Assessment of energy properties of maize and multi-crop pellets and environmental impact of their combustion

Biomass resources are very important raw materials for energy purposes in many countries of the world, and these renewable local sources of energy can replace fossil fuels, whose resources are decreasing and they have a negative impact on the environment. The presented paper provides new research results of multi-crop plants, such as herbaceous, fibrous and leguminous plants growing, harvesting and utilization for energy purposes. Maize biomass can be used not only for the production of fodder or biogas, but also for the production of solid biofuels. In this work were investigated these plants: maize, which is grown as a high-biomass perennial herbaceous plant, together with field beans, accumulating nitrogen in the roots and soil, and the third multi-crop plant was fibrous hemp, which overgrows weeds and contributes significantly to the reduction of CO2 in the environment. At the beginning plants were harvested and biofuel was prepared by drying, chopping, milling and production of biofuel pellets. The most important properties of pellets made from multi-crop plants and their mixtures, which are influencing the preparation and use of biofuels for energy, were investigated and determined. Investigations were carried out in the fields and laboratories of the Vytautas Magnus University Agriculture Academy and in the Lithuanian Energy Institute. After investigation of biomass pellet qualitative properties, it was determined that the density of all investigated sorts of pellets varied from 1106.5 to 1161.3 kg mE−3 dry matter (DM), and pellet moisture content reached 6.9 ± 1.6%. A lower heat value (LHV) was sufficiently high and varied from varied from 16.8 to 17.0 MJ kgE−1. Additionally, there were investigated the harmful emissions of gases CO2, CO, NOx and CxHy when these pellets were burned. All these results are in accordance with the requirements of standards.