Olha H. Life cycle assessment of thermal energy production from solid biofuels using energy efficiency and greenhouse gas emissions reduction indicators

Complex analysis of thermal energy production from wood and agriculture biofuels had been performed in the work. Life cycle assessment was used as a methodology and energy yield coefficient, greenhouse gases emission reduction as impact indicators. Values of energy yield coefficient at the level of 5, and greenhouse gases emission reduction at the level of 35% considered as limiting due to sustainability requirements during thermal energy production from solid biofuels. Next solid biofuels had been analysed: chips and pellets from forestry residues, bales and pellets from straw. The most important parameters of the life cycle had been defined together with their influence on the efficiency of the heat energy from solid biofuels. Using of life cycle assessment approach allowed improving the comparison of energy units that run on different types of biofuels. The limit values of transportation distance to achieve sustainable values of energy yield coefficient and greenhouse gas emissions reduction have been defined. It is shown that the use of wood chips and straw bales in distance transportation of raw materials up to 100 km reduces consumption of primary energy of fossil fuels in 10 and more times. Using pellets reduce consumption of primary energy in fossil fuels in five times. Specific greenhouse gas emissions from biomass combustion for heat production are in the range of 10-20 gCO2-eq./MJ that in 6-17 times less compared with fossil fuels usage. Reduction of greenhouse gas emissions by using wood and straw is at the level of 72-92% when transporting biomass at the distances that corresponds to the sustainable value of energy yield coefficient. Pelletization of forest residues is appropriate (in comparison with a chips) within appropriate values of energy efficiency indicators (energy yield coefficient is more that 2), and, if they are need to be transported to a distance of over 200 km. Straw pellets usage during they carriage by road is always characterized by lower rates the energy efficiency indicators and bigger greenhouse gases emissions compared to bales. However, acceptable technical and economic indicators limit the use of straw bales. In making practical logistics solutions recommended to use the maximum distance that corresponds to satisfactory payback period for the production of thermal energy - this data satisfy the range of appropriate values of energy efficiency.