Effects of different functional units on carbon footprint values of different carbohydrate-rich foods in China

The food sector produces large amounts of greenhouse gas (GHG) emissions, which has attracted attention of many researchers. Previous studies evaluated food carbon footprints (CFs) mainly based on food weight. Nutrient content of food could reflect food function better. However, different conclusions could be drawn based on different individual nutrients. The comprehensive trophic index has been used to evaluate food nutrition. In this study, CFs of nineteen carbohydrate-rich (CR) foods including grains, beans, root and tuber-food were investigated based on different functional units (weight, energy, protein, carbohydrate, and two comprehensive trophic indexes Nu(21) and Nu(11)). The CF rankings of the foods varied when weight based-, energy based-, and individual nutrient based functional units were used. Potato, cereal foods, and beans showed the low-CF advantage when weight based-, carbohydrate based-, and protein based functional unit was used, respectively. Covering more nutrients in the functional unit is beneficial to get closer to the truth of environmental impact of different foods. The comprehensive trophic index based functional unit was more appropriate for illustrating food CFs. Nu(21) method was fairer to evaluate food CF from the viewpoint of individual food, while Nu(11) method was more appropriate from the viewpoint of balanced diet. The results also exhibited that consumption of more brown rice and standard grade flour could be a feasible plan to reduce carbon emissions in nowadays. Meanwhile, enhancing rotation of coarse cereals and increasing consumption of coarse foods could cut a considerable amount of carbon emissions further. (C) 2018 Elsevier Ltd. All rights reserved.