Towards Life Cycle Assessment for the Environmental Evaluation of District Heating and Cooling: A Critical Review

District heating and cooling networks represent a compelling energy system solution due to their capacity to integrate renewable energies and leverage local surpluses of thermal resources. The meticulous design and optimization of network infrastructure are imperative to fully exploiting the potential of these energy systems. The Life Cycle Assessment of district heating and cooling networks for the purpose of environmental sustainability is a crucial and increasingly demanded aspect, particularly in light of the progressively stringent European regulations. The Life Cycle Assessment methodology could offer an evaluation throughout the entire life cycle of such networks. The proposed review scrutinizes the application of the Life Cycle Assessment methodology to evaluating the environmental profile of district heating and cooling systems. The methods, findings, and challenges are examined through a literature review and case study analysis. The results highlight variations in the climate profile influenced by the network generation type and multifunctionality approaches. The analysis revealed a range of emission factors, spanning from 11 gCO2eq/kWhth to 470 gCO2eq/kWhth for district heating and 6 gCO2eq/kWhth to 64 gCO2eq/kWhth for district cooling. The discussion emphasizes integrating district heating and cooling network management considerations and addressing methodological challenges. This study concludes by proposing future research directions for developing a universal LCA-based tool for district heating and cooling network analysis.