“…Aggarwal et al 20 recently reported using organosolv and alkaline pretreatment of RS for cellulose production with about 82% total removal of hemicellulose and lignin along with 90.4% of silica removal from RS. It was noted that % lignin removal was higher for A (9.2%) as compared to D (0.54%), % extractives removal was lower for A and no change was reported for D. Quick lime used during preparation of petha sweet, resulted in increase of ash content due to absorption of Ca 2+ ions in A 15 . EDX analysis indicated % calcium enhancement for A.…”
Section: Resultsmentioning
confidence: 96%
“…The surface roughness was enhanced after pretreatment which was higher for A as compared to D. Hence, PWW was more effective in enhancing the surface area of RS which is favourable for enzymatic and microbial attack leading biofuel production. This increment in surface area of RS can be attributed to lignin and hemicellulose degradation which increases the amorphous nature of cellulose 15 . Figure 1 Scanning electron micrograph of native ( RS ), distilled water pretreated ( D ) and PWW pretreated ( A ) rice straw.…”
Section: Resultsmentioning
confidence: 99%
“…Biochemical oxygen demand (BOD), chemical oxygen demand (COD), glucose, pH etc. (before and after soaking RS) were also analysed using standard methods 15 .…”
Section: Methodsmentioning
confidence: 99%
“…), physico-chemical (glycerol thermal, ultrasonication assisted acid and alkali, microwave assisted acid and alkali etc. ), biological (fungal and microbial consortium) and combined (combination of two or more pretreatments) are available 3 , 4 , 8 – 15 . Widely used and effective acid and alkali pretreatments are expensive and detrimental to the environment 3 .…”
Energy efficient and environment friendly pretreatment processes for the production of biofuel have remained elusive and the research is further compounded by the high cost of processing lignocellulosic biomass—an essential factor for producing sustainable biofuels. In the last few decades, a number of pretreatment methods have been proposed, specifically chemical pretreatments but are either expensive or harmful to the environment. To address this urgent need, we propose a green pretreatment method that utilises the highly alkaline by-product, petha wastewater to pretreat the lignocellulosic waste rice straw (RS). The effectiveness of the pretreatment was analysed by monitoring both enhanced cellulose content and reducing sugar yield along with removal of hemicellulose and lignin. We found that PWW pretreatment yielded five times more reducing sugar than native RS with 10.12% increment in cellulose content. SEM and EDX studies further revealed that our process enhanced surface roughness and carbon content (from 32.19% increased to 41.59% and 41.66% for A and D, respectively) along with reduction in silica content (from 8.68% in RS to 4.30% and 7.72% for A and D, respectively). XRD and FTIR analyses indicate crystallinity index (CI) and alteration in lignocellulosic structure of RS, respectively. Decrease in CI was about 43.4% in A whereas only 4.5% in D as compared to native RS (CI 54.55%). Thereby we found PWW to be better substitute of an alkali for pretreatment of RS with negligible environmental impacts.
“…Aggarwal et al 20 recently reported using organosolv and alkaline pretreatment of RS for cellulose production with about 82% total removal of hemicellulose and lignin along with 90.4% of silica removal from RS. It was noted that % lignin removal was higher for A (9.2%) as compared to D (0.54%), % extractives removal was lower for A and no change was reported for D. Quick lime used during preparation of petha sweet, resulted in increase of ash content due to absorption of Ca 2+ ions in A 15 . EDX analysis indicated % calcium enhancement for A.…”
Section: Resultsmentioning
confidence: 96%
“…The surface roughness was enhanced after pretreatment which was higher for A as compared to D. Hence, PWW was more effective in enhancing the surface area of RS which is favourable for enzymatic and microbial attack leading biofuel production. This increment in surface area of RS can be attributed to lignin and hemicellulose degradation which increases the amorphous nature of cellulose 15 . Figure 1 Scanning electron micrograph of native ( RS ), distilled water pretreated ( D ) and PWW pretreated ( A ) rice straw.…”
Section: Resultsmentioning
confidence: 99%
“…Biochemical oxygen demand (BOD), chemical oxygen demand (COD), glucose, pH etc. (before and after soaking RS) were also analysed using standard methods 15 .…”
Section: Methodsmentioning
confidence: 99%
“…), physico-chemical (glycerol thermal, ultrasonication assisted acid and alkali, microwave assisted acid and alkali etc. ), biological (fungal and microbial consortium) and combined (combination of two or more pretreatments) are available 3 , 4 , 8 – 15 . Widely used and effective acid and alkali pretreatments are expensive and detrimental to the environment 3 .…”
Energy efficient and environment friendly pretreatment processes for the production of biofuel have remained elusive and the research is further compounded by the high cost of processing lignocellulosic biomass—an essential factor for producing sustainable biofuels. In the last few decades, a number of pretreatment methods have been proposed, specifically chemical pretreatments but are either expensive or harmful to the environment. To address this urgent need, we propose a green pretreatment method that utilises the highly alkaline by-product, petha wastewater to pretreat the lignocellulosic waste rice straw (RS). The effectiveness of the pretreatment was analysed by monitoring both enhanced cellulose content and reducing sugar yield along with removal of hemicellulose and lignin. We found that PWW pretreatment yielded five times more reducing sugar than native RS with 10.12% increment in cellulose content. SEM and EDX studies further revealed that our process enhanced surface roughness and carbon content (from 32.19% increased to 41.59% and 41.66% for A and D, respectively) along with reduction in silica content (from 8.68% in RS to 4.30% and 7.72% for A and D, respectively). XRD and FTIR analyses indicate crystallinity index (CI) and alteration in lignocellulosic structure of RS, respectively. Decrease in CI was about 43.4% in A whereas only 4.5% in D as compared to native RS (CI 54.55%). Thereby we found PWW to be better substitute of an alkali for pretreatment of RS with negligible environmental impacts.
“…The specific energy applied in microwave pretreatment was almost 9 times higher than that of used in ultrasonication, resulting only 10-15% increases in biogas yield. Kumari and Singh [19] studied the production of methane and ethanol by ultrasonic assisted petha waste water pretreatment of rice straw. Their results indicated that the methane yield was about three times more than that of reactors without ultrasonication and the ethanol yield was about two times more than that of reactors without ultrasonication.…”
The fur is hard to decompose during the fermentation process of diseased swine carcasses. In order to enhance the enzymolysis of pigskin, the ultrasonic was proposed to use during the process of the enzymatic hydrolysis. The response surface optimization experiments were carried out with the DH (degree of hydrolysis) as the response value and the optimum conditions for enzymatic hydrolysis were determined. Based the optimum conditions, orthogonal experiments were carried out with ultrasonic frequency, power and time as variables, and optimal ultrasonic parameters were obtained. Without the assistance of ultrasonic, the descending order of influence factors on DH was, temperature＞SC(Substrate concentration)＞RES(The ratio of enzyme to substrate)＞pH. Moreover, the DH value is of 10.42% under the following optimal conditions: RES is of 16,006 U/g, the temperature is of 48.92°C, the SC is of 59.76 g/L and pH is of 10.43. Frequency has the greatest effect on DH, followed by power, and finally time. The optimum hydrolysis time is of 5 h, and the DH is of 22.94% were obtained under the following optimum ultrasonic pretreatment conditions: frequency combination is of (20,40,40), power is of 600 W and time is of 25 min. Comparing with the group without ultrasonic pretreatment, the DH for the ultrasonic assistance increased by 4%, the hydrolysis time was shorten by 3 h, and the total amino acids increased by 15.98%.
ARTICLE HISTORY
The current work illustrates a novel method of pre‐treating rice straw using ultrasound (US) as well as using ultrasound coupled with anaerobic digestion (AD) to intensify biogas production. The primary objectives were to evaluate the effectiveness of ultrasound in increasing the utilization of rice straw and to optimize the conditions for maximum biogas yield. Important parameters such as ultrasonic power (0.2–1 W/mL), duty cycle (20%–80%), and substrate loading (2%–10% w/v) were varied to understand their effects during pre‐treatment. The results showed that the maximum increase in soluble chemical oxygen demand (sCOD), with a final value of 13,500 mg/L (an increase of 64.63%), was achieved under optimum conditions of ultrasonic power of 0.4 W/mL, a duty cycle of 50%, and a substrate loading of 6% w/v. Additionally, the study evaluated the effect of low‐intensity US exposure during AD with pre‐treated rice straw at varying irradiation times (10–30 min) and duty cycles (20%–60%). The optimal conditions of ultrasonic time of 20 min and a duty cycle of 50% resulted in nearly four times higher biogas generation compared to untreated samples. The current research successfully demonstrates the efficient use of US in the feedstock pre‐treatment and also in AD process, leading to significant intensification in biogas production within a shorter time frame.
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