Effect Of Thermochemical Pretreatment Research Articles

Biogas production from thermochemically pretreated sweet potato root waste

This paper presents the results of batch anaerobic digestion (AD) of thermochemically pre-treated sweet potato root waste (SPW). This agricultural waste is available in massive quantities yet it has remained an unexploited resource amid the ever-increasing need for clean energy and waste disposal challenges. Therefore, the waste can be considered for energy production through AD. However, SPW has a complex amylopectin structure that is resistant to digestive enzymes during hydrolysis which could lead to a longer retention time in the digester. In this sense, the effect of thermochemical pre-treatment on biogas production from SPW was investigated by pre-treating the substrate with sodium hydroxide (NaOH) at (0.6 g/L–3.5 g/L), temperature (50 °C–90 °C) and pretreatment time (30–120 min). The central composite design was used to design the number of experiments. SPW was milled to a small size. The physicochemical characteristics of materials were determined using standard methods. The quality of biogas produced in terms of methane content was analysed. The results from the study revealed that thermochemical pre-treatment on SPW improved biogas and methane yields. The pre-treated SPW had superior results to the untreated one. It represented a 33.88% improvement from 28.23 mL/gSPW biogas yield for the untreated SPW to 37.8 mL/gSPW for the treated SPW at optimal conditions. The optimum conditions for biogas production were found at a NaOH concentration of 2.9 g/L, a heating temperature of 82 °C, and a pre-treatment time of 102 min. Methane content in the biogas also improved from 42% to 64% (22% increase). The digester retention time was also reduced from 22 to 16 days. It can therefore be concluded that thermochemical pre-treatment of SPW improves both biogas yield and methane content as well as improves the kinetics of AD.

Effect of Thermochemical Pretreatment on the Sugar Recovery from Casava Waste for Bioethanol Production: Process Optimization and Characterization

Effect of Thermochemical Pretreatment on the Sugar Recovery from Casava Waste for Bioethanol Production: Process Optimization and Characterization

The effect of thermochemical pre-treatment on biogas production efficiency from kitchen waste using a novel lab scale digester

The present study is developed for considering the effect of thermochemical pre-treatment on the biogas production process from kitchen waste. Parameters controlled by the experimental setup include mechanical stirring and temperature. Thermochemical pre-treatment included chemical pre-treatment by 3 and 6% (based on TS) NaOH for 1 h and thermal pre-treatment at 60, 90 and 120 °C for 30 min. The data of the production process were imported to SPSS software using a factorial experiment in a completed randomized design (CRD) and were analyzed by developing the logistic model. Based on the results, the effect of thermochemical pre-treatment was significant at a level of 0.05 and the correlation coefficient of the logistic model, on average was R2 = 0.99. And also, according to the results of the logistic model the delay time ( μ ) in the acidification phase also decreases with the increasing of sodium hydroxide and temperature in the thermochemical pretreatment. For chemical pre-treatment, there was a significant difference in the effect of 3 and 6% of NaOH on biogas production such that increasing the NaOH amount from 3 to 6% (at 120 °C) increased the biogas and methane production as 21.39 and 20.74% respectively. For thermal pre-treatment, increasing the temperature from 60 to 120 °C (in NaOH 6%) increased the biogas and methane production by 13.2 and 11.6%, respectively. The maximum biogas and methane production was related to NaOH 6% and temperature 120 °C (206.16 and 121.42 ml/g VS).

Effect of thermochemical pretreatment on lignin alteration and cell wall microstructural degradation in Eucalyptus globulus: comparison of acid, alkali, and water pretreatments

Pretreatment is an essential step to effectively hydrolyze lignocellulosic polysaccharides. In this paper, we investigated the degree of decompositions of lignin and cell wall structure using dilute acid, alkali, and water pretreatments to assess both chemical and ultrastructural alterations during pretreatment. The thioacidolysis method showed that β-O-4 linkages in lignin were mostly cleaved after all pretreatments, in which the highest decrease of β-O-4 units was for NaOH pretreatment, followed by hot water and H2SO4 pretreatments. The amounts of lignin degradation compounds, including vanillin and syringaldehyde, in the supernatant water also differed between the three pretreatments. Field-emission scanning electron microscopy revealed clear differences among the pretreatments in decomposing the ultrastructure of the inner surface of the fiber cell walls. Small pores were formed due to degradation of a part of the warty layer of the innermost surface in H2SO4 pretreatment. The warty layer was more degraded in hot water pretreatment and thus the cellulose microfibrils of the secondary walls were exposed. NaOH pretreatment showed that the warty layer was almost completely decomposed. The comparative study of different pretreatments using chemical methods and microscopic observations led to a better understanding of decomposition of wood cell walls by thermochemical pretreatment.

Effects of thermo-chemical pretreatment plus microbial fermentation and enzymatic hydrolysis on saccharification and lignocellulose degradation of corn straw

In order to increase corn straw degradation, the straw was kept in the combined solution of 15% (w/w) lime supernatant and 2% (w/w) sodium hydroxide with liquid-to-solid ratio of 13:1 (mL/g) at 83.92°C for 6h; and then added with 3% (v/v) H2O2 for reaction at 50°C for 2h; finally cellulase (32.3FPU/g dry matter) and xylanase (550U/g dry matter) was added to keep at 50°C for 48h. The maximal reducing sugars yield (348.77mg/g) was increased by 126.42% (P<0.05), and the degradation rates of cellulose, hemicellulose and lignin in pretreated corn straw with enzymatic hydrolysis were increased by 40.08%, 45.71% and 52.01%, compared with the native corn straw with enzymatic hydrolysis (P<0.05). The following study indicated that the combined microbial fermentation and enzymatic hydrolysis could further increase straw degradation and reducing sugar yield (442.85mg/g, P<0.05).

Effects of Thermo-chemical Pre-treatment on Bamboo for Biogas Production

The objective of this work was to develop various pre-treatment process, i.e. Ca(OH)2, NaOH, ammonium carbonate, H2SO4, maleic acid and combination of hydrothermal with H2SO4 in a batch anaerobic digestor of bamboo. Biogas efficiency of bamboo with and without pre-treatment was evaluated. The highest biogas production and methane yield were 820 ml/day and 72%, respectively, for hydrothermal + H2SO4 pre-treated bamboo followed by H2SO4, Ca(OH)2, maleic acid and ammonium carbonate. The results indicated that hydrothermal + H2SO4 pre-treatment could be an effective method for improving methane yield with bamboo.

Evaluation of thermochemical pretreatment and continuous thermophilic condition in rice straw composting process enhancement

The effects of thermochemical pretreatment and continuous thermophilic conditions on the composting of a mixture of rice straw residue and cattle manure were investigated using a laboratory-scale composting reactor. Results indicate that the composting period of rice straw can be shortened to less than 10days by applying alkali pre-treatment and continuous thermophilic composting conditions. The parameters obtained on day 9 of this study are similar to the criteria level published by the Canadian Council of Ministers of the Environment. The moisture content, organic matter reduction, pH level, electrical conductivity, total organic carbon reduction, soluble chemical oxygen demand reduction, total Kjeldahl nitrogen, carbon-to-nitrogen ratio, and germination index were 62.07%, 16.99%, 7.30%, 1058μS/cm, 17.00%, 83.43%, 2.06%, 16.75%, and 90.33%, respectively. The results of this study suggest that the application of chemical–biological integrated processes under thermophilic conditions is a novel method for the rapid degradation and maturation of rice straw residue.

Effect of Thermo-Chemical Pretreatment on Bioethanol Production from Corncobs

Currently, ethanol has gained significance since it is substantially used as an alternative biofuel. It can be produced by agro-industrial residuals such as corncobs. In ethanol production, hemicellulose and lignin are inhibitors of the enzymatic hydrolysis between cellulase and cellulose. They must be removed during in the pretreatment stage. In this research H2SO4 and NaOH were used as pretreatment solution at high temperature. The temperature were varied for 120 to 170 °C. The result showed that the optimal pretreatment condition of corncobs was using 2% (v/v) NaOH for 24 hr digestion in 1% (v/v) H2SO4 and then heating at 170 °C for 5 min. At this condition, the cellulose content of corncobs increased from 66.52% (untreated) to 92.25% (pretreated). Enzyme digestion of pretreated corncobs at an optimum condition yielded the reducing sugar level of 8.74 g/L. The optimum conditions were achieved at cellulase loading of 10 FPU/g and digestion time of 4 hr. Finally, the reducing sugar solution of 5 g/L was fermented with Zymomonas mobilis TISTR405 at 30°C and pH 5.0 for 48 hr, yielding ethanol of 1.8 g/l or 35.93% of the theoretical ethanol yield.

Effect of thermochemical pretreatment on sewage sludge and its impact on carboxylic acids production

This paper investigates the potential of converting sewage sludge into a useful product, namely carboxylic acids. To potentially enhance acid yields, the effect of pretreatment using 0.3 g lime/g dry biomass and water at 100 °C for 10–240 min was studied. The pretreated sludges were anaerobically fermented to mixed-acids using a mixed culture of microorganisms; methanogens were suppressed using iodoform. Batch fermentations were performed at 55 °C using ammonium bicarbonate buffer. The first batch experiments compared treated and untreated sludge as the only substrate. The second batch experiments used a mixture of sludge plus lime-treated bagasse (20:80 by weight). Analysis of liquor shows that the pretreatment were effective in solubilizing constituent compounds of sewage sludge. Nitrogen content and carboxylic acids increased with increasing pretreatment time. However, the soluble sugars peaked at 60 min, and then decreased with longer pretreatment time, showing that the solubilised sugars were undergoing intermolecular reactions, such as Maillard reactions. Fermentation experiments were a good indicator of the biodegradability of the pretreated sludges. Results clearly showed that lime-treating sludge, using even the minimum pretreatment time (10 min), negatively impacted acid production. The likely causes of this observation are attributed to the production of recalcitrant complexes and toxic compounds. Batch fermentation of untreated sludge yielded 0.34 g total acids/g VS fed, whereas sludge with 240-min lime pretreatment yielded only 0.20 g total acids/g VS fed. Co-fermentation of untreated sludge with pretreated bagasse gave a yield of 0.23 g total acids/g VS fed.

Effects of thermo-chemical pre-treatment on anaerobic biodegradability and hydrolysis of lignocellulosic biomass

The effects of different thermo-chemical pre-treatment methods were determined on the biodegradability and hydrolysis rate of lignocellulosic biomass. Three plant species, hay, straw and bracken were thermo-chemically pre-treated with calcium hydroxide, ammonium carbonate and maleic acid. After pre-treatment, the plant material was anaerobically digested in batch bottles under mesophilic conditions for 40 days. From the pre-treatment and subsequent anaerobic digestion experiments, it was concluded that when the lignin content of the plant material is high, thermo-chemical pre-treatments have a positive effect on the biodegradability of the substrate. Calcium hydroxide pre-treatment improves the biodegradability of lignocellulosic biomass, especially for high lignin content substrates, like bracken. Maleic acid generates the highest percentage of dissolved COD during pre-treatment. Ammonium pre-treatment only showed a clear effect on biodegradability for straw.

Effects of thermochemical pretreatment on the anaerobic digestion of waste activated sludge

Effects of pretreatment on the anaerobic digestion of waste activated sludge (WAS) were investigated in terms of VSS solubilization and methane production by batch experiments. The methods of pretreatment studied are NaOH addition (chemical), heating (thermal) and heating with NaOH addition (thermochemical) to the domestic WAS and to the combined WAS from domestic, commercial and industrial wastewaters. The thermochemical pretreatment gave the best result among three methods in the combined WAS, i.e., the VSS was solubilized by 40-50% and the methane production increased by more than 200% over the control when the WAS was heated at 130°C for 5 minutes with the dose 0.3 g NaOH/g VSS. In the domestic WAS, the VSS solubilization rate was 70-80% but the increase of the methane production was about 30% after thermochemically pretreated. The domestic WAS consists of 41% protein, 25% lipid and 14% carbohydrate on COD basis, and the solubilization rate of protein, which is the largest constituent of the WAS, was 63% in the thermochemical pretreatment. Although the effect of the thermochemical pretreatment on the methane production was higher to the combined WAS than to the domestic WAS, the methane production rate was 21.9 ml CH4/g VSSWAS·day in the domestic WAS and 12.8 ml CH4/g VSSWAS·day in the combined WAS.

Effects of thermochemical pretreatment on the anaerobic digestion of waste activated sludge

Effects of pretreatment on the anaerobic digestion of waste activated sludge (WAS) were investigated in terms of VSS solubilization and methane production by batch experiments. The methods of pretreatment studied are NaOH addition (chemical), heating (thermal) and heating with NaOH addition (thermochemical) to the domestic WAS and to the combined WAS from domestic, commercial and industrial wastewaters. The thermochenucal pretreatment gave the best result among three methods in the combined WAS, i.e., the VSS was solubilized by 40–50% and the methane production incresed by more than 200% over the control when the WAS was heated at 130°C for 5 minutes with the dose 0.3 g NaOH/g VSS. In the domestic WAS, the VSS solubilization rate was 70–80% but the increase of the methane production was about 30% after thermochemically pretreated. The domestic WAS consists of 41% protein, 25% lipid and 14% carbohydrate on COD basis, and the solubilization rate of protein, which is the largest constituent of the WAS, was 63% in the thermochemical pretreatment. Although the effect of the thermochemical pretreatment on the methane production was higher to the combined WAS than to the domestic WAS, the methane production rate was 21.9 ml CH4/g VSSwas·day in the domestic WAS and 12.8 ml CH4/g VSSwas·day in the combined WAS.