## 4 Use of Pet Food Waste for Energy Production  
Metals and alloys are susceptible to corrosion when frequently exposed to corrosive gases such as water vapor, CO\({}_{2}\), and H\({}_{2}\)S. The corrosion index of gases generated during the combustion of production waste was determined, as these gases can corrode the metallic pipes in the exhaust ducts. Mass loss, either in pipe wall thickness or surface area, is used as an indicator of the corrosion penetration rate. The most common unit used to  
Figure 2: Experimental setup diagram for the analysis of VOC material combustion and corrosion in test probe. quantify physical corrosion progression is mis per year (mpy) [28; 29]. The corrosion rate, \(\Theta\), expressed in mills per year (mpy), can be calculated from mass or thickness loss as  
\[\Theta=\frac{m}{A\,\rho\,t}\lambda \tag{1}\]  
where \(m\) is the mass loss in grams, \(A\) is the exposed surface area in cm\({}^{2}\), \(\rho\) is the material density in g cm\({}^{-3}\), \(t\) is the exposure time in hours, and \(\lambda\) is the conversion factor of 3.44882 \(\times\) 10\({}^{6}\) mills h cm\({}^{-1}\) a\({}^{-1}\) (this correction factor results from converting the units used in this study (g, cm, h) to the original units (lb, in, year)). Carbon steel AISI C1018 materials, each weighing approximately 60 g, with an average density of 9.3 g cm\({}^{-3}\) and a surface area of 24.11 cm\({}^{2}\), were used as corrosion samples. The experimental procedure utilized waste samples derived from dog and cat pet foods, along with three control fuels: Radiata pine sawdust, natural gas, and residential stove pellets. The tests were conducted over a five-hour period in a laboratory furnace (Memmert UM-500, Schwabach, Germany), which was specially modified for this purpose at temperatures ranging from 800 to 900 \({}^{\circ}\)C. An excess air ratio between 3 and 5 was maintained throughout the experiments. The pre-weighed metal specimens were exposed to the combustion exhaust gases for a defined duration. After exposure, they were reweighed to determine the mass loss, \(m\), which served as a measure of corrosion. GHG emissions were estimated in accordance with the GHG Protocol, the most widely adopted global framework and the standard applied by the company under study across its industrial operations. This protocol classifies emissions into three scopes:  
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the calorific value (expressed in GJ kg\({}^{-1}\)) and ash content of the analyzed material were determined, with the results shown in Table 1.  
These results are energetically favorable, considering that eucalyptus firewood has a higher heating value (HHV) ranging from 0.017176 to 0.017986 GJ kg\({}^{-1}\) and an ash content of 0.69%, as reported by [PERSON] et al. [32]. Therefore, the analyzed residues exhibit a high energy potential. Moreover, when compared to other agro-industrial byproducts commonly used as biofuels, these residues show superior energy content, with values comparable to those of corn cobs [33; 34]. In addition to calorific value, ash content and elemental composition are critical parameters for evaluating the potential of a biomass fuel to form deposits in the boiler and to cause corrosion, erosion, or abrasion to heat exchange surfaces and other components [35]. The presence of metals and non-metals, as determined via X-ray Fluorescence (XRF) and Atomic Absorption Spectrometry (AAS), is presented in Table 2. These results enable the estimation of trace metal emissions that may be released during the combustion of food waste. Such emissions can occur in non-volatile forms that remain in the ash or in volatile forms that vaporize at high combustion temperatures. Trace metals with notable environmental relevance include arsenic (As), cadmium (Cd), and lead (Pb). Additionally, highly volatile elements such as mercury (Hg) and selenium (Se) were also detected.