Growing Perennial Energy Crops with Different Cycles Improves Feedstock Flow to Bioenergy Plants: The Cases of Miscanthus Giganteous and Cynara Cardunculus.

Perennial grasses such as Miscanthus giganteous (miscanthus) have a great potential for bioenergy production in US. However, their growing cycles coincide and harvested approximately the same time; usually late in winter or early in spring season when plant moisture and chemical composition approach industrial requirements for feedstock processing. At harvest biomass feedstock availability is maximized, and in order to support such a high flow of biomass to Plants, logistics should be optimized and Plant storage capacities should be high also. Obviously such a scheme has limitations, e.g. biomass maintenance risks, and indicates a need for inclusion of more species (preferable perennials) with different harvesting periods in the production systems. In this context, Cynara cardunculus (cynara) a perennial C₃ herb can be an option. In areas with Mediterranean climate (e.g. 35–40°N), cynara’s growth cycle starts early in fall and ends mid-summer. On average across experiments carried out in the Mediterranean region, cynara’s feedstock at harvest (August) had 10–20% moisture content, 13–17 MJ/kg energy content, and 12–25 t/ha/y above ground dry biomass yields (experimental basis). Miscanthus experimental dry yields in the same region were 20–40 t/ha/y. The high biomass yields of both crops were mainly explained by the long-stay green period (leaf area index >3 for the most of growth cycle). Cynara has a compound inflorescence structure, with numerous heads per plant that contain oil (23%) and protein (18%) rich seeds with a seed harvest index of 15%. The crop is propagated by seeds and the establishment cost is much lower compared to miscanthus. These data are promising and may stimulate further research on the adaptability and productivity of this perennial herb in US for energy production.