The abrupt growth in energy demands and growing ecological concerns have evoked innovative and developing attitudes toward the utilization of fossil fuels and related products [1]. Rapid industrialization and population growth have led to estimates that energy requirements will double in the coming years’ [2]. It is noteworthy that currently global power generation in the transportation and industrials sectors are essentially dependent on fossil fuel products, such as oil (23 %), natural gas (22 %), and coal (27 %). Overall, 81 % of the essential energy utilized worldwide is generated mostly from non-sustainable resources, which are subject to exhaustion and price uncertainty. In addition, their utilization is accompanied by harmful ecological effects such as the emission of carbon dioxide (CO2), which is a widely recognized ozone-depleting substance [3]..

Concerns about exhaustion and climate issues have prompted people to swerve towards green and clean, sustainable energy sources. Efforts are being made by developing policies and implementing efficient measures to reduce greenhouse gas emissions [4]. Developed countries adopted the Kyoto Protocol to address climate change and global warming. Members of the protocol are obliged to consider different renewable energy sources to meet energy demands while maintaining low pollution levels and establishing a long-term sustainability project. Thus, a low-carbon society that supports both convenience and a blossoming populace has become an important driver of innovation. Biomass, a potential renewable fuel, has been extensively investigated as either biochar or biofuel. All types of performance assessments have been conducted for biomass related schemes, particularly for the retrofitting of existing coal power plants [5]. These investigations have prompted countries worldwide to include biomass as an accessory fraction in their national energy and climate change policies [6], [7].

In addition, owing to the advancement of modern technology, the hurdles to achieving a low-carbon society, high energy demands and economic concerns, can be effectively mitigated with the utilization of biomass [8]. Biomass is considered an efficient source of renewable energy. Gasification, which was earlier only used to supplement syngas, can now be extended to biofuel and electricity generation using different types of biomass [9], [10]. New alternatives to diesel and gasoline have been identified, mainly in the form of biofuels [11]. Biofuels derived from biomass have the advantages of extensive availability, accessibility, and sustainability. Recently, it has become widely known as the fourth most abundant energy resource after coal, oil, and gaseous petrol [12]. Given its growing importance, it is necessary to pay attention to the life cycle sustainability of designated biomass, specifically the agricultural practices and land areas required. Therefore, life cycle assessment (LCA) is used to evaluate the potential influence of biomass on the environment [13], [14].

The life cycle assessment is regarded as a highly useful tool for evaluating the impact of a fuel on the economy, society, and environment [15]. Investment in and commercial production of ethanol can be analyzed through life cycle assessment, which can guide modifications that will ultimately lead to sustainability. Investment in and commercial production of ethanol can be analyzed through life cycle assessment, which can lead to sustainability [16].

In the case of life cycle assessments (LCAs) of biomass-derived fuels, the main objective is to reduce hazardous elements that are a direct cause of climate change by adopting biomass resources. It allows quantitative estimation of the ecological impact throughout the life cycle of biofuels, which encompasses all stages from the growth of the raw material, the extraction, and its disposal [17], [18], [19]. These fuels include first-generation biofuels and second-generation bioethanol, with the latter expected to play a major role in the development of sustainable fuels in the future [20]. In addition, life cycle assessment is typically integrated with sensitivity analyses, making this combination an efficient methodology to decide the use of alternative fuels [21], [22]. A prominent example is the synthesis of bioethanol. The life cycle assessment was incorporated into the various processes involved in bioethanol synthesis to identify the impact of the respective phases on the environment, as reported by the National Renewable Energy Laboratory (NREL). During the harvest stage, the depletion of soil organic carbon increases carbon dioxide discharge. Similarly, there will be immediate and circuitous impacts as ranchers clear undisturbed environments for biomass plantations [23]. In addition, different cultivation practices have different impacts on the environment. Switching from a monoculture to a rotational system can have a significant ecological advantage from the perspective of land management [24]. Thus, life cycle assessments of biofuels have been used to evaluate the net impact on humans, ecosystems, weather, and other global conditions [25], [26]. However, it is very difficult to apply life cycle assessment to measure the environmental sustainability of various biofuels.

In this review, life cycle assessment applications for various biofuel sources, from lignocellulose to microalgae, are comparatively analyzed, and the environmental impacts of different biofuels are evaluated. More specifically, in contrast to previous life cycle assessment studies that focused on environmental effects, this review analyzes sustainable biodiesel characteristics and the natural effects of biofuel synthesis. The remainder of this paper is organized as follows. First, the methodology of life cycle assessments, including inventory analysis, impact assessment, and clarification, is presented. Then, the synthesis of biofuels is discussed. The main part of this review is divided into three sections: biodiesel, bioethanol, and biofuels from microalgae. Finally, prospects and challenges for the life cycle assessment of various biofuels are discussed.