THE EVALUATION OF BIOMASS OF THE Sida hermaphrodita AND Silphium perfoliatum FOR RENEWABLE ENERGY IN MOLDOVA

Perennial herbaceous crops can become the main basis for renewable energy production in agricultural ecosystems in future. To determine the plant species that are the most suitable for biomass production, their biological peculiarities and productivity, biochemical composition and thermophysical properties, social and ecological impact must be investigated thoroughly. The local varieties of perennial energy crops: Energo, Sida hermaphrodita and Vital, Silphium perfoliatum registered in the Catalogue of plant varieties and patented in the Republic of Moldova, which were cultivated in the experimental land of the Botanical Garden (Institute) of the ASM served as subjects of study. Maize and sunflower (for biogas production) and wheat straw (for biosolid fuel) control variants. It has been established that the gas forming potential of organic dry matter in silage varies from 458 l/kg in Sida hermaphrodita to 471 l/kg in Silphium perfoliatum. The best results of methane production were achieved by the silage of cv. Energo of Sida hermaphrodita – 4000 m/ha and cv. Vital of Silphium perfoliatum – 3675 m/ha, versus 3127 m/ha, maize silage, and 2881 m/ha, sunflower silage. The silage substrate of Sida hermaphrodita had higher content of methane (53.1%). The biomass of Sida hermaphrodita and Silphium perfoliatum was distinguished by high bulk density, moderate gross calorific values (18.3-18.7 MJ/kg.) and ash content (1.5-3.0%), but wheat straw – by low bulk density and low calorific value (17.0 MJ/kg) and high content of ash (5.1%). The potential of energy production of the local varieties of perennial energy crops was of 350-380 GJ/ha. The best results were achieved by cv. Vital, Silphium perfoliatum, due to its high productivity of dry biomass.