research progress of fuel ethanol refining and life cycle carbon footprint

Driven by the "dual carbon" goal, biomass liquid fuel has become an important solution to expand fossil fuel reserves, reduce greenhouse gas emissions and mitigate global warming and climate change because of its superior "carbon reduction" characteristics. Fuel ethanol, the world's largest liquid biofuel, is a viable renewable fuel with high vaporization heat, high octane number and cleaner combustion characteristics, and can be commercially produced. Lignocellulose, as the only renewable organic carbon reservoir, has the potential to replace fossil resources and plays a key role in the production of fuel ethanol in particular. This study focuses on the biorefining methods of fuel ethanol, and focuses on the latest progress of life cycle carbon footprint analysis. In this study, the basic principles and current status of ethanol technology are first described, and some challenges in the production of fuel ethanol from lignocellulosic biomass are pointed out, including cell wall stubbornness, multi-step pretreatment process, extended hydrolysis time, degradation product generation, and high production costs. Future research will focus on the development of an integrated set of technologies aimed at developing low energy, high efficiency and clean raw material pretreatment technologies, and developing low cost and high efficiency hydrolases to improve the efficiency of enzyme formulations. At the same time, through genetic engineering technology, the heat-resistant and anti-inhibition microbial strains were cultivated to comprehensively utilize pentose and hexose, so as to effectively increase the yield of ethanol. Life cycle evaluation studies of fuel ethanol production technologies have shown that fuel ethanol plays an important role in mitigating climate change and achieving net zero emission targets by sequestering carbon fixed during biomass growth compared to fossil fuels. Among them, the second generation of fuel ethanol performed best, followed by the first and third generation of fuel ethanol. However, there are still some problems in the evaluation process, such as inconsistent system boundary, insufficient data list and diversified evaluation models, so it is necessary to establish a unified standard to further improve the life cycle evaluation system. In addition, a comprehensive analysis of the cost-effectiveness of various ethanol technologies was conducted through a comprehensive life cycle economic assessment. Current pricing makes second-generation fuel ethanol more expensive than gasoline, prompting a focus on improving the efficiency and affordability of cellulase while driving the production of high-value by-products. The purpose of this paper is to provide important reference for the research of fuel ethanol refining technology in the future.