corsus presents comparison of different protein sources at the 14th International Life Cycle Assessment Conference for Food in Barcelona

Ulrike Eberle (PhD), Managing Director of corsus, used the example of alternative protein sources to explain that the choice of functional unit – the reference value to which the comparison of environmental impacts refers – has a major influence on the result of the comparison. Most life cycle assessments compare products on the basis of a mass-based functional unit. However, this comparison falls short in terms of the functionality of the food – especially when comparing different animal and plant protein sources. This is because proteins can be utilised differently by the human organism depending on their amino acid composition and bioavailability. This correlation is not taken into account in most studies, as only the mass of the product is taken as a basis (for example, the comparison between one kilogramme (or litre) of oat drink and one kilogramme (or litre) of cow’s milk). In the context of alternative protein sources, however, it is often discussed whether alternative protein sources, such as plant-based meat and milk alternatives, can also represent an adequate substitute in terms of nutrients. However, the inclusion of nutrient-related parameters in the functional unit is not carried out in most studies, although this can lead to completely different results in terms of environmental impact. For example, an oat drink causes only a third of the greenhouse gas emissions of cow’s milk if a mass-based functional unit is used. With a functional unit that takes the protein content into account, oat drink causes one third more greenhouse gas emissions.

When comparing different protein sources, in addition to the nutrient and protein content, the physiological utilisation of the proteins contained (protein quality) and the energy content are also decisive. corsus has developed a functional unit that takes into account energy density, nutrient density and protein quality, thus enabling an adequate comparison of proteins from animal and non-animal protein sources. It can also be used to compare different dosage forms. For example, a protein powder can be compared with a protein drink, as the water content would be reflected in the mass-based unit, but not in the nutrient density-based unit. This also minimises potential sources of greenwashing.

The proposed functional unit is based on the Nutrient Rich Food Index (NRF), which is a measure of nutrient density and takes into account beneficial and non-beneficial nutrients. Protein quality was included using the DIAAS (Dietary Indispensable Amino Acid Score), which is recommended by the FAO as a measure of protein quality and takes into account the digestibility and availability of essential amino acids. The DIAAS-adjusted NRF was developed on this basis.

Julian Quandt, Senior Consultant at corsus and lead author of the study: ‘The results are exciting. It shows that the environmental impact of a soya drink is far lower than that of cow’s milk for most categories, even when the nutrient content and protein quality of both products are taken into account. They are only in the same range for biodiversity.’ The picture is similar for oat drink. When nutrient density and protein quality are taken into account, it also performs significantly better than cow’s milk in almost all environmental impacts.