## 2 Materials and Methods
### Characterization Techniques  
CPH elemental composition was determined on a dry basis with an elementary analyzer (True Spec Leco CHNS mod. 4084), according to the norm CEN/TS 15104 (for  
Figure 1: Cocoa pod husks, after natural air-drying.  
determining the content of C, H, and N) and CEN/TS 15289 (for S). Oxygen (O) content was determined by calculating the difference, using the following expression:  
\[O\%=100\%-(\%C+\%N+\%H+\%S)\]  
A proximate analysis of the material samples was carried out according to technical specifications. The determination of moisture, volatile matter, and ashes was performed following UNE-EN 14774-2, UNE-EN 15148, and UNE-EN 14775 norms, respectively [20; 21; 22].  
Higher heating values (HHVs) were determined using a Parr 1351 adiabatic oxygen bomb calorimeter (UNE-EN 14918) [23].  
The ash fusibility test was conducted following the ASTM D 1857 standard [24]. The ashes were obtained by calcination at 815 \({}^{\circ}\)C in an oxidizing atmosphere and analyzed using a LECO AF-700 automatic device. The sample, shaped as a pyramid (triangular base and 19 mm height), was placed in a furnace with a maximum temperature of 1500 \({}^{\circ}\)C and a controlled heating rate of 8 \({}^{\circ}\)C/min. Ash composition was determined according to suitable technical specifications: samples obtained by calcination at 815 \({}^{\circ}\)C were analyzed to quantify major and minor elements, including Ca, K, P, S, Fe, Al, Mg, Na, and Si. The analysis employed wavelength-dispersive X-ray fluorescence (WDXRF) using a Bruker S8 Tiger spectrometer. The method was validated as an efficient alternative to standard techniques involving microwave digestion and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), showing consistent results with certified reference materials. Key analysis conditions included helium atmosphere, QuantExpress evaluation mode, and oxide quantification. The crystals used allowed measurement across energy ranges suitable for elements from O to U.  
Halogens (Cl and F) were determined after ash samples were added to boiling water (120 \({}^{\circ}\)C, 60 min). The resulting slurry was then filtrated, and the content of these elements were measured by ionic chromatography.  
The thermogravimetric behavior under inert and oxidant atmosphere was analyzed with a thermobalance (TGA/ DTG) (STA 449 F3 Jupiter--Netzsch) coupled with a mass spectrometer (QMS 403D Aeolos III--Netzsch) using Ar as carrier gas (100 mL-min\({}^{-1}\)) and Ar/O (80/20 mL-min\({}^{-1}\)), respectively, and a heating rate of 5 \({}^{\circ}\)C min\({}^{-1}\) from 40 \({}^{\circ}\)C to 800 \({}^{\circ}\)C. Mass spectrometry monitored the evolved gases, with specific m/z ratios tracked for H\({}_{2}\) (2), C (12), CH\({}_{3}\) (15), CH\({}_{4}\) (16), O\({}_{2}\) (16, 32), OH (17), H\({}_{2}\)O (18), CO/N\({}_{2}\) (28), CH\({}_{3}\)OH (31, 32), Ar (40), and CO\({}_{2}\) (44).  
All characterization analyses, including proximate and ultimate analysis, determination of higher heating values (HHVs), and ash fusibility tests, were performed in triplicate to ensure data reliability. The results are reported as mean values with standard deviations to ensure data reliability. The statistical analysis confirmed minimal variance across replicates, indicating high reproducibility of the measurement.