## 4 Conclusions  
The most relevant findings of this study were the following:  
* It can be inferred, from the characterization of the residues, that the moisture content was suitable for subsequent pelletizing without any previous drying process (less than 15%).
* Regarding ash content, all the residues were suitable for pellet production (A class) except for Ma4 residue, which was collected on the soil and showed a high ash content (9.68%). This fact pointed out that the contact with the soil had a negative effect on the subsequent valorization of the waste. Therefore, direct collection by harvesting machines is desirable.
* The heating values are within the optimum range established by the corresponding quality standard for pelletizing (more than 16 MJ/kg, dry basis).
* Concerning ash composition, SiO\({}_{2}\) and K\({}_{2}\)O values imply a possible low ash melting point, which would be interesting to check through combustion tests of the residues.
* With regard to the pyrolysis process, optimum characteristics were observed for corncob waste or samples with the majority of its content containing this residue (Ma1 and Ma2); no significant difference was found in the presence of leaves. In this case, the selective collection of residues was highly recommended. Moreover, the direct collection by harvesting machines (without any contact between residues and soil) was advisable, as the subsequent degradation produced unfavorable results in pyrolysis.
* Concerning the study of combustion process, better characteristics were observed when corncob waste and corn stalk were combined. On one hand, the wastes with a majority of its content containing corncob waste obtained lower ash content. On the other hand, the wastes with corn stalk had improved combustibility. In any case, the negative effect of the degradation of the waste collected on the soil can be observed.  
Therefore, it can be said that corn residues are a suitable biomass product that have an optimum behavior for energy use, that is, pellet production for domestic use, pellets for industrial use, direct electricity production or other thermal uses that can imply a valorization of corn crops. The results obtained pointed out the importance of the collection of the wastes by the time of their generation, avoiding contact with soil, as this would considerably worsen the thermal properties, especially for the subsequent densification at a small-scale, which would be the most profitable application for corn growers. Regarding the selective collection of wastes, it is highly advisable that, if the subsequent thermal use is going to be a pyrolytic process, not to require the removal of leaves, as better behavior was found for the separated corncob waste. In the case of combustion, although the samples with stalks improved the combustibility characteristics, this slight improvement did not compensate for the drawback related to the increase in ash content, especially for their use in small facilities. Consequently, selective collection is equally recommended.  
Conceptualization and methodology, M.T.M. and R.G.-M., investigation, M.T.M., R.G.-M., J.L.A., F.J.S., P.R. and A.B.-J.; writing--original draft preparation, R.G.-M.; writing--review and editing, M.T.M., R.G.-M. and J.A.; supervision, M.T.M., J.L.A. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by Junta de Extremadura and FEDER (Fondo Europeo de Desarrollo Regional \"Una manera de hacer Europa\") for its support through the economic aid for the project Application of the concept of circular economy to the management of bio-waste with limitations of use (IB18083), as well as research groups (GR18137, GR18057 and GR18035).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.