss in the second stage[57]. An increment in the T10 limit (the temperature at which 10% weight loss takes place) in the pretreated samples (288–304°C) is observed compared to raw rice straw (238°C), indicating an improvement in thermal stability after pretreatment. The increase in the T10 limit can be attributed to a decrease in amorphous hemicellulose and lignin fraction in the pretreated rice straw, which ultimately reduces the rate of thermal degradation. An increase in the thermal stability of rice straw after pretreatment is also reported by other researchers [52, 63].
Stage 2 of the TGA curve indicates a higher weight loss range (~ 55%) in pretreated rice straw samples than in raw rice straw (~ 45%). Weight loss at this stage could be assigned to the release of volatile organic compounds from raw and pretreated rice straw samples. In the case of pretreated samples, the higher decomposition range can be attributed to a significant reduction in lignin and the removal of minerals (Si, Mg, Ca) linked to ash content during the pretreatment step. Similar observations are reported by X. Chen et al. in their work on the thermal stability of cellulose fibers from rice straw[52]. Ash and inorganic minerals are left in samples after stage 3. The TGA curve also indicates the highest residue in the raw rice straw (32%) at 750°C compared to pretreated rice straw samples (22–25%) after stage 3. This can be attributed to the remaining high ash content and other minerals in the raw rice straw, whereas a significant portion of these minerals is removed from the straw cell wall during pretreatment.
BET analysis indicates an increasing trend in surface area and mean pore volume of the pretreated samples with an increase in pretreatment duration and temperature (S-5). BET surface area increased from 2.18 m2/grams (raw rice straw) to 3.52 (1hr, 120°C), 6.59 (1hr, 140°C), 7.71 (3hr, 120°C) and 12.55 m2/grams (3hr, 140°C) of the pretreated rice straw samples, respectively. The increase in BET surface area indicates the formation of crakes and cavities with increasing pretreatment temperature and duration. Moreover, an increase in total pore volume is also observed in pretreated rice straw samples with an increase in pretreatment severity (S-5). The increase in total pore volume may be attributed to the formation of pores during the removal of lignin from the straw cell wall. This is also validated in the aforementioned XRD, FTIR, and TGA analysis.
Furthermore, FESEM analysis provides insights into changes in the topography and the morphology of raw and pretreated samples (Fig. 5). The FESEM image of raw rice straw Fig. 5 (a) shows a few minor cracks on the surface, which could be formed during preprocessing (milling operation). However, no other significant changes can be observed in the straw cell wall of raw rice straw. FESEM micrographs of pretreated rice straw samples (Fig. 5 (b, c, d, e)) suggest that more numbers of pores (micro and nano) start forming on increasing the pretreatment duration and temperature, which can be linked to the formation of crakes and cavities on the straw cell wall. The structural morphology of the raw and pretreated rice straw samples suggests a noticeable effect of NADES pretreatment on the straw cell wall and the separation of cellulosic microfibrils from the inner structures. This also validates results obtained by XRD analysis. Moreover, the FESEM micrographs of the straw cell wall of pretreated rice straw samples indicate that removal/weakening of the lignin is in line with the FTIR analysis and BET results, indicating an increase in surface area and total pore volume. It is evident from the FESEM micrograph that the diameter of pretreated fibrils decreases significantly, which ultimately indicates more number of fibers in unit thickness. An increase in the number of fibers assists in creating a higher obstruction in the path of sound flow, thus ultimately leading to the higher dissipation of sound energy in the biomaterial.
The internal arrangement of fibers in the raw and pretreated rice straw samples can be analyzed by density, porosity, and tortuosity values, providing insights into their ability to dissipate sound energy. The density of raw rice straw is measured as 0.38 g/cm3, whereas with increasing pretreatment temperature and duration, a decrease in density 0.244 g/cm3 (1hr, 120°C), 0.234 g/cm3 (1hr, 140°C), 0.221 g/cm3 (3hr, 120°C), 0.202 g/cm3 (3hr, 140°C) being observed. The decrease in density is attributed to morphological changes in straw cell walls due to the formation of crakes and cavities, which ultimately led to a more porous structure in pretreated rice straw samples.
Table I Density, porosity, and tortuosity of raw and pretreated rice straw samples
| Material | Density (\(\varvec{\rho })\) (gm/cm3) | Porosity (\(\varvec{\varnothing })\) (%) | Tortuosity (a∞) |
|---|---|---|---|
| Raw rice straw | 0.382 | 65 | 1.260 |
| 1 hr, 120°C | 0.244 | 77.90 | 1.142 |
| 1 hr, 140°C | 0.234 | 81.42 | 1.114 |
| 3 hr, 120°C | 0.221 | 82.23 | 1.108 |
| 3 hr, 140°C | 0.202 | 82.37 | 1.107 |
The porosity calculated from density values suggests an increasing trend in pretreated rice straw samples [77.90% (1hr, 120°C), 81.42% (1hr, 140°C), 82.23% (3hr, 120°C), and 82.37% (3hr, 140°C)] compared to 65% in raw rice straw. The increasing porosity indicates the presence of void spaces in the pretreated rice straw samples, which will assist in the transformation of sound energy into thermal energy, leading to higher sound dissipation in the developed biomaterial. Furthermore, the inner structure of pores and orientation of fibers inside the biomaterials can be estimated by tortuosity. Tortuosity is an indication of a tortuous path of sound flow calculated from the empirical formula of porosity mentioned in Table I.
SAC indicates the frequency specific dissipation of sound energy in the developed biomaterial. Figure 6 shows a significant improvement in the SAC of the pretreated rice straw samples compared to raw rice straw. The frequency values are mentioned in the log scale (log10) for a better representation of SAC at lower frequencies (< 1000 Hz). Moreover, the noise reduction coefficient (NRC) is calculated to examine the effectiveness of the pretreatment on sound absorption performance. NRC is calculated as one-third octave average normal incidence SAC at 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz frequencies[46]. The NRC values of the raw and pretreated rice straw [(1hr, 120°C), (1hr, 140°C), (3hr, 120°C), and (3hr, 140°C)] are calculated as 0.41, 0.47, 0.50, 0.52, and 0.55, respectively.
The improved SAC in pretreated samples could be attributed to the presence of a large number of crakes and cavities in the pretreated rice straw compared to raw straw. The formation of crakes, cavities, and separation of cellulosic microfibrils from the main structure increases the porosity and ultimately assists in higher sound dissipation within the pretreated rice straw samples. The sound energy mainly dissipated through frictional and viscous losses. However, scattering and structural vibrations also contribute to sound dissipation within raw and pretreated rice straw samples. A comparative NRC of the developed biomaterials and commercially available alternatives such as glass wool, melamine foam, and acoustic foam is mentioned in supplementary (S-6). The sound absorption performance of the developed biomaterials is observed to be comparable with the commercial alternatives, indicating the scope of their applicability in commercial and industrial settings.
The effect of thickness on sound absorption performance is also examined for the raw and pretreated rice straw samples. The changes in SAC by an increase in the thickness of the samples from 25 mm to 50 mm are shown in Fig. 7. In general, an increase in thickness leads to higher resistance in the sound energy propagation and results in enhancement in sound dissipation within the material. However, after a certain thickness, the sound dissipation does not exhibit significant improvement, which is also suggested by some reports [64, 65]. This may be caused due to the reflection of sound waves from the surface of the material, leading to destructive interference with incoming waves and ultimately leading to minimal improvement in SAC. Noticeably, for the pretreated sample (1hr, 120°C), negligible improvement in NRC is observed with an increase in thickness from 25 to 50 mm. As exhibited in Fig. 7, the SAC of the 50 mm sample (1hr, 120°C) increases up to 200 Hz, dipped subsequently, and remains lower than the SAC of 25 mm samples until 1400 Hz, ultimately leading to similar NRC values. A similar dip in SAC at lower frequencies (less than 400 Hz) is also observed in other 50 mm samples, which may be attributed to either structural (orientation of pretreated fibers in 50 mm samples leading to minimal improvement in SAC due to higher reflection in a specific frequency band) or operational (dip due to superposition of incident and reflected waves for thicker samples in impedance tube) factors [66]. Interestingly, the fluctuations in sound dissipation are more prominent at lower frequencies (< 1500 Hz), whereas at medium to higher frequencies, the results indicate a gradual increase in SAC with thickness.
It has been observed that with an increase in the air gap to 10 mm, a significant increment in NRC takes place in raw (0.41 to 0.43) and pretreated rice straw samples [1hr, 120°C (0.47 to 0.50); 1hr, 140°C (0.50 to 0.54); 3hr, 120°C (0.52 to 0.56) and 3hr, 140°C (0.55 to 0.60)], respectively. With the introduction of an air gap behind the material, an increase in SAC at low frequencies can be attributed to the absorption of sound energy of larger wavelengths (Fig. 8). Noticeably, in the case of raw rice straw, a slight reduction in NRC is observed when the air gap increases from 20 mm to 30 mm. The reduction in NRC of raw rice straw from 0.43 to 0.42 could be attributed to the shifting of peaks towards the low-frequency range, which ultimately reduces the NRC. A similar drop in SAC after a certain air gap is observed by M.B. Mvubu et al. in studying the effect of air gap on the SAC of natural fibers[67]. Moreover, a shift in peaks toward lower frequency ranges can also be observed for the pretreated rice straw samples, leading to an almost similar NRC value (0.63) with a 30 mm air gap compared to a 20 mm air gap (0.62). The results also indicate that the increase in SAC may not be significant after a certain air gap.
The present study suggests that NADES pretreatment of rice straw enhances the cellulosic fraction (crystallinity index: 67.85%) compared to raw rice straw (crystallinity index: 45.72%). Moreover, FTIR analysis indicates the removal of lignin and hemicellulose in pretreated rice straw samples. Formation of crakes, cavities on the straw cell wall, and separation of cellulosic microfibrils enhances the SAC of the biomaterial, suggesting higher sound energy dissipation in the pretreated samples. 10 mm air gap shows significant enhancement in sound absorption in all samples; however, no significant improvement in acoustic properties is observed on further increasing the air gap to 20 mm or more. The NRC of the developed biomaterials (25 mm thickness) indicates comparable results with commercial alternatives, suggesting the possibility of their utilizability in commercial and industrial applications.
Funding
The authors would like to acknowledge the Department of Science and Technology, Govt. of India, for the financial support (DST/TDT/AGRO-52/2019).
Acknowledgment
Authors are thankful to the Central Research Facility, Workshop’s Makerspace Facility and Department of Chemical Engineering, IIT Delhi for support in testing and characterizations.
Competing Interests
There are no conflict of interest to declare.
Author Contributions
AN: Writing original draft, experimentation, data analysis, visualization.
JM: Experimentation, data analysis, visualization, writing-review and editing.
S: Experimentation, data analysis, visualization, writing-review and editing.
AKK: Conceptualization, methodology, visualization, supervision, writing- review and editing.
EA: Supervision, methodology, resources.
MAH: Conceptualization, methodology, resources, supervision, visualization, writing- review and editing original draft.
SF: Conceptualization, methodology, resources, supervision, project administration, visualization, writing- review and editing original draft.
Data Availability
Data is provided in the supplementary document. In case any other information is required, it will be available from the corresponding author on reasonable requests.
- Zhang, B., Jiang, Y., Balasubramanian, R.: Synthesis, formation mechanisms and applications of biomass-derived carbonaceous materials: A critical review. J Mater Chem A Mater. 9, 24759–24802 (2021). https://doi.org/10.1039/d1ta06874a
- Liu, Y., Nie, Y., Lu, X., Zhang, X., He, H., Pan, F., Zhou, L., Liu, X., Ji, X., Zhang, S.: Cascade utilization of lignocellulosic biomass to high-value products. Green Chemistry. 21, 3499–3535 (2019). https://doi.org/10.1039/c9gc00473d
- Bardhan, S.K., Gupta, S., Gorman, M.E., Haider, M.A.: Biorenewable chemicals: Feedstocks, technologies and the conflict with food production. Renewable and Sustainable Energy Reviews. 51, 506–520 (2015). https://doi.org/10.1016/j.rser.2015.06.013
- Verma, N., Kumar, V., Bansal, M.C.: Valorization of Waste Biomass in Fermentative Production of Cellulases: A Review. Waste Biomass Valorization. 12, 613–640 (2021). https://doi.org/10.1007/s12649-020-01048-8
- Ghosh, D., Dasgupta, D., Agrawal, D., Kaul, S., Adhikari, D.K., Kurmi, A.K., Arya, P.K., Bangwal, D., Negi, M.S.: Fuels and chemicals from lignocellulosic biomass: An integrated biorefinery approach. Energy and Fuels. 29, 3149–3157 (2015). https://doi.org/10.1021/acs.energyfuels.5b00144
- Alonso, D.M., Bond, J.Q., Dumesic, J.A.: Catalytic conversion of biomass to biofuels. Green Chemistry. 12, 1493–1513 (2010). https://doi.org/10.1039/c004654j
- Jaswal, A., Singh, P.P., Mondal, T.: Furfural-a versatile, biomass-derived platform chemical for the production of renewable chemicals. Green Chemistry. 24, 510–551 (2022). https://doi.org/10.1039/d1gc03278j
- Zhang, X., Lei, H., Chen, S., Wu, J.: Catalytic co-pyrolysis of lignocellulosic biomass with polymers: A critical review. Green Chemistry. 18, 4145–4169 (2016). https://doi.org/10.1039/c6gc00911e
- Ahmad, E., Alam, M.I., Pant, K.K., Haider, M.A.: Catalytic and mechanistic insights into the production of ethyl levulinate from biorenewable feedstocks. Green Chemistry. 18, 4804–4823 (2016). https://doi.org/10.1039/c6gc01523a
- Iglesias, J., Martínez-Salazar, I., Maireles-Torres, P., Martin Alonso, D., Mariscal, R., López Granados, M.: Advances in catalytic routes for the production of carboxylic acids from biomass: A step forward for sustainable polymers. Chem Soc Rev. 49, 5704–5771 (2020). https://doi.org/10.1039/d0cs00177e
- Melero, J.A., Iglesias, J., Garcia, A.: Biomass as renewable feedstock in standard refinery units. Feasibility, opportunities and challenges. Energy Environ Sci. 5, 7393–7420 (2012). https://doi.org/10.1039/c2ee21231e
- Delidovich, I., Leonhard, K., Palkovits, R.: Cellulose and hemicellulose valorisation: An integrated challenge of catalysis and reaction engineering. Energy Environ Sci. 7, 2803–2830 (2014). https://doi.org/10.1039/c4ee01067a
- Li, N., Zong, M.H.: (Chemo)biocatalytic Upgrading of Biobased Furanic Platforms to Chemicals, Fuels, and Materials: A Comprehensive Review. ACS Catal. 12, 10080–10114 (2022). https://doi.org/10.1021/acscatal.2c02912
- Combustion Gasification & Propulsion Laboratory: Crop Images with Residue details, http://lab.cgpl.iisc.ernet.in/Atlas/Downloads/CropImages_with_residuedetails.pdf
- Department of Agriculture and Farmers Welfare: Annual Report 2021-22. (2022)
- Chakrabarti, S., Khan, M.T., Kishore, A., Roy, D., Scott, S.P.: Risk of acute respiratory infection from crop burning in India: Estimating disease burden and economic welfare from satellite and national health survey data for 250 000 persons. Int J Epidemiol. 48, 1113–1124 (2019). https://doi.org/10.1093/ije/dyz022
- Zhao, S., Luo, Y.: Multiscale Modeling of Lignocellulosic Biomass Thermochemical Conversion Technology: An Overview on the State-of-the-Art. Energy and Fuels. 34, 11867–11886 (2020). https://doi.org/10.1021/acs.energyfuels.0c02247
- Calvo-Serrano, R., Guo, M., Pozo, C., Galán-Martín, Á., Guillén-Gosálbez, G.: Biomass Conversion into Fuels, Chemicals, or Electricity? A Network-Based Life Cycle Optimization Approach Applied to the European Union. ACS Sustain Chem Eng. 7, 10570–10582 (2019). https://doi.org/10.1021/acssuschemeng.9b01115
- Mika, L.T., Cséfalvay, E., Németh, Á.: Catalytic Conversion of Carbohydrates to Initial Platform Chemicals: Chemistry and Sustainability. Chem Rev. 118, 505–613 (2018). https://doi.org/10.1021/acs.chemrev.7b00395
- Allied Market Research: Acoustic Insulation Market Size, Trends and Forecast to 2030
- Kumar, P., Barrett, D.M., Delwiche, M.J., Stroeve, P.: Methods for pretreatment of lignocellulosic biomass for efficient hydrolysis and biofuel production. Ind Eng Chem Res. 48, 3713–3729 (2009). https://doi.org/10.1021/ie801542g
- Naresh Kumar, M., Ravikumar, R., Thenmozhi, S., Ranjith Kumar, M., Kirupa Shankar, M.: Choice of Pretreatment Technology for Sustainable Production of Bioethanol from Lignocellulosic Biomass: Bottle Necks and Recommendations. Waste Biomass Valorization. 10, 1693–1709 (2019). https://doi.org/10.1007/s12649-017-0177-6
- Kumar, N., Gautam, R., Stallings, J.D., Coty, G.G., Lynam, J.G.: Secondary Agriculture Residues Pretreatment Using Deep Eutectic Solvents. Waste Biomass Valorization. 12, 2259–2269 (2021). https://doi.org/10.1007/s12649-020-01176-1
- Han, T., Zhang, B., Li, H., Zhang, H., Yang, Y., Hu, L., Ren, X., Wang, S., Zheng, L., Han, X., Liu, G., Zhang, J., Fei, Q., Tang, Y., Yang, S., Bao, X., Bao, J.: Year-Round Storage Operation of Three Major Agricultural Crop Residue Biomasses by Performing Dry Acid Pretreatment at Regional Collection Depots. ACS Sustain Chem Eng. 9, 4722–4734 (2021). https://doi.org/10.1021/acssuschemeng.0c08739
- Sun, C., Liu, R., Cao, W., Yin, R., Mei, Y., Zhang, L.: Impacts of Alkaline Hydrogen Peroxide Pretreatment on Chemical Composition and Biochemical Methane Potential of Agricultural Crop Stalks. Energy and Fuels. 29, 4966–4975 (2015). https://doi.org/10.1021/acs.energyfuels.5b00838
- Qi, W., He, C., Wang, Q., Liu, S., Yu, Q., Wang, W., Leksawasdi, N., Wang, C., Yuan, Z.: Carbon-Based Solid Acid Pretreatment in Corncob Saccharification: Specific Xylose Production and Efficient Enzymatic Hydrolysis. ACS Sustain Chem Eng. 6, 3640–3648 (2018). https://doi.org/10.1021/acssuschemeng.7b03959
- Yuan, Z., Klinger, G.E., Nikafshar, S., Cui, Y., Fang, Z., Alherech, M., Goes, S., Anson, C., Singh, S.K., Bals, B., Hodge, D.B., Nejad, M., Stahl, S.S., Hegg, E.L.: Effective Biomass Fractionation through Oxygen-Enhanced Alkaline-Oxidative Pretreatment. ACS Sustain Chem Eng. 9, 1118–1127 (2021). https://doi.org/10.1021/acssuschemeng.0c06170
- Zhang, F., Yu, H., Li, L., Wang, H., He, Z., Jiang, E., Sun, Y., Li, Z., Yi, W., Xu, X.: Pretreatment Influence of an Imitative Deep Eutectic Solvent Composed of Biomass Light Oil and Choline Chloride on Boosting Selective Saccharification during Corn Stalk Pyrolysis. ACS Sustain Chem Eng. 9, 12813–12824 (2021). https://doi.org/10.1021/acssuschemeng.1c03359
- Ali Redha, A.: Review on Extraction of Phenolic Compounds from Natural Sources Using Green Deep Eutectic Solvents. J Agric Food Chem. 69, 878–912 (2021). https://doi.org/10.1021/acs.jafc.0c06641
- Dhar, P., Jose, A.M., Pilloni, G., Vinu, R.: Development of Novel Imidazole-Poly(ethylene glycol) Solvent for the Conversion of Lignocellulosic Agro-Residues to Valuable Chemicals. Ind Eng Chem Res. 58, 16033–16044 (2019). https://doi.org/10.1021/acs.iecr.9b00665
- Andhalkar, V.V., Ahorsu, R., Domínguez De María, P., Winterburn, J., Medina, F., Constantí, M.: Valorization of Lignocellulose by Producing Polyhydroxyalkanoates under Circular Bioeconomy Premises: Facts and Challenges, (2022)
- Kumar, A.K., Sharma, S.: Recent updates on different methods of pretreatment of lignocellulosic feedstocks: a review. Bioresour Bioprocess. 4, 7 (2017). https://doi.org/10.1186/s40643-017-0137-9
- Chiranjeevi, T., Mattam, A.J., Vishwakarma, K.K., Uma, A., Peddy, V.C.R., Gandham, S., Ravindra Velankar, H.: Assisted Single-Step Acid Pretreatment Process for Enhanced Delignification of Rice Straw for Bioethanol Production. ACS Sustain Chem Eng. 6, 8762–8774 (2018). https://doi.org/10.1021/acssuschemeng.8b01113
- Smullen, E., Finnan, J., Dowling, D., Mulcahy, P.: The environmental performance of pretreatment technologies for the bioconversion of lignocellulosic biomass to ethanol. Renew Energy. 142, 527–534 (2019). https://doi.org/10.1016/j.renene.2019.04.082
- Clarke, C.J., Tu, W.C., Levers, O., Bröhl, A., Hallett, J.P.: Green and Sustainable Solvents in Chemical Processes. Chem Rev. 118, 747–800 (2018). https://doi.org/10.1021/acs.chemrev.7b00571
- Hansen, B.B., Spittle, S., Chen, B., Poe, D., Zhang, Y., Klein, J.M., Horton, A., Adhikari, L., Zelovich, T., Doherty, B.W., Gurkan, B., Maginn, E.J., Ragauskas, A., Dadmun, M., Zawodzinski, T.A., Baker, G.A., Tuckerman, M.E., Savinell, R.F., Sangoro, J.R.: Deep Eutectic Solvents: A Review of Fundamentals and Applications, (2021)
- Francisco, M., Van Den Bruinhorst, A., Kroon, M.C.: Low-transition-temperature mixtures (LTTMs): A new generation of designer solvents. Angewandte Chemie - International Edition. 52, 3074–3085 (2013). https://doi.org/10.1002/anie.201207548
- Kumar, A.K., Parikh, B.S., Shah, E., Liu, L.Z., Cotta, M.A.: Cellulosic ethanol production from green solvent-pretreated rice straw. Biocatal Agric Biotechnol. 7, 14–23 (2016). https://doi.org/10.1016/j.bcab.2016.04.008
- Hossain, M.A., Rahaman, M.S., Yelle, D., Shang, H., Sun, Z., Renneckar, S., Dong, J., Tulaphol, S., Sathitsuksanoh, N.: Effects of polyol-based deep eutectic solvents on the efficiency of rice straw enzymatic hydrolysis. Ind Crops Prod. 167, 113480 (2021). https://doi.org/10.1016/j.indcrop.2021.113480
- Kumar, A.K., Parikh, B.S., Pravakar, M.: Natural deep eutectic solvent mediated pretreatment of rice straw: bioanalytical characterization of lignin extract and enzymatic hydrolysis of pretreated biomass residue. Environmental Science and Pollution Research. 23, 9265–9275 (2016). https://doi.org/10.1007/s11356-015-4780-4
- Arenas, J.P., Crocker, M.J.: Recent trends in porous sound-absorbing materials. Sound and Vibration. 44, 12–17 (2010)
- Kalauni, K., Pawar, S.J.: A review on the taxonomy, factors associated with sound absorption and theoretical modeling of porous sound absorbing materials. Journal of Porous Materials. 26, 1795–1819 (2019). https://doi.org/10.1007/s10934-019-00774-2
- S. K. Sharma, S. R. Shukla, A.K. Sethy: Acoustical-behaviour-of-natural-fibresbased-composite-boards-as-soundabsorbing-materialsJournal-of-the-Indian-Academy-of-Wood-Science.pdf. Journal of the Indian Academy of Wood Science . 17, 66–72 (2020)
- Cao, L., Fu, Q., Si, Y., Ding, B., Yu, J.: Porous materials for sound absorption. Composites Communications. 10, 25–35 (2018). https://doi.org/10.1016/j.coco.2018.05.001
- Yang, T., Hu, L., Xiong, X., Petrů, M., Noman, M.T., Mishra, R., Militký, J.: Sound absorption properties of natural fibers: A review. Sustainability (Switzerland). 12, 1–25 (2020). https://doi.org/10.3390/su12208477
- Raj, M., Fatima, S., Tandon, N.: Recycled materials as a potential replacement to synthetic sound absorbers: A study on denim shoddy and waste jute fibers. Applied Acoustics. 159, 107070 (2020). https://doi.org/10.1016/j.apacoust.2019.107070
- Yang, H.-S., Kim, D.-J., Kim, H.-J.: Rice straw-wood particle composite for sound absorbing wooden construction materials. Bioresource Technology . 86, 117–121 (2003)
- Huang, C.H., Lin, J.H., Lou, C.W., Tsai, Y.T.: The efficacy of coconut fibers on the sound-absorbing and thermal-insulating nonwoven composite board. Fibers and Polymers. 14, 1378–1385 (2013). https://doi.org/10.1007/s12221-013-1378-7
- Sakthivel, S., Senthil Kumar, S., Solomon, E., Getahun, G., Admassu, Y., Bogale, M., Gedilu, M., Aduna, A., Abedom, F.: Sound absorbing and insulating properties of natural fiber hybrid composites using sugarcane bagasse and bamboo charcoal. J Eng Fiber Fabr. 16, 155892502110448 (2021). https://doi.org/10.1177/15589250211044818
- Kumar, A.K., Sharma, S., Shah, E., Patel, A.: Technical assessment of natural deep eutectic solvent (NADES) mediated biorefinery process: A case study. J Mol Liq. 260, 313–322 (2018). https://doi.org/10.1016/j.molliq.2018.03.107
- E1050 − 19: Standard Test Method for Impedance and Absorption of Acoustical Materials Using a Tube, Two Microphones and a Digital Frequency Analysis System. (2020)
- Chen, X., Yu, J., Zhang, Z., Lu, C.: Study on structure and thermal stability properties of cellulose fibers from rice straw. Carbohydr Polym. 85, 245–250 (2011). https://doi.org/10.1016/j.carbpol.2011.02.022
- Salehi, S.M.A., Karimi, K., Behzad, T., Poornejad, N.: Efficient conversion of rice straw to bioethanol using sodium carbonate pretreatment. Energy and Fuels. 26, 7354–7361 (2012). https://doi.org/10.1021/ef301476b
- Petridis, L., Smith, J.C.: Conformations of Low-Molecular-Weight Lignin Polymers in Water. ChemSusChem. 9, 289–295 (2016). https://doi.org/10.1002/cssc.201501350
- Hu, S., Hsieh, Y. Lo: Preparation of activated carbon and silica particles from rice straw. ACS Sustain Chem Eng. 2, 726–734 (2014). https://doi.org/10.1021/sc5000539
- Satlewal, A., Agrawal, R., Bhagia, S., Das, P., Ragauskas, A.J.: Rice straw as a feedstock for biofuels: Availability, recalcitrance, and chemical properties. Biofuels, Bioproducts and Biorefining. 12, 83–107 (2018). https://doi.org/10.1002/bbb.1818
- Azwa, Z.N., Yousif, B.F., Manalo, A.C., Karunasena, W.: A review on the degradability of polymeric composites based on natural fibres. Mater Des. 47, 424–442 (2013). https://doi.org/10.1016/j.matdes.2012.11.025
- Qiu, X., Wan, X., Wang, Z., Li, Z., Li, J., Li, X., Zhang, Z.: A simple and universal strategy for construction and application of silica-based flame-retardant nanostructure. Compos B Eng. 238, 109887 (2022). https://doi.org/10.1016/j.compositesb.2022.109887
- Park, S., Baker, J.O., Himmel, M.E., Parilla, P.A., Johnson, D.K.: Cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance. (2010)
- Kshirsagar, S.D., Waghmare, P.R., Chandrakant Loni, P., Patil, S.A., Govindwar, S.P.: Dilute acid pretreatment of rice straw, structural characterization and optimization of enzymatic hydrolysis conditions by response surface methodology. RSC Adv. 5, 46525–46533 (2015). https://doi.org/10.1039/c5ra04430h
- Pan, M., Zhao, G., Ding, C., Wu, B., Lian, Z., Lian, H.: Physicochemical transformation of rice straw after pretreatment with a deep eutectic solvent of choline chloride/urea. Carbohydr Polym. 176, 307–314 (2017). https://doi.org/10.1016/j.carbpol.2017.08.088
- Thulluri, C., Balasubramaniam, R., Velankar, H.R.: Generation of highly amenable cellulose-Iβ via selective delignification of rice straw using a reusable cyclic ether-assisted deep eutectic solvent system. Sci Rep. 11, 1591 (2021). https://doi.org/10.1038/s41598-020-80719-x
- Hartati, I., Sulistyo, H., Sediawan, W.B., Azis, M.M., Fahrurrozi, M.: Microwave-Assisted Urea-Based-Hydrotropic Pretreatment of Rice Straw: Experimental Data and Mechanistic Kinetic Models. ACS Omega. 6, 13225–13239 (2021). https://doi.org/10.1021/acsomega.1c01084
- Bujoreanu, C., Nedeff, F., Benchea, M., Agop, M.: Experimental and theoretical considerations on sound absorption performance of waste materials including the effect of backing plates. Applied Acoustics. 119, 88–93 (2017). https://doi.org/10.1016/j.apacoust.2016.12.010
- Lim, Z.Y., Putra, A., Nor, M.J.M., Yaakob, M.Y.: Sound absorption performance of natural kenaf fibres. Applied Acoustics. 130, 107–114 (2018). https://doi.org/10.1016/j.apacoust.2017.09.012
- Kriiger, J., Quickert, M.: Technical Note Determination of Acoustic Absorber Parameters in Impedance Tubes. Applied Acoustics. 50, 79–89 (1997)
- Mvubu, M.B., Anandjiwala, R., Patnaik, A.: Effects of air gap, fibre type and blend ratio on sound absorption performance of needle-punched non-woven fabrics. J Eng Fiber Fabr. 14, 155892501984087 (2019). https://doi.org/10.1177/1558925019840874