Cradle to Grave Life Cycle Assessment of Mexican Forest Pellets for Residential Heating

This study applies environmental life cycle assessment to quantify and compare the environmental profile of the production and use of wood pellets for residential heating (baseline) and compares the pellet system with two different alternative systems for residential heating in Mexico: (1) the use of LPG heater and (2) one electricity heater powered by three different sources of electricity. The baseline system boundaries include the stages of forest management, transportation, industrial, distribution, wood pellet energy conversion, and ash management. First-hand data and measurements of the emission profiles in the field and laboratory were developed. The functional unit was 1 MJ of thermal energy for residential heating. Environmental impacts were calculated for six impact categories from the ReCiPe midpoint method. Furthermore, a sensitivity analysis was performed to evaluate the influence of the allocation criteria (mass and economic) as well as adopting different values for the electricity sources (system's hotspots). The results obtained for each impact category show a relatively wide range of variation when the five scenarios of the heating systems are compared and analyzed. Electricity heater powered with photovoltaic electricity is better for all the impact categories analyzed. The performance of pellets and LPG is very close, but the pellets have lower impacts on global warming (three times), fossil resource scarcity (four times), and acidification. Therefore, the use of pellets in an efficient boiler is a promising option for residential heating.