Effect of power ultrasound and Fenton reagents on the biomethane potential from steam-exploded birchwood

Stimulating biogas production from steam-exploded birch wood using Fenton reaction and fungal pretreatment

Delignification of steam-exploded birch wood (SEBW) was stimulated using a pretreatment method including Fenton reaction (FR) and fungi. SEBW was employed as a substrate to optimize the Fe(III) and Fe(II) dosage in FR. Maximum iron-binding to SEBW was obtained at pH 3.5. FR pretreatment increased biological methane yields from 257 mL/g vS in control to 383 and 352 mL/ g vS in samples with 0.5 mM Fe(II) and 1.0 mM Fe(III), respectively. Further enzymatic pretreatment using a commercial cellulase cocktail clearly improved methane production rate but only increased the final methane yields by 2-9 %. Finally, pretreatments with the fungi Pleurotus ostreatus (PO) and Lentinula edodes (LE), alone or in combination with FR, were carried out. SEBW pretreated with only LE and samples pretreated with PO and1 mM Fe(III) + H₂O₂ increased the methane production yield to 420 and 419 mL/g vS respectively. These pretreatments delignified SEBW up to 25 %.

Facile Synthesis of Carbon- and Nitrogen-Doped Iron Borate as a Highly Efficient Single-Component Heterogeneous Photo-Fenton Catalyst under Simulated Solar Irradiation

The development of a heterogeneous catalyst for use in environmental remediation remains a challenging and attractive research endeavor. Specifically, for Fenton reactions, most research approaches have focused on the preparation of iron-containing heterostructures as photo-Fenton catalysts that utilize visible light for enhancing the degradation efficiency. Herein, the synthesis and novel application of C,N-doped iron borates are demonstrated as single-component heterogeneous photo-Fenton catalysts with high Fenton activity under visible light. Under the optimal conditions, 10 mg of the catalyst is shown to achieve effective degradation of 10 ppm methylene blue (MB) dye, Rhodamine B (RhB) dye, and tetracycline (TC) under simulated solar irradiation with a first-order rate constant of k = 0.218 min^-1, 0.177 min^-1, and 0.116 min^-1, respectively. Using MB as a model system, the C,N-doped iron borate exhibits 10- and 26-fold increases in catalytic activity relative to that of the 50 nm hematite nanoparticles and that of the non-doped iron borate, respectively, in the presence of H₂O₂ under the simulated solar irradiation. Furthermore, the optimum reaction conditions used only 320 equivalents of H₂O₂ with respect to the concentration of dye, rather than the several thousand equivalents of H₂O₂ used in conventional heterogeneous Fenton catalysts. In addition, the as-prepared C,N-doped iron borate achieves 75% MB degradation after 20 min in the dark, thus enabling the continuous degradation of pollutants at night and in areas with poor light exposure. The stability and recyclability of C,N-doped iron borate for the oxidation of MB was demonstrated over three cycles with insignificant loss in photo-Fenton activity. The high Fenton activity of the C,N-doped iron borate is considered to be due to the synergistic action between the negatively-charged borate ligands and the metal center in promoting the Fenton reaction. Moreover, carbon and nitrogen doping are shown to be critical in modifying the electronic structure and increasing the conductivity of the catalyst. In view of its synthetic simplicity, high efficiency, low cost of reagents, and minimal cost of operation (driven by natural sunlight), the as-prepared heterogeneous single-component metal borate catalyst has potential application in the industrial treatment of wastewater.

Wood‑feeding termites as an obscure yet promising source of bacteria for biodegradation and detoxification of creosote-treated wood along with methane production enhancement

This study aims to explore distinct bacterial strains from wood-feeding termites and to construct novel bacterial consortium for improving the methane yield during anaerobic digestion by degrading birchwood sawdust (BSD) and removing creosote (CRO) compounds simultaneously. A novel bacterial consortium CTB-4 which stands for the molecularly identified species Burkholderia sp., Xanthomonas sp., Shewanella sp., and Pseudomonas mosselii was successfully developed. The CTB-4 consortium showed high efficiency in the removal of naphthalene and phenol. It also revealed reduction in lignin, hemicellulose, and cellulose by 19.4, 52.5, and 76.8%, respectively. The main metabolites after the CRO degradation were acetic acid, succinate, pyruvate, and acetaldehyde. Pretreatment of treated BSD mixed with CRO enhanced the total methane yield (162 L/kg VS) by 82.7% and biomass reduction by 54.7% compared to the untreated substrate. CRO showed a toxicity decrease of >90%, suggesting the efficiency of constructed bacterial consortia in bioremediation and biofuel production.

Pretreatment for biorefineries: a review of common methods for efficient utilisation of lignocellulosic materials

The implementation of biorefineries based on lignocellulosic materials as an alternative to fossil-based refineries calls for efficient methods for fractionation and recovery of the products. The focus for the biorefinery concept for utilisation of biomass has shifted, from design of more or less energy-driven biorefineries, to much more versatile facilities where chemicals and energy carriers can be produced. The sugar-based biorefinery platform requires pretreatment of lignocellulosic materials, which can be very recalcitrant, to improve further processing through enzymatic hydrolysis, and for other downstream unit operations. This review summarises the development in the field of pretreatment (and to some extent, of fractionation) of various lignocellulosic materials. The number of publications indicates that biomass pretreatment plays a very important role for the biorefinery concept to be realised in full scale. The traditional pretreatment methods, for example, steam pretreatment (explosion), organosolv and hydrothermal treatment are covered in the review. In addition, the rapidly increasing interest for chemical treatment employing ionic liquids and deep-eutectic solvents are discussed and reviewed. It can be concluded that the huge variation of lignocellulosic materials makes it difficult to find a general process design for a biorefinery. Therefore, it is difficult to define "the best pretreatment" method. In the end, this depends on the proposed application, and any recommendation of a suitable pretreatment method must be based on a thorough techno-economic evaluation.