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Biochar (BC) was prepared by carbonizing sludge from agricultural lignocellulosic waste fermentation and then used to adsorb lambda‐cyhalothrin (LM), malathion (MA), and oxamyl (OX) as potential pesticides in agrochemical industrial wastewater. Additionally, the photodegradation performance of ZnO and ZnO/Fe was evaluated using various catalyst doses in a constructed parabolic solar collector reactor. The optimal ZnO catalyst dose and reaction time was 1.0 g/L and 135 min. OX, MA, and LM removal increased from 38%, 30%, and 24% in pristine ZnO to 55%, 70%, and 46.9% in the case of the addition of BC with ZnO (ZnO/BC), respectively. The doping of ZnO with iron did not improve the photodegradation efficiency due to the reduction of crystallinity and catalyst affinity towards the pollutants after introducing those ions. The mechanism of degradation was proposed, and the by‐products generated were identified. The total cost was estimated for pure ZnO, the addition of BC with ZnO (ZnO/BC), and the addition of BC with iron‐doped ZnO (ZnO/Fe/BC). The highest binding energy of −44.74 was recorded for BC–OX complex, followed by BC–LM at −42.97. The adsorption of LM, MA, and OX by ZnO/BC is primarily due to the hydrophobic interaction, hydrogen bonding, and π–π interaction. After three cycles of recycling ZnO/BC, the degradation efficiency remained 55–52.5% for OX, 70–65% for MA, and 46.9–42.8% for LM, indicating excellent reusability and stability of the composite catalyst. The low cost of the solar‐light‐driven ZnO/BC process may improve the technique's feasibility for large‐scale implementation. Pesticide removal using cost‐effective materials is critical in industrial wastewater treatment. We conducted a comprehensive practical and computational study on pesticide removal in this manuscript, as well as an economic analysis of the process's cost. Herein, the performance of pure ZnO, ZnO loaded on biochar (BC; ZnO/BC), and ZnO doped with iron (ZnO/Fe) besides the addition of BC (ZnO/Fe/BC) for the degradation of three types of pesticides was evaluated.

In arid regions, agricultural production is critically challenged by water scarcity, elevated temperatures, and high resource dependency. This study assesses an integrated water-energy-food (WEF) nexus approach tailored for small-scale farming to optimize resource use through innovative combinations of open-field, greenhouse, and agrivoltaic systems. Comparing typical farming practices (base case) with a WEF-enhanced scenario, we measured water and power consumption, crop yield, economic returns across three seasons, and conducted a comprehensive cost-benefit analysis. The WEF scenario demonstrated a 5.4% reduction in water use due to efficient irrigation techniques and produced all required power from solar energy. Crop production and profits were higher under the WEF scenario, in which the net profit per unit area was $1.1 greater. The utilization of a reverse osmosis desalination unit was pivotal in reducing water costs and enhancing economic viability. Notably, the study highlighted significant CO2 emission reductions with the WEF approach, underscoring its potential in climate change mitigation. By maximizing land use, diversifying crop types, and extending growing periods, the WEF nexus approach presents a viable solution for enhancing sustainability, profitability, and resource security in arid environments. This research offers crucial insights for stakeholders in optimizing agricultural production within the constraints of water and energy resources.

Solid wastes from domestic, industrial and agricultural sectors cause acute economic and environmental problems. These issues can be partly solved by anaerobic digestion of wastes, yet this process is incomplete and generates abundant byproducts as digestate. Therefore, cultivating mixotrophic algae on anaerobic digestate appears as a promising solution for nutrient recovery, pollutant removal and biofuel production. Here we review mixotrophic algal cultivation on anaerobic waste digestate with focus on digestate types and characterization, issues of recycling digestate in agriculture, removal of contaminants, and production of biofuels such as biogas, bioethanol, biodiesel and dihydrogen. We also discuss applications in cosmetics and economical aspects. Mixotrophic algal cultivation completely removes ammonium, phosphorus, 17β-estradiol from diluted digestate, and removes 62% of zinc, 84% of manganese, 74% of cadmium and 99% of copper.

The world is experiencing an energy crisis and environmental issues due to the depletion of fossil fuels and the continuous increase in carbon dioxide concentrations. Microalgal biofuels are produced using sunlight, water, and simple salt minerals. Their high growth rate, photosynthesis, and carbon dioxide sequestration capacity make them one of the most important biorefinery platforms. Furthermore, microalgae's ability to alter their metabolism in response to environmental stresses to produce relatively high levels of high-value compounds makes them a promising alternative to fossil fuels. As a result, microalgae can significantly contribute to long-term solutions to critical global issues such as the energy crisis and climate change. The environmental benefits of algal biofuel have been demonstrated by significant reductions in carbon dioxide, nitrogen oxide, and sulfur oxide emissions. Microalgae-derived biomass has the potential to generate a wide range of commercially important high-value compounds, novel materials, and feedstock for a variety of industries, including cosmetics, food, and feed. This review evaluates the potential of using microalgal biomass to produce a variety of bioenergy carriers, including biodiesel from stored lipids, alcohols from reserved carbohydrate fermentation, and hydrogen, syngas, methane, biochar and bio-oils via anaerobic digestion, pyrolysis, and gasification. Furthermore, the potential use of microalgal biomass in carbon sequestration routes as an atmospheric carbon removal approach is being evaluated. The cost of algal biofuel production is primarily determined by culturing (77%), harvesting (12%), and lipid extraction (7.9%). As a result, the choice of microalgal species and cultivation mode (autotrophic, heterotrophic, and mixotrophic) are important factors in controlling biomass and bioenergy production, as well as fuel properties. The simultaneous production of microalgal biomass in agricultural, municipal, or industrial wastewater is a low-cost option that could significantly reduce economic and environmental costs while also providing a valuable remediation service. Microalgae have also been proposed as a viable candidate for carbon dioxide capture from the atmosphere or an industrial point source. Microalgae can sequester 1.3 kg of carbon dioxide to produce 1 kg of biomass. Using potent microalgal strains in efficient design bioreactors for carbon dioxide sequestration is thus a challenge. Microalgae can theoretically use up to 9% of light energy to capture and convert 513 tons of carbon dioxide into 280 tons of dry biomass per hectare per year in open and closed cultures. Using an integrated microalgal bio-refinery to recover high-value-added products could reduce waste and create efficient biomass processing into bioenergy. To design an efficient atmospheric carbon removal system, algal biomass cultivation should be coupled with thermochemical technologies, such as pyrolysis.

The nations that comprise the Gulf Cooperation Council (GCC) are located in one of the most water-stressed regions in the world. This region has faced serious socioeconomic and environmental development issues as a result of its increasing water demand over time. The extreme aridity, high rates of evaporation, and scarcity of nonrenewable groundwater resources in the GCC countries pose a significant threat to food security. This study aims to explore the impact of climate change on the potential availability of irrigation water in the State of Kuwait, which serves as an example of all GCC nations. A modeling scheme using CropWat8 was developed to study the impact of four climate change scenarios (encompassing the past, present, and future) on the net and gross irrigation water requirements (NIWR and GIWR) for selected agricultural crops, while also determining optimum irrigation schedules. Scenario 1 represented past climate conditions (1996–2006), while Scenario 2 represented the current situation (2007–2021). Projected scenarios (3 and 4) were analyzed using Representative Concentration Pathways (RCP) 4.5 and RCP 8.5, which were adopted by the IPCC to project the concentrations of greenhouse gases (GHG) emissions for 2060. The simulation results showed that compared with the current GHG levels, the increase in GHG emissions also increased the demand for NIWR by a minimum of 8.2% and a maximum of 15% for the same agricultural areas and cropping patterns. The measured GIWR in the field was 1915 m3, while the simulated NIWR was 1724 m3. With a drip irrigation efficiency of 90%, the model adequately demonstrated the validity of the CropWat8 package for simulating the climate impact on crop water requirements with a precision of approximately 92.2%. These findings suggest that the GCC countries should develop strategies to minimize GHG emissions and adopt innovative solutions for better management of water resources.

The rising occurrence of emerging contaminants in sludges both inhibits the anaerobic digestion of sludges and induces health issues when sludges are recycled in agriculture, calling for methods to remove contaminants. Here we review emerging pollutants in wastewater treatment plants, before and after anaerobic digestion. We present their inhibitory effects and remediation methods to alleviate inhibition. Pharmaceuticals have been detected in about 50% of the sludge samples. Sewage sludge contaminants include 19% of diuretics, 16–21% of lipid-modifying agents, hydrochlorothiazide, diclofenac, furosemide, clarithromycin, atorvastatin, and carbamazepine. Levels of antibiotics, azithromycin, ciprofloxacin, and estrone range from 500 to 600 ng/g in sludges from wastewater treatment plants. Remediation methods comprise electrooxidation, ultrasonication, thermal hydrolysis, ozonation, and bioaugmentation. Fermenting the sludges with acidogenic bacteria reduces the level of emerging pollutants in the supernatant. Nonetheless, liquid digestates still contains emerging pollutants such as sunscreen octocrylene at 147 ug/L and acetaminophen at 58.6 ug/L. As a result, pretreatment of sludge containing emerging pollutants is required.

The feasibility, cost, and air quality impacts of using electrical grids to shift water use from drought-stricken regions to areas with more water availability were examined. Power plant cooling represents a large portion of freshwater withdrawals in the United States, and shifting where electricity generation occurs can allow the grid to act as a virtual water pipeline, increasing water availability in regions with drought by reducing water consumption and withdrawals for power generation. During a 2006 drought, shifting electricity generation out of the most impacted areas of South Texas (∼10% of base case generation) to other parts of the grid would have been feasible using transmission and power generation available at the time, and some areas would experience changes in air quality. Although expensive, drought-based electricity dispatch is a potential parallel strategy that can be faster to implement than other infrastructure changes, such as air cooling or water pipelines.

The impact of partial and full COVID lockdowns in 2020 on vehicle miles traveled (VMT) in Kuwait was estimated using data extracted from the Directions API of Google Maps and a Python script running as a cronjob. This approach was validated by comparing the predictions based on the app to measuring traffic flows for 1 week across four road segments considered in this study. VMT during lockdown periods were compared to VMT for the same calendar weeks before the pandemic. NOx emissions were estimated based on VMT and were used to simulate the spatial patterns of NOx concentrations using an air quality model (AERMOD). Compared to pre-pandemic periods, VMT was reduced by up to 25.5% and 42.6% during the 2-week partial and full lockdown episodes, respectively. The largest reduction in the traffic flow rate occurred during the middle of these 2-week periods, when the traffic flow rate decreased by 35% and 49% during the partial and full lockdown periods, respectively. The AERMOD simulation results predicted a reduction in the average maximum concentration of emissions directly related to VMT across the region by up to 38%, with the maximum concentration shifting to less populous residential areas as a result of the lockdown. Graphical Abstract

This paper presents an integrated framework in which an air quality dispersion model is combined with an economic dispatch model to address the environmental tradeoffs of a cost-optimized fuel allocation strategy. A unit commitment dispatch model was developed to re-allocate fuel between power generation and desalination plants. Then, an air quality dispersion model was run for a 1-year period to simulate the spatiotemporal transport of pollutants and the possible formation of air pollution hotspots. The results showed that optimizing fuel allocation can reduce the associated fuel cost by as much as 16.5% of the total cost (1.08 billion USD). The optimized fuel allocation approach resulted in reducing the base case emissions of NOx, SO 2 , CO, and PM 10 by 25%, 4.6%, 3.1%, and 7.6%, respectively. However, the air quality impact of the optimized fuel allocation scheme was not as favorable. The 1-h-averaged maximum concentration of SO 2 increased, and NOx concentrations were slightly above the allowable limits. Although fewer pollutants were emitted over the study period in the optimized fuel allocation case, the variability in how fuel was allocated between power and desalination plants concentrated emissions near residential areas. As a result of this trend, the maximum 1-h concentrations of all pollutants increased, with increases ranging from 1% for CO to 29% for PM 10 . In addition, the total number of hourly SO 2 concentration violations increased dramatically, leading to additional hotspot areas. Therefore, the effectiveness of any environmental-economic fuel dispatch strategy should be tested based on additional indicators such as the allowable limits of pollutant concentrations and not exclusively the overall emissions of the system. This approach could promote the selection of the most economic fuel dispatch method while simultaneously considering regional air quality impacts.

The prediction of dispersion of gases emitted from rooftop stacks in a built environment is important for preventing or minimizing their harmful effects on human health. In this study, the wind flow and dispersion of exhaust gas emitted from rooftop stacks on buildings in an urban environment under different atmospheric thermal stabilities were investigated using numerical simulations. The wind flow field and dispersion contaminants were simulated using a computational fluid dynamics model with the k-ε turbulent schemes being resolved by the Reynolds-averaged Navier–Stokes approach. An isolated building was modeled under conditions of varying thermal stratification of the boundary layers (neutral, unstable, and stable conditions). The diffusion flow field within the building wake zone was investigated for various stack sites (center, right side, and left side). Experiments were conducted in a wind tunnel to validate the numerical simulation results, by using the data qualitatively and quantitatively. The numerical simulation results were consistent with the experimental observations. The results indicated that the pollutant concentration of the plume spread was high near the stack and decreased with increasing distance from the stack. Under stable conditions, the flow motion and separation increased in the wake zone, and the pollutant concentration of the lateral spread at the average human height decreased. Under unstable conditions, the flow of the vortex circulation was fast and strong, and the pollutant concentration of the vertical spread was high.