## 3 Results and Discussion
### Chemical Characteristic of Mashes and Fermentation Results
Despite some differences between the process indicators depending on the type of processed waste bread and the method of the mash preparation, it can be stated that these indicators are comparable to those obtained during the processing of grain raw materials commonly used in the distilling industry for the production of ethanol [36; 37; 38; 43]. A brief economic analysis of the process carried out in the framework of our study, comparing it to traditional methods, indicates that this solution is economically attractive and in line with the principles of the circular economy. The cost of raw materials represents approximately 50% of the total production costs when traditional starchy raw materials (maize and rye) are used for the production of spirit. The utilisation of waste bread for ethanol production appears to be advantageous for both the distillery and the bakery. It is possible to achieve a significant increase in profitability by reducing the cost of raw materials for a distillery by up to ten times that of grain cereals. For bakeries, the net cost of the operation is zero, and in addition, waste management costs are eliminated [49]. In turn, when assessing the pressureless methods of mash preparation (PLS, NSH) used for the processing of waste bread, it is important to consider their competitive solutions in relation to pressure-thermal methods that rely on the use of pressure devices (i.e., steamers). These pressureless methods offer a cost-effective alternative, as they do not  
Figure 3: Fermentation indices of waste bread-based mashes. Different letters indicate significant differences (\(p\) < 0.05) between mean values of intake of sugars (lowercase letters) and fermentation efficiency (capital letters). require specialized or expensive equipment. The elimination of the processing of the raw material at high temperatures (approximately 150 \({}^{\circ}\)C) in favour of starch liquefaction carried out at a temperature of approximately 90 \({}^{\circ}\)C results in thermal energy savings of up to 50%. Nevertheless, the consumption of electricity during the grinding of the raw material processed using the PLS method may result in a total energy saving of 20-34% in comparison to the pressure-thermal methods [50]. Additionally, the implementation of simultaneous saccharification and fermentation (SSF) methods increases thermal energy savings, as the distinct step of separate saccharification at a temperature of approximately 65 \({}^{\circ}\)C is eliminated. This solution also ensures a high fermentation efficiency of 96% of the theoretical efficiency. An alternative and promising solution to the PLS-SSF strategy, which allows for the maximum reduction of investment costs and energy savings, with slightly lower process efficiency (up to about 88% of theoretical yield), might be the method of native starch hydrolysis (NSH). It should be noted, however, that the critical point of pressureless methods of processing starch raw materials, especially of native starch hydrolysis (NSH), is the risk of microbiological contamination. This can be effectively minimised by using protection with hop \(\alpha\)-acids preparations dedicated for the distilling industry [51]. Nevertheless, in order to fully assess the feasibility of the process, other technical and economic factors throughout the entire value chain should also be taken into consideration. These include fluctuations in the composition of bakery waste, the collection of waste bread, and the methods of ethanol recovery and purification [52].