Process design for acidic and alcohol based deep eutectic solvent pretreatment and high pressure homogenization of palm bunches for nanocellulose production.

This research aimed to study on nanocellulose production from palm bunch using process design and cost analysis. Choline chloride based deep eutectic solvent pretreatment was selected for high-purity cellulose separation at mild condition, followed by nano-fibrillation using mechanical treatment. Three types of choline chloride-based deep eutectic solvents employing different hydrogen-bond donors (HBDs) namely lactic acid, 1,3-butanediol and oxalic acid were studied. The optimal cellulose extraction condition was choline chloride/lactic acid (ChLa80C) pretreatment of palm empty bunch at 80 °C followed by bleaching yielding 94.96%w/w cellulose content in product. Size reduction using ultrasonication and high-pressure homogenization produced nanocellulose at 67.12%w/w based on cellulose in raw material. Different morphologies of nanocellulose were tunable in the forms of nanocrystals, nano-rods and nanofibers by using dissimilar deep eutectic solvents. This work offered a sustainable and environmentally friendly process as well as provided analysis of DES pretreatment and overview operating cost for nanocellulose production. Application of nanocellulose for the fabrication of highly functional and biodegradable material for nanomedicine, electronic, optical, and micromechanical devices is achievable in the near future.

Fabrication and Characterization of Functional Biobased Membranes from Postconsumer Cotton Fabrics and Palm Waste for the Removal of Dyes.

Textile industries currently face vast challenges for the active removal of colored wastewater. Indeed, sustainable, recyclable, and green approaches are still lacking to achieve this aim. Thus, the present study explored the utilization of highly functional, green, recyclable, fully bio-based, and cost-effective composite membranes from post-consumer cotton fabrics and palm waste for wastewater treatment purposes. Highly functional cellulose nanofibers (CNF) were produced from waste cotton fabrics and filter paper using an acid hydrolysis technique. The yield of nanofibers extracted from waste cotton fabrics and filter paper was 76.74 and 54.50%, respectively. The physical, chemical, and structural properties of nanofibers were studied using various advanced analytical techniques. The properties of isolated nanofibers were almost similar and comparable to those of commercial nanofibers. The surface charge densities were -94.0, -80.7, and -90.6 mV for the nanofibers of palm waste, cotton fibers, and filter paper, respectively. After membrane fabrication using vacuum and hot-pressing techniques, the characteristics of the membrane were analyzed. The results showed that the average pore size of the palm-waste membrane was 1.185 nm, while it was 1.875 nm for membrane from waste cotton fibers and filter paper. Congo red and methylene blue dyes were used as model solutions to understand the behavior of available functional groups and the surface ζ-potential of the membrane frameworks' interaction. The membrane made from palm waste had the highest dye removal efficiency, and it was 23% for Congo red and 44% for methylene blue. This study provides insights into the challenges associated with the use of postconsumer textile and agricultural waste, which can be potentially used in high-performance liquid filtration devices for a more sustainable society.

Integrative process for rubberwood waste digestibility improvement and levulinic acid production by hydrothermal pretreatment with acid wastewater conversion process.

This study aimed to develop an integrative process for converting rubberwood waste into sugars, methane, and levulinic acid. Sulfuric acid pretreatment at pH 2.5 yielded the highest glucose of 182.5 g/kg rubberwood waste. Replacing the acid solution with sulfuric acid wastewater led to 11.0% lower glucose yield than that obtained using sulfuric acid. However, the cost reduction equals the difference in revenues between sulfuric acid wastewater and sulfuric acid, resulting in similar total cost and revenue. Furthermore, thermal reactions of the process water resulted in the highest yield of levulinic acid, 17.9% at 220 °C. Meanwhile, anaerobic digestibility of enzymatic hydrolysis residue was increased using inoculum from a digester treating pig farm wastewater owing to the acetoclastic pathway. These co-products potentially returned additional revenues, accounting for 45.8% of the total revenue. These findings highlight the potential pathway for valorization of rubberwood waste via the integrated approach with acid wastewater pretreatment.

Integrated process for the production of fermentable sugar and methane from rubber wood.

Pretreatment is required for the enhancement of the bioconversion of lignocellulosic biomass. This study aimed to develop an integrated process producing efficient biochemical conversion of rubber wood waste (RW) into co-biofuels, fermentable sugar and methane. The glucan conversion was enhanced to 93.8% with temperature (210 °C) and delignification by organosolv pretreatment (OS). Thereafter, anaerobic digestion of the residue left after enzymatic hydrolysis was conducted which further improved the methane yield (205.5 LCH4/kg VS) by 33% over hydrothermal pretreatment (154.3 LCH4/kg VS). Delignification during OS plays a key role in improving the degradability of RW resulting in efficient energy recovery (11.23 MJ/kg pretreated RW) which was clearly higher than an integrated process based on hydrothermal (HT) or HT plus process water. Scaled up to a biorefinery, the integrated process based on OS would economically produce fermentable sugar while other value-added chemicals might be produced from the process water.

Enhanced enzymatic hydrolysis and methane production from rubber wood waste using steam explosion.

Rubber wood waste (RW) requires due to its recalcitrance a pretreatment step before efficient biochemical conversion is possible. Non chemical steam explosion pretreatment was adopted to enhance enzymatic hydrolysis and anaerobic digestion with severity from 2.70 to 4.35. RW treated at severity 4.35 (214 °C for 10 min) gave the highest 83.9 L CH4/kgVS effectiveness in anaerobic digestibility together with 45.2% hydrolysability in terms of glucan conversion. The intense pretreatment decreased particle size and degraded most of the hemicellulose, resulting in increased specific surface and better access for enzymes to cellulose. Additionally, the energy yield of steam exploded RW was enhanced by combined enzymatic hydrolysis with anaerobic digestion, in comparison to enzymatic hydrolysis or anaerobic digestion alone. This allowed for an efficient steam explosion pretreatment with co-production of sugar and methane. This study provides a technical approach for efficient biofuel production from RW after steam explosion pretreatment. Valorization of lignin-rich residue generated from the integrated process may increase value of RW, but assessing this requires further study.

Effects of size and thermophilic pre-hydrolysis of banana peel during anaerobic digestion, and biomethanation potential of key tropical fruit wastes.

Methane production potential of tropical fruit wastes, namely lady-finger banana peel, rambutan waste and longan waste were compared using BMP assay and stoichiometric modified Buswell and Mueller equation. Methane yields based on volatile solid (VS) were in the order of ground banana peel, chopped banana peel, chopped longan waste, and chopped rambutan waste (330.6, 268.3, 234.6 and 193.2 mLCH4/gVS) that corresponded to their calculated biodegradability. In continuous operations of banana peel digestion at feed concentrations based on total solid (TS) 1-2%, mesophilic single stage digester run at 20-day hydraulic retention time (20-day HRT) failed at 2%TS, but successfully recovered at 1.5%TS. Pre-hydrolysis thermophilic reactor (4-d HRT) was placed as pre-treatment to mesophilic reactor (20-d HRT). Higher biogas (with an evolution of H2) and energy yields were obtained and greater system stability was achieved over the single stage digestion, particularly at higher solid feedstock. The best performance of two stage digestion was 68.5% VS destruction and energy yield of 2510.9kJ/kgVS added at a feed concentration of 2%TS.

Bio-desulfurization of biogas using acidic biotrickling filter with dissolved oxygen in step feed recirculation.

Triple stage and single stage biotrickling filters (T-BTF and S-BTF) were operated with oxygenated liquid recirculation to enhance bio-desulfurization of biogas. Empty bed retention time (EBRT 100-180 s) and liquid recirculation velocity (q 2.4-7.1 m/h) were applied. H2S removal and sulfuric acid recovery increased with higher EBRT and q. But the highest q at 7.1 m/h induced large amount of liquid through the media, causing a reduction in bed porosity in S-BTF and H2S removal. Equivalent performance of S-BTF and T-BTF was obtained under the lowest loading of 165 gH2S/m(3)/h. In the subsequent continuous operation test, it was found that T-BTF could maintain higher H2S elimination capacity and removal efficiency at 175.6±41.6 gH2S/m(3)/h and 89.0±6.8% versus S-BTF at 159.9±42.8 gH2S/m(3)/h and 80.1±10.2%, respectively. Finally, the relationship between outlet concentration and bed height was modeled. Step feeding of oxygenated liquid recirculation in multiple stages clearly demonstrated an advantage for sulfide oxidation.

Oxidation of hydrogen sulfide in biogas using dissolved oxygen in the extreme acidic biofiltration operation.

This work aimed to investigate the interactive effects of empty bed retention time (EBRT), specific hydraulic loading rate (q) and initial pH (pHi) of the aerated recirculating liquid to remove H2S in extreme acidic biofiltration. Biogas containing H2S 6395±2309ppm and CH4 79.8±2.5% was fed to the biofilter as pH of the high dissolved oxygen recirculating liquid swung between pHi to 0.5. Response surface methodology was employed that gave the H2S removal relationship model with R(2) 0.882. The predicted highest H2S removal within the studied parameter ranges was 94.7% at EBRT 180.0s, q 4.0m(3)/m(2)/h and pHi 3.99. Results from separate runs at a random condition were not statistically different from the model prediction, signifying a validity of the model. Additionally, CH4 content in the exit biogas increased by 4.7±0.4%. Acidithiobacullus sp. predominance in the consortia of this extreme acidic condition was confirmed by DGGE.

Recovery of plastic wastes from dumpsite as refuse-derived fuel and its utilization in small gasification system.

An effort to utilize solid wastes at dumpsite as refuse-derived fuel (RDF) was carried out. The produced RDF briquette was then utilized in the gasification system. These wastes were initially examined for their physical composition and chemical characteristics. The wastes contained high plastic content of 24.6-44.8%, majority in polyethylene plastic bag form. The plastic wastes were purified by separating them from other components through manual separation and trommel screen after which their content increased to 82.9-89.7%. Subsequently, they were mixed with binding agent (cassava root) and transformed into RDF briquette. Maximum plastic content in RDF briquette was limit to 55% to maintain physical strength and maximum chlorine content. The RDF briquette was tested in a down-draft gasifier. The produced gas contained average energy content of 1.76 MJ/m(3), yielding cold gas efficiency of 66%. The energy production cost from this RDF process was estimated as USD0.05 perkWh.