In practice, products cannot solely be designed to minimize persistence at end-of-life; products must satisfy multiple, often competing, design objectives. Using literature data for several plastics, we calculated MIs to optimize a beam with a solid square cross-section in terms of financial (cost) and sustainability metrics (embodied GHG emissions and environmental lifetime). The choice of material had much greater effects on environmental lifetime than on cost or embodied GHG emissions. The median MIs for cost or embodied GHG emissions spanned less than one order of magnitude. In contrast, the MI for environmental lifetime spanned nearly three (Figure ). were lower, and PA, PHA, and PUR were higher than polyolefins). These same materials, though, had properties that reduced the MI for environmental persistence (i.e., shorter lifetimes than polyolefins). While MIs are helpful, they cannot, on their own, quantify the tradeoffs between competing design objectives. To address this, value functions can be used to systematically weigh the relative value of any given combination of MIs by forming a compound objective for optimization. Value functions are defined by converting the performance (e.g., mass, energy, time) to value (e.g., monetary value or cost) using exchange constants (e.g., price per kg).