Co-pyrolysis of sewage sludge and biomass waste into biofuels and biochar: A comprehensive feasibility study using a circular economy approach.

Enormous annual sewage sludge (SS) volumes pose global environmental challenges owing to contamination and significant greenhouse gas emissions. Here, we investigated the economic viability of co-pyrolyzing SS and biomass waste to produce biofuels (bio-oil and gas) and biochar. Net present worth (NPW) analysis, the sale product break-even price, and sludge handling price (SHP) were used to determine the profitability of co-pyrolysis compared with SS pyrolysis alone and conventional treatment methods. In this study, the sale prices of biochar based on quality (i.e., stability, carbon sequestration effectiveness, and heavy metal content) were estimated to be 2.24, 1.44, and 0.98 CAD/kg for high-, medium-, and low-grade biochar. The bio-oil prices, estimated based on the higher heating values of bio-oil and diesel, ranged from 0.80 to 1.22 CAD/kg. Sawdust (SD) and wheat straw (WS) were the chosen co-pyrolysis feedstocks, with four mixing ratios (20, 40, 60, and 80 wt%). Economically, SD (40 wt% mixing ratio) co-pyrolysis achieved the best performance, with a maximum NPW of 8.71 million CAD. SD single and co-pyrolysis were the only profitable scenarios. Moreover, SS single pyrolysis and WS co-pyrolysis exhibited higher profitability than conventional SS treatment methods, with SHPs of 65 and 40 CAD/1000 kg dry sludge, respectively. Sensitivity analysis highlighted the dependence of economic performance on biochar and bio-oil market value. This study offers the first economic analysis of this approach and enhances our understanding of the potential of co-pyrolysis for biofuel and biochar production, providing innovative solutions for the environmental challenges of SS disposal.

Ruminal content biochar supplementation for enhanced biomethanation of rice straw: Focusing on biochar characterization and dose optimization.

Anaerobic digestion (AD) of agricultural wastes is a promising approach for energy recovery and crop residue management. However, its recalcitrant chemical structure hinders microbial hydrolysis and reduces biomethane production under AD. Biochar supplementation has been proven to promote the digestibility and biomethanation of lignocellulosic substrates. Therefore, this study investigated the influence of different pyrolysis temperatures (450 °C, 550 °C, and 650 °C) on the physicochemical properties of biochar. Furthermore, the impact of ruminal content biochar supplementation (1 %, 2 %, and 3 %) on the AD of rice straw with rumen fluid as inoculum has been investigated. The ruminal content biochar (RUCB) supplemented reactors showed an increment in biomethane yield and the highest cumulative biomethane yield 243.11 mL/g volatile solids (VS)) was recorded at 2 % RUCB supplementation, followed by 227.12 mL/g VS at 1 % RUCB supplementation and 162.86 mL/g VS at 3 % RUCB supplementation (P > 0.05). Compared to the control reactors (128.68 mL/g VS), RUCB supplemented reactors exhibited 1.88-fold, 1.76-fold, and 1.26-fold increments in biomethane yield due to pH stabilization and facilitation of microbial biofilm formation on the biochar. The correlation analysis showed that biomethane production is positively correlated with VS reduction (R2 = 0.9852). This study proposed a potential strategy to utilize ruminal content waste as a feedstock for biochar production and its application in AD for accelerating the biomethanation of rice straw.

Effect of nano-metal doped calcium peroxide on biomass pretreatment and green hydrogen production from rice straw.

In this study, calcium peroxide was modified and doped with metal-based nanoparticles (NP) to enhance the efficiency of pretreatment and biohydrogen generation from RS. The findings revealed that the addition of MnO2-CaO2 NPs (at a dosage of 0.02 g/g TS of RS) had a synergistic effect on the breakdown of biomass and the production of biohydrogen. This enhancement resulted in a maximum hydrogen yield (HY) of 58 mL/g TS, accompanied by increased concentrations of acetic acid (2117 mg/L) and butyric acid (1325 mg/L). In contrast, RS that underwent pretreatment without the use of chemicals or NP exhibited a lower HY of 28 mL/g TS, along with the lowest concentrations of acetic acid (1062 mg/L) and butyric acid (697 mg/L). The outcome showed that supplementation of NP stimulated the pretreatment of RS and improved the formation of acetic and butyric acid through the regulation of metabolic pathways during acidogenic fermentation.

A comparative study of Cellulomonas sp. and Bacillus sp. in utilizing lignocellulosic biomass as feedstocks for enzyme production.

The demand for enzymes is increasing continuously due to their applications in various avenues. The pectin-hydrolyzing bacteria, Cellulomonas sp. and Bacillus sp., isolated from forest soil have the potential to produce industrially important enzymes (pectinase, PGase, Cellulase, and xylanase). However, these bacteria have different optimal cultural conditions for pectinase production. The optimal cultural conditions for Cellulomonas sp. were room temperature (25-26℃), pH 7, 1% inoculum volume, and 1.5% citrus pectin with 8.82 ± 0.92 U/mL pectinase activity. And Bacillus sp. illustrated the highest pectinase activity (12.35 ± 0.72 U/mL) at room temperature, pH 10, 1% inoculum volume, and 1.5% pectin concentration. Among the different agro-wastes, the orange peel was found to be the best substrate for pectinase, PGase, and cellulase activity whereas barley straw for xylanase activity. Further, Cellulomonas sp. and Bacillus sp. illustrated higher pectinase activity from commercial pectin compared to orange peel showing their preference for commercial citrus pectin. In addition, the optimization by the Box-Behnken design increased pectinase activity for Cellulomonas sp., while a noticeable increase in activity was not observed in Bacillus sp. Besides, all the agro-wastes exploited in this study can be used for pectinase, PGase, and xylanase production but not cellulase. The study revealed that each bacteria has its specific optimal conditions and there is a variation in the capacity of utilizing the various lignocellulosic biomass.

Anti-Inflammatory, Anti-Bacterial, and Anti-Fungal Activity of Oligomeric Proanthocyanidins and Extracts Obtained from Lignocellulosic Agricultural Waste.

It has now been proven that many pathogens that cause infections and inflammation gradually mutate and become resistant to antibiotics. Chemically synthesized drugs treating inflammation most often only affect symptoms, but side effects could lead to the failure of human organs' functionality. On the other hand, plant-derived natural compounds have a long-term healing effect. It was shown that sea buckthorn (SBT) twigs are a rich source of biologically active compounds, including oligomeric proanthocyanidins (PACs). This study aimed to assess the anti-pathogenic and anti-inflammatory activity of water/ethanol extracts and PACs obtained from the lignocellulosic biomass of eight SBT cultivars. The anti-pathogenic activity of extracts and PACs was studied against pathogenic bacteria Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Bacillus cereus and fungus Candida albicans in 96-well plates by the two-fold serial broth microdilution method. The anti-bacterial activity of purified PACs was 4 and 10 times higher than for water and water/ethanol extracts, respectively, but the extracts had higher anti-fungal activity. Purified PACs showed the ability to reduce IL-8 and IL-6 secretion from poly-I:C-stimulated peripheral blood mononuclear cells. For the extracts and PACs of SBT cultivar 'Maria Bruvele' in the concentration range 0.0313-4.0 mg/mL, no toxic effect was observed.

High value-added lignin extracts from sugarcane by-products.

This study evaluates the production of lignin bioactive extracts from sugarcane bagasse (SCB) and straw (SCS) alkaline black liquors using greener precipitating agents (methane sulfonic acid (MSA), formic acid (FA) and lactic acid (LA)) as replacers of sulfuric acid (SA), the most common one used in industry. Results showed that the highest precipitation yield was achieved by LA when applied to SCB (14.5 g extract/100 g SCB). Lignin SCB extracts were similar in composition in terms of total carbohydrates (61-70 %), lignin (22-30 %) and inorganics (1.6-2.6 %). Regarding the SCS extracts, similar yields were obtained among all extracts, however, differences in composition were observed between SA and greener precipitating agents, particularly in terms of sugar content. All extracts exhibited radical scavenging activity; overall the extracts were more effective in the scavenging of ABTS radical. FA was the most promising alternative to SA to recover lignin bioactive extracts. This work suggests organic acids as good candidates for obtaining valuable extracts from alkaline pulping of SCB and SCS instead of the conventional sulfuric acid.

Preparation of nanolignin rich fraction from bamboo stem via green technology: assessment of its antioxidant, antibacterial and UV blocking properties.

This work reports the preparation of nano lignin-rich fraction material via green technology from the holistic use of lignocellulosic biomass bamboo. The bamboo is first chemically treated, followed by acid precipitation to extract bamboo-derived macro lignin-rich fraction material. The nano lignin-rich fraction material was then prepared via ultrasonication technique from the extracted bamboo-derived macro lignin-rich fraction material. The confirmation of the distinct lignin functional groups in the extracted lignin-rich fractions has been done by FTIR. Surface morphology by FESEM and TEM revealed spherical nano-lignin-rich fraction materials from extracted bamboo-derived macro lignin-rich fraction materials. DPPH assays indicated that both the obtained fractions depict beneficial antioxidant characteristics. They were found to be effective in terms of their antibacterial activity against both gram-positive bacteria Staphylococcus aureus (S.aureus) and gram-negative bacteria Escherichia coli (E.coli), using the disc diffusion method. These fractions have UV blocking property, and nano-lignin-rich fraction material acts as a more potential UV blocking agent than others. Thus, the nano-lignin-rich fraction material has great potential as a high antioxidant, antibacterial, and UV blocking agent useful in biomedical applications.Highlights Extraction of macro-lignin rich fraction material using chemical treatment of lignocellulosic biomass bamboo via refluxing followed by acid precipitation.Preparation of nano-lignin rich fraction material from extracted bamboo-derived macro-lignin rich fraction material via ultrasonication technique as a green technology.Structural and surface morphology of the extracted macro-lignin & nano lignin-rich fraction materials have been analyzed by XRD, FTIR, EDX, SEM and TEM.The macro lignin & nano lignin-rich fraction materials showed good antioxidant, antibacterial activity and UV-blocking properties, but the nano-lignin rich fraction material exhibited more efficient properties.

Green synthesis of nanostructures from rice straw food waste to improve the antimicrobial efficiency: New insight.

Applications for nanotechnology, which is constantly gaining prominence, have been found in a variety of industrial applications. Due to the multiple benefits associated with it, including an eco-friendly, pollution-free, cost-effective, and non-toxic synthesis method, the green way to synthesize nanostructures utilizing waste biomasses has become one of the key focuses of the current researches globally. Additionally, lignocellulasic biomass (LCB), which is a waste of the food crops, can be used as one of the potential substrates for the synthesis of a variety of nanostructures. Among different types of LCB, rice straw is a potential food waste biomass and can be efficiently employed during the synthesis of different types of nanostructures for a range of technological applications. Here, diverse phenolic compounds found in rice straw as well as reducing sugars can be used as natural reducing and capping agents to prepare a range of nanostructures. Based on the aforementioned facts, the objective of this review is to investigate the viability of using rice straw to produce nanostructured materials using rice straw as a renewable biosource following an environmentally friendly method. Additionally, it is noted that various organic compounds present on the surface of nanostructures produced using rice straw extract/hydrolyzate through a green approach may be more successful in terms of antibacterial efficacy, which might be of considerable interest for a variety of biomedical applications. Based on the possibility of enhancing the antimicrobial activity of developed nanostructures, the review also provides overview on the feasibility, characteristics, and availability of using rice straw extract in the synthesis of nanostructures. Additionally, the constraints of the present and potential futures of the green synthesis methods using rice straw wastes have been explored.

Potato waste as feedstock to produce biohydrogen and organic acids: A comparison of acid and alkaline pretreatments using response surface methodology.

The effects of physicochemical pre-treatment were evaluated on hydrogen (H2) production and organic acids from hydrolyzed potato peel. Central composite design (CCD) and response surface methodology (RSM) were used to evaluate the effects of different substrate concentrations on a wet basis (38.8-81.2 g.L-1) and hydrolyser ratios (6M NaOH and 30% HCl: 1.6-4.4% v.v-1; and H2SO4: 2.2-7.8% v.v-1). The experiments were conducted in batch reactors at 37 °C, using a heat-treated microbial consortium. The maximum H2 production potential (P), lag phase (λ), and maximum H2 production rate (Rm) were evaluated for untreated and pre-treated potato peel waste. H2 production was positively influenced under hydrolyzed substrate concentrations ≥75 g.L-1 in the three CCDs performed. Only the increase in the H2SO4 proportions (≥5% v.v-1) had a negative influence on H2 production. Increasing the 30% HCl and 6M NaOH proportions did not significantly influence the cumulative H2 production. The highest hydrogen production was obtained after alkaline pre-treatment by dark fermentation (P: 762.09 mL H2.L-1; λ: 14.56 h; Rm: 38.39 mL H2.L-1.h-1). Based on the CCD and RSM, the highest H2 production (1060.10 mL H2.L-1) was observed with 81.2 g.L-1 hydrolyzed potato peel with 3.0% v.v-1 of 6M NaOH. The highest yield liquid metabolites were acetic (513.70 mg. g-1 COD) and butyric acids (491.90 mg. g-1 COD).

Enhanced tolerance of Cupriavidus necator NCIMB 11599 to lignocellulosic derived inhibitors by inserting NAD salvage pathway genes.

Polyhydroxybutyrate (PHB) is a bio-based, biodegradable and biocompatible plastic that has the potential to replace petroleum-based plastics. Lignocellulosic biomass is a promising feedstock for industrial fermentation to produce bioproducts such as polyhydroxybutyrate (PHB). However, the pretreatment processes of lignocellulosic biomass lead to the generation of toxic byproducts, such as furfural, 5-HMF, vanillin, and acetate, which affect microbial growth and productivity. In this study, to reduce furfural toxicity during PHB production from lignocellulosic hydrolysates, we genetically engineered Cupriavidus necator NCIMB 11599, by inserting the nicotine amide salvage pathway genes pncB and nadE to increase the NAD(P)H pool. We found that the expression of pncB was the most effective in improving tolerance to inhibitors, cell growth, PHB production and sugar consumption rate. In addition, the engineered strain harboring pncB showed higher PHB production using lignocellulosic hydrolysates than the wild-type strain. Therefore, the application of NAD salvage pathway genes improves the tolerance of Cupriavidus necator to lignocellulosic-derived inhibitors and should be used to optimize PHB production.

Effects of hydrochar derived from hydrothermal treatment of sludge and lignocellulose mixtures on soil properties, nitrogen transformation, and greenhouse gases emissions.

In this study, hydrochar samples derived from hydrothermal treatment (HTT) of sludge and sludge-biomass mixtures were applied to a sandy soil and their effects on soil properties, soil nutrients, greenhouse gas (GHG) emissions, and soluble heavy metals were investigated. The application of untreated sludge and hydrochar derived from HTT of sludge at 180 °C led to the highest soluble nitrate, CO2 and N2O emissions, followed by the application of hydrochar samples derived from HTT of sludge-biomass mixtures at 180 °C. Although the application of hydrochar samples derived from HTT of sludge alone and sludge-biomass mixtures at 240 °C in sandy soil led to the lowest emissions of CO2 and N2O, it resulted in lower levels of soil electrical conductivity (EC), cation exchange capacity (CEC) and soluble phosphorus. The application of hydrochar samples derived from HTT at 240 °C led to the production of CH4 and lower nitrate-N contents than hydrochar samples derived from HTT at 180 °C. These results indicated that the soils containing hydrochar samples from HTT at 240 °C were anaerobic, which might inhibit the growth of plants. The application of hydrochar samples derived from HTT of sludge-biomass at 180 °C led to significantly improved contents of soil soluble phosphorus (2.56 and 2.84 g kg-1 soil) and soil nitrate-N (160.2 and 263.2 mg kg-1 soil) at the end of 60 days of incubation. However, these contents were lower than the contents of soluble phosphorus (3.71 and 4.45 g kg-1 soil) and nitrate-N (528.3 and 583.2 mg kg-1 soil) with the application of untreated sludge and sludge derived from HTT of sludge alone at 180 °C. Although more studies are needed to understand the mechanisms and effects on different soils, this study provides useful insights into the application of hydrochar derived from sludge-biomass mixture in soil.

Effects of lignocellulosic biomass type on nutrient recovery and heavy metal removal from digested sludge by hydrothermal treatment.

Sludge is a nutrient-rich organic waste generated from wastewater treatment plants. However, the application of sludge as a nutrient source is limited by its high contents of water and pollutants. In this study, the effects of biomass type on nutrient recovery and heavy metal removal from digested sludge by hydrothermal treatment (HTT) were investigated. Blending biomass with digested sludge for HTT at 180-240 °C increased the recovery of nitrogen in the treated solids. At the HTT temperature of 240 °C, HTT with hardwood sawdust led to the highest nitrogen recovery of 70.6%, compared to the lowest nitrogen recovery of 36.5% without biomass. Blending biomass slightly decreased the recovery of phosphorus compared to those without biomass. Nevertheless, the lowest phosphorus recovery of 91.3% with the use of hardwood sawdust at the HTT temperature of 240 °C was only ∼7.0% less than that without biomass. Blending biomass reduced the contents of macro-metals such as Ca, Fe, Mg and Al in treated solids but the metal contents varied with different biomasses. Regarding the heavy metals, the use of rice husk did not decrease the contents of Ni and Co while blending bagasse did not decrease the content of Cr at HTT temperatures of 210 °C and 240 °C compared to the use of other biomasses. The different effects of biomass type on nutrient recovery and heavy metals were likely related to the types and abundances of organic acids such as acetic acid, oxygen-containing functional groups such as C-OH and COOH, oxide minerals such as silica from biomasses and the overall effects of these factors. This study provides very useful information in selection of lignocellulosic biomass for HTT of sludge for nutrient recovery and heavy metal removal.

D-Lactic acid production from agricultural residues by membrane integrated continuous fermentation coupled with B vitamin supplementation.

BACKGROUND: D-Lactic acid played an important role in the establishment of PLA as a substitute for petrochemical plastics. But, so far, the D-lactic acid production was limited in only pilot scale, which was definitely unable to meet the fast growing market demand. To achieve industrial scale D-lactic acid production, the cost-associated problems such as high-cost feedstock, expensive nutrient sources and fermentation technology need to be resolved to establish an economical fermentation process. RESULTS: In the present study, the combined effect of B vitamin supplementation and membrane integrated continuous fermentation on D-lactic acid production from agricultural lignocellulosic biomass by Lactobacillus delbrueckii was investigated. The results indicated the specific addition of vitamins B1, B2, B3 and B5 (VB1, VB2, VB3 and VB5) could reduce the yeast extract (YE) addition from 10 to 3 g/l without obvious influence on fermentation efficiency. By employing cell recycling system in 350 h continuous fermentation with B vitamin supplementation, YE addition was further reduced to 0.5 g/l, which resulted in nutrient source cost reduction of 86%. A maximum D-lactate productivity of 18.56 g/l/h and optical purity of 99.5% were achieved and higher than most recent reports. CONCLUSION: These findings suggested the novel fermentation strategy proposed could effectively reduce the production cost and improve fermentation efficiency, thus exhibiting great potential in promoting industrial scale D-lactic acid production from lignocellulosic biomass.

Catalytic pyrolysis of lignocellulosic biomass for bio-oil production: A review.

Catalytic pyrolysis has been widely explored for bio-oil production from lignocellulosic biomass owing to its high feasibility and large-scale production potential. The aim of this review was to summarize recent findings on bio-oil production through catalytic pyrolysis using lignocellulosic biomass as feedstock. Lignocellulosic biomass, structural components and fundamentals of biomass catalytic pyrolysis were explored and summarized. The current status of bio-oil yield and quality from catalytic fast pyrolysis was reviewed and presented in the current review. The potential effects of pyrolysis process parameters, including catalysts, pyrolysis conditions, reactor types and reaction modes on bio-oil production are also presented. Techno-economic analysis of full-scale commercialization of bio-oil production through the catalytic pyrolysis pathway was reviewed. Further, limitations associated with current practices and future prospects of catalytic pyrolysis for production of high-quality bio-oils were summarized. This review summarizes the process of bio-oil production from catalytic pyrolysis and provides a general scientific reference for further studies.

Phyllosilicate derived catalysts for efficient conversion of lignocellulosic derived biomass to biodiesel: A review.

The efforts have been made to review phyllosilicate derived (clay-based) heterogeneous catalysts for biodiesel production via lignocellulose derived feedstocks. These catalysts have many practical and potential applications in green catalysis. Phyllosilicate derived heterogeneous catalysts (modified via any of these approaches like acid activated clays, ion exchanged clays and layered double hydroxides) exhibits excellent catalytic activity for producing cost effective and high yield biodiesel. The combination of different protocols (intercalated catalysts, ion exchanged catalysts, acidic activated clay catalysts, clay-supported catalysts, composites and hybrids, pillared interlayer clay catalysts, and hierarchically structured catalysts) was implemented so as to achieve the synergetic effects (acidic-basic) in resultant material (catalyst) for efficient conversion of lignocellulose derived feedstock (non-edible oils) to biodiesel. Utilisation of these Phyllosilicate derived catalysts will pave path for future researchers to investigate the cost-effective, accessible and improved approaches in synthesising novel catalysts that could be used for converting lignocellulosic biomass to eco-friendly biodiesel.

Medium supplementation and thorough optimization to induce carboxymethyl cellulase production by Trichoderma reesei under solid state fermentation of nettle biomass.

In the present study, the production of cellulase by Trichoderma reesei under solid-state fermentation of nettle biomass was promoted through supplementation of the culture media using carbonaceous additives and comprehensive optimization of the cultivation via the Taguchi method. CMCase activities about 5.5-6.1 U/gds were obtained by fermentation of the autoclave-pretreated biomass, among various chemical and physical pretreatments. Then, several additives including Tween 80, betaine, carboxymethyl cellulose, and lactose were individually or in combination added to the culture media to induce the enzyme production. The results proved that such additives could act as either inducers or inhibitors. Furthermore, CMCase activity surprisingly increased to 14.0 U/gds by supplementing the fermentation medium with the optimal mixture of additives including 0.08 mg/gds Tween 80, 0.4 mg/gds betaine, and 0.2 mg/gds carboxymethyl cellulose. Factor screening according to Plackett-Burman design confirmed that the levels of Urea and MgSO4 among basal medium constituents as well as pH of the medium were significantly affected CMCase production. By optimizing the levels of these factors, CMCase activity of 18.8 U/gds was obtained, which was noticeably higher than that of fermentation of the raw nettle. The applied procedure can be promisingly used to convert the nettle biomass into valuable products.

Research and economic perspectives on an integrated biorefinery approach for the simultaneous production of polyhydroxyalkanoates and biohydrogen.

Alarming environmental impacts have been resulted across the globe due to the recovery and consumption of fossil fuels. The elevated global carbon footprint has paved the way to an alternative to combat the prevalent pollution. On the other hand, the fossil-based plastics produced from the byproducts of petroleum remain intact in the environment leading to pollution. Fossil abated bioproducts are in high demand due to the increase in pollution. This call to utilize feedstock for simultaneous production of biologically useful products through carbon capture utilisation where the leftover carbon-rich substrate is converted into usable chemicals like bioplastics, methanol, urea and various other industrially essential components. The present review extensively focuses on the research and economic perspectives of an integrated biorefinery and addresses technical breaches, bottlenecks, and efficient strategies for the simultaneous production of biohydrogen and polyhydroxyalkanoates.

Enhanced conversion of biomass to furfurylamine with high productivity by tandem catalysis with sulfonated perlite and ω-transaminase whole-cell biocatalyst.

Production of bio-based chemicals from renewable bioresource is a key driver for moving towards sustainable industry. Furfurylamine is known as an important furfural-upgrading product in organic synthesis, as well as monolithic synthetic pharmaceuticals, fibers, additives and polymers. In one-pot manner, biomass was tandemly catalyzed to furfurylamine with sulfonated Sn-PL catalyst and recombinant ω-transaminase biocatalyst. Sn-PL (2.4 wt%) catalyzed bamboo shoot shell, corncob and rice straw (75.0 g/L) to 76.5-113.0 mM furfural at 44.7-58.5 % yield in γ-valerolactone-water (2:8, v:v) at 170 ℃. The obtained biomass slurries containing furfural were biotransformed to furfurylamine at high yield (0.39-0.42 g furfurylamine/g xylan in biomass) with ω-transaminase biocatalyst using isopropylamine (3.0 mol isopropylamine/mol furfural) as amine donor at 35 ℃. Such a chemoenzymatic one-pot process combined the advantages of both solid acids and whole-cells catalysts, which provided an efficient and sustainable approach for preparing an important bio-based furan chemical furfurylamine.

Pretreatment of Mango (Mangifera indica L. Anacardiaceae) Seed Husk for Bioethanol Production by Dilute Acid Treatment and Enzymatic Hydrolysis.

One of the targets of the Sustainable Development Goals is clean and affordable energy. This is also the aim of the Biofuels Act of 2007 in the Philippines. However, this law is confronted with challenges such as the limitation of lignocellulosic feedstock, specifically available for bioethanol production. The present study sought to address the issue by exploring the potential of mango seed husk (MSH), a by-product of the mango industry, in bioethanol production. MSH is considered a waste material and its utilization also permit value-addition as this can serve as an alternative and affordable source of feedstock in energy production. Two pretreatment strategies are employed to exploit the cellulose and hemicellulose content of MSH, namely, dilute acid treatment and enzymatic hydrolysis. Results show that the %H2SO4 resulting in the highest glucose concentration and yield is 4% v/v at 95 °C hydrolysis temperature, 1:10 (w/v) solid-to-solvent ratio, and 60-min hydrolysis time. For enzymatic hydrolysis using a commercial enzyme preparation, the reaction time up to 72 h did not affect glucose concentration and yield at the following conditions: 50 °C hydrolysis temperature, 150 rpm, pH 5.0, 10% solids loading, and 4% enzyme loading. This could be attributed to the lignin and non-structural compounds present in MSHs. However, a combined process strategy of dilute acid pretreatment followed by enzymatic hydrolysis in the pretreatment of MSH contributes to an increased concentration and yield of sugars in the hydrolysates, which is advantageous for bioethanol production. Graphical Abstract.

Hydrothermal liquefaction of Prosopis juliflora biomass for the production of ferulic acid and bio-oil.

The objective of this work was to study the hydrothermal liquefaction (HTL) of Prosopis juliflora biomass for the production of ferulic acid and bio-oil. Biomass was processed with various solvents (NaOH, KOH, HCl and H2SO4) to produce ferulic acid (FA). FA oxidation was carried out using the Nano ZnO catalyst to produce an optimum vanillin yield of 0.3 g at 70 °C with 0.4% catalyst loading for a time of 60 min. The spent solid residue was then processed using HTL at 5 MPa pressure and a temperature range of 240-340 °C. Various biomass loading (2.5 g to 12.5 g) was taken for a fixed water content of 200 mL. Bio-oil optimum yield was 22.5 wt% for 10 g/200 mL of biomass loading ratio. The optimum temperature was 300 °C for a processing time of 1 h. The catalyst showed the reusable capability of two three consecutive cycles.