Environmental rating ecolabels (ERE) represent a new generation of consumer-oriented communication tools. They aim to derive product environmental ratings from the assessment of multiple environmental impacts, thereby facilitating comparison of the environmental performance of products. This type of ecolabel has developed rapidly in Europe in recent years. However, their fragmented development means that numerous ERE schemes now co-exist with nearly as many distinct methodologies underpinning them. While most approaches are based on Life Cycle Assessment (LCA) calculations, they differ significantly in key methodological aspects – e.g. LCA modelling assumptions, impact category selection, aggregation of LCA results (including addition of non-LCA information) and conversion of aggregated numerical results into (usually categorical) ratings. The lack of harmonisation and scientific scrutiny to which ERE schemes have so far been subject represents a threat to the fulfilment of their original purpose: fair and evidence-based product comparisons in support of sustainable consumption decisions.

The work presented in this thesis characterises the emerging ERE landscape and examines key methodological aspects of ERE which require further development and harmonisation to achieve increased scientific robustness and credibility. Through four interlinked papers, this thesis demonstrates that designing and developing ERE schemes is a complex undertaking. From the LCA modelling stage to the display of a product rating, multiple and interrelated methodological stages exist, combining both empirical and normative decisions. Chapters 3 to 5 demonstrate that these methodological choices – specifically the design of the rating approach (Chapter 3), product categorisation considerations (Chapter 4), and the selection of secondary LCI datasets (Chapter 5) – can have a substantial impact on the ratings awarded to products.

Methodological development must therefore be approached in a rigorous, transparent and evidence-based way if these instruments are to gain widespread traction, providing effective and trustworthy information to apprise consumption choices. A pioneering framework (Chapter 2) is provided to guide the development of robust ERE schemes. Additional research areas are identified, notably to better understand and manage uncertainty. The work presented in this thesis is grounded in sector specific case studies and provides relevant recommendations for ERE scheme developers, policy makers and industry actors.