Prospects and technological advancement of bioethanol ecofuel production

Energy, the economy, and the environment are the key drivers for the advancement of modern technologies for the community [1, 2]. The nonrenewable fossil fuels, for example petrol, diesel, crude oil, natural gas, etc., are the main sources of energy in the world. The global energy consumption of fossil fuels is increasing significantly due to rapid global industrialization and motorization [3]. In 2017, global primary energy consumption reached 13,511.2 million tons of oil equivalent (Mtoe), of which oil shares were about 34.21% (4621.9 Mtoe) of the total consumption [4]. Fossil fuel accounts for nearly 85.18% of the total global energy consumption, approximately half of which is used by the transport sector. Considering the current consumption rate of fossil fuels, the reserve of fossil fuels is expected to be diminished in the next 40–50 years [5]. The high cost of fossil fuels and environmental pollution are also limiting the use of fossil fuels and forcing us to harness alternative solutions. The utilization of fossil fuels in vehicles is responsible for more than 70% of the world’s total carbon monoxide (CO) emissions, 40% of all nitrogen oxide (NOx) emissions, 19% of all carbon dioxide (CO2) missions, and 14% of all greenhouse gas emissions [6]. One gallon of gasoline emits approximately 8 kg of CO2. In 2011, global CO2 emissions reached about 34 billion tons, causing a global carbon emission cost of more than $1.2 trillion per year [7]. Therefore, the emphasis is on the production of environmentally sustainable and low-cost fuels as alternatives to gasoline. Bioethanol is a nonpetroleum-based renewable and sustainable liquid fuel that is considered a promising option to meet the increasing energy crisis. Although ethanol contains lower energy content compared to gasoline (66%–68% of pure gasoline), the high octane number (106–110) of ethanol increases the performance of the gasoline-ethanol blend [8, 9]. Moreover, bioethanol contains higher oxygen content (roughly 34.7%) compared to no oxygen in gasoline [10]. The high oxygen content in bioethanol leads to clean combustion [11]. Consequently, the combustion of bioethanol reduces the emission of toxic substances when compared with gasoline combustion. It is estimated that bioethanol can reduce up to 90% of CO2 and 60%–80% of SO2 emissions when blended with 95% gasoline fuel [12]. Table 8.1 shows the comparison of the GHG emission and energy intensity among gasoline and various bioethanols. Therefore, bioethanol is considered the cutting-edge technology for the production of low-emission renewable energy. In addition to these, the higher heat of vaporization of ethanol enhances the volumetric efficiency of gasoline when blended with ethanol [16]. However, the selection of a suitable microorganism, the harnessing of promising feedstocks, and the development of proficient bioethanol technology are the key challenges. In recent years, research and development have been carried out for developing bioethanol technology that is feasible for commercial implementation. In this study, an overview of bioethanol as an ecofuel, including the history, potential resources, current technological status, challenges, and future scopes, is presented. The chapter is structured as follows: Section 8.2 highlights the historical background of ethanol production. Section 8.3 presents a brief description of current bioethanol production technology. Section 8.4 discusses the major bioethanol feedstock potential and current global cellulosic ethanol production plant status in detail. Moreover, the challenges of the existing technologies and future prospects for cellulosic ethanol production are presented in Section 8.5.