1 Introduction

Ethanol fuel production has gained significant attention as a sustainable alternative to fossil fuels. The global dependency on fossil fuels has led to environmental concerns, including greenhouse gas (GHG) emissions and climate change. Ethanol, a biofuel, offers a cleaner energy profile by reducing CO₂ emissions and providing a renewable energy source. In Brazil, for instance, ethanol production from sugarcane has reached 27 billion liters, accounting for 27% of the world's total biofuel production, and is recognized for its high energy balance and cost-effectiveness (Coelho and Goldemberg, 2019). The shift towards biofuels is driven by the need to mitigate climate change, reduce crude oil dependency, and promote energy security (Bordonal et al., 2018).

Sugarcane is a highly efficient biofuel feedstock due to its high photosynthetic efficiency and widespread cultivation in tropical and subtropical regions. It is particularly significant in countries like Brazil, where it has been a cornerstone of the biofuel industry since the 1970s (Castro et al., 2018). Sugarcane's ability to produce not only ethanol but also valuable by-products such as bagasse, vinasse, and sugarcane straw enhances its commercial potential (Ajala et al., 2021). The integration of sugarcane ethanol production with other agricultural practices, such as cattle feed, further optimizes land use and reduces GHG emissions (Souza et al., 2019). Additionally, sugarcane's non-burning harvesting methods and efficient nitrogen use contribute to its sustainability and environmental benefits (Bordonal et al., 2018).

This study aims to explore the theoretical basis and commercial potential of sugarcane in ethanol fuel production. It will examine the historical context and current state of sugarcane ethanol production, including technological advancements and policy impacts. The review will also assess the environmental and economic sustainability of sugarcane as a biofuel feedstock, highlighting its role in reducing GHG emissions and promoting renewable energy. Furthermore, the study will discuss the potential for integrating sugarcane ethanol production with other agricultural and industrial processes to enhance its commercial viability and environmental benefits. By consolidating existing knowledge and identifying research priorities, this study seeks to provide a comprehensive understanding of the application of sugarcane in ethanol fuel production and its future prospects.

2 Theoretical Basis of Ethanol Production from Sugarcane

2.1 Chemical composition of sugarcane relevant to ethanol production

Sugarcane (Saccharum spp.) is a tropical perennial grass belonging to the family Poaceae, widely used for sugar production. The primary components of sugarcane relevant to ethanol production include sucrose, glucose, and fructose, which are fermentable sugars. Additionally, sugarcane bagasse, the fibrous residue remaining after juice extraction, contains lignocellulosic materials that can be utilized for second-generation ethanol production (Dias et al., 2013). The high sugar content in sugarcane makes it an efficient feedstock for ethanol production, contributing significantly to the global biofuel supply (Talukdar et al., 2017).

2.2 Biochemical pathways for ethanol production from sugarcane

The biochemical pathways for ethanol production from sugarcane primarily involve the fermentation of sugars. The process begins with the extraction of juice from sugarcane, which contains high concentrations of sucrose. This sucrose is then hydrolyzed into glucose and fructose, which are subsequently fermented by yeast (typically Saccharomyces cerevisiae) to produce ethanol and carbon dioxide. The overall reaction can be summarized as: [C₆H₁₂O₆→2C₂H₅(OH)₂+2CO₂]. In addition to first-generation ethanol production from sugarcane juice, second-generation ethanol can be produced from lignocellulosic biomass (bagasse and cane trash) through processes involving pretreatment, enzymatic hydrolysis, and fermentation (Dias et al., 2013; Khatiwada et al., 2016).

2.3 Conversion technologies: fermentation and distillation processes

The conversion of sugarcane to ethanol involves several key technologies, including fermentation and distillation. During fermentation, the extracted sugarcane juice is mixed with yeast in large fermentation tanks, where the sugars are converted to ethanol and carbon dioxide. The fermentation process typically takes 24 to 48 hours, after which the ethanol concentration in the mixture reaches around 10%-15% (Goldemberg and Guardabassi, 2010; Dias et al., 2015). Following fermentation, the ethanol is separated from the fermentation broth through distillation. The distillation process involves heating the mixture to vaporize the ethanol, which is then condensed and collected as a concentrated ethanol solution. This solution is further dehydrated to produce anhydrous ethanol, which is suitable for use as fuel (Goldemberg and Guardabassi, 2010). Advances in distillation technology, such as the use of molecular sieves and azeotropic distillation, have improved the efficiency and yield of ethanol production (Dias et al., 2015).

2.4 Advances in biotechnology enhancing ethanol yield

Recent advances in biotechnology have significantly enhanced the yield and efficiency of ethanol production from sugarcane. Genetic engineering of sugarcane varieties has led to the development of high-yielding and disease-resistant strains, which can produce more fermentable sugars per hectare (Goldemberg and Guardabassi, 2010). Additionally, the identification and utilization of key enzymes involved in the hydrolysis of lignocellulosic biomass have improved the efficiency of second-generation ethanol production (Talukdar et al., 2017).

Biotechnological innovations, such as the development of genetically modified yeast strains with higher ethanol tolerance and productivity, have also contributed to increased ethanol yields. These yeast strains can ferment sugars more efficiently and withstand the inhibitory effects of high ethanol concentrations, leading to higher overall ethanol production (Dias et al., 2013; Talukdar et al., 2017). Furthermore, process optimization techniques, including thermal integration and the use of more efficient equipment, have reduced energy consumption and increased the sustainability of ethanol production from sugarcane (Ensinas et al., 2009).

In summary, the theoretical basis of ethanol production from sugarcane encompasses the chemical composition of sugarcane, the biochemical pathways for ethanol production, the conversion technologies involved, and the biotechnological advances that enhance ethanol yield. These factors collectively contribute to the commercial potential and sustainability of sugarcane as a feedstock for ethanol fuel production.

3 Agronomic Aspects of Sugarcane Cultivation

3.1 Ideal agronomic conditions for sugarcane growth

Sugarcane thrives in tropical and subtropical climates, requiring specific agronomic conditions to maximize yield and quality. Optimal growth conditions include well-drained, fertile soils with a pH range of 5 to 8, and an annual rainfall of 1 500 to 2 500 mm, ideally distributed throughout the growing season. Temperature plays a crucial role, with the ideal range being 20 ℃ to 30 ℃. Adequate sunlight and a frost-free environment are also essential for optimal photosynthesis and growth (Talukdar et al., 2017; Coelho and Goldemberg, 2019).

3.2 Advances in sugarcane breeding for biofuel production

Recent advancements in sugarcane breeding have focused on enhancing traits that are beneficial for biofuel production. These include increasing biomass yield, improving sugar content, and enhancing resistance to pests and diseases. Genetic improvement efforts are leveraging modern biotechnological tools to understand and manipulate the complex sugarcane genome. This has led to the development of varieties with better biomass degradability, which is crucial for efficient conversion to biofuels. The large phenotypic variation in Saccharum germplasm and the application of genomics technologies have been pivotal in identifying key biofuel traits and establishing targets for genetic manipulation (Hoang et al., 2015; Jaiswal et al., 2017).

3.3 Sustainable practices in sugarcane cultivation

Sustainability in sugarcane cultivation involves practices that minimize environmental impact while maintaining economic viability. Mechanized harvesting of green cane, which eliminates the need for pre-harvest burning, has been widely adopted to reduce air pollution and improve soil health. Additionally, the use of agricultural residues such as bagasse and cane trash for bioelectricity and second-generation ethanol production contributes to a circular economy. Integrated pest management, efficient water use, and soil conservation techniques are also critical components of sustainable sugarcane farming (Goldemberg et al., 2008; Pereira and Ortega, 2010; Walter et al., 2014).

3.4 Impact of climate change on sugarcane yield and quality

Climate change poses significant challenges to sugarcane cultivation, affecting both yield and quality. Changes in temperature and precipitation patterns can lead to water stress, increased pest and disease incidence, and altered growth cycles. However, sugarcane's resilience and adaptability to varying climatic conditions make it a viable crop under changing environmental scenarios. Research indicates that with appropriate agronomic practices and continued genetic improvement, sugarcane can maintain its productivity and quality even under projected climate change conditions. The potential for sugarcane ethanol to offset CO₂ emissions further underscores its role in mitigating climate change impacts (Coelho et al., 2006; Jaiswal et al., 2017; Malik et al., 2019).

By integrating these agronomic aspects, sugarcane cultivation can be optimized for both economic and environmental sustainability, ensuring its continued viability as a major feedstock for ethanol fuel production.

4 Commercial Potential and Economic Viability

4.1 Global and regional market trends for ethanol fuel

The global market for ethanol fuel has seen significant growth, driven by the need for renewable energy sources and the reduction of greenhouse gas emissions. Brazil, a leading producer of sugarcane ethanol, has demonstrated the potential for ethanol to displace a substantial portion of crude oil consumption. By 2045, Brazilian sugarcane ethanol could replace up to 13% of global crude oil consumption, balancing forest conservation and future land demand for food (Jaiswal et al., 2017). The success of Brazil's ethanol program has spurred interest in other regions, including Mexico, where sugarcane-based ethanol could meet a significant portion of gasoline demand (Aburto and Martinez-Hernandez, 2021).

4.2 Economic analysis of sugarcane-based ethanol production

The economic viability of sugarcane-based ethanol production is influenced by several factors, including market prices, production costs, and technological advancements. In Brazil, the production of ethanol from sugarcane is highly competitive compared to other biofuel sources, such as corn ethanol in the USA (Chum et al., 2014). The use of sugarcane residues, such as bagasse and cane trash, for bioelectricity and second-generation ethanol production further enhances the economic potential by optimizing the use of biomass (Khatiwada et al., 2016). Additionally, the integration of sugarcane biorefineries can lead to diversified product portfolios, reducing disposal costs and improving overall profitability (Formann et al., 2020).

The research of Khaire et al. (2021) depicts the pretreatment process of lignocellulosic biomass, a critical step in converting plant material into biofuels and other valuable products (Figure 1). Lignocellulosic biomass is composed of cellulose, hemicellulose, and lignin. These components form a complex and rigid structure that makes it challenging to break down. The pretreatment process aims to disrupt this structure, making the cellulose and hemicellulose more accessible for enzymatic hydrolysis. The image shows that after pretreatment, the biomass is separated into solid residues and hydrolysate. The solid residues primarily contain lignin, while the hydrolysate contains soluble sugars and other components released from the cellulose and hemicellulose. This breakdown is essential for subsequent fermentation processes, where microorganisms convert the sugars into bioethanol or other biofuels. Effective pretreatment enhances the efficiency of these processes, leading to higher yields of fermentable sugars and more sustainable biofuel production.

4.3 Cost-benefit analysis and comparison with other biofuel sources

Sugarcane ethanol has a favorable energy balance and lower greenhouse gas emissions compared to other biofuels. The renewable energy ratio (RER) for sugarcane ethanol is significantly higher than that of corn ethanol, making it a more efficient and sustainable option (Chum et al., 2014). In Mexico, the minimum ethanol-selling price (MESP) of sugarcane ethanol is competitive with other gasoline oxygenates, such as methyl tert-butyl ether (MTBE), providing economic benefits and reducing CO₂ emissions (Aburto and Martinez-Hernandez, 2021). The potential for productivity gains through genetic modifications and geographical expansion further enhances the cost-effectiveness of sugarcane ethanol (Goldemberg and Guardabassi, 2010).

4.4 Government policies and incentives supporting ethanol production

Government policies and incentives play a crucial role in the development and expansion of ethanol production. In Brazil, the Proálcool program initiated in the 1970s provided significant support for the ethanol industry, leading to its current success (Castro et al., 2018). The Brazilian government has since shifted to private investments, making the industry competitive without the need for subsidies (Coelho et al., 2006). In Mexico, government support for ethanol production could help decarbonize gasoline and improve air quality, particularly in metropolitan areas (Aburto and Martinez-Hernandez, 2021). Effective legislation and policies are essential to control environmental impacts and promote sustainable practices in ethanol production.

5 Technological Innovations and Improvements

5.1 Innovations in sugarcane harvesting and processing

Recent advancements in sugarcane harvesting and processing have significantly enhanced the efficiency and sustainability of ethanol production. Mechanized harvesting of green cane, which eliminates the need for burning, has been introduced to improve air quality and reduce environmental impact (Goldemberg et al., 2008). Additionally, the integration of first and second-generation ethanol production processes allows for the optimal use of sugarcane bagasse and trash, thereby increasing the overall ethanol yield and reducing waste (Dias et al., 2012; Dias et al., 2013).

5.2 Advances in fermentation technology

Fermentation technology has seen substantial improvements, particularly in the use of different fermentation strategies and yeast strains. The simultaneous saccharification and fermentation (SSF) process, optimized for sugarcane bagasse, has achieved high ethanol yields with reduced enzyme loads (Guilherme et al., 2019). Moreover, innovative fermentation processes such as low-temperature and vacuum extractive fermentation have been shown to increase ethanol production while reducing energy consumption (Palacios-Bereche et al., 2014). The use of genetically modified yeast strains capable of fermenting xylose has also enhanced ethanol yields from sugarcane bagasse (Wang et al., 2019).

5.3 Integration of co-products and by-products to enhance profitability

The integration of co-products and by-products in the ethanol production process can significantly enhance profitability. Sugarcane bagasse and trash, which are by-products of sugarcane processing, can be used as feedstock for second-generation ethanol production or as fuel for electricity generation (Dias et al., 2013; Khatiwada et al., 2016). This dual-use approach not only maximizes the utilization of biomass but also provides flexibility in production based on market conditions. Additionally, the use of post-harvest sugarcane residue for ethanol production further contributes to the economic viability of the process (Dawson and Boopathy, 2007).

5.4 Role of genetic engineering and synthetic biology in improving yields

Genetic engineering and synthetic biology play a crucial role in improving ethanol yields from sugarcane. Research has identified key enzymes that can accelerate the ethanol production process, making it more efficient (Talukdar et al., 2017). The development of genetically modified yeast strains that can ferment both glucose and xylose has also been a significant breakthrough, leading to higher ethanol yields from lignocellulosic biomass (Wang et al., 2019). Furthermore, the use of whole sugarcane lignocellulosic biomass, including bagasse, straw, and tops, has been shown to improve the overall efficiency and yield of second-generation ethanol production (Pereira et al., 2015).

By leveraging these technological innovations and improvements, the ethanol production industry can achieve higher efficiency, sustainability, and profitability, thereby contributing to the global demand for renewable energy sources.

6 Environmental and Sustainability Considerations

6.1 Environmental benefits of using sugarcane ethanol

The use of sugarcane ethanol presents several environmental benefits. One of the primary advantages is the reduction in greenhouse gas (GHG) emissions compared to fossil fuels. Sugarcane ethanol production requires minimal fossil fuel input, making it a renewable energy source with a lower carbon footprint (Pereira and Ortega, 2010). Additionally, the mechanized harvesting of green cane eliminates the need for burning, which significantly improves air quality in both metropolitan and rural areas (Goldemberg et al., 2008; Galdos et al., 2013). The co-generation of electricity from sugarcane by-products further enhances the environmental profile by displacing fossil fuel-based electricity (Silalertruksa et al., 2015).

6.2 Life cycle assessment of sugarcane ethanol production

Life cycle assessments (LCA) of sugarcane ethanol production have been conducted to evaluate its environmental impacts comprehensively. Studies have shown that the global warming potential (GWP) of sugarcane ethanol is significantly lower than that of gasoline. For instance, the GWP for 1 liter of ethanol produced in Ecuador was reported as 0.60 kg CO₂ eq, which is substantially lower than fossil fuel alternatives (Arcentales-Bastidas et al., 2022). In Brazil, the integration of first- and second-generation ethanol production has been shown to reduce environmental impacts further by utilizing bagasse and trash for ethanol production, thereby decreasing land use and GHG emissions (Maga et al., 2018). The LCA studies also highlight the importance of sustainable agricultural practices and efficient industrial processes to minimize environmental burdens (Amores et al., 2013; Hiloidhari et al., 2021).

6.3 Impact on greenhouse gas emissions and carbon footprint

The production and use of sugarcane ethanol have a positive impact on reducing GHG emissions and the overall carbon footprint. Mechanized harvesting and the elimination of pre-harvest burning have led to significant reductions in black carbon emissions, which have a net warming effect and cause health problems. The transition to mechanized harvesting has reduced the GWP of ethanol production by 46% and black carbon emissions by seven times compared to traditional methods (Galdos et al., 2013). Furthermore, the use of sugarcane by-products for electricity generation contributes to a negative GWP impact, as it displaces fossil fuel-based electricity (Silalertruksa et al., 2015; Arcentales-Bastidas et al., 2022).

6.4 Challenges and solutions for sustainable production

Despite the environmental benefits, there are several challenges associated with the sustainable production of sugarcane ethanol. Large-scale production can lead to deforestation, soil degradation, and water resource depletion if not managed properly (Pereira and Ortega, 2010). The competition between food and fuel production is another concern, as it can impact food security (Bordonal et al., 2018). To address these challenges, best management practices such as non-burning harvesting, efficient use of fertilizers, and the adoption of circular economy strategies are essential (Silalertruksa et al., 2015). Additionally, the integration of first- and second-generation ethanol production can enhance sustainability by increasing ethanol yield per hectare and reducing environmental impacts (Maga et al., 2018).

In conclusion, while sugarcane ethanol offers significant environmental benefits, careful management and sustainable practices are crucial to mitigate its potential negative impacts and ensure its long-term viability as a renewable energy source.

7 Case Studies and Real-world Applications

7.1 Successful examples of sugarcane ethanol production in various countries

Sugarcane ethanol production has seen significant success in various countries, with Brazil being the most prominent example. Brazil's sugarcane ethanol industry has become a model for other nations due to its efficiency and scale. The country produces a substantial portion of the world's sugarcane ethanol, contributing significantly to its energy matrix and reducing its dependence on fossil fuels (Goldemberg et al., 2008; Jaiswal et al., 2017). The success of Brazil's ethanol program has spurred interest in other countries, including India, which is exploring the potential of sugarcane as a biofuel crop to enhance rural development and create job opportunities (Talukdar et al., 2017).

7.2 Analysis of Brazil's ethanol program and its global impact

Brazil's ethanol program, initiated in the 1970s, has had a profound impact both domestically and globally. The program has led to the development of a robust sugarcane ethanol industry that not only meets a significant portion of the country's fuel needs but also contributes to global CO₂ emission reductions (Figure 2). Brazilian sugarcane ethanol can offset up to 86% of CO₂ emissions compared to crude oil, making it a crucial component in the fight against climate change (Jaiswal et al., 2017). The program's success has demonstrated the viability of large-scale ethanol production and has influenced biofuel policies worldwide, including the adoption of similar programs in other sugarcane-producing countries (Goldemberg et al., 2008; Goldemberg and Guardabassi, 2010).

The research of De Figueiredo et al. (2023) illustrates the greenhouse gas (GHG) emissions and offset potential associated with sugarcane straw management and recovery operations, focusing on their use for bioelectricity and second-generation ethanol (Ethanol 2G) production. The total additional GHG emissions from these operations amount to 1 465 kg CO₂ eq ha^-1, primarily from diesel use (217 kg CO₂ eq ha^-1), soil CO₂ (644 kg CO₂ eq ha^-1), and soil N₂O (604 kg CO₂ eq ha^-1). However, the recovery of straw and its subsequent utilization for electricity generation and ethanol production provides significant GHG offsets. Electricity generation from recovered straw avoids 562 kg CO₂ eq ha^-1, while the production of Ethanol 2G avoids a substantial 3 743 kg CO₂ eq ha^-1. The overall GHG balance reveals a net reduction of 2 320 kg CO₂ eq ha^-1 when considering the emissions and offsets, highlighting the environmental benefits of utilizing sugarcane straw for renewable energy and biofuel production. This process not only mitigates GHG emissions but also supports sustainable agricultural practices.

7.3 Comparative study of different production models and practices

Different production models and practices have been employed in sugarcane ethanol production, each with its own set of advantages and challenges. In Brazil, the integration of sugarcane mills with microalgae biorefineries has been explored to enhance sustainability and economic feasibility. This integrated approach can reduce greenhouse gas emissions and improve the overall efficiency of ethanol production (Klein et al., 2019). Additionally, the use of lignocellulosic biomass, such as bagasse and cane trash, for second-generation ethanol production has been investigated (Figure 3). This method optimizes the use of agricultural residues and industrial co-products, providing a sustainable alternative to traditional energy sources (Khatiwada et al., 2016).

The research of Vieira et al. (2020) illustrates the comprehensive processing of sugarcane and sugarcane bagasse to produce first-generation (1G) and second-generation (2G) ethanol, along with various byproducts. The process begins with juice extraction from sugarcane, resulting in bagasse and sugarcane juice. The juice undergoes evaporation and centrifugation to separate molasses, which is then used in fermentation to produce 1G ethanol. Simultaneously, bagasse is pretreated using methods like organosolv, acid, alkaline, or ionic liquids to break down its complex structure. The solid fraction from pretreatment is further processed in fermentation to produce 2G ethanol. Throughout the process, byproducts such as electricity, thermal energy, CO₂, and vinasse are generated. Electricity and thermal energy are used within the processing facilities, while CO₂ can be utilized or released. Vinasse, a nutrient-rich byproduct, is often used as fertilizer, completing the cycle by returning valuable nutrients to the sugarcane plantation. This integrated approach enhances resource efficiency and sustainability in ethanol production.

7.4 Lessons learned from large-scale implementations

The large-scale implementation of sugarcane ethanol production in Brazil has provided several valuable lessons. One key lesson is the importance of government support and policy frameworks in fostering the growth of the biofuel industry. Programs like RenovaBio have been instrumental in promoting the commercialization of low-carbon biofuels and establishing mechanisms for decarbonization credits (Klein et al., 2019). Another lesson is the need to balance biofuel production with environmental conservation and food security. While sugarcane ethanol offers significant CO₂ emission reductions, it is crucial to manage land use effectively to avoid negative impacts on biodiversity and food production (Goldemberg et al., 2008; Jaiswal et al., 2017). Finally, technological advancements, such as genetic recombination and the development of key enzymes, have the potential to further enhance the efficiency and sustainability of sugarcane ethanol production (Talukdar et al., 2017).

By examining these case studies and real-world applications, we can gain a comprehensive understanding of the theoretical basis and commercial potential of sugarcane in ethanol fuel production.

8 Future Prospects and Research Directions

8.1 Potential advancements in sugarcane cultivation and processing

Advancements in sugarcane cultivation and processing are crucial for enhancing ethanol production efficiency. Genetic recombination and breeding programs have shown promise in increasing sugarcane yield and improving agronomic practices, which can significantly reduce production costs and environmental impacts (Goldemberg and Guardabassi, 2010; Walter et al., 2014). Integrating cold tolerance traits from species like Saccharum spontaneum and Miscanthus could expand sugarcane cultivation to temperate zones, thus increasing the geographical range of production (Lam et al., 2009). Additionally, the development of breeder-friendly DNA markers associated with desirable traits can enhance selection efficiency and shorten breeding cycles.

8.2 Emerging technologies in ethanol production

Emerging technologies in ethanol production focus on optimizing the use of sugarcane biomass and improving conversion efficiencies. Second-generation (2G) ethanol production, which utilizes lignocellulosic biomass such as bagasse and cane trash, presents a significant opportunity for increasing ethanol output without expanding agricultural land (Khatiwada et al., 2016; Ungureanu et al., 2022). Innovative cascading processes that valorize sugarcane residues into bioplastics, bio-fertilizers, and biogas can further enhance the sustainability and economic viability of sugarcane biorefineries (Formann et al., 2020). Moreover, advancements in genetic engineering and enzyme technology are expected to accelerate the fermentation process, making ethanol production more efficient (Talukdar et al., 2017).

8.3 Predictions for future market trends and demands

The global demand for renewable energy sources is expected to drive the expansion of sugarcane ethanol production. Studies predict that Brazilian sugarcane ethanol could displace up to 13% of global crude oil consumption by 2045, significantly reducing CO₂ emissions (Jaiswal et al., 2017). The potential for geographical expansion and productivity gains in sugarcane cultivation suggests that ethanol could replace a substantial portion of global gasoline consumption before second-generation technologies become fully competitive (Goldemberg and Guardabassi, 2010). However, market trends will also be influenced by factors such as biofuel support policies, carbon taxes, and energy prices (Khatiwada et al., 2016).

8.4 Key areas for further research and development

Key areas for further research and development include improving the sustainability of large-scale ethanol production and addressing environmental concerns. Research should focus on minimizing the negative impacts of sugarcane cultivation, such as soil erosion, water usage, and CO₂ emissions (Pereira and Ortega, 2010). Additionally, the development of sustainable waste management practices for by-products like vinasse, bagasse ash, and filter cake is essential for reducing environmental risks and enhancing the circular bioeconomy (Formann et al., 2020; Ungureanu et al., 2022). Further studies on the socio-economic impacts of expanding sugarcane ethanol production, particularly in developing countries, are also necessary to ensure that the benefits are equitably distributed (Talukdar et al., 2017).

By addressing these research directions, the sugarcane ethanol industry can continue to grow sustainably, meeting future energy demands while minimizing environmental impacts.

9 Concluding Remarks

The research on the application of sugarcane in ethanol fuel production has revealed several critical insights. Firstly, sugarcane biorefineries in Brazil have demonstrated the potential to optimize the use of sugarcane biomass, particularly bagasse and cane trash, for both electricity and second-generation (2G) ethanol production. This optimization is influenced by factors such as energy prices, biofuel support, and carbon tax. Additionally, Brazilian sugarcane ethanol has been identified as a scalable solution to reduce CO₂ emissions, with the potential to displace up to 13% of global crude oil consumption by 2045 while balancing forest conservation and food production demands.

Sugarcane's high biomass production capacity and favorable energy input/output ratio make it an excellent feedstock for biofuel production. Genetic improvements in sugarcane varieties could further enhance biomass degradability and ethanol yield. The sustainability of ethanol production from sugarcane is also notable, with significant reductions in CO₂ emissions and improvements in air quality, although concerns about land use and environmental impacts remain. Moreover, the integration of sugarcane mills with microalgae biorefineries under the RenovaBio program could further improve the sustainability and economic feasibility of ethanol production.

The findings from these studies have several implications for the biofuel industry. The optimization of sugarcane biomass use in biorefineries can lead to more efficient and sustainable energy production, potentially reducing reliance on fossil fuels and lowering greenhouse gas emissions. The scalability of sugarcane ethanol production, particularly in Brazil, suggests that it could play a significant role in global efforts to transition to renewable energy sources and mitigate climate change.

The potential for genetic improvements in sugarcane varieties highlights the importance of continued research and development in biotechnology to enhance biofuel production efficiency. Additionally, the integration of sugarcane mills with other biorefinery processes, such as microalgae production, could create new opportunities for value generation and further reduce the carbon footprint of biofuel production. The lessons learned from Brazil's experience with sugarcane ethanol production can also inform biofuel policies and practices in other countries, particularly in terms of achieving economic competitiveness and environmental sustainability.

Sugarcane has proven to be a highly promising feedstock for ethanol fuel production, offering numerous environmental, economic, and social benefits. The ability to produce ethanol efficiently from both the sugar and lignocellulosic components of sugarcane, coupled with the potential for genetic improvements and biorefinery integration, positions sugarcane as a key player in the future of renewable energy. However, it is essential to address the environmental and social challenges associated with large-scale ethanol production, such as land use changes and competition with food production, to ensure the sustainability of this biofuel source.

In conclusion, the application of sugarcane in ethanol fuel production holds significant commercial potential and can contribute substantially to global efforts to reduce greenhouse gas emissions and transition to renewable energy sources. Continued research, technological advancements, and supportive policies will be crucial in realizing the full potential of sugarcane as a sustainable biofuel crop.

Acknowledgments

We extend our sincere thanks to two anonymous peer reviewers for their invaluable feedback on the initial draft of this paper, whose critical evaluations and constructive suggestions have greatly contributed to the improvement of our manuscript.

Conflict of Interest Disclosure

The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.

References

Aburto J., and Martinez-Hernandez E., 2021, Is sugarcane a convenient feedstock to provide ethanol to oxygenate gasolines in mexico? A process simulation and techno-economic-based analysis, Frontiers in Energy Research, 8: 612647.

https://doi.org/10.3389/fenrg.2020.612647

Ajala E., Ighalo J., Ajala M., Adeniyi A., and Ayanshola A., 2021, Sugarcane bagasse: a biomass sufficiently applied for improving global energy, environment and economic sustainability, Bioresources and Bioprocessing, 8: 1-25.

https://doi.org/10.1186/s40643-021-00440-z

Amores M., Mele F., Jiménez L., and Castells F., 2013, Life cycle assessment of fuel ethanol from sugarcane in Argentina, The International Journal of Life Cycle Assessment, 18: 1344-1357.

https://doi.org/10.1007/s11367-013-0584-2

Arcentales-Bastidas D., Silva C., and Ramirez A., 2022, The environmental profile of ethanol derived from sugarcane in Ecuador: a life cycle assessment including the effect of cogeneration of electricity in a sugar industrial complex, Energies, 15(15): 5421.

https://doi.org/10.3390/en15155421

Bordonal R., Carvalho J., Lal R., Figueiredo E., Oliveira B., and Scala N., 2018, Sustainability of sugarcane production in Brazil. A review, Agronomy for Sustainable Development, 38: 1-23.

https://doi.org/10.1007/s13593-018-0490-x

Castro R., Alves R., Nascimento C., and Giudici R., 2018, Assessment of sugarcane-based ethanol production, In Fuel Ethanol Production from Sugarcane, pp.3-22.

https://doi.org/10.5772/intechopen.78301

Chum H., Warner E., Seabra J., and Macedo I., 2014, A comparison of commercial ethanol production systems from Brazilian sugarcane and US corn, Biofuels, Bioproducts and Biorefining, 8(2): 205-223.

https://doi.org/10.1002/bbb.1448

Coelho S., Goldemberg J., Lucon O., and Guardabassi P., 2006, Brazilian sugarcane ethanol: lessons learned, Energy for Sustainable Development, 10(2): 26-39.

https://doi.org/10.1016/S0973-0826(08)60529-3

Coelho S., and Goldemberg J., 2019, Sustainability and environmental impacts of sugarcane biofuels, In Sugarcane Biofuels, Status, Potential, and Prospects of the Sweet Crop to Fuel the World, pp.409-444.

https://doi.org/10.1007/978-3-030-18597-8_18

Dawson L., and Boopathy R., 2007, Use of post-harvest sugarcane residue for ethanol production, Bioresource Technology, 98(9): 1695-1699.

https://doi.org/10.1016/j.biortech.2006.07.029

De Figueiredo E.B., Jayasundara S., de Oliveira Bordonal R., Rodrigo A., and Panosso N.L.S.J., 2023, Greenhouse gas emissions and offset potential from sugarcane straw for bioenergy production in Brazil, Carbon Footprints, 2: 9.

https://doi.org/10.20517/cf.2022.21

Dias M., Junqueira T., Jesus C., Rossell C., Filho R., and Bonomi A., 2012, Improving second generation ethanol production through optimization of first generation production process from sugarcane, Energy, 43(1): 246-252.

https://doi.org/10.1016/j.energy.2012.04.034

Dias M., Filho R., Mantelatto P., Cavalett O., Rossell C., Bonomi A., and Leal M., 2015, Sugarcane processing for ethanol and sugar in Brazil, Environmental Development, 15: 35-51.

https://doi.org/10.1016/j.envdev.2015.03.004

Ensinas A., Modesto M., Nebra S., and Serra L., 2009, Reduction of irreversibility generation in sugar and ethanol production from sugarcane. Energy, 34(5): 680-688.

https://doi.org/10.1016/j.energy.2008.06.001

Formann S., Hahn A., Janke L., Stinner W., Sträuber H., Logroño W., and Nikolausz M., 2020, Beyond sugar and ethanol production: value generation opportunities through sugarcane residues, Frontiers in Energy Research, 8: 579577.

https://doi.org/10.3389/fenrg.2020.579577

Galdos M., Cavalett O., Seabra J., Nogueira L., and Bonomi A., 2013, Trends in global warming and human health impacts related to Brazilian sugarcane ethanol production considering black carbon emissions, Applied Energy, 104: 576-582.

https://doi.org/10.1016/j.apenergy.2012.11.002

Goldemberg J., Coelho S., and Guardabassi P., 2008, The Sustainability of Ethanol Production from Sugarcane, In Renewable Energy, pp.321-345.

https://doi.org/10.1016/j.enpol.2008.02.028

Goldemberg J., and Guardabassi P., 2010, The potential for first-generation ethanol production from sugarcane, Biofuels, Bioproducts and Biorefining: Innovation for a Sustainable Economy, 4(1): 17-24.

https://doi.org/10.1002/bbb.186

Guilherme A., Dantas P., Padilha C., Santos E., and Macêdo G., 2019, Ethanol production from sugarcane bagasse: use of different fermentation strategies to enhance an environmental-friendly process, Journal of Environmental Management, 234: 44-51.

https://doi.org/10.1016/j.jenvman.2018.12.102

Hiloidhari M., Haran S., Banerjee R., and Rao A., 2021, Life cycle energy-carbon-water footprints of sugar, ethanol and electricity from sugarcane, Bioresource Technology, 330: 125012.

https://doi.org/10.1016/j.biortech.2021.125012

Hoang N., Furtado A., Botha F., Simmons B., and Henry R., 2015, Potential for genetic improvement of sugarcane as a source of biomass for biofuels, Frontiers in Bioengineering and Biotechnology, 3: 182.

https://doi.org/10.3389/fbioe.2015.00182

Jaiswal D., Souza A., Larsen S., LeBauer D., Miguez F., Sparovek G., Bollero G., Buckeridge M., and Long S., 2017, Brazilian sugarcane ethanol as an expandable green alternative to crude oil use, Nature Climate Change, 7(11): 788-792.

https://doi.org/10.1038/nclimate3410

Khaire K.C., Moholkar V. S., and Goyal A., 2021, Bioconversion of sugarcane tops to bioethanol and other value added products: an overview, Materials Science for Energy Technologies, 4: 54-68.

https://doi.org/10.1016/j.mset.2020.12.004

Khatiwada D., Leduc S., Silveira S., and Mccallum I., 2016, Optimizing ethanol and bioelectricity production in sugarcane biorefineries in Brazil, Renewable Energy, 85: 371-386.

https://doi.org/10.1016/j.renene.2015.06.009

Klein B., Chagas M., Watanabe M., Bonomi A., and Filho R., 2019, Low carbon biofuels and the New Brazilian National Biofuel Policy (RenovaBio): a case study for sugarcane mills and integrated sugarcane-microalgae biorefineries, Renewable and Sustainable Energy Reviews, 115: 109365.

https://doi.org/10.1016/j.rser.2019.109365

Lam E., Shine J., Silva J., Lawton M., Bonos S., Calvino M., Carrer H., Silva-Filho M., Glynn N., Helsel Z., Ma J., Richard E., Souza G., and Ming R., 2009, Improving sugarcane for biofuel: engineering for an even better feedstock, GCB Bioenergy, 1(3): 251-255.

https://doi.org/10.1111/j.1757-1707.2009.01016.x

Maga D., Thonemann N., Hiebel M., Sebastião D., Lopes T., Fonseca C., and Girio F., 2018, Comparative life cycle assessment of first- and second-generation ethanol from sugarcane in Brazil, The International Journal of Life Cycle Assessment, 24: 266-280.

https://doi.org/10.1007/s11367-018-1505-1

Malik K., Verma D., Srivastava S., Mehta S., Kumari N., Khushboo, Verma A., Kumar M., Chand S., Tiwari A., and Singh K., 2019, Sugarcane production and its utilization as a biofuel in India: status, perspectives, and current policy, In Sugarcane Biofuels: Status, Potential, and Prospects of the Sweet Crop to Fuel the World, pp.123-138.

https://doi.org/10.1007/978-3-030-18597-8_6

Palacios-Bereche R., Ensinas A., Ensinas A., Modesto M., Nebra S., and Nebra S., 2014, New alternatives for the fermentation process in the ethanol production from sugarcane: Extractive and low temperature fermentation, Energy, 70: 595-604.

https://doi.org/10.1016/j.energy.2014.04.032

Pereira C., and Ortega E., 2010, Sustainability assessment of large-scale ethanol production from sugarcane, Journal of Cleaner Production, 18(1): 77-82.

https://doi.org/10.1016/j.jclepro.2009.09.007

Pereira S., Maehara L., Machado C., and Farinas C., 2015, 2G ethanol from the whole sugarcane lignocellulosic biomass, Biotechnology for Biofuels, 8: 1-16.

https://doi.org/10.1186/s13068-015-0224-0

Silalertruksa T., Gheewala S., and Pongpat P., 2015, Sustainability assessment of sugarcane biorefinery and molasses ethanol production in Thailand using eco-efficiency indicator, Applied Energy, 160: 603-609.

https://doi.org/10.1016/j.apenergy.2015.08.087

Souza N., Fracarolli J., Junqueira T., Chagas M., Cardoso T., Watanabe M., Cavalett O., Filho S., Dale B., Bonomi, A., and Cortez L., 2019, Sugarcane ethanol and beef cattle integration in Brazil, Biomass and Bioenergy, 120: 448-457.

https://doi.org/10.1016/j.biombioe.2018.12.012

Talukdar D., Verma D., Malik K., Mohapatra B., and Yulianto R., 2017, Sugarcane as a potential biofuel crop, In Sugarcane Biotechnology: Challenges and Prospects, pp.123-137.

https://doi.org/10.1007/978-3-319-58946-6_9

Ungureanu N., Vlăduț V., and Biriș S., 2022, Sustainable valorization of waste and by-products from sugarcane processing, Sustainability, 14(17): 11089.

https://doi.org/10.3390/su141711089

Vieira S., Barros M.V., Sydney A.C.N., Piekarski C.M., de Francisco A.C., de Souza Vandenberghe L.P., and Sydney E.B., 2020, Sustainability of sugarcane lignocellulosic biomass pretreatment for the production of bioethanol, Bioresource Technology, 299: 122635.

https://doi.org/10.1016/j.biortech.2019.122635

Walter A., Galdos M., Scarpare F., Leal M., Seabra J., Cunha M., Picoli M., and Oliveira C., 2014, Brazilian sugarcane ethanol: developments so far and challenges for the future, Wiley Interdisciplinary Reviews: Energy and Environment, 3(1): 70-92.

https://doi.org/10.1002/wene.87

Wang Z., Dien B., Rausch K., Tumbleson M., and Singh V., 2019, Improving ethanol yields with deacetylated and two-stage pretreated corn stover and sugarcane bagasse by blending commercial xylose-fermenting and wild type Saccharomyces yeast, Bioresource Technology, 282: 103-109.

https://doi.org/10.1016/j.biortech.2019.02.123