Comparison of two perennial energy crops for biomass production at the end of their life cycle

Abstract

Nowadays fossil fuels are decreasing, causing the world's interest in renewable energy sources to rapidly grow. One of the most interesting renewable and ecologically pure fuels is biomass, which is considered to be carbon neutral. Biomass is a promising source of energy, as it can be used directly as an energy resource. Its quality characteristics such as gross calorific value and ash content are of paramount importance so as to improve the combustion process. Furthermore, during the last three decades, there has been an increasing interest in the production of biomass pellets for domestic and industrial use. Alternative feed stocks will need to be sourced to meet the demand for biomass pellets. Investigation for new energy crops that produce high amounts of biomass under low inputs and of high energy efficiency are the main tasks of this field. Therefore, the aim of this study is to assess the biomass yield and the quality characteristics (gross calorific value and ash content) of two perennial energy crops (Cynara cardunculus L. and Panicum virgatum L.) growing in a typical soil (Fluventic Xerochrept) of the main agricultural land of central Greece. The comparison for both cultivated crops was made in order to show the results during their 8th growing year. The examined factors were the irrigation (two levels: irrigated and rainfed) and the nitrogen fertilization (two levels: 0 and 80 kg N ha-1) as well as their effect on the dry biomass yield and the gross calorific value. It was found that higher dry biomass yield was produced from cardoon (21.3 vs. 14.23 t ha-1), while the higher average gross calorific value was observed for switchgrass biomass (17.31 vs. 15.65 Mj kg-1). Finally, multiplying the dry biomass yield (t ha-1) with the gross calorific value (Mj kg-1) it was found that 334 and 245 Gj ha-1 from a cardoon and a switchgrass cultivation could be produced, respectively. Cardoon has better results than switchgrass probably due to the fact that switchgrass is growing from March till October; while cardoon’s growing period is from October to June and in such areas precipitation is in shortage during summer months. Both crops could achieve high amounts of energy per hectare and thus their introduction in future land use systems, for an environmentally friendly energy production should be seriously taken into consideration. © 2020, Eesti Pollumajandusulikool. All rights reserved.