Abstract Life cycle assessment (LCA) is a method that has been applied on numerous different types of product systems. Most of these LCA studies concern full-market existing systems. In our common search for a more sustainable society, new technology systems are proposed of which the environmental sustainability still needs to be proven. These emerging technologies often only function at lab- or pilot-scale, and process data are also only available at these scales, and not at observed full-market scales. Performing LCAs of emerging technology systems poses challenges because relevant observations are lacking with regards to the projected final system, projected unit process data, projected characterization factors of new chemicals, etc. These challenges are increasingly recognized and addressed by the LCA community. In this contribution we discuss these challenges, with a special focus on ongoing research and recent developments.