# Analysis of the Sugarane Biomass Use to Produce Green Hydrogen: Brazilian Case Study
## 5 Environmental Impacts and Sustainable Solutions
### 2G Ethanol Production  
Brazil is recognized for producing 1G sucrose ethanol at the lowest cost globally (USD 0.3396 L\({}^{-1}\)) and utilizing bioelectricity as a proven, cost-efficient technology (USD 360 GJ\({}^{-1}\)). 2G technology, in addition to being a robust process, is expected to maintain low costs and deliver an attractive energy balance [74]. To evaluate the energy potential of emerging biomass technologies, it is relevant to compare the energy output from the complete combustion of sugarcane biomass (17.33 MJ kg\({}^{-1}\)) with that of its primary cell wall components: cellulose polysaccharides (44%), hemicellulose (25%), and the hydrophobic, aromatic macromolecule lignin (28%). These components hold potential for both ethanol production and energy generation [67]. According to experimental data reported by [PERSON] et al. (2020), it is possible to estimate that the volume of 2G ethanol produced from 1 metric ton is equivalent to 24.6 L (594 MJ). During the pretreatment stage, 122 kg\(\cdot\)ton\({}^{-1}\) of solid fraction (comprising cellulose and lignin) is processed. Of this, 40 kg\(\cdot\)ton\({}^{-1}\) is consumed during fermentation, while the remaining 82 kg\(\cdot\)ton\({}^{-1}\), composed of solid lignin residue, is utilized in the cogeneration process, contributing 1705 MJ. This energy is subsequently reused in the sugarcane juice extraction process. The energy content of 2G ethanol was calculated using the total volume produced and the density of hydrated ethanol, determined to be 0.809 kg\(\cdot\)L\({}^{-1}\)[75]. This results in a higher heating value of 29.85 MJ\(\cdot\)kg\({}^{-1}\)[76], translating to an energy yield of 594 MJ\(\cdot\)ton\({}^{-1}\) of processed biomass. These values underscore the significant energy potential of 2G ethanol as a renewable fuel. Figure 12 provides an overview of the sugarcane processing pathway for 2G ethanol production. As observed in Figure 2, after harvesting, sugarcane undergoes a grinding process to extract SB. Typically, SB is utilized to produce high-pressure steam and generate electricity, serving as a crucial energy source in cogeneration plants. This practice ensures energy self-sufficiency and reduces the environmental impacts of industrial operations [68]. Additionally, a portion of the SB is diverted for pretreatment steps, such as organosolv, acid, alkaline, or ionic liquid processes, which facilitate the breakdown of biomass into components for 2G ethanol production. The solid fraction remaining from the pretreatment stage contributes to energy generation and fertilizer production, further enhancing the efficiency and sustainability of the sugarcane processing system. The solid fraction of sugarcane bagasse that is diverted from direct energy production, which is rich in lignin--the most abundant aromatic polymer in nature--can still be used  
Figure 12: Sugarcane processing to produce 2G ethanol. Adapted from [68]. for energy generation to support industrial self-sufficiency. However, the energy surplus is reduced, as lignin constitutes approximately 1/5 to 1/3 of SB [77]. Due to its high storage content of phenolic compounds, lignin is considered an alternative source to produce various polymers and biomaterials [78]. Thus, while lignin in sugarcane bagasse reduces the energy surplus, it offers significant potential for producing valuable polymers and biomaterials. The chemical pretreatment of sugarcane bagasse, a widely used method for breaking down lignocellulosic into its monomeric and oligomeric units for bioconversion into ethanol, involves the use of dilute acids, alkaline solutions, organosolv processes, and ionic liquids [68]. As one of the largest bioinadustries, the ethanol sector--particularly with the emergence of 2G ethanol--faces a growing need for technological advancements and sustainable approaches.