James Sherwood 

In this work, a new metric called ‘Service-weighted Product Level Absolute Sustainability’ is proposed as a numerical indicator to determine if a product is sustainable. The service offered by a product was found to be crucial to normalize its environmental impact and permit comparisons between products. Service-weighted Product Level Absolute Sustainability is demonstrated here with examples of water use for laundry and food production. The maximum justifiable environmental impact of these products has been calculated based on their performance, i.e., the quantity of clothes washed or nutritional content. Now the environmental impact of products can be rationalized as either sustainable or unsustainable, informing sustainable choices by manufacturers as well as consumers.