**1. Introduction**

Maize, also known as corn, since its domestication from 9000 years ago, is one of the most important cereal crops globally, serving as a staple food for millions of people and a valuable feedstock for livestock [1]. Corn (dry grain) is annually cultivated on a projected 206 Mha of land worldwide, making it the second most extensively grown crop globally after wheat with a peak production and productivity of 1210 million tonnes and 5879 kg/ha, respectively [2]. Taking into consideration of area stagnation of wheat and rice, maize is set to overtake wheat in terms of acreage by 2030 [3]. Notably, the Americas, encompassing the United States, Brazil, and Argentina, are significant maize

producers due to their favorable climate, extensive agricultural infrastructure, and technological advancements along with other important maize-producing regions involving China, India and South Africa, where suitable agro-climatic conditions and dedicated cultivation efforts contribute to substantial maize yields [4]. Corn production plays a diverse and critical role in global food security, economic development, and agricultural sustainability. It is widespread across the globe, with specific regions emerging as major contributors to the global supply. Trend analysis has shown that the maize production has increasing significantly thanks to upsurge in productivity (by six times from 1961 to 2021) making it a potential crop for alternative use like biofuel (**Figure 1**).

Since being necessary is the essence of the invention, the impending energy crisis has sparked curiosity about the production of biofuel. In the upcoming years, there will be a dramatic increase in the global consumption of liquid petroleum. By 2025, the energy demand is predicted to increase by more than 50% if the current trend holds [5]. Most crucially, an endless need for finite petroleum resources cannot be a long-term viable solution. Therefore, we must begin working towards carrying a switch from the non-renewable energy source of carbon to renewable vis-à-vis sustainable bio-resources prior to situations starting to slip out of our purview. In this way, the corn-to-biofuel notion can serve as a road map.

Biofuel, derived from renewable biomass sources, has emerged as an important alternative to fossil fuels by diversifying the energy sources [6] due to its potential to mitigate climate change, enhance energy security, and promote sustainable development [7]. Because vegetation assimilates CO2 over its growth phase during the reaction of photosynthesis biofuels have been recognized as carbon-neutral energy sources [8]. In this context, biofuels, a healthier option to petroleum, are gaining popularity because they are environmentally friendly and compassionate to the environment. Utilizing these fuels may assist reduce environmental changes and the pollutants that come from automobiles. Biofuels are produced through various methods, including biomass conversion processes such as fermentation, pyrolysis, and transesterification. Biomass feedstocks can range from crops like sugarcane,

#### **Figure 1.**

*Area, production, productivity trend of corn from 1961 to 2021 (data collected from http://www.fao.org/faostat).*

**Figure 2.** *Percentage share of biofuel by different leading countries (data obtained from OECD-FAO, 2021 [13]).*

corn, and soybeans, to agricultural residues, forest residues, and even algae [9]. These feedstocks are transformed into liquid fuels, such as ethanol and biodiesel, or gaseous fuels like biogas. The two most prevalent kinds of biofuels employed nowadays are ethanol and biodiesel, which fall under the first generation of biofuels. Other types of biofuels include methanol, biodiesel, biogas, and Syngas. Ethanol is produced from cellulose-based feedstocks [10] such as corn, sugarcane, discarded potatoes, and others [11]. It is frequently used with petrol as an additional ingredient to raise the octane level and lower greenhouse gas emissions (GHG) [12]. With outputs totaling 1436 petajoules in 2021, the United States was the world's top manufacturer of biofuel followed by Brazil with statistics of about 840 petajoules, sharing 48.2 and 26.7%, respectively of the world total biofuel production (**Figure 2**, [13]).

Corn has been a major crop in the United States and many other countries around the world. In recent years, it has also become an important source of biofuel production due to its high starch content that can be converted into ethanol through different processes by fermentation [14]. The use of corn for biofuels has gained significant attention as an alternative to fossil fuels, which has the potential to reduce GHG emissions and promote energy security. However, the use of corn for biofuels has also raised concerns regarding its impact on food security, the environment, and the economy.
