2.2.1. Policy Initiatives

Several problems are faced in the production of biofuels, among which the production costs above the fluctuating price of fossil fuels stand out, and the ecological challenges during biofuels production. The challenges faced are explained in this section.

Various industry considerations (climate change, pricing ambiguity, and geopolitical uncertainty) are taken into account to explore the utility of substituting biofuels for traditional petroleum-based fuels as a clean energy alternative. Therefore, the U.S. renewable fuel standard (RFS2) was mainly designed to motivate biofuel production, relying on reducing the greenhouse gas emission related to petroleum fuels [19].

Different types of biofuels produced at a global level have overcome 35 billion gallons during transportation in 2015, and by 2023 will reach 62 billion gallons. The International Energy Agency (IEA) evaluate that biofuels have the probability of supplying continuously from their ongoing share of 3% to about 27% of total transportation by liquid [20].

At this moment, our world´s main objective is to maintain economic development without increasing environmental degradation. Bio-based industries can dramatically alleviate pollution and ecological damage after the industrial revolution [21]. Twenty years ago, Rio's acknowledgment of environment and development took the first step to solve this unorganized scheme for the future. In this session, several countries reviewed the matter of social, scientific, and technological development. The use of agricultural residues was one of the activities affecting all the fields [22]. This valorization consolidates the utilization of second-generation biorefineries.

### 2.2.2. Market Challenges

One of the dominant objectives in manufacturing renewable fuels is encompassing the target price of 0.79 \$L−<sup>1</sup> [23], agreed by the Bioenergy Technologies Office (BETO). Scientists can enhance renewable fuel generation's industrial growth by utilizing non-profitable biomass such as forest residues as a feedstock and producing yields from selling co-products [23]. The shortage of fossil fuel has led to increasing concern regarding greenhouse gas emissions and air pollution. This has resulted in rising interest in bioethanol production from natural resources like algal strains, notably from lignocellulosic biomass via enzymatic route. The estimation for biofuel growth by 2020 will be 4% of road transport applications, and according to USDA, global ethanol production will grow to 40% by 2022 [24]. The main aim of the biorefinery is to produce broad-spectrum merchandise in a cost-effective and eco-friendly way. Therefore, second-generation biofuel production is the most feasible process to generate bioethanol in competition with food resources and fertile land. Hence, in the long run, bioethanol production from lignocellulosic material through enzymatic hydrolysis is a valuable process, along with a probability of huge output [25]. It has been reported that 44% cost of biofuel production in 2G ethanol production is from enzymes. The researchers recommended that on-site or near-site enzyme generation encourages access to the remarkable decrease in enzymes' value up to 30–70% carrying its interpreted purification and logistics [25,26]. According to another author, the cost of enzymes at 15% and 35% solid pretreated loading during enzymatic hydrolysis varies from 34.63% to 36.38%, respectively [25,27].

### 2.2.3. Social and Socio-Economic Issues

The problem that is being faced regarding the depletion of fossil fuels is the involvement in energy security, particularly in the countries that are energy-dependent because of constant clashes in the oil-exporting countries and climate change as a result of the burning of fossil fuels. All these problems are arising due to fossil fuels: society realized biofuels to solve these problems. Specifically, the thriving biofuel sector could administer the opportunity to develop rural areas and generate job opportunities for the local residents, working towards the development of healthy, efficient communities and reducing

the emission of greenhouse gases. Recently, some issues regarding biofuel generation and its use have appeared, such as biofuels' effect on energy and food markets, working conditions and workers' rights regarding occupational health, the disparity of biofuel policies, the land change, etc. should also be recognized [28].
