Value-Added Use of Waste PET in Rubberized Asphalt Materials for Sustainable Pavement

Waste poly(ethylene terephthalate) (PET) drinking bottles and end-of-life scrap rubber tires are common municipal solid wastes discarded and produced every day, which are usually disposed of in landfills and stockpiles, occupying a great quantity of land and causing serious environmental issues. This study aims to first turn waste PET into two value-added derived additives under the chemical treatment of two amines, namely triethylenetetramine (TETA) and ethanolamine (EA), respectively, and then adopt them in association with crumb rubber (CR) to modify virgin bitumen for preparing various rubberized asphalt mixtures. Subsequently, the high- and low-temperature properties of the rubberized binder modified by PET additives (PET-TETA and PET-EA) were comparatively characterized through dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests, while the rutting resistance, fatigue resistance, and dynamic modulus of the further fabricated mixtures were evaluated and validated through mixture tests. The results obtained indicate that 2 wt.% PET-TETA and PET-EA contribute to increase the rutting failure temperature of asphalt rubber from 82.2 °C to 85.5 °C and 84.2 °C, respectively, retaining the high grade of PG 82; the low-temperature grade of asphalt rubber slightly decreased from PG-28 to PG-22 as the additive was added; the rut depth slightly changed from 3.10 mm to nearly 3.70 mm; and PET-TETA exhibits the potential to be capable of extending the fatigue life of asphalt rubber in contrast with PET-EA at different stress levels within 450 kPa. Based on the findings of this study, the developed recycling approach is considered to be applicable to not only alleviate the environmental concerns caused by the landfills and stockpiles of those wastes but also make them valuable for building more durable pavement.

Thermo-economic analysis of the potential for electricity generation by integrating a Rankine cycle with municipal solid waste incineration

Municipal Solid Wastes generated by human activities increase as the population grows; in Ocaña city, Norte de Santander, Colombia, these wastes reach a monthly production of about 2660 tons, made up of 65.6% waste food, 15.3% plastics, 9.9% toilet paper, 3.6% paperboard, 2.6% textile residues, 1.6% paper, 0.8% wood wastes, and 0.1% rubber. This work estimates the energy potential from municipal solid wastes for electricity generation and their production costs. A multicriteria decision analysis allowed selecting the best technology for the wastes processing based on their energy content. For the evaluated criteria, the incineration process showed priority. A model developed in the engineering equation solver software allowed calculating the electrical energy potential by integrating the incineration process with a Rankine cycle. By implementing a thermo-economic assessment, the electricity generation costs were determined, where the inversion, installation, operation, and maintenance costs were considered. 1974 KW of electrical power with generation costs of $300/KWh and a payback period of 2.5 years show the feasibility of this process.

Degradation of polystyrene by tropical bacterial and fungal isolates

Plastic waste is one of the major contributing factors to the growth of municipal solid wastes globally. It is a threat to public health and negatively impact the aquatic and terrestrial animals due to its persistence in the environment. Bacterial and fungal isolates were tested for their ability to degrade polystyrene. The cultures were grown on mineral salts medium supplemented with polystyrene as the sole carbon source in 250 mL conical flasks. The polystyrene reduced from 1 g (week 0) to 0.7g (week 7). Statistical analysis of variance (one-way ANOVA) shows a significant difference between the reduction in weight of polystyrene in the experimental flask compared to the control (P<0.05). Gas chromatography mass spectrometry analysis of biodegradation products shows that some toxic polystyrene constituents such as O-xylene, cis-9-hexadecenal and 3-phenol pentadecyl were removed.

Biorefinery Based on Waste Biomass

In a broad sense, all materials with a biological origin can be called biomass, which includes those materials that have been obtained from the direct conversion of solar energy, such as plants and crops, their residues, the materials obtained from their industrial transformation as well as subproducts and residues and the organic fraction of the municipal solid wastes [...]

High prevalence of Antibiotic Resistance Bacteria isolated from Municipal Solid Waste Dumpsite, Bahir Dar, Ethiopia

Background The emergence of antibiotic resistance (ABR) among environmental microbes has been challenging global health. ABR can be transferred to human-associated bacteria aggravating the spread of antimicrobial resistance. Due to poor solid waste disposal practices, municipal solid waste dumpsite (MSWDS) can be a reservoir for antimicrobial resistant microorganisms, such as bacteria. This study aimed to assess the prevalence of antibiotic resistance (ABR) bacteria at Bahir Dar city MSWDS. Methods Soil samples were collected from three randomly selected sites within the dumpsite from November 2020 to May 2021. Bacteria were isolated, identified and tested for ABR using standard procedures. Results In this study, 71 distinct colonies were isolated and identified to ten bacterial genera based on cultural characteristics and biochemical tests. The pooled antibiotic résistance rate was 85.9%. Resistance to the tested antibiotics ranged between 0% for erythromycin and 100% for amoxicillin among the bacterial isolates. High proportions of the isolates were found to be resistant to amoxicillin (100%), vancomycin (87%) and nalidixic acid (73.3%). Substantial proportions of the isolates were also resistant to Streptomycin (54.5%), sulfonamide (50%) and tetracycline (48.5%). On the other hand, high sensitivity rates to erythromycin (90.91%), ciprofloxacin (83.10%), chloramphenicol (77.46%) and gentamicin (63.49%) were recorded. All isolates related to Staphylococcus spp., and most isolates related to Pseudomonas, Escherichia, Klebsiella, Salmonella, Enterococcus, Citrobacter, Shigella and Proteus species were resistant at least to one antibiotic drug. The overall multidrug resistance (MDR) rate was 49.3%, and a high rate of MDR was demonstrated among isolates related to Escherichia spp. (75%), Staphylococcus spp. (68.8%), Pseudomonas spp. (62.5%) and Klebsiella spp. (60%), where each isolate resisted at least 5 antibiotic drugs. Conclusion From the present study, it can be concluded that a high incidence of ABR exists in Bahir Dar city MSWDS. The occurrence of the high level of ABR to commonly used antibiotics in this study demands a proper waste management system, as well as surveillance programs to monitor for antimicrobial resistance determinants in municipal solid wastes. Moreover, detailed studies on the isolates and ABR genes will give a better insight into the prevalence of ABR in the waste dumpsite.