Greenhouse Gas Emission Reductions in a District Heating and Cooling System by Using Woody Biomass

Abstract

A life cycle assessment of greenhouse gas (GHG: CO2, CH4, N2O) emissions for a district heating and cooling (DHC) system using woody biomass was conducted, and reductions in emissions from substitution of fossil fuels with woody biomass were analyzed in Shiwa, Iwate Prefecture. From the process of log production to heating, the life cycle GHG emissions of the DHC system were 70.8 kg-CO2-eq/GJ-heat. Of these emissions, the majority (92%) originated from the heating process. Substitution of liquefied petroleum gas (LPG) with wood chips resulted in a reduction of GHG emissions of 92.4 kg-CO2-eq/GJ-heat. With this substitution taken into account, the net GHG emissions of the DHC system were 21.6 kg-CO2-eq/GJ-heat, which indicated that the DHC system had the potential to reduce GHG emissions. The GHG emission reductions generated by the DHC system would not be obtained if the heat usage efficiency were reduced from the current 29% to less than 23%. Conversely, if the heat usage efficiency were improved to 75%, reductions in GHG emissions corresponding three times the current levels could be obtained. The GHG emission reductions could also increase if kerosene or heavy oil were used as a substitute for the currently used LPG. However, compared to the significant impact of heat usage efficiency, the substitution of fossil fuels had a relatively minor effect on the reduction of GHG emissions.