Raquel García-Mateos

The valorization of agricultural residues assumes a pivotal position in the circular economy by transforming waste into a useful and environmentally friendly product, with the cultivation of corn, as one of the world’s predominant crops, being crucial. This article aimed to investigate the feasibility of using residues from corn crop as biofuels, going more in-depth into determining the effect that crop variety may have on its thermal qualities. Specifically, 12 samples of corn crop residues were studied in three main groups: conventional, forage, and transgenic varieties. To achieve this, proximate and ultimate analyses, thermogravimetric analyses, and differential scanning calorimetry were conducted, along with a study of gas emissions and a statistical comparison of different varieties. From the results obtained, it is worth highlighting the low ash content in all the samples (between 5.55% and 8.42%) and high calorific values (higher than 17 MJ/kg in all cases), as well as optimal thermal results for all the samples studied in both pyrolysis and combustion processes. Significant differences were found between the different varieties; in particular, it was observed that the forage variety presented more optimal conditions for its application in both processes. This may represent a potential competitive advantage for the forage varieties.

The corn crop is one of the most important crops worldwide. However, the management of the residues generated is not efficient enough, which diminishes the competitiveness of this crop. An interesting option for the valorization of these wastes is their thermal use. In order to make the management of this residue as much efficient as possible, it is vital to know the different processes related to a corn harvest, and try to adapt the use of this waste depending on its characteristics. Thus, in this work, and on the basis of a conventional corn harvest, a differentiated analysis of the residue generated was carried out, including its characterization and assessing its behavior during pyrolysis and combustion. The results pointed out the importance of collecting residue immediately after its generation and avoiding its contact with the soil as this factor tends to worsen its thermal properties and ash content. Concerning the selective collection, it is highly advisable if the subsequent thermal use is going to be a pyrolytic process. In the case of combustion, even though the samples that contain corn stalk showed better combustion properties, this improvement did not outweigh the adverse effects related to the increase in ash content, especially for its pelletizing.