The upsurge in energy needs is the primary influencing factor for the shift of attention from conventional hydrocarbon resources to unconventional resources. In the process of exploiting unconventional oil resources such as oil sands, priority pollutants such as heavy metals are released into the environment. Thus, there are health and environmental risks associated with exploration and mining practices. This study seeks to present an overview of the health and environmental effects of these toxic metals in oil sands. Predominantly, the sources of these pollutants in oil sands are biogenic processes and weathering of source rocks. The toxicity of metals is dependent upon the nature of the metals as well as its affinity to bond with the silicate matrix. The consumption of plants and water from rivers, lakes, and streams with proximity to oil sand deposits could pose severe health risks to consumers, as significant amounts of Hg and other toxic metals are leached during oil recovery and other developmental processes. This review pointed to the use of membrane-based processes and other integrated approaches as vital remediation strategies employed for the restoration of resources to their pristine state and metal recovery. It is recommended that exploration practices and technologies should be improved towards the reduction of on-site metal pollution or off-site metallic contamination during refining or waste management.

Fly ash (FA) is a solid waste generated from coal combustion processes every year from thermal power plant. FA was considered as a problem for the environment, but also proves to be beneficial for the agricultural crops. This review begins with the utilization of FA as a soil ameliorant, its role in enhancing the plant growth and impact of elemental uptake from FA on plant growth. FA improves the physical, chemical and biological property of the soil which thereby enhances the crop productivity. Then, it focusses on phytotoxicity of various heavy metals in plants such as chromium, arsenic, lead, zinc, etc., followed by analyzing the defense mechanism of the plants against these heavy metal stresses which is due to the presence of toxic heavy metals present in FA resulting in the generation of reactive oxygen species which further causes oxidative stress. Finally, the review analyzes the influence of heavy metals on the antioxidative system of various plant species which helps in understanding the usage of optimum concentration of FA amendment in the soil for plant cultivation and to further explore the key features regulating the heavy metal damage and utilization of FA in agriculture.

This paper makes a novel attempt to test the validity of the environmental Kuznets curve hypothesis in the context of Bangladesh using deforestation propensities as indicators of environmental adversities and controlling for energy consumption, agricultural land coverage and population growth rate. Using annual frequency data from 1972 to 2018, the short- and long-run elasticity estimates from the autoregressive distributed lag-error correction modeling approach provide statistical support to the nonlinear inverted-U-shaped association between economic growth and deforestation practices in Bangladesh. Thus, the results validate the deforestation-induced environmental Kuznets curve hypothesis in the context of Bangladesh. The elasticity estimates also reveal that energy consumption promotes deforestation activities in the long run but not in the short run. Besides, higher population growth rate and agricultural land expansion are found to account for greater deforestation propensities both in the short and long runs. Furthermore, the vector error correction model and the Hacker and Hatemi-J Granger causality exercises reveal the causal impacts of economic growth on deforestation propensities, both in the short and the long runs. Therefore, the overall results, in a nutshell, indicate a trade-off between economic and environmental welfares during the initial phases of economic growth in Bangladesh which can be anticipated to fade away in the long run. The overall results impose critically important policy implications regarding effective means to reduce deforestation practices in Bangladesh.

Field study was conducted during winter seasons (November–March) of 2015–2016 and 2016–2017 at the Research Farm of Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India, with an aim to investigate the crop productivity, energy and C budget, carbon footprint and economic sustainability of peanut cultivation fertilized with varied levels of nitrogen under polythene mulching. The experiment laid out in split-plot design comprised of two mulching practices as the main-plot treatments and seven doses of N with or without supplementation of Rhizobium bio-fertilizer as the sub-plot treatments. Fertilization with 100% recommended dose of nitrogen (RDN) +  Rhizobium under polythene mulching brought about significant enhancement in pod yield over other nutrient management practices. The effects on yield attributing characters were similar to that of pod yield. Energy indices namely net energy gain, energy productivity, energy intensiveness and energy profitability were the highest with 100% RDN +  Rhizobium, irrespective of mulching situations. However, the maximum values of specific energy and nutrient energy ratio were recorded when the crop received 50% RDN with and without Rhizobium, respectively, under mulching and non-mulching situations. Human energy profitability was always greater under mulching situations over non-mulching. Total estimated carbon footprints improved with increase in N level from 0 to 100% RDN with Rhizobium under polythene mulching over non-mulching situations. Highest value of C sustainability index was also observed with polythene covering particularly with the application of 100% RDN +  Rhizobium. This treatment combination also proved its superiority with respect to economic benefits in peanut cultivation.

The integrated catalytic oxidation and biological treatment of the spent caustic wastewater (SCWW) discharged from the petrochemical industry were carried out in the present investigation. The SCWW was characterized by COD 19,246–21,054 mg/L, sulphide 4280–5092 mg/L, and phenol compounds 2349–2716 mg/L. The BOD/COD of the wastewater was around 0.196–0.216 mg/L, indicating a poor biodegradable nature. The integrated treatment scheme attempted in the present investigation comprised techniques such as catalytic functionalization oxidation reactor (CFOR), heterogeneous activated carbon Fenton catalytic oxidation (HAFCO), Fenton activated carbon catalytic oxidation (FACCO) and fluidized immobilized cell carbon oxidation (FICCO). The integrated catalytic reactors demonstrated 100% efficiency in removing sulphide, without emitting them into the atmosphere, 96.7% in removing phenol, 95.3% in removing COD and 99.2% in removing BOD. The removal of dissolved organics from SCWW by integrated oxidation process was confirmed through instrumental analysis such as UV–visible and Fourier transform infrared spectroscopy.

Tropical plants Jatropha curcas and Moringa oleifera produce non-edible oil seeds which can be considered as feedstock to produce biodiesel. Along the processing steps, several by-products are produced. This work is focused on the thermochemical use of Jatropha and Moringa husk in order to increase the overall value chain of their utilization. Comprehensive characterization studies and their assessment for calorific utilization are quite limited in the literature. The scope of the paper is a comprehensive fuel characterization based on the results, with focus on thermochemical utilization pathways. Proximate analysis shows that Jatropha and Moringa husk have low moisture content (9.19 and 6.25%, respectively) and ash (< 5%) and high content of volatile components. Higher values of C, N and S for M. oleifera in comparison with J. curcas husk were obtained. M. oleifera seed husk shows the highest LHV (20.83 MJ kg⁻¹). The ash melting analysis of husk shows melting points above 1500 °C. By simulation of the gasification process, the LHV, the amount of gas producer and energy output are estimated. The energy produced by simulation of gasification demonstrates that it is enough to cover the energy needs involved in a biodiesel facility with capacity of 800 L of biodiesel per day.