Fractionation of oil palm fronds using ethanol-assisted deep eutectic solvent: Influence of ethanol concentration on enhancing enzymatic saccharification and lignin ß-O-4 content.

Numerous fractionation methods have been developed in recent years for separating components such as cellulose, hemicellulose, and lignin from lignocellulosic biomass wastes. Deep eutectic solvents (DES) have recently been widely investigated as captivating green solvents for biomass fractionation. However, most acidic-based deep eutectic solvent fractionation produces condensed lignin with low ß-O-4 content. Besides, most DESs exhibit high viscosity, which results in poor mass transfer properties. This study aimed to address the challenges above by incorporating ethanol into the deep eutectic solvent at various concentrations (10-50 wt%) to fractionate oil palm fronds at a mild condition, i.e., 80 °C, 1 atm. Cellulose residues fractionated with ethanol-assisted deep eutectic solvent showed a maximum glucose yield of 85.8% when 20 wt% of ethanol was incorporated in the deep eutectic solvent, significantly higher than that achieved by pure DES (44.8%). Lignin extracted with ethanol-assisted deep eutectic solvent is lighter in color and higher in ß-O-4 contents (up to 44 ß-O-4 per 100 aromatic units) than pure DES-extracted lignin. Overall, this study has demonstrated that incorporating ethanol into deep eutectic solvents could enhance the applicability of deep eutectic solvents in the complete valorization of lignocellulosic biomass. Highly enzymatic digestible cellulose-rich solid and ß-O-4-rich lignin attained from the fractionation could serve as sustainable precursors for the production of biofuels.

Recent advances in the application of alcohols in extracting lignin with preserved ß-O-4 content from lignocellulosic biomass.

Utilizing lignocellulosic biomass wastes to produce bioproducts is essential to address the reliance on depleting fossil fuels. However, lignin is often treated as a low-value-added component in lignocellulosic wastes. Valorization of lignin into value-added products is crucial to improve the economic competitiveness of lignocellulosic biorefinery. Monomers obtained from lignin depolymerization could be upgraded into fuel-related products. However, lignins obtained from conventional methods are low in ß-O-4 content and, therefore, unsuitable for monomer production. Recent literature has demonstrated that lignins extracted with alcohol-based solvents exhibit preserved structures with high ß-O-4 content. This review discusses the recent advances in utilizing alcohols to extract ß-O-4-rich lignin, where discussion based on different alcohol groups is considered. Emerging strategies in employing alcohols for ß-O-4-rich lignin extraction, including alcohol-based deep eutectic solvent, flow-through fractionation, and microwave-assisted fractionation, are reviewed. Finally, strategies for recycling or utilizing the spent alcohol solvents are also discussed.

Analysis on the changes of fertilization intensity and efficiency in China's grain production from 1980 to 2019.

BACKGROUND: Relieving serious non-point source pollution of nitrogen (N), phosphorus (P), and potassium (K) is an urgent task in China. It is necessary to explore the changing characteristics of chemical fertilization intensity (FI) and efficiency to provide references. A new method of 'relative productivity proportion weight', which was simpler than data envelope analysis, was proposed to construct models of fertilizer allocation efficiency (FAE) and chemical fertilizer integrated efficiency (FIE) by considering NPK multi-inputs and the grain output scale, respectively. RESULTS: During 1980-2014, the FIs of NPK chemical fertilizers in China showed a significant growing trend. After reaching the highest value of 339 kg ha-1 in 2014, FIs were reduced to 303 kg ha-1 in 2019, higher than the 225 kg ha-1 maximum safe usage internationally recognized. Meanwhile, the pattern of change of FAE was one of 'decreasing to increasing', with values of 1 in 1980, 0.66 in 2003, and 0.80 in 2019. FIE basically showed an increasing trend, which could be divided into three stages: the first stage of low efficiency during 1980-2009, the second stage of medium efficiency after 2010, and the third stage of high efficiency after 2018. CONCLUSION: From 1980 until 2019, a reduction of FAE from 1 to 0.80 with an average of 0.75 was observed in China. FIE was found between 0.65 and 0.85 and had the potential of upgrading by 15-35%. Therefore, China needs to improve the fertilizer use efficiency in order to strive for negative growth of chemical fertilizer intensity and ecological agriculture construction. © 2022 Society of Chemical Industry.

Elucidating the enhanced decomposition of alkyl hydroperoxides on oxygen vacancy rich TiO2-x surfaces using DFT for polyethylene decomposition.

Effective photocatalytic polyethylene degradation by TiO2 is hindered by the sluggish kinetics of alkyl hydroperoxide decomposition. Introduction of oxygen vacancies onto TiO2 destabilizes the hydroperoxide O-O bond due to mid-gap states and the elevated Fermi level. Downshift of the d-band center by oxygen vacancies also enhanced adsorbate-surface interactions and lowered the activation energy barrier from Gibbs calculations. Experimental evidence additionally substantiated enhanced polyethylene degradation on TiO2-x compared to TiO2.

The application of green solvent in a biorefinery using lignocellulosic biomass as a feedstock.

The high dependence on crude oil for energy utilization leads to a necessity of finding alternative sustainable resources. Solvents are often employed in valorizing the biomass into bioproducts and other value-added chemicals during treatment stages. Unfortunately, despite the effectiveness of conventional solvents, hindrances such as expensive solvents, unfavourable environmental ramifications, and complicated downstream separation systems often occur. Therefore, the scientific community has been actively investigating more cost-effective, environmentally friendly alternatives and possess the excellent dissolving capability for biomass processing. Generally, 'green' solvents are attractive due to their low toxicity, economic value, and biodegradability. Nonetheless, green solvents are not without disadvantages due to their complicated product recovery, recyclability, and high operational cost. This review summarizes and evaluates the recent contributions, including potential advantages, challenges, and drawbacks of green solvents, namely ionic liquids, deep eutectic solvents, water, biomass-derived solvents and carbon dioxide in transforming the lignocellulosic biomass into high-value products. Moreover, research opportunities for future developments and potential upscale implementation of green solvents are also critically discussed.

Investigation into Lewis and Brønsted acid interactions between metal chloride and aqueous choline chloride-oxalic acid for enhanced furfural production from lignocellulosic biomass.

Furfural has been identified as a valuable biobased platform chemical that can be further converted into bioenergy and biochemicals. Furfural is derived from lignocellulosic biomass and can also be regarded as a sustainable alternative to petrochemical products. Herein, the performance of trivalent metal chlorides (FeCl3, AlCl3) and tetravalent metal chlorides (SnCl4, TeCl4) as Lewis acidic cocatalysts was investigated in an aqueous choline chloride-oxalic acid (16.4 wt% H2O) deep eutectic solvent (DES) system for producing furfural from oil palm fronds (OPFs). The metal chlorides with greater electrical field gradients were stronger Lewis acids that enhanced both furfural production and degradation reactions. The main degradation product in this reaction system was humin, and this result was confirmed by FTIR analysis. By subjecting OPFs to an aqueous DES reaction (120 °C, 45 min) with SnCl4 (2.50 wt%), a furfural yield of 59.4% was obtained; without incorporated metal chlorides, the furfural yield was 46.1%. Characterization studies showed synergistic Lewis and Brønsted acid interactions between metal chlorides and DES components. Overall, the residual OPFs showed high glucan content, which led to the production of glucose (71.4%) as a byproduct via enzymatic hydrolysis. Additionally, the aqueous DES system was recycled and reused for several additional runs. The proposed aqueous DES system presents a promising biorefinery approach for the conversion of OPFs to biochemicals.

Comparison of fertilizer use efficiency in grain production between developing countries and developed countries.

BACKGROUND: The investigation of chemical fertilization intensity (FI) and efficiency can provide basal data for decision-making in food production and environmental impact assessments of fertilization. The present study aimed to compare trends of the FI and efficiency during 1961-2018 in developed and developing countries using a simple method. RESULTS: The FI in China increased rapidly from approximately 5 kg ha-1 in 1961 to the highest value of 282 kg ha-1 in 2014, and then decreased to approximately 231 kg ha-1 in 2018. Although the fertilizer allocation efficiency (FAE) showed a slight downward trend, a slight upward trend was observed for fertilizer integrated efficiency (FIE). FIs in India, Iran and Turkey continuously increased from 5 kg ha-1 in 1961 to 116, 49(148 in 2006),120 kg ha-1 in 2018, respectively, whereas FAEs showed a significant fluctuation around horizontal direction or downward trends and their FIEs showed a slight fluctuation downward. The FIs of Britain, Germany and France, excluding USA, increased rapidly from approximately 200-400 kg ha-1 in 1960s to peaks of 430-530 kg ha-1 in 1980s, decreasing to 150-340 kg ha-1 around 2010, and then increased to the current level of 200-350 kg ha-1 , whereas FAEs and FIEs increased rapidly. CONCLUSION: France and Germany were found to have moderate chemical fertilizer input and the highest FIE. Thus, their experiences of ecological agricultures in both countries could provide good examples for developing countries to follow. In brief, models of FAE and FIE are an easier way of reflecting fertilizer efficiencies in developed and developing countries. © 2021 Society of Chemical Industry.

Sequential pretreatment with alkaline hydrogen peroxide and choline chloride:copper (II) chloride dihydrate - Synergistic fractionation of oil palm fronds.

In this study, a novel Type II deep eutectic solvent (DES) namely, choline chloride:copper(II) chloride dihydrate (ChCl:CuCl2·2H2O) was used to pretreat oil palm fronds (OPFs). The sequential pretreatment with alkaline hydrogen peroxide (0.25 vol%, 90 min) at ambient conditions and a Type II DES (90 °C, 3 h) at a later stage resulted in a delignification of 55.14% with high xylan (80.79%) and arabinan (98.02%) removals. The characterizations of pretreated OPFs confirmed the excellent performance of DES in OPF fractionation. Thus, the application of a Type II DES at ambient pressure and relatively lower temperature was able to improve the lignin and hemicellulose removals from OPFs.

Sequential ultrasonication and deep eutectic solvent pretreatment to remove lignin and recover xylose from oil palm fronds.

This study demonstrated the effect of two-pot sequential pretreatment, comprising of ultrasound assisted deep eutectic solvent (DES) with the aim to investigate the effects of ultrasound amplitude and duration in enhancing delignification. Oil palm fronds (OPF) were ultrasonicated in a water medium, followed by a pretreatment using DES (choline chloride:urea). Fourier transform infra-red spectroscopy, X-ray diffraction, field emission scanning electron microscope, Brunauer-Emmet-Teller and solubilised lignin concentration were conducted to confirm the effectiveness of ultrasound assisted DES on the pretreatment of OPF. The recommended ultrasound conditions were determined to be 70% amplitude and duration of 30 min, where the sequential DES pretreatment was able to reduce lignin content of OPF to 14.01%, while improving xylose recovery by 58%.

One-pot furfural production using choline chloride-dicarboxylic acid based deep eutectic solvents under mild conditions.

The performances of various anhydrous and aqueous choline chloride-dicarboxylic acid based deep eutectic solvents (DESs) were evaluated for furfural production from oil palm fronds without any additional catalyst. The effects of different carbon chain length dicarboxylic acids and water content in each DES on furfural production were investigated. Oil palm fronds, DES and water (0-5 ml) were mixed and reacted in an oil bath (60-300 min). Reacted oil palm fronds had the potential to be reused as cellulose-rich-valuable by-products. At 100 °C, aqueous choline chloride-oxalic acid (16.4 wt% H2O) produced the highest furfural yield of 26.34% and cellulose composition up to 72.79% in the reacted oil palm fronds. Despite operating at suitable reaction duration for dicarboxylic acid with longer carbon chain length, aqueous choline chloride-malonic acid and aqueous choline chloride-succinic acid performed poorly with furfural yield of less than 1%.

Facile synthesis of CaFe2O4 for visible light driven treatment of polluting palm oil mill effluent: Photokinetic and scavenging study.

In this paper, a facile synthesis method for CaFe2O4 is introduced that produces a catalyst capable of significant photocatalytic degradation of POME under visible light irradiation. The co-precipitation method was used to produce two catalysts at calcination temperatures of 550 °C and 700 °C dubbed CP550 and CP700. CP550 demonstrated the maximum COD removal of 69.0% at 0.75 g/L catalyst loading after 8 h of visible light irradiation which dropped to 61.0% after three consecutive cycles. SEM images indicated that the higher calcination temperature of CP700 led to annealing which reduced the pore volume (0.025 cm3/g) and pore diameter (10.3 nm) while simultaneously creating a smoother and more spherical surface with lower SBET (9.73 m2/g). In comparison, CP550 had a rough hair-like surface with higher SBET (27.28 m2/g) and pore volume (0.077 cm3/g) as evidenced by BET analysis. XRD data indicated the presence of CaFe5O7 in the CP550 composition which was not present in CP700. The presence of Wustite-like FeO structures in CaFe5O7 are likely the cause for lower photoluminescence intensity profile and hence better charge separation of CP550 as these structures in CaFe2O4 have been known to increase resistivity and electron localization. The COD removal of CP550 dropped from 69.0% to just 7.0% upon adding a small quantity of isopropanol into the reaction mixture indicating hydroxyl radicals as the primary reactive oxidative species.

Production of bio-hydrogen from dairy wastewater using pretreated landfill leachate sludge as an inoculum.

Bio-hydrogen production from wastewater using sludge as inoculum is a sustainable approach for energy production. This study investigated the influence of initial pH and temperature on bio-hydrogen production from dairy wastewater using pretreated landfill leachate sludge (LLS) as an inoculum. The maximum yield of 113.2 ± 2.9 mmol H2/g chemical oxygen demand (COD) (12.8 ± 0.3 mmol H2/g carbohydrates) was obtained at initial pH 6 and 37 °C. The main products of volatile fatty acids were acetate and butyrate with the ratio of acetate:butyrate was 0.4. At optimum condition, Gibb's free energy was estimated at -40 kJ/mol, whereas the activation enthalpy and entropy were 65 kJ/mol and 0.128 kJ/mol/l, respectively. These thermodynamic quantities suggest that bio-hydrogen production from dairy wastewater using pretreated LLS as inoculum was effective and efficient. In addition, genomic and bioinformatics analyses were performed in this study.

Evaluating new bio-hydrogen producers: Clostridium perfringens strain JJC, Clostridium bifermentans strain WYM and Clostridium sp. strain Ade.TY.

Three newly discovered H2 producing bacteria namely Clostridium perfringens strain JJC, Clostridium bifermentans strain WYM and Clostridium sp. strain Ade.TY originated from landfill leachate sludge have demonstrated highly efficient H2 production. The maximum H2 production attained from these isolates are in the descending order of strain C. perfringens strain JJC > C. bifermentans strain WYM > Clostridium sp. strain Ade.TY with yield of 4.68 ± 0.12, 3.29 ± 0.11, and 2.87 ± 0.10 mol H2/mol glucose, respectively. The result has broken the conventional theoretical yield of 4 mol H2/mol glucose. These isolates were thermodynamically favourable with Gibbs free energy between -33 and -35 kJ/mol (under process conditions: pH 6, 37 °C and 5 g/L glucose). All three isolates favour butyrate pathway for H2 production with the ratio of acetate and butyrate of 0.77, 0.65 and 0.80 for strain JJC, WYM and Ade.TY, respectively. This study reported provides a new insight on the potential of unique bacteria in H2 production.

Transformation of oil palm fronds into pentose sugars using copper (II) sulfate pentahydrate with the assistance of chemical additive.

Among the chemical pretreatments available for pretreating biomass, the inorganic salt is considered to be a relatively new but simple reagent that offers comparable pentose (C5) sugar recoveries as the conventional dilute acid hydrolysis. This study investigated the effects of different concentrations (1.5-6.0% (v/v)) of H2O2 or Na2S2O8 in facilitating CuSO4·5H2O pretreatment for improving pentose sugar recovery from oil palm fronds. The best result was observed when 0.2 mol/L of CuSO4·5H2O was integrated with 4.5% (v/v) of Na2S2O8 to recover 8.2 and 0.9 g/L of monomeric xylose and arabinose, respectively in the liquid fraction. On the other hand, an addition of 1.5% (v/v) of H2O2 yielded approximately 74% lesser total pentose sugars as compared to using 4.5% (v/v) Na2S2O8. By using CuSO4·5H2O alone (control), only 0.8 and 1.0 g/L xylose and arabinose, respectively could be achieved. The results mirrored the importance of using chemical additives together with the inorganic salt pretreatment of oil palm fronds. Thus, an addition of 4.5% (v/v) of Na2S2O8 during CuSO4·5H2O pretreatment of oil palm fronds at 120 °C and 30 min was able to attain a total pentose sugar yield up to ∼40%.

Deep eutectic solvent and inorganic salt pretreatment of lignocellulosic biomass for improving xylose recovery.

Deep eutectic solvents (DESs) have received considerable attention in recent years due to their low cost, low toxicity, and biodegradable properties. In this study, a sequential pretreatment comprising of a DES (choline chloride:urea in a ratio of 1:2) and divalent inorganic salt (CuCl2) was evaluated, with the aim of recovering xylose from oil palm fronds (OPF). At a solid-to-liquid ratio of 1:10 (w/v), DES alone was ineffective in promoting xylose extraction from OPF. However, a combination of DES (120°C, 4h) and 0.4mol/L of CuCl2 (120°C, 30min) resulted in a pretreatment hydrolysate containing 14.76g/L of xylose, remarkably yielding 25% more xylose than the CuCl2-only pretreatment (11.87g/L). Characterization studies such as FE-SEM, BET, XRD, and FTIR confirmed the delignification of OPF when DES was implemented. Thus, the use of this integrated pretreatment system enabled xylose recoveries which were comparable with other traditional pretreatments.

Reusing colored industrial wastewaters in a photofermentation for enhancing biohydrogen production by using ultrasound stimulated Rhodobacter sphaeroides.

One-time ultrasonication pre-treatment of Rhodobacter sphaeroides was evaluated for improving biohydrogen production via photofermentation. Batch experiments were performed by varying ultrasonication amplitude (15, 30, and 45%) and duration (5, 10, and 15 min) using combined effluents from palm oil as well as pulp and paper mill as a single substrate. Experimental data showed that ultrasonication at amplitude 30% for 10 min (256.33 J/mL) achieved the highest biohydrogen yield of 9.982 mL H2/mLmedium with 5.125% of light efficiency. A maximum CODtotal removal of 44.7% was also obtained. However, when higher ultrasonication energy inputs (>256.33 J/mL) were transmitted to the cells, biohydrogen production did not improve further. In fact, 20.6% decrease of biohydrogen yield (as compared to the highest biohydrogen yield) was observed using the most intense ultrasonicated inoculum (472.59 J/mL). Field emission scanning electron microscope images revealed the occurrence of cell damages and biomass losses if ultrasonication at 472.59 J/mL was used. The present results suggested that moderate ultrasonication pre-treatment was an effective technique to improve biohydrogen production performances of R. sphaeroides.

Effect of adding brewery wastewater to pulp and paper mill effluent to enhance the photofermentation process: wastewater characteristics, biohydrogen production, overall performance, and kinetic modeling.

Although a significant amount of brewery wastewater (BW) is generated during beer production, the nutrients in the BW could be reused as a potential bio-resource for biohydrogen production. Therefore, improvements in photofermentative biohydrogen production due to a combination of BW and pulp and paper mill effluent (PPME) as a mixed production medium were investigated comprehensively in this study. The experimental results showed that both the biohydrogen yield and the chemical oxygen demand removal were improved through the combination of BW and PPME. The best biohydrogen yield of 0.69 mol H2/L medium was obtained using the combination of 10 % BW + 90 % PPME (10B90P), while the reuse of the wastewater alone (100 % BW and 100 % PPME) resulted in 42.3 and 44.0 % less biohydrogen yields than the highest yield, respectively. The greatest light efficiency was 1.97 % and was also achieved using the combination of both wastewaters at 10B90P. This study revealed the potential of reusing and combining two different effluents together, in which the combination of BW and PPME improved the nutrients and light penetration into the mixed production medium.

Photocatalytic degradation of industrial pulp and paper mill effluent using synthesized magnetic Fe2O3-TiO2: Treatment efficiency and characterizations of reused photocatalyst.

In this work, heterogeneous photocatalysis was used to treat pulp and paper mill effluent (PPME). Magnetically retrievable Fe2O3-TiO2 was fabricated by employing a solvent-free mechanochemical process under ambient conditions. Findings elucidated the successful incorporation of Fe2O3 into the TiO2 lattice. Fe2O3-TiO2 was found to be an irregular and slightly agglomerated surface morphology. In comparison to commercial P25, Fe2O3-TiO2 exhibited higher ferromagnetism and better catalyst properties with improvements in surface area (58.40 m2/g), pore volume (0.29 cm3/g), pore size (18.52 nm), and band gap (2.95 eV). Besides, reusability study revealed that Fe2O3-TiO2 was chemically stable and could be reused successively (five cycles) without significant changes in its photoactivity and intrinsic properties. Additionally, this study demonstrated the potential recovery of Fe2O3-TiO2 from an aqueous suspension by using an applied magnetic field or sedimentation. Interactive effects of photocatalytic conditions (initial effluent pH, Fe2O3-TiO2 dosage, and air flow-rate), reaction mechanism, and the presence of chemical oxidants (H2O2, BrO3-, and HOCl) during the treatment process of PPME were also investigated. Under optimal conditions (initial effluent pH = 3.88, [Fe2O3-TiO2] = 1.3 g/L, and air flow-rate = 2.28 L/min), the treatment efficiency of Fe2O3-TiO2 was 98.5% higher than the P25. Based on Langmuir-Hinshelwood kinetic model, apparent rate constants of Fe2O3-TiO2 and P25 were 9.2 × 10-3 and 2.7 × 10-3 min-1, respectively. The present study revealed not only the potential of using magnetic Fe2O3-TiO2 in PPME treatment but also demonstrated high reusability and easy separation of Fe2O3-TiO2 from the wastewater.

Isolation, characterization and the potential use of starch from jackfruit seed wastes as a coagulant aid for treatment of turbid water.

Fruit wastes constituting up to half of total fruit weight represent a large pool of untapped resources for isolation of starch with diverse applications. In this work, the possibility of isolating starch from tropical fruit wastes and its extended application as a natural coagulant was elucidated. Amongst the 12 various parts of fruit wastes selected, only jackfruit seeds contained more than 50% of total starch content. Using alkaline extraction procedures, starch has been successfully isolated from local jackfruit seeds with a yield of approximately 18%. Bell-shaped starch granules were observed under SEM with a granule size ranging from 1.1 to 41.6 µm. Detailed starch characteristics were performed to provide a comparison between the isolated seed starch and also conventional starches. Among them, chemical properties such as the content of starch, amylose, amylopectin and the corresponding molecular weights are some of the key characteristics which governed their performance as natural coagulants. The potential use of isolated seed starch as an aid was then demonstrated in both suspensions of kaolin (model synthetic system) and Chlorella sp. microalga (real-time application) with plausible outcomes. At optimized starch dosage of 60 mg/L, the overall turbidity removal in kaolin was enhanced by at least 25% at a fixed alum dosage of 2.1 mg/L. Positive turbidity and COD removals were also observed in the treatment of Chlorella suspensions. Starches which served as bridging agents aided in the linkage of neighbouring microflocs and subsequently, forming macroflocs through a secondary coagulation mechanism: adsorption and bridging.

Characterization of Matured Vermicompost Derived from Valorization of Palm Oil Mill Byproduct.

The valorization process involves transforming low-value materials such as wastes into high-value-added products. The current study aims to determine the potential of using a valorization process such as vermicomposting technology to convert palm oil mill byproduct, namely, decanter cake (DC), into organic fertilizer or vermicompost. The maturity of the vermicompost was characterized through various chemical and instrumental characterization to ensure the end product was safe and beneficial for agricultural application. The vermicomposting of DC showed significantly higher nutrient recovery and decreases in C:N ratio in comparison with the controls, particularly in the treatment with 2 parts DC and 1 part rice straw (w/w) (2DC:1RS). 2DC:1RS vermicompost had a final C:N ratio of 9.03 ± 0.12 and reasonably high levels of calcium (1.13 ± 0.05 g/kg), potassium (25.47 ± 0.32 g/kg), magnesium (4.87 ± 0.19 g/kg), sodium (7.40 ± 0.03 g/kg), and phosphorus (3.62 ± 0.27 g/kg). In addition, instrumental characterization also revealed a higher degree of maturity in the vermicompost. Ratios of 2921:1633 and DTG2:DTG3 also showed significant linear correlations with the C:N ratio, implying that those ratios could be used to characterize the progression of vermicompost maturity during the valorization process of DC.