Influence of double-cut harvest system on biomass yield, quality and biogas production from C4 perennial grasses

Highlights: • Double-cut harvest system contributed to the increase of dry matter yield compared to a single-harvest system. • Double-cut harvest system influenced on C/N ratio and lignin content decreasing in the perennial grasses biomass. • The biomass of perennial C4 grasses harvested two times in a growing season was susceptible for ensiling. • Double-cut harvest system did not influenced on the biogas yield obtained from switchgrass and big bluestem. -- Abstract: This study's aim was to determine the impact of two harvests per year on the yield, biomass quality, and suitability for ensiling and biogas production of cordgrass (Spartina pectinata Bosc ex Link), switchgrass (Panicum virgatum, var. Dacotah) and big bluestem (Andropogon gerardii, var. Bison). Grasses were harvested at the end of June (I harvest) and at the beginning of October (II harvest). Single harvest at the beginning of October was also conducted. Biomass from I and II harvest was ensiled and then subjected to anaerobic digestion. There were no differences between dry matter yield of investigated grasses from I and a single harvest, which indicated the validity of two harvests per year in order to increase biomass yield during a growing season. Double-cut harvest system had an effect on C/N ratio and lignin content decreasing in the biomass compared to a single harvest. Biomass from I and II harvest was suitable for ensiling. Double-cut harvest system did not influence on biogas yield from switchgrass and big bluestem. Cordgrass and big bluestem have been found to be better feedstock than switchgrass for biogas production in Polish climate conditions because they offered higher methane yield per hectare.