Heating systems LCA: comparison of biomass-based appliances

Biomass provides an attractive solution for residential heating systems based on renewable fuels, even though biomass-based domestic heating systems are recognized as significant particulate matter emitters; thus, a life cycle assessment (LCA) approach was used in the study to compare two different appliances: a wood stove and a pellet stove, both modeled according to the best available technologies definition. System boundaries of each scenario refer to a cradle-to-grave approach, including production, use and disposal of the heating appliance, as well as the preparation of biomass feedstock. The assessment of environmental impacts was performed assuming 1 MJ of thermal energy as the reference flow, considering the categories of particulate matter formation, human toxicity, climate change, and fossil fuel depletion, according to the ReCiPe 1.07 method. Finally, the comparison was extended to certain innovative heating systems in order to qualitatively evaluate potential improvements in residential heating performances. The results show that the wood stove reaches the highest scores in the categories of particulate matter formation and negative effects for human toxicity, as a consequence of the stove's lower combustion efficiency, which would lead to a preference for the pellet stove. However, when climate change affecting human health and the ecosystem, and fossil depletion are considered, the choice appears more uncertain due to the energy consumption from the pelletizing step. Alternative technologies (e.g., solar panels in combination with a gas boiler) show better scores related to fine particles emission reduction, even if a worsening in other categories is observed. The results were validated by a sensitivity analysis. The study suggests that a LCA approach can support the choice of the best domestic heating system, helping to promote policy initiatives on a sound basis and to understand which are the main key levers to act for reducing the total environmental burdens of biomass-based heating appliances.