An absolute environmental sustainability assessment of food

The food sector is a major user of land and freshwater and a source of considerable greenhouse gas (GHG) emissions. This puts pressure on Earth systems and jeopardizes the future of food production. The environmental impact of foods is well understood, but our interpretation lacks the context to judge whether those impacts are sufficiently small to describe a food as environmentally sustainable or not. In this work, we describe a metric that converts the environmental impact of foods into a quantitative environmental sustainability scale (performance-weighted environmental sustainability, PwES). Land use, freshwater use, and GHG emission impacts of common foods have been weighted by their nutritional content and normalized so that values greater than 100% are considered unsustainable. Our findings concur with the conventional wisdom that the high impact of meat is unsustainable, whereas vegetables are typically produced sustainably. Further to this, the PwES metric was used to establish rational targets for sustainable food supply and design nutritious and environmentally sustainable meal plans. It was found that without reductions to the environmental impact of food, it is very difficult to eat sustainably. A high-bread vegan diet could be found that provided minimum nutritional requirements and was environmentally sustainable.