Production and characteristics of biomass for Arundo donax, Pennisetum purpureum, and P. Purpureum × P. Glaucum in a short-rotation crop system in humid tropical conditions in Costa Rica

The high global demand for fossil fuels has led to the search for alternative sources of renewable energy, such as the production of biomass from short-rotation crops (SRC). This study evaluated three grass species (Arundo donax, Pennisetum purpureum, and P. purpureum × P. glaucum) in SRC systems planted at 10³ plants ha^-1 in humid tropical conditions in Costa Rica, considering biomass production, moisture content, and energy and chemical properties at four harvest ages (12, 18, 24, and 30 months). The results showed that the height of all species varied between 0.9 and 3.5 m at the different harvests, while the production of dry biomass varied between 2.52 and 39.25 Mg ha^-1. As for their chemical properties, the ash content varied between 5.9% and 10.2%, volatile matter varied between 73.3% and 81.9%, and net calorific value varied between 15.86 and 18.94 MJ kg^-1. In the three species, the production of biomass was greater at the 12-month and 18-month harvests; at later harvests, biomass production began to decrease, leading to increased moisture and ash contents, lower volatile matter, and lower calorific value. The biomass quality and production of A. donax were different from those of P. purpureum.