Evaluation of methane production from maize silage by harvest of different plant portions

In this paper, we present the results of experimental field tests carried out in Northern Italy that aim to evaluate the anaerobic methane potential (BMP) of different portions of ensiled maize hybrids. The BMP production is evaluated considering the possibility of harvesting and ensiling: the whole plant; the plant cut at 75 cm of height; the ear only; the plant without the ear. For the different solutions, the results are reported as specific BMP and as average biogas production achievable per hectare. The methane production by harvesting and ensiling the whole plant (10,212 and 10,605 m3 ha−1, for maize class 600 and 700, respectively) is higher than the ones achievable by the other plant portions (7961 and 7707 m3 ha−1, from the ear; 9523 and 9784 m3 ha−1, from the plant cut at 75 cm; 3328 and 3554 m3 ha−1, from the plant without the ear, for maize class 600 and 700, respectively). The harvest of the whole plant, although it is the most productive solution, could not be the best solution under an economic and environmental point of view. Harvesting only the ear can be interesting considering the new Italian subsidy framework and for the biogas plants fed by biomass transported over long distances.