• Energy Research

At ethanol plants, the control of acetaldehyde emissions is accomplished by scrubbers and regenerative thermal oxidizers. However, their operation imposes substantial operating costs. Alternatively, two biotrickling filters were operated in parallel under acetaldehyde loadings ranging from 4 to 136 g m-3 hr-1. One filter was operated at room temperature while the other one was heated to 60 °C, to mimic hot drier emissions. The unheated filter maintained 100% removal efficiency up to 45.28 g m-3 hr-1 loading rate at 30-s empty bed residence time. Highest elimination capacity recorded was 112 g m-3 hr-1 at 83.2% removal efficiency. The heated filter achieved removal efficiency larger than 60% at influent concentrations of 200 ppmv and lower, however, removal was significantly lower at 400 and 600 ppmv influent concentrations. Performance was improved by reseeding with cooking compost resulting in increased thermophilic bacterial population. Main byproduct formed was acetic acid with traces of formic acid. Mathematical modelling was used to successfully describe acetaldehyde concentration profiles.

The treatment of gaseous contaminants, such as hydrogen sulfide (H2S), is often carried out with adsorbent materials that are disposed of after saturation. The reuse of such materials promotes sustainability and the reduction in unnecessary waste. Granular activated carbon (GAC) is a well-known adsorbent used to capture gaseous H2S which can be reused. It is hypothesized that it can also concentrate contaminants for future treatment, thereby reducing secondary treatment costs. Cyclic adsorption/desorption experiments were completed with samples of GAC to investigate the feasibility of implementing the concept of repeated H2S adsorption/desorption in the construction of a pilot odor control device. A column filled with GAC was exposed to a stream of H2S gas and then heated to 500 °C to regenerate the carbon. The concentration of H2S at the inlet and outlet of the column was measured at regular intervals. Three samples of GAC had an average adsorption efficiency of 82% over the course of three cycles and were regenerated to 70% of initial adsorptive capacity after one cycle, and 60% after two cycles. These results indicate that after being saturated with H2S, GAC can be regenerated at high temperatures, evidence that H2S may become concentrated during the process. Additional characterization experiments confirmed that the sulfur content of the carbon increased after adsorption and decreased after thermal regeneration. The procedures demonstrated in this experiment were further utilized with a pilot device designed to provide a low-cost method for reducing odors in landfill gas.

Ethanol is a significant source of energy as a biofuel; however, its production using corn involves the generation of harmful emissions from both fermentation tanks and dryers. Scrubbers control the emissions from fermentation tanks, while the emissions from the dryers are controlled by regenerative thermal oxidizers. Potential alternatives to these energy- and water-intensive technologies are biotrickling filters (BTFs). In this study, two BTFs were operated in parallel to treat formaldehyde and methanol emissions in a volumetric ratio of 4:1, one at 25°C (mesophilic), and the other at 60°C (thermophilic). The mesophilic BTF simulated emissions from fermentation tanks, while the thermophilic BTF simulated emissions from dryers. Both beds were operated at an empty bed residence time of ~30 s and influent formaldehyde concentrations of 20, 50, and 100 parts per million per volume (ppmv). Formaldehyde polymerization was reduced in this study by adding NaOH to pH levels of 7.0–7.4 and heating the solution to a temperature of 60°C. BTFs have successfully removed formaldehyde at typical ethanol plants emissions ~21 ppmv. The BTF technology have the potential in replacing the conventional air treatment methods used at ethanol plants. Implications: Currently, ethanol plants remove and treat hazardous air pollutants (HAPs) using wet scrubbers from the fermenter off-gasses and using thermal oxidizers to combust off-gasses. The utilization of biotrickling filters (BTFs) for HAP removal generally and formaldehyde particularly has wide implication in the field of renewable energy. Utilizing BTFs in the 200+ ethanol plants in USA will save cost and reduce water and energy needs significantly. BTFs can reduce an ethanol plant’s carbon intensity (CI) by 1 to 3 g CO2/MJ. This can result in roughly $50 million per year in additional revenue in Nebraska for instance.

Due to intensive utilization and extensive production, plastic waste is becoming a serious threat to the environment and human health. The situation is even worse in countries such as the United Arab Emirates (UAE), where single-use plastic water bottles add to the load of plastic pollution. The main objective of this survey was to assess the extent of bottled water utilization by the UAE residents and their awareness of the environmental concerns arising from single-use plastic bottles. The aim was also to evaluate their willingness to shift towards using biodegradable plastic bottles. This study involved the feedback of 2589 respondents living in the UAE. The eigenvalue decomposition (EVD) was applied to determine the most responsible variables explaining the variability of our data set. A chi-square analysis was also used to determine the significance among the responses. Most of the respondents to this survey were UAE nationals (79.8%) of ages ranging from 21 to 35 years (42%), who were educated, with most holding a university degree (69.6%). Regardless of their gender, age, occupation, education, and income, a large group of respondents (40.7%) was concerned about the impact of their purchased items on the environment; however, the frequency of plastic products recycled was observed to be low (49.7%). According to the findings of this survey, 42.4% of the respondents were likely to purchase 100% biodegradable bottles, and about 70% of the respondents expressed a willingness to spend at least AED 1 more for purchasing 100% biodegradable bottles.

Wastewater with 0.2, 0.4, 0.8, 1.0 mg/L free chlorine was biologically treated using co-immobilized microalgae/bacteria. In contrast, non-pretreated wastewater was treated with beads (control) and blank beads (blank) under the same operating condition. Results showed that NaClO pretreatment removed 8-33% total nitrogen (TN), 31-45% true color and 0.7-2.5 log CFU/mL aerobic-bacteria. At the end of treatment, maximum algal biomass (2,027 dry weight mg/L) was achieved with 0.2 mg/L free chlorine. Bacterial growth in wastewater was decreased by NaClO pretreatment before reaching 7.2-7.7 log CFU/mL on the fifth day. Beads with microorganisms (control) removed 15% more chemical-oxygen-demand (COD), 16% more TN, and 13% more total phosphate (PO43-) than blank. Pretreatment with 0.2 mg/L free chlorine increased TN removal from 75% to 80% while pollutants removal was substantially decreased with 0.4-1.0 mg/L free chlorine. Considering algal biomass growth and pollutants removal, 0.2 mg/L free chlorine pretreatment was recommended for microalgae/bacteria co-immobilized system.

Research on self-healing concrete has flourished in recent years. This paper aims to comprehensively understand the current research situation and future development directions of self-healing concrete. It summarizes and analyzes the publications on self-healing concrete from 1974 to 2021 to reveal the current key research topics and development trends and identifies the most productive research constitutes. The bibliometric analysis software Biblioshiny was used to analyze 1433 documents written by 2961 authors and published in 450 sources retrieved from Scopus. The analysis included an overview of the leading information and an analysis of the authors, countries, universities/institution, publications, and keywords. Results obtained from the author analysis suggest that tracking the work of the most productive authors is essential, as it will provide researchers with valuable information, such as possible leads and ideas for future research work and collaboration opportunities. Countries, universities/institutes, and publications analysis revealed that more collaboration leads to more exposure and a higher citation rate, significantly promoting self-healing research development. A keywords analysis highlighted the focus areas in self-healing concrete and presented potential gaps in the literature. The findings of this study will provide scholars with a comprehensive understanding of the current research work in the field of self-healing concrete and its future directions. Results can also benefit stakeholders in making effective decisions to direct the development of the self-healing industry.

An artificial neural network (ANN) approach with response surface methodology (RSM) technique has been applied to model and optimize the removal process of Brilliant Green dye by batch electrocoagulation process. A multilayer perceptron (MLP) - ANN model has been trained by four input neurons which represent the reaction time, current density, pH, NaCl concentration, and two output neurons representing the dye removal efficiency (%) and electrical energy consumption (kWh/kg). The optimized hidden layer neurons were obtained based on a minimum mean squared error. The batch electrocoagulation process was optimized using central composite design with RSM once the ANN network was trained and primed to anticipate the output. At optimized condition (electrolysis time 10 min, current density 80 A/m2, initial pH 5 and electrolyte NaCl concentration 0.5 g/L), RSM projected decolorization of 98.83% and electrical energy consumption of 14.99 kWh/kg. This study shows that the removal of brilliant green dye can be successfully carried out by a batch electrocoagulation process. Therefore, the process is successfully trained by ANN and optimized by RSM for similar applications.

Due to rising population and industrialization, two-thirds of the world’s population may suffer water scarcity by 2025. Biodesalination is a promising sustainable practice targeting salt removal from seawater by micro-organisms, using lower energy consumption and resulting in less environmental impact. This study examined the evolution of biodesalination from 2007 to 2022 by applying bibliometric analysis. A scoping review was also conducted through content analysis of biodesalination publications. Using the Scopus database, the research trends, major contributors in the field, and recent advancements were identified. The study investigated a total of 80 peer-reviewed journal articles in the field of biodesalination. Results of the bibliometric analysis revealed that publications peaked in 2022 and citations in 2021, with values of 14 and 473, respectively. Results also revealed that the research trend in biodesalination is leaning towards the use of microbial desalination cells. Furthermore, advancements in the field focused on enhancing the nutrient medium to yield better growth rates for algae and cyanobacteria and improve desalination efficiencies to up to 40%. Other modifications focused on introducing microbial strains with increased salinity tolerance. Finally, an outline of future research potential was presented, focusing on nutrient medium modifications, specifically the substitution of chloride and sodium salts in the medium with nitrate and potassium minerals.