The OPTINORFARM project aims to develop a user-friendly optimization tool for advisers and farmers. This tool integrates greenhouse gas emission measurements but also recognizing the importance of other environmental impacts. Therefore, additional assessment metrics were explored in this technical report. The report is a literature review of different functional units (FU) used in Life Cycle Assessment (LCA) of multifunctional agricultural systems, evaluating their advantages and limitations. A qualitative analysis highlights the need to align metric selection with study goals and stakeholder requirements. For farming systems, using at least two FUs is recommended for a comprehensive evaluation.
Mass-based FUs are the most widely used due to their flexibility, while nutritional-based units are valuable for consumer-relevant assessments, such as protein quality. Economic metrics are less common in LCAs but provide useful insights for farm management. Land use is another key metric, balancing production efficiency with sustainability. Resource optimization metrics have future potential but are rarely applied. In addition, ecosystem services and consumer willingness to pay offer valuable perspectives for market-driven sustainability efforts.