An original way of handiling co-products with a biophysical approach in LCAs of ivestock systems

A new biophysical procedure to handle co-products in LCAs of livestock systems, combining subdivision of the system and allocation, has been developed. Systems were divided into animal classes, defined as dedicated to specific physiological functions (e.g. growth) and so to specific products (e.g. animals for meat). When allocation is needed, the environmental burdens of the animal class were attributed to the co-products pro rata the feed energy required to produce them (biophysical causality). This has been applied on cattle, sheep, goat, pig, poultry, rabbit and fish production systems. On the example of some dairy and pig systems, it is shown that the attribution of the burdens to the different co-products of a system changes from one impact category to another. Indeed some resource consumption or emissions are specific to an animal class and then, to a product. A sensitivity analysis, considering five other allocation procedures, allows considering their respective advantages and limits.