ABSTRACT
There is a worldwide continuous increase in energy consumption. As reported by the U.S. Energy Information Administration (2016), it has been estimated to increase by 48% within 2012–2040. The transportation sector alone consumes approximately 25% of energy and estimated to increase by 1.4%/year within 2012–2040. The worldwide consumption of energy is mainly from nonrenewable sources (petroleum, natural gas, and coal), which approximately represent 83%, and nearly half of which comes from crude oil (Yi et al., 2019). The rest of energy demands are covered by renewable sources, such as biofuels, hydropower, solar energy, wind energy, etc. (Misra et al., 2018). However, there is a worldwide decrease in the high grade oil reserves, which are characterized by low viscosity and low asphaltene, sulfur, and nitrogen contents (Alves et al., 2015). This consequently led to the increase in the generation of polluting gases, which adds to the problem of global climate change and adversely affected the human health. The presence of sulfur in motor fuels has critical harming effect on the catalytic converters in motorized engines, increasing the combustion-related emissions, that is, the particulate matters (PMs), CO, CO2, SOx, and NOx , which, consequently, increases global warming and air and water pollution (Srivastava, 2012; Abd Al-Khodor and Albayati, 2020). Moreover, high concentration of sulfur in fuels dramatically decreases the efficiency and lifetime of emission gas treatment systems in cars (Mužic and Sertié-Bionda, 2013). Incomplete combustion of fossil fuels causes emission of aromatic sulfur and nitrogen compounds; oxidation of these compounds in the atmosphere would lead to the aerosol of sulfuric and nitric acids (Porto et al., 2018). For example, NOx emission is significantly increased by 66%, corresponding to an increase in sulfur content of gasoline from 40 to 150 mg/L. It has been reported that approximately 73% of the produced SO2 is from anthropogenic origin and 282is due to the combustion of petroleum and its derivatives. The NOx and CO2 are thought by many to be the primary causes of “chemical smog” as well as “greenhouse gas” (GHG) accumulation. It has also been reported that sulfur is the main cause of emissions of PM. All of those aforementioned harmful emissions affect the stratospheric ozone, increasing the hole in the Earth’s protective ozone layer (Larentis et al., 2011). It has been reported that approximately 2% sulfur in diesel fuel can be directly converted to PM emissions. The PM and SOx are known to be carcinogenic. The visible, dark black component of smoke is carbon that has incompletely burned. The soot resulted from the use of the lower quality fuel (i.e., less refined one), which contains a large amount of mutagenic and carcinogenic polyaromatic hydrocarbons (PAHs). Diesel exhaust is considered the most carcinogenic exhaust and accounts for approximately 25% of all smoke and soot in the atmosphere. It has been reported that relatively high concentration of SO2 (>100 ppm) expresses harmful effects on the human respiratory system, where it can cause mortality within short time exposure to 400–500 ppm. Besides, very low concentrations of 1–2 ppm SO2 would be enough to express sever damage to plant (Schmidt et al., 1973). Moreover, upon the emissions of SO2 and NO2 in the atmosphere, they react with hydrogen producing the weak sulfurous acid, strong sulfuric acid, and nitric acid, which is the main cause of acid rain and haziness that reduces the average temperature of the affected area and leads to climate change (Sadare et al., 2017). About 25% of the acidity of rain is due to the presence of nitric acid ( HNO3 ), and approximately 75% is related to the presence of sulfuric acid ( H2SO4 ) (see Scheme 6.1). Acid rain has many negative impacts on the ecosystem and environment; for example, it causes soil pollution, destroys green area, kills forests, and damages crops, leather, cars, and buildings. It also poisons lakes and rivers leading to a devastating effect on their fauna and flora and falling in fish population. Also, the presence of high levels of sulfate in water affects the human health, as it causes diarrhea and dehydration. Acid rains cause degradation of many soil minerals producing metal ions that are then washed away in the runoff, causing the release of toxic ions, such as Al3+ , into the water streams; moreover, loss of important minerals, such as Ca2+ (see Scheme 6.1), from the soil would kill trees and damage crops and cause solid erosion. Acid rains have also a negative impact on building and monuments.
