Abstract: Choosing the most sustainable process route for any new product or process innovation is fast becoming an expectation, but the R&D chemists and engineers tasked with making this decision face a dilemma. The sooner we account for sustainability criteria in our designs and thinking the more effectively they will be embedded in the outcomes, but the earlier we try to probe the sustainability credentials of the options the less data there is and the less certain we can be in our decision making. Britest has been seeking to address this dilemma for early stage process development through a Horizon Europe collaboration (ETERNAL) starting from and extending the well-established Britest process understanding toolkit. The aim is to enable project teams to carry out a pre-LCA assessment to select the most promising options, anticipating and articulating some of the key questions that will need to be addressed by continuing research. This presentation will 1) introduce a decision making tool which both covers the economic, environmental and social aspects of sustainability, and embraces the uncertainty inherent at the early stages of projects; 2) exemplify the use of process understanding tools as an to aid to finding and assessing opportunity to reduce the impacts of a process and its associated up- and downstream supply chains, and 3) propose an enhancement to a method for setting cost-effective impact reduction targets.