Suitability of giant reed (Arundo donax L.) for anaerobic digestion: Effect of harvest time and frequency on the biomethane yield potential

This study aimed to investigate the potential of giant reed for biomethane production by examining the influence of harvest time and frequency on the Biochemical Methane Potential (BMP), the kinetics of biomethane accumulation in batch reactors and the expected methane yield per hectare. The crop was cut at five different times, regrowths from early cuts were harvested in autumn and BMP of each cut was assessed. The highest BMP (392 NL kg VS−1) and the best kinetics of methane production were associated to juvenile traits of the crop. By coupling the early cuts with the corresponding regrowths (double harvest), the dry biomass (from 35 to 40 Mg ha−1) equaled that obtained by a single cut at end of the season (38 Mg ha−1), while the methane yield per hectare (11,585-12,981 Nm3 ha−1) exceeded up to 35% the methane produced with a single harvest at crop maturity (9452 Nm3 ha−1).