Steam explosion pretreatment of wheat straw to improve methane yields: Investigation of the degradation kinetics of structural compounds during anaerobic digestion

In this study, wheat-straw lignocelluloses were liquefied in liquefaction solvents. Polyethyleneglycol 400 (PEG 400) and ethylene glycol (EG) were used as main liquefaction solvents. The effect of liquefaction time and liquefaction solvents on the properties of liquefied products was investigated. As the reaction time increased, the hydroxyl value, residue content and viscosity decreased, and the acid value decreased gradually in the previous period of time then increased. The optimum liquefaction conditions were as follows: wheat-straw lignocelluloses with steam-explosion pretreatment, the main liquefaction reagent of PEG 400, auxiliary liquefaction solvents of glycerin, catalyst of sulfuric acid, liquefaction temperature of 150°C, liquefaction time of 4 h. The hydroxyl value of liquefaction product was 206 mgKOH/g, the residue content was 0.19% and the viscosity was 88 mPa•s.

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Anaerobic Digestion of Steam-Exploded Wheat Straw and Co-Digestion Strategies for Enhanced Biogas Production

Applied Sciences ◽

10.3390/app10228284 ◽

2020 ◽

Vol 10 (22) ◽

pp. 8284

Author(s):

Fokion Kaldis ◽

Denise Cysneiros ◽

James Day ◽

Kimon-Andreas G. Karatzas ◽

Afroditi Chatzifragkou

Keyword(s):

Anaerobic Digestion ◽

Wheat Straw ◽

Steam Explosion ◽

Biogas Production ◽

Inorganic Nitrogen ◽

Rapeseed Meal ◽

Gas Production ◽

Distillers Grains With Solubles ◽

Dried Distillers Grains ◽

Pre Treatment

Wheat straw (WS) is considered a favourable substrate for biogas production. However, due to its rigid structure and high carbon to nitrogen (C/N ratio), its biodegradability during anaerobic digestion (AD) is usually low. In the present study, the effect of steam explosion pre-treatment on WS, combined with C/N adjustment with inorganic nitrogen, on biogas production was evaluated. Additionally, co-digestion of WS with protein-rich agri-industrial by-products (dried distillers’ grains with solubles (DDGS) and rapeseed meal (RM)) was assessed. Steam explosion enhanced biogas production from WS, whereas the addition of NH4Cl was beneficial (p < 0.05) for the digestion of steam-exploded wheat straw (SE). Furthermore, mono-digestion of the four different substrates seemed to be efficient in both inoculum to substrate ratios (I/S) tested (3.5 and 1.75 (w/w)). Finally, during co-digestion of WS and SE with DDGS and RM, an increase in the cumulative methane production was noted when higher amounts of DDGS and RM were co-digested. This study demonstrated that DDGS and RM can be used as an AD supplement to stimulate gas production and improve wheat straw biodegradability, while their addition at 10% on an AD system operating with WS can enhance gas yields at levels similar to those achieved by steam-exploded straw.

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Effect of steam explosion on physicochemical properties of waste activated sludge and the performance of anaerobic digestion

Water Science & Technology ◽

10.2166/wst.2018.227 ◽

2018 ◽

Vol 77 (11) ◽

pp. 2687-2698 ◽

Cited By ~ 3

Author(s):

Yan Zhang ◽

Peng Han ◽

He Liu ◽

Lihui Zhang ◽

Hongbo Liu ◽

...

Keyword(s):

Anaerobic Digestion ◽

Physicochemical Properties ◽

Steam Explosion ◽

Biogas Production ◽

Hydrolysis Time ◽

Severity Factor ◽

Capillary Suction ◽

Pretreatment Condition ◽

Steam Explosion Pretreatment ◽

Hydrolysis Temperature

Abstract The effect of steam explosion on physicochemical properties of sludge and the performance of anaerobic digestion (AD) was investigated. The steam explosion was conducted under different combinations of temperature and time, ranging 151–198 °C and 4–12 min respectively. The capillary suction time (CST) and viscosity of the sludge was increased with particle size decreased by improved hydrolysis temperature and prolonged hydrolysis time. The best sludge solubilization achieved was 41.3% under pretreatment condition of 198 °C and 4 min. Biogas production was enhanced with the improved sludge solubilization, and a linear correlation was found between biogas production and the severity factor (logR0) of steam explosion. However, the biogas productivity was reduced when the logR0 was increased from 3.79 to 3.96, probably owing to the generation of refractory organics during the high severity pretreatment. The temperature of 198 °C and the time of 8 min were the recommended operation parameters of steam explosion pretreatment for sludge AD, which could improve biogas production by 99.7 mL/g VSfed. The pH and NH4+-N during sludge AD was increased by steam explosion pretreatment; however, no inhibition on biogas production was observed.

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Effect of Semi-Continuous Anaerobic Digestion on the Substrate Solubilisation of Lignin-Rich Steam-Exploded Ludwigia grandiflora

Applied Sciences ◽

10.3390/app11104452 ◽

2021 ◽

Vol 11 (10) ◽

pp. 4452

Author(s):

Pranshu Bhatia ◽

Masaaki Fujiwara ◽

Maria Cecilia D. Salangsang ◽

Jun Qian ◽

Xin Liu ◽

...

Keyword(s):

Anaerobic Digestion ◽

Steam Explosion ◽

Hydraulic Retention Time ◽

Loading Rate ◽

Biogas Production ◽

Organic Loading Rate ◽

Biogas Yield ◽

Steam Explosion Pretreatment ◽

The Stability ◽

Ludwigia Grandiflora

In this study, semi-continuous anaerobic digestion of lignin-rich steam-exploded Ludwigia grandiflora (Lignin = 25.22% ± 4.6% total solids) was performed to understand better the effect of steam explosion on the substrate solubilisation and inhibitors formation during the process. Steam explosion pretreatment was performed at 180 °C for 30 min at a severity factor of 3.8 to enhance the biogas yield of the lignocellulosic biomass. The semi-continuous anaerobic digestion was performed in a continuously stirred tank reactor for 98 days at an initial hydraulic retention time of 30 days and an organic loading rate of 0.9 g-VS L−1day−1. The performed steam explosion pretreatment caused biomass solubilisation, resulting in enhanced biogas production during the process. During the anaerobic digestion process, the average biogas yield was 265 mL g-VS−1, and the pH throughout the operation was in the optimum range of 6.5–8.2. Due to fluctuations in the biogas yield, the hydraulic retention time and organic loading rate were changed on day 42 (50 days and 0.5 g-VS L−1day−1) and on day 49 (40 days and 0.7 g-VS L−1day−1), and 1 M of NaOH was added to the liquid fraction of the steam-exploded L. grandiflora during the latter part of the operation to maintain the stability in the reactor. Therefore, the steam explosion pretreatment helped in the degradation of L. grandiflora by breaking the lignocellulose structure. In addition, changes in the operating conditions of the anaerobic digestion led to an increase in the biogas production towards the end of the process, leading to the stability in the CSTR.

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