The field of bioethanol production has seen rapid advancements in the past few decades. Despite the advancements, bioethanol production’s recent trends cannot prove effective and efficient transportation fuel. Fossil fuels, which currently power-ups most energy demands, from nonrenewable energies, meaning it will bring adverse effects to the environment, including ozone layer depletion and global warming. It makes bioethanol the best alternative to fossil fuels, owing to the fact than it is considered carbon-neutral. In some parts of the world, bioethanol is utilized as an alternative fuel by using the lignocellulosic (LC) residues, and prioritizing its production as better feedstocks available could fulfill the void created in the transportation fuel sector. Separate hydrolysis and co-fermentation (SSCF) and Pre-hydrolysis and simultaneous saccharification and co-fermentation (PSSCF) are superior to all techniques to achieve saccharification, hexose, and pentose fermentation in a one-pot reaction. For the feedstock modification, the genome engineering and cell wall modification are advanced methods so far. As of not long ago, there is no cost-effective and financially achievable pretreatment technique for the removal of lignin that could be industrialized to satisfy the worldwide requirement for bioethanol. In this review we provide the present scenario of energy demand and advancement on bioethanol technology and challenges. Mainly, altering the LC biomass composition, the robust enzyme that enables to hydrolyzed and maximum fermentable sugar yield, and effectively fermenting bacteria and yeast, which is genetically engineered for simultaneous fermentation with the high rate, is future stepping research which should be emphasized in the bioethanol industry. Graphical abstract

The spread of COVID-19 is posing significant challenges to the household (HH) waste management sectors putting waste personnel and concerned bodies under massive pressure. The chain of collection, segregation, recycling, and disposal of household generated wastes is interrupted. This study aimed to assess how the household waste management chain was disrupted by novel coronavirus in Nepal and find the perception of the people towards the existing household waste management system (HHWMS). A descriptive online survey was carried out among 512 people using a cross-sectional research design and data was collected through a self-administered questionnaire method. Both descriptive, as well as inferential tests, were conducted using SPSS software. The finding of this study showed that 62.3% of respondents were not satisfied with the present HHWMS. Furthermore, there was a significant association of the satisfaction level of household waste management during coronavirus outbreak with gender, waste volume change in lockdown, PPE for waste collectors, and education on waste handling techniques provided by the government sector at 5% level of significance (p < 0.05). Proper HH waste management has become a challenge, and to address this some innovative works such as awareness programs for people, health and hygiene related support to waste workers, and effective policy formulation and implementation should be done by the Government of Nepal.

The development of high-performance photocatalysts is vital for combating water pollution and microbial contamination. In this study, visible-light-active Z-scheme heterojunction nanocomposites composed of Co₃O₄ and Nb₂O₅ (CNNC) were synthesized via co-crystallization and subsequent high-pressure annealing to enhance photocatalytic and antimicrobial performance. Structural and optical analyses via XRD, FESEM, TEM, XPS, and PL confirmed the heterojunction formation between porous Co₃O₄ nanoparticles (CONP) and columnar orthorhombic Nb₂O₅ nanoparticles (NONP). The CNNC exhibited significantly improved photocatalytic activity, achieving degradation efficiencies of 95.1% for methylene blue, 72.6% for tetracycline, and 90.0% for Congo red within 150 min. Kinetic studies showed that CNNC’s rate constants were 367% and 466% of those of CONP and NONP, respectively. Moreover, CNNC demonstrated a strong antibacterial effect on Staphylococcus aureus and Escherichia coli with ZOI values of 9.3 mm and 6.8 mm, respectively. Mechanistic analysis revealed that the Z-scheme charge-transfer pathway improved charge separation and reduced electron–hole recombination, contributing to the promoted photocatalytic efficiency. The nanocomposite also showed robust stability and recyclability over five times. These results highlight the promise of CNNC as a bifunctional, visible-light-driven photocatalyst for pollutant decomposition and microbial control.

A facile two-step synthesis of ternary hetero-composites of ZnO, CuO, and single-walled carbon nanotubes (SWCNTs) was developed through a recrystallization process followed by annealing. A series of nanocomposites were prepared by varying the weight ratio of copper(II) acetate hydrate and zinc(II) acetate dihydrate and keeping the weight ratio of SWCNTs constant. The results revealed the formation of heterojunctions (ZnO–SWCNT–CuO, ZSC) of three crystal structures adjacent to each other, forming a ternary wurtzite-structured nanoparticles along with defects. Enhanced charge separation (electron-hole pairs), reduced band gap, defect-enhanced specific surface area, and promoted oxidation potential were key factors for the enhanced photocatalytic activity of the ternary nanocomposites. OH^• radicals were the main active species during dye degradation, and O₂^−• and h⁺ were also involved to a lesser extent. A type II heterojunction mechanism approach is proposed based on the charge carrier migration pattern. Among the synthesized nanocomposites, the sample prepared using copper(II) acetate hydrate and zinc(II) acetate dihydrate in a 1: 9 ratio (designated a ZSC3) showed the highest photocatalytic activity. ZSC3 achieved 99.2% photodecomposition of methylene blue in 20 min, 94.1% photodecomposition of Congo red in 60 min, and 99.6% photodecomposition of Rhodamine B in 40 min under simulated sunlight. Additionally, ZSC3 showed excellent reusability and stability, maintaining 96.7% of its activity even after five successive uses. Based on overall results, the ZSC sample was proposed as an excellent candidate for water purification applications.