A multifunctional cellulose- and starch-based composite hydrogel with iron-modified biochar particles for enhancing microalgae growth.

A multifunctional polysaccharide-based hydrogel was studied as an additive for enhancing microalgae growth. The hydrogel was fabricated by physically and chemically crosslinking renewable ingredients of carboxymethyl cellulose (CMC), arrowroot starch, and activated biochar modified with iron using a bio-crosslinker of oxidized sucrose and a plasticizer of glycerol. The optimum formula for the hydrogel with a high swelling ratio, BET surface area, and electrical conductivity was found to include 1 g starch, 3 g CMC, 1.5 g biochar, 15 mL oxidized sucrose, and 1.5 mL glycerol in 200 mL deionized water. The algal yield and cell concentration after 14 days of growth in a Bold basal medium with an optimum concentration of 2.5 g hydrogel/L increased by 65.7 % and 92.2 %, respectively, compared to those of the control without the hydrogel. However, if the hydrogel concentration in the culture increased to 12.5 g/L, the algal yield was decreased by 67.8 % compared to the control due to oxidative injury. The hydrogel additive could significantly increase the nitrogen but decrease the carbon, hydrogen, and sulfur contents of the microalgae. The algal yield with 2.5 g/L hydrogel additive improved by 13.9 % compared to the algal yield with the same amounts of individual non-crosslinked hydrogel ingredients.

Meso-Microporous Carbon Nanofibrous Aerogel Electrode Material with Fluorine-Treated Wood Biochar for High-Performance Supercapacitor.

A supercapacitor is an electrical energy storage system with high power output. With worldwide awareness of sustainable development, developing cost-effective, environmentally friendly, and high-performance supercapacitors is an important research direction. The use of sustainable components like wood biochar in the electrode materials for supercapacitor uses holds great promise for sustainable supercapacitor development. In this study, we demonstrated a facile and powerful approach to prepare meso-microporous carbon electrode materials for sustainable and high-performance supercapacitor development by electrospinning polyacrylonitrile (PAN) with F-treated biochar and subsequent aerogel construction followed by stabilization, carbonization, and carbon activation. The resultant carbon nanofibrous aerogel electrode material (ENFA-FBa) exhibited exceptional specific capacitance, attributing to enormously increased micropore and mesopore volumes, much more activated sites to charge storage, and significantly greater electrochemical interaction with electrolyte. This electrode material achieved a specific capacitance of 407 F/g at current density of 0.5 A/g in 1 M H2SO4 electrolyte, which outperformed the state-of-the-art specific capacitance of biochar-containing electrospun carbon nanofibrous aerogel electrode materials (<300 F/g). A symmetric two-electrode cell with ENFA-FBa as electrode material showed an energy density of 11.2 Wh/kg at 125 W/kg power density. Even after 10,000 cycles of charging-discharging at current density of 10 A/g, the device maintained a consistent coulombic efficiency of 53.5% and an outstanding capacitance retention of 91%. Our research pointed out a promising direction to develop sustainable electrode materials for future high-performance supercapacitors.

Hemp biochar impacts on selected biological soil health indicators across different soil types and moisture cycles.

Application of crop residues and biochar have been demonstrated to improve soil biological and chemical properties in agroecosystems. However, the integrated effect of organic amendments and hydrological cycles on soil health indicators are not well understood. In this study, we quantified the impact of hemp residue (HR), hemp biochar (HB), and hardwood biochar (HA) on five hydrolytic enzymes, soil microbial phospholipid (PLFA) community structure, pH, permanganate oxidizable carbon (POXC) soil organic carbon (SOC), and total nitrogen (TN). We compared two soil types, Piedmont and Coastal Plain soils of North Carolina, under (i) a 30-d moisture cycle maintained at 60% water-filled pore space (WFPS) (D-W1), followed by (ii) a 7-day alternate dry-wet cycle for 42 days (D-W2), or (iii) maintained at 60% WFPS for 42 days (D-W3) during an aerobic laboratory incubation. Results showed that HR and HB significantly increased the geometric mean enzyme activity by 1-2-fold in the Piedmont soil under the three moisture cycles and about 1.5-fold under D-W in the Coastal soil. In the presence of HA, the measured soil enzyme activities were significantly lower than control under the moisture cycles in both soil types. The shift in microbial community structure was distinct in the Coastal soil but not in the Piedmont soil. Under D-W2, HR and HB significantly increased POXC (600-700 mg POXC kg-1 soil) in the Coastal soil but not in the Piedmont soil while HA increased nitrate (8 mg kg-1) retention in the Coastal soil. The differences in amendment effect on pH SOC, TN, POXC, and nitrate were less distinct in the fine-textured Piedmont soil than the coarse-textured Coastal soil. Overall, the results indicate that, unlike HA, HR and HB will have beneficial effects on soil health and productivity, therefore potentially improving soil's resilience to changing climate.

Production and modification of hydrochar from anaerobically digested cattail for adsorbing ammonium and phosphorous in wastewater.

Water contamination by nitrogen and phosphorus ions has a direct consequence of eutrophication to the ecosystem. The objective of this study is to investigate the production of hydrochars by acetic acid or sodium hydroxide assisted hydrothermal carbonization (HTC), various activation methods, and the potential of hydrochar as an adsorbent to remove NH4+-N and PO43--P from wastewater. The results showed that acetic acid or sodium hydroxide assisted HTC and activation with magnesium chloride or air could improve the surface properties of hydrochar. Acetic acid modification generated extensive oxygenated functional groups, while sodium hydroxide modification produced hydrochar with a high N/C ratio and surface aromaticity. Treating hydrochar with magnesium chloride could impregnate nano-magnesium particles on the hydrochar, thereby improving the ability to remove N and P. Air activation of hydrochar resulted in more oxygen containing functional groups. The NH4+-N and PO43--P adsorption capacities of these hydrochars ranged from 92.6 to 122.4mg/g and 1.6 to 15.8mg/g, respectively. The adsorption capacity of hydrochars in swine wastewater is similar to the results of artificial wastewater. The results suggested that Mg-nanoparticle dispersion and oxygen-containing functional groups played a major role in adsorption than ion exchange and physisorption.

Thermophilic anaerobic digestion of cattail and hydrothermal carbonization of the digestate for co-production of biomethane and hydrochar.

Thermophilic anaerobic digestion (AD) of cattail followed by hydrothermal carbonization (HTC) was studied. The intent of the research was to develop agricultural waste-based biorefining technologies for bioenergy production along with value-added products. Cattail was anaerobically digested at 55 °C for 14 days and protein and cellulose components were partially degraded. The average methane yield was 230-280 mL/g volatile solids and the total solids decreased by 33-55%. When the particle size of cattail was reduced from 1 in. to 1 mm, the lag phase was shortened from 1.48 to 0 d. Following the AD process of cattail, the AD digestate was hydrothermally carbonized at 250 °C for 4 h, yielding approximately 6.7-7.5 wt % gaseous products, 64 wt % liquid products and 28 wt % hydrochar. The gaseous products contained >5000 ppm H2S and liquid products possessed fewer chemicals and higher ratio of phenolic compounds compared to the liquid products from HTC of original cattail. The hydrochar had a higher carbon content (76.8-79.8%) and a higher specific surface area (∼10 m2/g) than those of the feedstock. Hydrochar was further activated by using Na2CO3, NaHCO3 and NaCl. The activation process increased the carbon content and specific surface area to 84-93% and 250-630 m2/g, respectively.

Two-stage thermophilic anaerobic co-digestion of corn stover and cattle manure to enhance biomethane production.

Two-stage thermophilic anaerobic co-digestion of cattle manure and corn stover was conducted to increase biomethane production. The first stage pre-digestion of corn stover was studied based on the following treatment variables: corn stover to liquid fraction of digestate (CS:LFD) ratio (1:7, 1:10, 1:13, 1:14), digestion temperature (55 °C, 60 °C) and digestion time (3, 7, 14 days). The reduction in lignin, cellulose and hemicellulose (LCH) was between 3.97% and 11.98%, which increased the biodegradability of corn stover. Corn stover pre-digested with a CS:LFD ratio of 1:10 at 55 °C for a period of 3 and 7 days was subjected to anaerobic co-digestion with cattle manure. The highest biomethane yield was observed on day 21 with a value of 357.41 mL/g volatile solids (VS) for untreated corn stover, 446.84 mL/g VS for corn stover pre-digested for 3 days and 518.58 mL/g VS for corn stover pre-digested for 7 days with LFD. The VS conversion efficiency for co-digestion of cattle manure with untreated corn stover, corn stover pre-digested for 3 days and 7 days was 42.8%, 43.3% and 51.8%, respectively, on day 21, which was higher than that (34.0%) of cattle manure only.

Aerobic treatment of swine manure to enhance anaerobic digestion and microalgal cultivation.

Aerobic treatment of swine manure was coupled with anaerobic digestion and microalgal cultivation. A 14-day aerobic treatment reduced the total solid content of swine manure by >15%. Ammonia and carbon dioxide were stripped by the air supplied, and this off-gas was further used to aerate the culture of Chlorella vulgaris. The microalgal growth rates in Bristol medium and the wastewater with the off-gas increased from 0.08 to 0.22 g/L/d and from 0.15 to 0.24 g/L/d, respectively. Meanwhile, the aerobically treated swine manure showed a higher methane yield during anaerobic digestion. The experimental results were used to establish a demonstration unit consisting of a 100 L composter, a 200 L anaerobic digester, a 60 L tubular photobioreactor, and a 300 L micro-open raceway pond.

Thermogravimetric and calorimetric characteristics during co-pyrolysis of municipal solid waste components.

The thermogravimetric and calorimetric characteristics during pyrolysis of wood, paper, textile and polyethylene terephthalate (PET) plastic in municipal solid wastes (MSW), and co-pyrolysis of biomass-derived and plastic components with and without torrefaction were investigated. The active pyrolysis of the PET plastic occurred at a much higher temperature range between 360°C and 480°C than 220-380°C for the biomass derived components. The plastic pyrolyzed at a heating rate of 10°C/min had the highest maximum weight loss rate of 18.5wt%/min occurred at 420°C, followed by 10.8wt%/min at 340°C for both paper and textile, and 9.9wt%/min at 360°C for wood. At the end of the active pyrolysis stage, the final mass of paper, wood, textile and PET was 28.77%, 26.78%, 21.62% and 18.31%, respectively. During pyrolysis of individual MSW components at 500°C, the wood required the least amount of heat at 665.2J/g, compared to 2483.2J/g for textile, 2059.4J/g for paper and 2256.1J/g for PET plastic. The PET plastic had much higher activation energy of 181.86kJ/mol, compared to 41.47kJ/mol for wood, 50.01kJ/mol for paper and 36.65kJ/mol for textile during pyrolysis at a heating rate of 10°C/min. H2O and H2 peaks were observed on the MS curves for the pyrolysis of three biomass-derived materials but there was no obvious H2O and H2 peaks on the MS curves of PET plastic. There was a significant interaction between biomass and PET plastic during co-pyrolysis if the biomass fraction was dominant. The amount of heat required for the co-pyrolysis of the biomass and plastic mixture increased with the increase of plastic mass fraction in the mixture. Torrefaction at a proper temperature and time could improve the grindability of PET plastic. The increase of torrefaction temperature and time did not affect the temperature where the maximum pyrolytic rates occurred for both biomass and plastic but decreased the maximum pyrolysis rate of biomass and increased the maximum pyrolysis rate of PET plastic. The amount of heat for the pyrolysis of biomass and PET mixture co-torrefied at 280°C for 30min was 4365J/g at 500°C, compared to 1138J/g for the pyrolysis of raw 50% wood and 50% PET mixture at the same condition.

Uses of miscanthus press juice within a green biorefinery platform.

This study assesses some uses of nutrient-rich juice mechanically extracted from freshly harvested Miscanthus x giganteus (MxG) as part of a green biorefinery system. The juice was used for culturing Saccharomyces cerevisiae and lactic acid bacteria. MxG juice was further used as substrate for fermentation to produce lactic acid using Lactobacillus brevis and Lactobacillus plantarum. The results show that MxG juice was a highly nutritious source for the cultivation of bacteria. Higher concentrations of MxG juice used as culture media, resulted in higher cell growth both aerobically and anaerobically. The highest ethanol yield of 70% theoretical and concentration of 0.75g/100ml were obtained from S. cerevisiae cultivated with 90% (v/v) MxG juice media and used for miscanthus solid fraction fermentation. 11.91g/L of lactic acid was also successfully produced from MxG juice through SSF.

Effects of fertilizer application and dry/wet processing of Miscanthus x giganteus on bioethanol production.

The effects of wet and dry processing of miscanthus on bioethanol production using simultaneous saccharification and fermentation (SSF) process were investigated, with wet samples showing higher ethanol yields than dry samples. Miscanthus grown with no fertilizer, with fertilizer and with swine manure were sampled for analysis. Wet-fractionation was used to separate miscanthus into solid and liquid fractions. Dilute sulfuric acid pretreatment was employed and the SSF process was performed with saccharomyces cerevisiae and a cocktail of enzymes at 35°C. After pretreatment, cellulose compositions of biomass of the wet samples increased from 61.0-67.0% to 77.0-87.0%, which were higher than the compositions of dry samples. The highest theoretical ethanol yield of 88.0% was realized for wet processed pretreated miscanthus, grown with swine manure. Changes to the morphology and chemical composition of the biomass samples after pretreatment, such as crystallinity reduction, were observed using SEM and FTIR. These changes improved ethanol production.

Green biorefinery of fresh cattail for microalgal culture and ethanol production.

Green biorefinery represents an appropriate approach to utilize the fresh aquatic biomass, eliminating the drying process of conventional bioenergy-converting system. In this study, fresh cattails were homogenized and then filtered, whereby cattails were separated into a fiber-rich cake and a nutrient-rich juice. The juice was used to cultivate microalgae Chlorella spp. in different media. In addition, the solid cake was pretreated with the sonication, and used as the feedstock for ethanol production. The results showed that the cattail juice could be a highly nutritious source for microalgae that are a promising feedstock for biofuels. Sugars released from the cattail cake were efficiently fermented to ethanol using Escherichia coli KO11, with 8.6-12.3% of the theoretical yield. The ultrasonic pretreatment was not sufficient for pretreating cattails. If a dilute acid pretreatment was applied, the conversion ratio of sugars from cattails has the potential to be over 85% of the theoretical value.

Optimization of cultural conditions for conversion of glycerol to ethanol by Enterobacter aerogenes S012.

The aim of this research is to optimize the cultural conditions for the conversion of glycerol to ethanol by Enterobacter aerogenes S012. Taguchi method was used to screen the cultural conditions based on their signal to noise ratio (SN). Temperature (°C), agitation speed (rpm) and time (h) were found to have the highest influence on both glycerol utilization and ethanol production by the organism while pH had the lowest. Full factorial design, statistical analysis, and regression model equation were used to optimize the selected cultural parameters for maximum ethanol production. The result showed that fermentation at 38°C and 200 rpm for 48 h would be ideal for the bacteria to produce maximum amount of ethanol from glycerol. At these optimum conditions, ethanol production, yield and productivity were 25.4 g/l, 0.53 g/l/h, and 1.12 mol/mol-glycerol, repectively. Ethanol production increased to 26.5 g/l while yield and productivity decreased to 1.04 mol/mol-glycerol and 0.37 g/l/h, respectively, after 72 h. Analysis of the fermentation products was performed using HPLC, while anaerobic condition was created by purging the fermentation vessel with nitrogen gas.

Co-liquefaction of swine manure and crude glycerol to bio-oil: model compound studies and reaction pathways.

The reaction pathways of co-liquefaction of swine manure and crude glycerol to bio-oil (ester compounds) were investigated. Swine manure was hydrothermal treated (340 °C, 27.5 MPa, 15 min) with a number of model compounds in a high pressure batch reactor under inert atmosphere. The compounds were methanol, pure glycerol, mixture of pure glycerol, pure methanol and H(2)O, and commercial fatty acids (linoleic acid). The chemical composition of the bio-oil was analyzed by GC/MS. Glycerol, methanol and water showed synergistic effects on manure liquefaction, increasing the oil yield as high as 65%. A maximum oil yield of 79.96% was obtained when linoleic acid reacted with swine manure. Based on the results, the reaction pathways were proposed. Esterification reactions occurred not only because the crude glycerol have methanol, but also because methanol can be produced from hydrothermal reactions of glycerol.

Dilute-sulfuric acid pretreatment of cattails for cellulose conversion.

The use of aquatic plant cattails to produce biofuel will add value to land and reduce emissions of greenhouse gases by replacing petroleum products. Dilute-sulfuric acid pretreatment of cattails was studied using a Dionex accelerated solvent extractor (ASE) varying acid concentration (0.1-1%), treatment temperature (140-180 °C), and residence time (5-10 min). The highest total glucose yield for both the pretreatment and enzyme hydrolysis stages (97.1% of the cellulose) was reached at a temperature of 180 °C, a sulfuric acid concentration of 0.5%, and a time of 5 min. Cattails pretreated with 0.5% sulfuric acid are digestible with similar results at enzyme loadings above 15 FPU/g glucan. Glucose from cattails cellulose can be efficiently fermented to ethanol with an approximately 90% of the theoretical yield. The results in this study indicate that cattails are a promising source of feedstock for advanced renewable fuel production.

Swine manure/crude glycerol co-liquefaction: physical properties and chemical analysis of bio-oil product.

The aim of this work was to investigate the principal structural and physico-chemical changes of bio-oils associated with liquefaction of swine manure with crude glycerol and its key fraction, free fatty acids. Bio-oils have been obtained from liquefaction processes at 340 °C. They were subjected to various physico-chemical characterization methods. FTIR data indicated a reduction in aliphatic structures and an increase in more oxidized and, probably, more polycondensed aromatic components resulting from the addition of crude glycerol to swine manure. GC-MS data indicated that the addition of crude glycerol facilitated the esterification reaction in sub-critical water to convert organic acids contained in bio-oil into various kinds of esters. The dynamic viscosity of bio-oil decreased dramatically by adding crude glycerol into the swine manure.

Hot-water pretreatment of cattails for extraction of cellulose.

To date in the US, production of renewable fuels, particularly ethanol, is primarily from food crops that are high in sugar and starch. The use of arable land for fuel rather than food production and the use of a food source for fuel rather than food have created issues in pricing and availability of traditional foods and feed. The use of cattails to produce biofuel will add value to land and also reduce emissions of greenhouse gases by replacing petroleum products. In order to investigate the feasibility of converting cattails into cellulosic ethanol, a hot-water pretreatment process was studied using a Dionex accelerated solvent extractor (ASE) varying treatment temperature and time. The pretreatment at 190°C for more than 10 min could effectively dissolve the xylan fraction of cattails as soluble oligomers. Both the glucose yield and xylose yield obtained from the pretreated cattails increased with the escalation of the final pretreatment temperature, treatment time or enzyme loading. When cattails were pretreated at 190°C for 15 min, the highest glucose yield of 77.6% from the cellulose was achieved in 48 h using a cellulase loading of 60 FPU/g glucan. The yeast Saccharomyces cerevisiae (ATCC 24858) was able to ferment glucose released by cattail cellulose, resulting in approximately 88.7 ± 2.8% of the theoretical ethanol yield. The higher enzyme loading of 60 FPU/g glucan will significantly increase costs. It is recommended that further studies be carried out using cattails as a feedstock for bio-fuels, especially to optimize the economics of biological conversion processes for cattails with regard to reducing enzyme usage, energy input, glucose yield and xylose yield.

Enhancement of alpha- and beta-galactosidase activity in Lactobacillus reuteri by different metal ions.

The hydrolysis of oligosaccharides and lactose is of great importance to the food industry. Normally, oligosaccharides like raffinose, stachyose, and verbascose which are rich in different plants like soy bean are considered indigestible by the human gut. Moreover, many humans suffer from lactose intolerance due to the absence of effective enzyme that can digest lactose. alpha-Galactosidase can digest oligosaccharides like raffinose, while beta-galactosidases can hydrolyze lactose. Therefore, selection of microorganisms safe for human use and capable of producing high levels of enzymes becomes an attractive task. The objective of this study was to investigate the enhancement of alpha- and beta-galactosidase activity in Lactobacillus reuteri by different metal ions. Ten millimolar of Na(+), K(+), Fe(2+), and Mg(2+) and 1 mM of Mn(2+) were added separately to the growth culture of six strains of L. reuteri (CF2-7F, DSM20016, MF14-C, MM2-3, MM7, and SD2112). Results showed that L. reuteri CF2-7F had the highest alpha- and beta-galactosidase activity when grown in the medium with added Mn(2+) ions (22.7 and 19.3 Gal U/ml, respectively). 0.0274% of Mn(2+) ions lead to 27, 18% enhancement of alpha- and beta-galactosidase activity over the control group, and therefore, it could be added to the growth culture of CF2-7F to produce enhanced levels of alpha- and beta-galactosidase activity. The addition of Fe(2+) led to a significant (P < 0.01) decrease in the activity of both enzymes for most strains. This study shows that modified culture medium with that 0.0274% Mn(2+) can be used to promote the production for alpha- and beta-galactosidase in L. reuteri CF2-7F, which may lead to enhancement of alpha- and beta-galactosidase activity and have a good potential to be used in the food industry.

Separate and concentrate lactic acid using combination of nanofiltration and reverse osmosis membranes.

The processes of lactic acid production include two key stages, which are (a) fermentation and (b) product recovery. In this study, free cell of Bifidobacterium longum was used to produce lactic acid from cheese whey. The produced lactic acid was then separated and purified from the fermentation broth using combination of nanofiltration and reverse osmosis membranes. Nanofiltration membrane with a molecular weight cutoff of 100-400 Da was used to separate lactic acid from lactose and cells in the cheese whey fermentation broth in the first step. The obtained permeate from the above nanofiltration is mainly composed of lactic acid and water, which was then concentrated with a reverse osmosis membrane in the second step. Among the tested nanofiltration membranes, HL membrane from GE Osmonics has the highest lactose retention (97 +/- 1%). In the reverse osmosis process, the ADF membrane could retain 100% of lactic acid to obtain permeate with water only. The effect of membrane and pressure on permeate flux and retention of lactose/lactic acid was also reported in this paper.

Succinic acid production from cheese whey using Actinobacillus succinogenes 130 Z.

Actinobacillus succinogenes 130 Z was used to produce succinic acid from cheese whey in this study. At the presence of external CO(2) supply, the effects of initial cheese whey concentration, pH, and inoculum size on the succinic acid production were studied. The by-product formation during the fermentation process was also analyzed. The highest succinic acid yield of 0.57 was obtained at initial cheese whey concentration of 50 g/L, while the highest succinic acid productivity of 0.58 g h(-1) L(-1) was obtained at initial cheese whey concentration of 100 g/L. Increase in pH and inoculum size caused higher succinic acid yield and productivity. At the preferred fermentation condition of pH 6.8, inoculum size of 5% and initial cheese whey concentration of 50 g/L, succinic acid yield of 0.57, and productivity of 0.44 g h(-1) L(-1) were obtained. Acetic acid and formic acid were the main by-products throughout the fermentation run of 48 h. It is feasible to produce succinic acid using lactose from cheese whey as carbon resource by A. succinogenes 130 Z.

Semicontinuous production of lactic acid from cheese whey using integrated membrane reactor.

Semicontinuous production of lactic acid from cheese whey using free cells of Bifidobacterium longum with and without nanofiltration was studied. For the semicontinuous fermentation without membrane separation, the lactic acid productivity of the second and third runs is much lower than the first run. The semicontinuous fermentation with nanoseparation was run semicontinuously for 72 h with lactic acid to be harvested every 24 h using a nanofiltration membrane unit. The cells and unutilized lactose were kept in the reactor and mixed with newly added cheese whey in the subsequent runs. Slight increase in the lactic acid productivity was observed in the second and third runs during the semicontinuous fermentation with nanofiltration. It can be concluded that nanoseparation could improve the lactic acid productivity of the semicontinuous fermentation process.