Ammonia Pretreatment Research Articles

Aqueous Ammonia Pre-treatment of Wheat Straw: Process Optimization and Broad Spectrum Dye Adsorption on Nitrogen-Containing Lignin.

Biorefineries need cost-efficient pretreatment processes that overcome the recalcitrance of plant biomass, while providing feasible valorization routes for lignin. Here we assessed aqueous ammonia for the separation of lignin from hydrothermally pretreated wheat straw prior to enzymatic saccharification. A combined severity parameter was used to determine the effects of ammonia concentration, treatment time and temperature on compositional and physicochemical changes [utilizing elemental analysis, cationic dye adsorption, FTIR spectroscopy, size-exclusion chromatography (SEC), and 31P nuclear magnetic resonance (NMR) spectroscopy] as well as enzymatic hydrolysability of straw. Pretreatment at the highest severity (20% NH3, 160°C) led to the maximum hydrolysability of 71% in a 24 h reaction time at an enzyme dosage of 15 FPU/g of pretreated straw. In contrast, hydrolysabilities remained low regardless of the severity when a low cellulase dosage was used, indicating competitive adsorption of cellulases on nitrogen-containing lignin. In turn, our results showed efficient adsorption of cationic, anionic and uncharged organic dyes on nitrogen-containing lignin, which opens new opportunities in practical water remediation applications.

Effects of urea ammonia pretreatment on the batch anaerobic fermentation efficiency of corn stovers.

In order to enhance the biogas production and provide nitrogen sources for the growth of microorganisms, experiments on urea ammonia pretreatment of corn stovers were implemented at (35±1)°C to investigate the effects of urea ammonia pretreatment on the batch anaerobic fermentation efficiency of corn stovers. This study assessed the effects of urea ammonia contents (2%, 4%, and 6%) and moisture contents (30%, 50%, 70% and 90%) on the physical structures of lignocelluloses and the efficiency of biogas production from anaerobic fermentation of corn stovers. The results indicated that the methane production reached 230.31 mL/g VS (volatile solids) at pretreatment with 4% urea ammonia and 70% moisture contents for the batch anaerobic fermentation, which was 26.6% higher than that of the untreated group. The degradation rates of cellulose and hemicellulose were 66.34% and 75.47% after the anaerobic fermentation, respectively, which were about 22.6% and 20.9% higher than that of the untreated group, respectively. Thus, it was concluded that urea ammonia pretreatment can improve the efficiency of biogas production from anaerobic fermentation of corn stovers. Keywords: corn stovers, urea ammonia pretreatment, batch anaerobic fermentation, methane production, degradation DOI: 10.25165/j.ijabe.20191204.4835 Citation: Li Q, Yang F L, Zheng G X, Guan Z J. Effects of urea ammonia pretreatment on the batch anaerobic fermentation efficiency of corn stovers. Int J Agric & Biol Eng, 2019; 12(4): 169–173.

Improving physicochemical characteristics and anaerobic digestion performance of rice straw via ammonia pretreatment at varying concentrations and moisture levels

Abstract Rice straw physicochemical characteristics and anaerobic digestion (AD) performance via ammonia pretreatment at varying ammonia concentrations (2%, 4%, and 6%) and moisture contents (30%, 50%, 70%, and 90%) under a mild condition were investigated. The results showed that the ammonia pretreatment effectively damaged the rice straw structure, increased the soluble organic concentration, and improved rice straw hydrolysis and AD performance. After pretreatment, the ester bond and ether bond were ruptured in lignocellulose and the volatile fatty acids (VFAs) were within the range of 1457.81–1823.67 mg·L−1. In addition, ammonia pretreatment had high selectivity on lignin removal, resulting in a maximum lignin removal rate of 50.80%. The highest methane yield of rice straw was 250.34 ml·(g VS)−1 at a 4% ammonia concentration coupled with a 70% moisture content, which was 28.55% higher than that of the control. The result showed that ammonia pretreatment of rice straw is technically suitable to enhance AD performance for further application.

Free ammonia pretreatment improves anaerobic methane generation from algae

Anaerobic methane generation from algae is hindered by the slow and poor algae biodegradability. A novel free ammonia (NH3 i.e. FA) pretreatment technology was proposed in this work to enhance anaerobic methane generation from algae cultivated using a real secondary effluent. The algae solubilisation was 0.05-0.06 g SCOD/g TCOD (SCOD: soluble chemical oxygen demand; TCOD: total chemical oxygen demand) following FA pretreatment of 240-530 mg NH3-N/L for 24 h, whereas the solubilisation was only 0.01 g SCOD/g TCOD for the untreated algae. This indicates that FA pretreatment at 240-530 mg NH3-N/L could substantially enhance algae solubilisation. Biochemical methane potential tests revealed that FA pretreatment on algae at 240-530 mg NH3-N/L is able to significantly enhance anaerobic methane generation. The hydrolysis rate (k) and biochemical methane potential (P0) of algae increased from 0.21 d-1 and 132 L CH4/kg TCOD to 0.33-0.50 d-1 and 140-154 L CH4/kg TCOD, respectively, after the algae was pretreated by FA at 240-530 mg NH3-N/L. Further analysis indicated that FA pretreatment improved k of both quickly and slowly biodegradable substrates, and also increased P0 of the slowly biodegradable substrate although it negatively affected P0 of the quickly biodegradable substrate. This FA technology is a closed-loop technology.

Hydrodynamic Analysis of Hydrolysis of the Rice Husk Cellulose by Using CFD Modeling

The importance of the rule and the demand of glucose trigger the seeking of the alternative materials to produce glucose. One of the alternatives used is the utilization of biomass such as the rice husk to produce glucose. Rice husk is the agricultural residue whose availability is very abundant. In this research, rice husk contained cellulose (42.2 %), hemicellulose (17.04 %), and lignin (20.46 %). First step to produce the glucose from rice husk was pretreatment stages (Soaking in Aqueous Ammonia pretreatment and Acid pretreatment). Furthermore it was followed by the acid hydrolysis step by using dilute H2SO4 solution. The concentration of H2SO4 used in this work was 1, 2, and 3 N with the various hydrolysis times of 30, 60, 90, 120, and 150 min. The result showed that increasing of hydrolysis time slightly increased glucose concentration. The highest glucose concentration was about 21.51% at H2SO4 concentration of 2 N and the hydrolysis time of 150 min. CFD modeling (ANSYS Fluent 16) was performed to investigate the hydrodynamic phenomena during hydrolysis. The hydrodynamic analysis showed that the best mixing occurred at H2SO4 concentration of 2 N for 150 min. It is a good agreement with the experimental finding.

Optimization of soaking in aqueous ammonia pretreatment for anaerobic digestion of African maize bran

In this study, maize bran biomass was subjected to soaking in aqueous ammonia (SAA) pretreatment to reduce and eliminate lignin, a major component that hinders biological digestibility. The effect of SAA pretreatment on the mesophilic anaerobic digestion of maize bran were investigated by using statistical techniques on batch anaerobic test. Response surface methodology by the central-composite design has verified the effects and the interactions of three variables, pretreatment temperature (10–110 °C), pretreatment time (1–11 h) and solid to liquid (S/L) ratio (0.068–0.307) on the responses: methane yield (MY), methane productivity rate (MPR), delignification and sugar recovery were monitored keenly. The optimal regions predicted via overlay plots for the multiple response falls within the following ranges: pretreatment temperatures between 55 and 70 °C, pretreatment time of 5 to 8 h and S/L ratio of 0.14 to 0.185. The optimal conditions were found at 72.5 °C, an S/L ratio of 0.14, and 7.02 h resulting to an MY of 293.8 mL/g COD, and an MPR of 106.0 mL CH4/g VSS-day. The model equations for the multiple responses were within p < 0.05 meaning it is significant and is fitted to the data sets. Validation experiments has confirmed that the pretreatment conditions with optimal responses presented are in close agreement comparing the ones obtained from the experiment and that as estimated by the model.

Production of prebiotic xylooligosaccharide from aqueous ammonia-pretreated rice straw by β-xylosidase of Weissella cibaria.

This study focuses on the development of a new strategy xylooligosaccharide (XOS) production from aqueous ammonia-pretreated rice straw (A-PRS), followed by β-xylosidase hydrolysis produced by the newly identified strain Weissella cibaria FB069. We report a higher efficiency of A-PRS, including the removal of lignin and increase in cellulose and xylan content, compared to that of the alkali and stream explosion methods. Using the ammonia pretreatment method, rice straw was used to obtain 32·4% xylan. The crude xylanase from W. cibaria was used to hydrolyse A-PRS over different hydrolysis times. The highest XOS yield (131mg XOS per gram rice straw) was observed after 10h. XOS produced from the PRS was tested on stimulation effect on Bifidobacterium and Lactobacillus. The possibility of XOS production from PRS using β-xylosidase with strong prebiotic properties. We investigated the new strain for signification production of XOS. The two-stage process here described could help to further explore the optimization conditions for prebiotic production. Additionally, the stimulation effect of XOS from alternative source has a promising prospect in functional food.

Quantifying reductions in soaking in aqueous ammonia pretreatment severity and enzymatic hydrolysis conditions for corn stover pellets

The benefits of using pelleted corn stover compared to loose corn stover with low severity soaking in aqueous ammonia pretreatment and reduced enzyme loadings were studied. Loose and pelleted corn stover were treated with the same set of pretreatment and hydrolysis conditions. A range of low to high severity pretreatment conditions and enzyme loadings were tested to determine conditions to achieve 90% glucose yields. Glucose yields from pelleted biomass reached 90% with reduced pretreatment severities, enzyme loadings, hydrolysis time, or various combinations of these. At the highest enzyme loadings, use of pelleted corn stover enabled reductions in hydrolysis time up to 58%. It also allowed 80% reduction in enzyme loading at higher pretreatment conditions. At moderate pretreatment levels, either enzyme loadings can be reduced by 40% or hydrolysis time by up to 48%. Using pelleted biomass as a biorefinery feedstock allows flexibility in production with different processing options.

Ethanolic ammonia pretreatment for efficient biogas production from sugarcane bagasse

Sugarcane bagasse (SCB), as an abundant lignocellulosic waste, was subjected to ethanolic ammonia pretreatment followed by anaerobic digestion to produce biogas. Ammonia pretreatment was performed with 10% v/v aqueous ammonia solution at 50 and 70 °C for 12 and 24 h. Furthermore, the effect of addition of ethanol to the pretreatment mixture at different concentrations (5, 25, and 50% v/v) was investigated. Two scenarios for biogas production from SCB were considered and compared in terms of equivalent gasoline production per unit mass of biomass: (1) biogas production from the pretreatment separated solid and liquid fractions, and (2) biogas production from the whole pretreatment slurry. The highest methane yield of 298.0, 248.6, and 299.3 ml/g VS (volatile solids) were attained from the liquid fraction, solid fraction, and the whole slurry of pretreatment at 70 °C, respectively. Whereas, methane yield from untreated SCB was only 105.6 ml/g VS. Generally, the methane production yield by pretreatments at 70 °C was more than those at 50 °C. The maximum equivalent gasoline from each ton of SCB for scenarios 1 and 2 were 172 and 182 L, respectively, obtained after pretreatment at 70 °C for 12 h with 10% ammonia +50% ethanol, whereas it was 103 L from untreated SCB.

Optimization of dilute sulfuric acid, aqueous ammonia, and steam explosion as the pretreatments steps for distillers’ dried grains with solubles as a potential fermentation feedstock

Distillers’ dried grains with solubles (DDGS) is the by-product of bioethanol production from starch-rich grains through dry-mill fermentation. In this study, dilute sulfuric acid hydrolysis, aqueous ammonia, and steam explosion as the pre-treatment methods were optimized. The central composite response surface methodology (RSM) design was used for optimization of dilute acid pretreatment, aqueous ammonia pretreatment. The steam explosion trials were evaluated. The results show that the dilute acid pretreatment at 121 °C is the most effective way of obtaining simple fermentable sugars (0.382 g/g DDGS). The levels of furfural and HMF was also 5.2 mg/g DDGS) and 1.6 mg/g DDGS, respectively, in the dilute sulfuric acid pretreated DDGS. On the other hand, maximum sugar yield for ammonia pretreatment was 0.129 g/g DDGS and 0.055 g/g DDGS for the steam pretreatment, while no significant amounts of furfural and HMF were observed for these two pretreatment methods.

Closing ammonia loop in efficient biogas production: Recycling ammonia pretreatment of wheat straw

We propose an integrated system for simultaneous ammonia recovery, ammonia pretreatment, biogas upgrading, and fertiliser production in biogas production. Ammonia stripping and absorbing played an important role as they significantly affected the ammonia recovery and biogas upgrading performance. Ammonia stripping with biogas was used to remove ammonia from biogas slurry at various conditions. The ammonia removal efficiency reached 99.30% at 10% CO2 content, 90 °C and 6 h stripping time. Ammonia absorption of ammonia-bearing biogas achieved crystalline ammonium and biogas upgrading. The obtained crystalline ammonium was used for recovering ammonia. The ammonia pretreatment and anaerobic digestion results showed that wheat straw pretreated with 0.70% ammonia concentration and 105 °C obtained the highest biogas yield of 538.1 mL g−1, which was 31.9% higher than untreated wheat straw. The process in this study shows a great potential in biogas production by recycling ammonia for pretreatment of feedstocks and biogas purification associated with producing fertilisers.

Effect of ammonia pretreatment on crystal quality of N-polar GaN grown on SiC by metalorganic chemical vapor deposition

In this study, the effect of NH3 pre-treatment is investigated to obtain high-quality nitrogen-polar GaN grown on a SiC substrate. The GaN/AlN/C-face 4° off-cut SiC structure is successfully grown with pre-treatment temperatures of 1250, 1300, and 1350 °C. The hillock and inversion domain density, surface roughness, and crystal quality of each sample were evaluated. As the temperature increased from 1250 °C to 1350 °C, the overall crystal quality of the N-polar GaN was greatly improved with reduced hillock and inversion domain densities and smoothed surface. The X-ray rocking curve full-width at half maximum of the (00-2) and (10-2) planes were 374 and 420 arcsec, respectively, for the pre-treatment of 1350 °C.

Technologies for Lignocellulose Pretreatment to Produce Fuel Ethanol

Bioethanol is one of the alternatives to fossil fuels. Bioethanol production from lignocellulose has advantages on source richness, but it has poor performance on the conversion yield. In order to destroy the structure of lignocellulose and promote the cellulose and other components release, lignocellulose treatment was necessarily prior to bioethanol fermentation. In this paper, eight methods for lignocellulose pretreatment were reviewed, including physical method, dilute acid pretreatment method, dilute alkali pretreatment method, steam pretreatment method, ammonia pretreatment methods, organic solvent pretreatment method, ionic liquid pretreatment method and biological pretreatment, and those principles and novel progresses were briefly introduced.

Hybrid dilute sulfuric acid and aqueous ammonia pretreatment for improving butanol production from corn stover with reduced wastewater generation

An efficient hybrid pretreatment method was developed for butanol production from corn stover using dilute sulfuric acid (DA) and aqueous ammonia (AA). With the optimized AA concentration, treatment temperature and time of 10% AA, 80 °C and 24 h, the hybrid pretreatment could effectively dissolve hemicellulose and lignin with solid recovery rate of 37.45% and lignin reduction rate of 86.77% compared to those of 57.75% and 45.84% from single DA pretreatment. By washing 1 time after each step treatment, sugar yield and butanol production were increased to 401.76 mg/g-CS and 10.89 g/L from 346.04 mg/g-CS and 9.33 g/L obtained without washing. Compared with conventional single DA and AA pretreatment methods, wastewater generation was reduced to 0.83 L/g-butanol from 2.11 and 3.46 L/g-butanol, indicating this hybrid pretreatment could be an effective approach for improving butanol production from lignocellulosic feedstocks.

The effects of aqueous ammonia-pretreated rice straw as solid substrate on laccase production by solid-state fermentation.

Chemical composition and physical structure of solid substrate have significantly impacts on fermentation performance. The aqueous ammonia was used to pretreat rice straw. Furthermore, the feasibility of pretreatment to improve laccase production was also evaluated in terms of the enzymatic digestibility, chemical structure, physical structure, and laccase production. The results showed that aqueous ammonia pretreatment could modify chemical compositions, destroy rigid structure of the lignocellulosic substrate, increase enzymatic digestibility and change water state, which were beneficial to facilitate the fungus growth and nutrition utilization. Pretreatment of lignocellulosic substrate with aqueous ammonia at 80°C gave the best effect on laccase production, yielding 172.74U/g laccase at 14days, which was 3.4 times higher than that of the control. The aqueous ammonia pretreatment could alternate the physicochemical characteristics of lignocellulosic substrate, resulting in the improved laccase production, which was a promising method that might be explored in solid-state fermentation.

Effects of urea ammonia pretreatment on the batch anaerobic fermentation efficiency of corn stovers

Effects of urea ammonia pretreatment on the batch anaerobic fermentation efficiency of corn stovers

Delignification and hydrolyzation of mycorrhizal black locust biomass pretreated with aqueous ammonia

Arbuscular mycorrhizae (AM) fungi can increase the biomass of host plants that are used as biofuel feedstock. However, little is known about the effects of AM fungi during aqueous ammonia pretreatment of biomass to remove lignin or on the enzymatic hydrolysis of cellulose. The analysis of mycorrhizal colonization (Rhizophagus irregularis or Glomus versiforme) on stems of black locust (Robinia pseudoacacia) plants in their first and second year of growth revealed that the presence of AM fungi and the growth time significantly influenced the lignin and cellulose content of untreated black locust but had no effect on the content of stems pretreated with aqueous ammonia. The presence of AM fungi and/or the growth time also affected the black locust stem structure and the chemical structure of lignin. Hydrolysis of mycorrhizal and non-mycorrhizal biomass produced similar glucose yields (except for the second-year R. irregularis biomass, which produced significantly less glucose than the other treatments). The results suggest that mycorrhizal black locust biomass is a suitable substrate for biofuel production.

Free Ammonia Pretreatment To Improve Bio-hydrogen Production from Anaerobic Dark Fermentation of Microalgae

Microalgae are third generation feedstocks for bio-hydrogen production to achieve a low carbon economy. Nevertheless, the bio-hydrogen production from microalgae is generally low. In this study, an...

Secretome analysis of the basidiomycete Phanerochaete chrysosporium grown on ammonia-treated lignocellulosic biomass from birch wood

Ammonia pretreatment is a promising technique for enhancing enzymatic saccharification of lignocellulosic biomass. However, an enzymatic cocktail suitable for the breakdown of pretreated biomass samples is still being developed. The basidiomycete Phanerochaete chrysosporium is a well-studied fungus with regard to bioconversion of lignocellulosic biomass. In the present work, we analyzed proteins secreted by P. chrysosporium grown on untreated and ammonia-treated birch wood meal. Fungal growth, xylanase activity, and extracellular protease activity increased in the media containing the ammonia-treated biomass; however, cellulase production decreased compared to that observed in the untreated biomass. Secreted extracellular proteins were separated by two-dimensional electrophoresis and identified by liquid chromatography ion–trap mass spectrometry. Fifty-five spots corresponding to secreted proteins were chosen for further analysis. In the culture with ammonia-treated biomass, the relative concentration of a xylanase belonging to glycoside hydrolase (GH) family 11 increased, while acetyl xylan esterases belonging to carbohydrate esterase family 1 decreased. Moreover, GH family 10 xylanases were promoted proteolysis in the culture of ammonia-treated biomass, leading to the loss of family 1 carbohydrate-binding modules. These results indicated that P. chrysosporium produced enzymes related to the recognition of structural changes on xylan with de-acetylation and introduction of nitrogen by ammonia pretreatment of birch wood meal.

Soaking in Aqueous Ammonia (SAA) Pretreatment of Whole Corn Kernels for Cellulosic Ethanol Production from the Fiber Fractions

Corn fiber is a co-product of commercial ethanol dry-grind plants, which is processed into distillers dried grains with solubles (DDGS) and used as animal feed, yet it holds high potential to be used as feedstock for additional ethanol production. Due to the tight structural make-up of corn fiber, a pretreatment step is necessary to make the cellulose and hemicellulose polymers in the solid fibrous matrix more accessible to the hydrolytic enzymes. A pretreatment process was developed in which whole corn kernels were soaked in aqueous solutions of 2.5, 5.0, 7.5, and 10.0 wt% ammonia at 105 °C for 24 h. The pretreated corn then was subjected to a conventional mashing procedure and subsequent ethanol fermentation using a commercial strain of natural Saccharomyces cerevisiae with addition of a commercial cellulase. Pretreatment of the corn with 7.5 wt% ammonia solution plus cellulase addition gave the highest ethanol production, which improved the yield in fermentation using 25 wt% solid from 334 g ethanol/kg corn obtained in the control (no pretreatment and no cellulase addition) to 379 g ethanol/kg corn (a 14% increase). The process developed can potentially be implemented in existing dry-grind ethanol facilities as a “bolt-on” process for additional ethanol production from corn fiber, and this additional ethanol can then qualify as “cellulosic ethanol” by the Environmental Protection Agency’s (EPA’s) Renewable Fuels Standard and thereby receive RINs (Renewable Identification Numbers).