Effect of Harvest Time and Frequency on Biomass Quality and Biomethane Potential of Common Reed (Phragmites australis) Under Paludiculture Conditions

This study examined the effect of harvest time (from May to September) and dry matter partitioning on biomethane potential and methane yield per unit area of Phragmites australis cultivation under paludiculture conditions. The experimental site is part of a larger experimental platform (San Niccolò, Pisa) located within the Massaciuccoli Lake Basin in Central Italy (Tuscany, IT). The study also took into account the double cut strategy by evaluating the regrowth from June to September. Biomethane potentials ranged from 384 to 315 and from 412 to 283 NL CH4 kg VS−1(normal liters of methane per kg of volatile solids) for leaves and stems, respectively. About digestion kinetics, maximum daily production rate (Rmax) was significantly affected by harvest time and not by plant partitioning. Along the harvest season, biomethane yield per unit area was mostly driven by the biomass yield showing an increasing trend from May (1659 Nm3 ha−1) to September (3817 Nm3 ha−1). The highest value was obtained with the double harvest option (4383 Nm3 ha−1), although it was not statistically different from the single harvest carried out in September. Owing to its remarkably lower yields, P. australis cannot be considered along the same lines as crops conventionally used for biogas production, but it may represent an interesting option for paludiculture cropping systems by coupling peatland restoration with bioenergy production. September harvest management seemed the most feasible option, although further investigation on crop lifespan is needed.