2.2.4. Sustainability

For biofuel sustainability, it is necessary to deal with the various complex and conflicting estimates at stake. Hence, the biofuel capability to grant to one particular value cannot guide any definite conclusion regarding biofuel's overall sustainability. The range of the sustainability opinion may differ depending on individuals' inclination, the time scale, and the geographical region. The five pillars of the sustainability theory encompasses social, economic, environmental, legal, and cultural considerations. In a recent study, research proposed estimating various biofuel sustainability objectives for France by 2030, along with a stakeholder-driven perspective; the stakeholders recognize 22 different sustainability standards for biofuels. Therefore, they had a shallow level of agreement between the various professions (feedstock producers, biofuel producers, refining industry, fuel distributors, car manufacturers, end-users, government, and non-governmental organization (NGOs)). The sustainability evaluation initiation, a set of indicators, has been recognized by stakeholders authorized to quantify biofuel's scope to fulfill each of their criteria. There were seventeen biofuel objectives evaluated regarding economic, social, environmental, cultural, and legal considerations, allowing the identification of each biofuel's strengths and weaknesses. Biofuel sustainability evaluation needs a review of a wide variety of different objectives to endure with their multidimensional impacts. Therefore, the biofuel capability to accomplish one particular goal cannot reach any infinite conclusion regarding overall biofuel sustainability, policy efficiency, and if it has a positive or negative impact [29].

Many studies are done on the use of various organic wastes to produce biofuel. These processes have been reported to be successful in response to global challenges like fossil fuel dependency, production cost optimization, and waste management. In addition, the matter of emission control and after so many investigations, everyone concluded that biofuel production from organic waste has an excellent possibility for sustainable and economic development while confirming minimal environmental influence and overall production cost [30].

Despite the advantages that lignocellulosic residues represent for the production of biofuels e.g., value added to crops, reducing GHG emissions and not competing with food, some issues must be critically evaluated [1,16]. Currently, crop residues are used in animal feed or left in the field to avoid erosion, or incorporated by plowing for the recycling of nutrients. Therefore, its use in a massive way could break the balance in the carbon-nitrogen relationship, decrease the amount of nutrients, and affect the soil, causing a severe problem in agricultural land quality [16]. Therefore, it must be established for residues, and the extraction limit of biomass in the corn crop case must also be established. Some data mention that 40% of the residues can be collected in an intensive cultivation system and up to 70% of the residues in a no-tillage system to keep the low risk of material organic and soil structure loss [31].
